Coastal Habitat Architecture for Productive Trophic Transfer in Marine Food Webs and Ecosystem-Based Watershed Management to Address the Interdependent Challenges of Climate Change

Haruka Yoshimura, Ph.D.

Fig. 1-1. Recreational Excursion at Hama-goten, Kunichika Toyohara (1835–1900), originally published 1890 (Image courtesy of the National Diet Library, Japan). At the sea entrance of moat system of Edo Castle (Fig. 2-2b), a lesser branch of the Tokugawa family reclaimed marshland and constructed Japanese traditional wooden palace with landscaping garden in 1654 (Tokyo: 35°40′ N, 139°46′ E). Situated on the military strategic point and facing the sea on two sides, the palace was transferred to the ruling line of the shogun family in 1704 and became known as Hama‑goten (浜御殿, “seashore palace,” Fig. 2-2a). This multi-color print in the Meiji era (1868–1912) illustrates how the seashore palace served as a venue for recreational activities for the shogun family and their retainers. Owing to its strategic defensive importance, the surrounding Shiba-ura (芝浦) area was allocated to the mansions of feudal lords and high‑ranking shogunate officials. Their estates, with gardens incorporating seawater‑filled ponds, were enclosed by seawater‑filled moats (Fig. 2-2). Japanese decision‑makers and architects recognized the critical role of nursery habitats in inshore and nearshore fishery management—a core component of governance for food security. Accordingly, the seawater‑filled ponds in gardens and moats were intentionally designed as nursery grounds for numerous species of fish and crustaceans (Smith et al. 2011). A large residential district for ruling‑class families (Fig. 2-2) thus functioned simultaneously as a protected coastal marine sanctuary. Shiba-ura was particularly noted for its nursery grounds for shrimp—especially the small native species shiba‑ebi (芝海老, Metapenaeus joyneri, Fig. 5‑1), which were abundant and spawned prolifically, giving the species its name derived from the Shiba district (芝). The abundance of shrimp and low-trophic level fish species enhanced both the quantity and quality of commercially important fisheries species by supporting effective trophic transfer pathways within the food web (Fig. 4) (Smith et al. 2011). Hiroshige’s works vividly depict the rich and diverse fisheries resources of the Shibaura district (Fig. 5).

Fig. 1-2. The Nishi-Honganji at Tsukiji, Teppōzu, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the British Museum, via the ukiyo-e.org by Resig J). In this print, Hiroshige highlights the architecture of a fishing community integrated into urban planning. In traditional indigenous engineering, Japanese architects created prolific fishing grounds close to fishing settlements by designing coastal structures that enhanced nearshore fisheries productivity. The name Tsukiji (築地, lit., “constructed land,” Fig. 2-2‑c) itself indicates that the area was reclaimed from the sea. The shallow marine zone off the western shore of the Sumida‑gawa River estuary (Fig. 2-2e), adjacent to the Shiba‑ura district, was reclaimed in 1658 following the great fire of 1657. Fishermen from Tsukuda‑jima Island (佃島, completed in 1644, Fig. 2-2f), originally from Settsu in Osaka Prefecture, played an active role in the reclamation work. On this newly created land, the high roof of the Tsukiji Honganji Monastery (Fig. 2-2d), belonging to the Jōdo Shinshū school (浄土真宗, Pure Land), stands prominently in the distance. The monastery’s wooden building in Asakusa had been destroyed in the great fire of 1657. The main building at the Tsukiji site was completed in 1658—the year after the fire—because the Tsukuda‑jima fishermen, themselves followers of Jōdo Shinshū, possessed the construction logistics expertise required for intensive reclamation. Due to the defensive and military strategic importance of the inshore area connected to Edo Castle’s moat system, the surrounding district housed the mansions of feudal lords and military elites, including firearms specialists. Consequently, a firearms training center was established there, giving rise to the name Teppōzu (鉄砲洲, “Firearm Bar”). Fishing boats casting nets and anglers in a pleasure boat in the middle distance suggest the abundance of fisheries resources in the inshore waters before Edo Castle. The shoreline of the reclaimed land is reinforced with dry‑stone walls equipped with stepped piers for small ports where fishing boats were moored. Two irregularly shaped rocky reef bars were placed offshore as coastal defense structures. Together, the dry‑stone walls and rocky reefs stabilized the shoreline: the interstices between stones dissipated wave energy and reduced wave reflection, providing safe harborage for moored fishing vessels. Commercially valuable species—such as spiny lobsters (ise‑ebi, 伊勢海老, Panulirus, Fig. 5‑1), prized in high‑class Japanese cuisine, and abalone (awabi, 鮑, Haliotis, Fig. 5‑4), valued for sashimi and Edo‑style sushi—were harvested from these rocky reefs. Ancient Japanese decision‑makers and architects understood the risks associated with the “tragedy of the commons” (Hardin 1968) in fisheries management. Because fisheries resources are common‑pool resources with open access, overexploitation and habitat degradation can easily occur. Japanese architects therefore developed distinctive architectural and spatial designs for fishing communities to mitigate this problem. As shown in this print, the placement of fishing settlements and moats served to protect prolific fishing grounds by limiting open access to commercially valuable marine resources.

Fig. 1-3. Bowl of Sushi, Hiroshige, 1830s (via Wikipedia). Catches of fish and shellfish from the elaborately engineered, highly productive fishing grounds near the shore of Tsukiji were delivered immediately to the large fish market known as Uogashi (魚河岸) in Edo’s commercial center. The freshness and flavor of fish and shellfish harvested from the inshore waters in front of Edo Castle formed the foundation of Edo‑style sushi, or Edo‑mae sushi (江戸前寿司), a culinary culture rooted in the everyday life of Edo’s townspeople. This exquisite cuisine originated from the value‑added use of freshly caught marine products taken from the nearshore waters directly “in front of” (mae, 前) Edo (江戸) Castle—the inshore sea area of what was then the world’s largest metropolis. The toppings in this assorted sushi include cooked kuruma‑ebi prawns (Marsupenaeus japonicus, Fig. 5‑2) or shiba‑ebi shrimp (Metapenaeus joyneri, Fig. 5‑1); on the lower left, vinegared fillets of konoshiro (鰶, Konosirus punctatus) or sappa (鯯, Sardinella zunasi) in the family Clupeidae (which includes herrings and sardines); and on the lower right, tai (鯛, red seabream, Pagrus major, Fig. 5‑3), whose loin is lightly seared around the edges before slicing. Sushi rolls appear beneath and in front of these topping sushis.

Fig. 2-1. Location of Edo (former name of the city of Tokyo). Legend: A: Edo Castle B: reclaimed marshland on the east bank of the Sumida-gawa River.

Fig. 2-2. Placement of extensive nursery habitats (including Hama‑goten Palace, a, Fig. 1‑1) and fishing communities together with prolific fishing grounds (Tsukiji, 築地, c, Fig. 1‑2) in the coastal urban planning of Edo. Data from the Reproduced 1856 Edo Map Verified by Actual Measurement in the Encyclopedia of EDO-MEIJI-TOKYO, edited by Keiji Nakagawa, APP Co., Ltd., 2004 (ISBN: 4-901441-30-2), processed by Dr. Sotaro Tanaka (Remote sensing). Legend: a: Hama‑goten Palace (浜御殿) b: sea opening of the Edo Castle moat system c: Tsukiji reclaimed land (築地) d: Tsukiji Hongan-ji Monastery e: Sumida‑gawa River (隅田川) f: Tsukuda‑jima Island (佃島). In the urban planning of Edo, prolific fishing grounds were elaborately shaped in conjunction with engineered pathways for the movement of essential nutrients, forming continuous habitats that supported trophic pathways and steps within the food web (Fig. 4). Rivers supply silicic acid (dissolved Si‑containing compounds), a vital nutrient for diatom‑dominated phytoplankton—the foundation of marine food webs—from land to coastal waters (e.g., Milliman 1997; Conley 2002; Katz et al. 2024). Accordingly, the prolific fishing grounds were placed at the estuary of the Sumida‑gawa River (e). Edo was a densely wooded city (e.g., Fig. 9‑3, 4, 5 in https://harukanoor4.blogspot.com/2023/10/). Deep forests were incorporated into the gardens of ruling‑class families on the reclaimed land of Tsukiji (Fig. 1‑2), playing an important role in supplying essential nutrients—such as Fe‑containing organic compounds in the form of humus, leaf litter, and detritus—to the sea (Kuma and Matsunaga1995). The Tsukiji fishing grounds were surrounded by extensive nursery habitats. To avoid overexploitation and habitat degradation associated with the “tragedy of the commons” (Hardin 1968), the large residential districts of ruling‑class families—functioning as productive coastal nursery habitats—were maintained as “forbidden areas,” thereby restricting access to abundant fisheries resources. From an architectural perspective, these productive coastal nursery habitats were safeguarded by an intricate moat system constructed with rocks of high silica content, which created habitats for benthic diatoms. Through silica uptake and biogenic silica production, benthic diatoms play a key role in enhancing coastal ecosystem productivity (Rousseau et al. 2002; Leynaert et al. 2009, 2011). The carefully engineered coastal zone provided continuous habitats that shaped trophic pathways and steps within the food web (Fig. 4), resulting in abundant and diverse fisheries resources (Fig. 5). The moat construction project began soon after Ieyasu Tokugawa (徳川家康, 1542–1616) settled in Edo in 1590. Excavated soil was used to fill an inlet near the citadel of Edo Castle. In 1603, additional soil was excavated from a plateau north of the castle to extend the reclaimed land (Endoh 2004). Subsequently, the shallow sea area off the reclaimed land was filled after the great fire of 1657, creating the area known as Tsukiji (築地, lit., “constructed land”). In Tsukiji, a fishing community—including prolific fishing grounds—was established to supply affordable, high‑quality fresh marine resources to the people. 

1.     Introduction

 

1.1. Land governance in the era of climate change

 

1.1.1.      Watershed management for resilient regional hydrological cycle under shifting precipitation regimes

 

The intensification of extreme precipitation events and the increasing risk of flooding across all climate regions—driven by a modified hydrological cycle under climate change—have been widely warned (e.g., Trenberth 2011; Tabari 2020).

Patterns of precipitation have already begun to shift. In 2024, unprecedented torrential rains caused flooding and extensive damage in regions suffering from chronic drought (NASA https://www.bluemarble.nasa.gov/images/event/152279/2024-flooding-in-the-northern-hemisphere).

In April 2024, heavy rainfall triggered flash flooding across eastern parts of the United Arab Emirates—an area known for its dry desert climate— inundating roads and disrupting transportation. Up to 250 mm (10 inches) of rain fell in less than 24 hours in a region that typically receives only 140–200 mm (5.5–8 inches) per year.

In September 2024, intense rainfall struck parts of the desert in southeast Morocco. Preliminary satellite analysis indicates that more than 200 mm (8 inches) of rain fell in areas of the Sahara Desert in North Africa—equivalent to a year’s worth of precipitation. Satellite imagery shows normally dry lakes filling with water.

On 29 October 2024, torrential rainfall triggered flash floods in southern and eastern Spain, regions that had long suffered from chronic drought (Calvo-Sancho et al. 2026). Torrents of muddy water destroyed homes and swept away bridges and vehicles, leaving more than 200 people dead, thousands displaced, and many still missing. In parts of Valencia along the Mediterranean coast, rainfall totals exceeded 300 mm (12 inches)—roughly equivalent to the region’s annual precipitation—on that single day.

Forests are active determinants of the water cycle (Sheil 2018). At the beginning of the 21st century, the modified hydrological cycle—marked by extreme precipitation and drought events—has posed deepening water-related challenges. Therefore, flood-water management that incorporates solutions to restore the hydrological cycle is urgently required. Japanese traditional indigenous watershed management, including strategic placement of forests and woodlands, was based on a concept how forests function as hydrological regulators (https://harukanoor4.blogspot.com/2016/). The engineered landscapes that functioned as hydrological regulators provide valuable insights into approaches for restoring the hydrological cycle.

1.1.2.     An inclusive approach to fisheries management in the era of climate change

 

In Japan, inland and marine fisheries resources were historically diverse and abundant, owing to unique watershed management practices and a coherent coastal planning strategy. The abundance of fisheries resources was shaped by engineered pathways of essential nutrients movement and the creation of continuous habitats that formed effective steps for food webs (https://harukanoor4.blogspot.com/2022/; https://harukanoor4.blogspot.com/2023/).

Fisheries management is closely connected to major policy issues: hazard mitigation (Temmerman et al. 2013; Spalding et al. 2014), erosion control (Mentaschi et al. 2018; Vousdoukas et al. 2020), food security (Garcia and Rosenberg 2010), social resilience (Adger et al. 2005; Goes et al. 2020), natural carbon sinks on land and in the ocean that remove atmospheric CO₂ via photosynthesis (Canadell et al. 2007), and CO₂ sequestration in a vast area of ocean known as “blue carbon” (phytoplankton: Field et al. 1998, Falkowski et al. 1998, Falkowski 2002; coastal vegetation: Duarte et al. 2005, Duarte 2017). Japanese traditional indigenous civil engineering harnessed natural systems and processes to enhance fisheries productivity while simultaneously providing coastal protection, erosion control, climatic comfort in summer, and social and economic resilience.

 

1.2. Addressing the interdependent challenges of climate change

 

There is growing recognition that nature-based solutions can effectively address the interdependent challenges of climate change while supporting biodiversity and securing ecosystem services (e.g., Seddon et al. 2020).  

Japan’s traditional indigenous civil engineering—its unique watershed management and coherent coastal planning strategy—shaped complex and prolific aquatic ecosystems, and secured the food security through abundant fisheries resources. These Japanese traditional planning and management systems have been tested and proven over a millennium. Therefore, this successful historical ecosystem-based approach offers valuable guidance for inclusive solutions to climate challenges worldwide.

 

1.3. Aim of this article

 

Policies and practices addressing the interdependent challenges of climate change require successful ecosystem-based approaches. This article highlights Japan’s original landscapes of traditional engineering, focusing on the architecture of vegetated coastal wetlands in estuarine and coastal areas, as well as river and lake (pond) engineering within watershed management.

Hiroshige Utagawa (歌川広重, 1797–1858) depicted the landscapes that were intricately shaped by Japanese architects. His prints serve as historical records documenting Japan’s original landscapes of traditional engineering. Hiroshige’s realistic notations are accurate representations of traditional design and Eastern engineering philosophy, informed by his background as a samurai—the ruling class responsible for land governance. In addition, historical Japanese maps indicate the placement of constructed ecosystem structures.

First, key aspects of the ecosystem-based approaches—constructed coastal wetlands (Fig. 3), and the architecture of habitats for diatoms-dominated phytoplankton—are outlined. Then, the constructed coastal wetlands and prolific fishing grounds in Edo, Shibaura, are examined. The systemic coastal infrastructure in Shibaura was carefully engineered with rocks and sand to replicate natural habitats and to shape effective transfer pathways within food webs (Fig. 4).

Major challenges of climate change include constrained agricultural productivity due to summer high temperatures and impacts on safe drinking water access. As ecosystem-based approaches to these interconnected issues, this article discusses unique design and engineering techniques in traditional watershed management, including energy and material flows. Accordingly, numerous features of Japanese traditional engineering in reclaimed marshland in Edo (Fig. 2-1-B) are presented.

 

2.     Encouraging examples of Japanese traditional ecosystem-based solutions

 

2.1. Essential role of constructed coastal wetlands in shaping complex and prolific coastal ecosystems

 

Japan historically implemented a coherent national coastal strategy in land governance—unique in its ability to translate learning-based knowledge into the architectural design of diverse nursery habitats that supported resilient fisheries integrated with coastal protection.

Abundant inshore and nearshore fisheries resources are sustained through trophic transfer within marine food webs. Shrimp, in particular, play a crucial role in the diet of nearly all commercially important fisheries species at some stage of their life history (Moyle and Cech 2004). Shrimp productivity depends strongly on the area of vegetated wetlands. For example, in the northern Gulf of Mexico, the mean annual yield of shrimp caught inshore is highly correlated with the extent of vegetated wetlands (Boesch and Turner 1984). Because of the essential link between nursery grounds and fisheries productivity, the loss of vegetated coastal wetlands leads to declines of fisheries (Chesney et al. 2000).  

Low-trophic level species—such as anchovy, sardine, and herring—and invertebrates such as shrimps play a central role in shaping complex and prolific inshore and nearshore marine ecosystems. They provide critical pathways and transfer steps within marine food webs (Smith et al. 2011). Ancient Japanese architects understood the ecological importance of shrimp and low-trophic-level fish species in fisheries resources management. Consequently, large areas of the vegetated coastal wetlands—nursery and feeding habitats for these species—were strategically placed and protected as a marine sanctuary.

Several shrimp species live and spawn offshore as adults, while their eggs and planktonic larvae move shoreward into semi-enclosed estuaries, including intertidal salt marshes and associated networks of tidal creeks, embayments, and salt marsh pools. The microscopic eggs and larval stages pass through barrier such as naturally shaped earthen embankments and benefit from predator refuge and abundant food that support rapid growth. As they mature, shrimp migrate back to the ocean to spawn (e.g., Odum 1971; Fig. 3). In Edo’s Shibaura district, seawater-filled ponds in gardens and moats were intentionally designed as semi-enclosed vegetated wetlands (Figs. 1-1, 2-2).

This successful historical ecosystem-based approach to designing estuarine and coastal vegetated wetlands offers practical guidance for contemporary coastal governance. Ecosystem structure and function in estuarine and coastal seas have been severely degraded by human activity (Lotze et al. 2006; Diaz and Rosenberg 2008), and global fisheries landings have declined since the late 1980s (Pauly et al. 2003; Pauly and Zeller 2016). 

Fig. 3. Life history of shrimp that use vegetated coastal wetlands as nursery grounds (after Odum 1971). Adult shrimp spawn offshore. The microscopic larval stages (nauplius, zoea, mysis) move shoreward and pass through natural or artificial earthen embankments into intertidal coastal wetlands (salt marshes). Within these wetlands and their networks of tidal creeks, bays, and salt marsh pools, shrimp benefit from predator refuge and abundant food during critical life history stages, enabling rapid growth. As they mature, shrimp migrate back into deeper bay waters and adjacent sea, where they are harvested. Vegetated coastal wetlands thus serve as nurseries for prolific coastal fisheries (Boesch and Turner 1984; Chesney et al. 2000). In Eastern philosophy of fisheries resource management, the architecture of the semi-enclosed estuarine and coastal vegetated wetlands—nursery and feeding habitats of shrimp and low-trophic level species— was of critical importance for governing food security. Accordingly, a wide variety of designs adapted to local geography and environmental conditions were developed. In Shibaura, Edo, seawater-filled ponds in gardens and moats functioned as semi-enclosed vegetated wetlands (Fig. 1-1). Canal construction contiguous to estuarine was integrated with engineered vegetated wetlands (Fig. 8).  

 

2.2. Watershed management to safeguard sustainable fisheries harvests

 

2.2.1.     Basis of marine food webs: Diatom-dominated phytoplankton 

 

Carbon fixation by marine phytoplankton via photosynthesis accounts for approximately half of global annual net primary production (Field et al. 1998; Falkowski 2002). Marine phytoplankton—the primary producers that form the foundation of marine food webs and are often referred to as ocean’s invisible forests (Falkowski 2002)—consist of tiny single-celled algae, including diatoms, dinoflagellates, and haptophytes (e.g., Simon et al. 2009). Among these, silica-shelled diatoms are the most essential group of eukaryotic phytoplankton supporting productive coastal fisheries (Armbrust 2009). They are estimated to contribute roughly 40% of marine primary productivity (Tréguer et al. 2018).

A portion of diatoms sinks into deep ocean, where carbon is sequestrated over geological timescales. In this process, known as the biological pump, the silica shells of diatoms provide ballast that enhances the transport of carbon to the deep ocean (Tréguer et al. 2018). Thus, diatom productivity plays a key role in climate change mitigation and adaptation.

However, diatoms face significant—mostly negative—impacts from human activities. Nutrient enrichment of water bodies (eutrophication and pollution) causes harmful algae blooms (e.g., Anderson et al. 2008; Heisler et al. 2008), which degrade fisheries resources by collapsing diatom-dominated phytoplankton communities, the basis of marine food webs. The key to preventing excessive nutrient inputs is to keep large quantities of undesirable nutrients on land and out of the water bodies (Tilman et al. 2001; Diaz and Rosenberg 2008).

To close the nutrient cycle—critical for sustaining fisheries resources—Edo prohibited the disposal of any kind of waste into urban areas and water bodies (rivers, streams, lakes, and seas) in 1655 (Endoh 2004). Human excreta and animal waste were used for fertilization and soil improvement, and a clean seawater policy was practiced throughout Japan.

 

2.2.2.     Architecture of land-sea interactions

 

Diatoms, single-celled planktonic microalgae protected by silica shells (frustule), act as primary producers forming the base of aquatic food webs (e.g., Armbrust 2009; Saxena et al. 2021). Accordingly, diatom blooms require abundant dissolved silica in addition to other essential nutrients (Smetacek 1998).

 The architecture of land-sea interactions is critical because rivers transport essential nutrients—such as dissolved silica compounds—to the sea, supporting the base of marine food webs (Humborg et al. 1997; Milliman 1997; Katz et al. 2024). Rivers also supply iron-containing organic compounds in the form of humus, leaf litter and detritus (e.g., Kuma and Matsunaga 1995). Some phytoplankton, including diatoms, grow better at cooler temperatures (Boyce et al. 2010, 2014; Toseland et al. 2013). Japan developed unique river-engineering designs that functioned as transport corridors for essential nutrients and cool freshwater from terrestrial environments to the ocean (https://harukanoor4.blogspot.com/2023/10/).

  

2.2.3.     Engineered free-flowing rivers

 

To safeguard sustainable fisheries harvests, architecture of free-flowing rivers (Dynesius and Nilsson 1994; Nilsson et al. 2005) together with non-fragmented nursery and feeding habitats, is essential for managing anadromous fishes (e.g., salmon, which return from the sea to spawn in freshwater) and catadromous fishes (e.g., eels, which spawn in the ocean and spend most of their lives in inland or brackish waters).

Ancient Japanese architects developed unique river-engineering systems, including:

Non-continuous levee systems that retain floodwaters within engineered detention areas (e.g., Okuma 1981).

Riffle-pool sequences that create diverse habitats.

These systems require extensive floodplains (Figs, 9, 14, 15). Dense riparian forests, highly connected with mountain forests, were established across these flood plains, forming transport corridors for essential nutrients—such as iron and silica compounds in the form of humus, leaf litter, and detritus—along with cool freshwater flowing from land to sea (https://harukanoor4.blogspot.com/2023/10/).

Fig. 4. Schematic illustration of a prolific marine food web in Shibaura, Edo. Silica-shelled diatoms, the most essential group of eukaryotic marine phytoplankton, form the base of marine food webs and support productive coastal fisheries (Armbrust 2009; Tréguer et al. 2018). River engineering that shapes land-sea interactions is critical because rivers transport dissolved silica to the sea (Humborg et al. 1997; Milliman 1997; Katz et al. 2024) along with iron-rich organic matter such as humus, leaf litter, and detritus (e.g., Kuma and Matsunaga 1995). Diatom proliferation plays a key role in climate change mitigation and adaptation: a portion of diatoms sinks into deep ocean, where carbon is sequestrated over geological timescales via the biological pump (Field et al. 1998, Falkowski et al. 1998, Falkowski 2002). Their Silica shells provide ballast that enhances carbon transport to depth (Tréguer et al. 2018). In Edo, vegetated coastal wetlands—nurseries for many fish and invertebrates—were carefully constructed (Figs.1-1, 2-2, 8). These wetlands play a crucial role in managing the productivity and stock of commercially important fisheries resources (Boesch and Turner 1984; Chesney et al. 2000). Within these wetlands, marine phytoplankton with rapid rates of primary production support high abundances of forage fish such as anchovies, sardines, and herrings (Fig. 4). Low-trophic level species, including anchovy, sardine, herring, and shrimp, act as the key trophic links transferring phytoplankton production to larger predators (Smith et al. 2011). A large area of the vegetated coastal wetlands was protected as a marine sanctuary in Edo (https://harukanoor4.blogspot.com/2023/). The constant, abundant supply of low-trophic-level fish and shrimp from this sanctuary activated trophic transfer within inshore and nearshore marine food webs. The decorative depiction of the large predator fish red seabream (鯛), vividly colored and swimming in seawater-filled ponds and moats (Fig. 5-3), indicates that the Japanese decision-makers and architects successfully constructed inshore and nearshore marine food webs of significant ecological and economic value in a state of equilibrium.

2.3. Key role of biological processes in the silica cycle: Benthic diatoms

 

2.3.1.     Primary production by benthic diatoms

 

Diatoms are major contributors to phytoplankton blooms in aquatic ecosystems, acting as the primary producers that form the base of the food web in both marine and freshwater environments (e.g., Saxena et al. 2021). While most diatoms are free-floating plankton, but some live on the bottom, attached to surfaces such as plants or rocks, or within sediments.

Benthic habitats on the sea floor play a significant role in supporting prolific fisheries by providing diverse transfer passways from primary production upward through the food web. However, human activities have severely impacted benthic diatom primary production. Coastal dead zones have expanded exponentially since the 1960s, resulting in the loss of potential food energy for fisheries. These degraded benthic zones now exhibit low annual secondary production and often lack benthic fauna entirely (Moyle and Cech 2004; Diaz and Rosenberg 2008). Thus, restoring benthic habitats is urgently needed to rebuild ecosystem resilience as part of climate strategies.

Benthic diatoms play a key role in the silica cycle of coastal ecosystems, supporting blooms of diatom-dominated phytoplankton—the basis of marine food webs (Rousseau et al. 2002; Leynaert et al. 2009, 2011).

Diatoms require dissolved silica to build their frustules, the siliceous component of their cell walls. Silicic acid inputs to coastal waters originate predominantly from rivers and adjust seas (e.g, Milliman 1997; Conley 2002; Katz et al. 2024), but biogenic silica production by benthic diatoms also plays a critical in coastal ecosystem productivity (Rousseau et al. 2002). Benthic diatoms increase dissolved silica concentration at the sediment–water interface (Leynaert et al. 2009). This enrichment regulates blooms of diatom-dominated phytoplankton and promotes favorable phytoplankton species composition from the seafloor to the surface (Leynaert et al. 2011).

Benthic diatoms, invisible to the naked eye, require surfaces having a high silica content—such as natural rocks (granite/andesite), plants, and/or sediments—to attach and uptake Si for biogenic silica production. Because silicon is a major element in Earth’s crust, natural rocks such as granite and andesite contain abundant silica (SiO2). Masonry structures made of natural rocks—such as rocky reefs, dry-stone walls and stepped piers—therefore provide ideal high-silica surfaces for benthic diatom colonization and silica uptake.    

On continental shelves and slopes, most bottoms are soft and relatively featureless, composed of sand, silt, broken shells, and other fine materials (Moyle and Cech 2004). As Si is a basic component of nearly all parent materials, nearshore soft bottoms contain abundant silica and numerous small pores that create vast surface area. These conditions allow benthic diatoms to attach and actively produce biogenic silica, forming the basis of coastal ecosystem productivity.

However, deposition of human effluent—such as fertilizer runoff, treated sewage discharge, combined sewer overflows, and urban stormwater—alters the availability of essential silicic acid for benthic diatoms. The resulting loss of benthic diatom primary production leads to reduced secondary productivity (Diaz and Rosenberg 2008).

 

2.3.2.     Critical role of salt marshes in the silica cycle of coastal ecosystems

 

The occurrence of Si (used here as a generic term for silicon compounds) in plants depends on their ability to accumulate Si. Salt marshes are dominated by salt-tolerant plants such as Poaceae (grasses), Cyperaceae (sedges), and Equisetaceae (horsetails), all of which accumulate high levels of silica (Currie and Perry 2007). The presence of silica in their cell walls creates favorable conditions for benthic diatoms to attach and uptake Si for biogenic silica production. After these plants complete their life cycle, a portion of their silica-rich biomass becomes buried in sediments, forming habitats for benthic diatoms.  

Salt marshes thus produce organic materials with high silica content, creating ideal conditions for benthic diatom growth. Active biogenic silica production by benthic diatoms enriches silicic acid in shallow coastal systems, enhancing blooms of diatom-dominated phytoplankton—the basis of marine food webs. Therefore, salt marshes play a critical role in the silica cycle of coastal ecosystems and form the foundation of productive coastal and nearshore fisheries.

 

2.3.3.      Negative impacts of concrete structure on benthic diatom-based marine productivity

 

Hard coastal protection measures are now widely used around the world. In Europe alone, 22,000 km² of the coastline are artificially covered with concrete or asphalt. More than 50 % of the Mediterranean coasts are dominated by concrete, with over 1,500 km of artificial shoreline, including harbors and ports (Airoldi and Beck 2007). Approximately 14% of the total US coastline—22,842 km of continental shoreline—has been hardened and armored (Gittman et al. 2015).

Benthic diatoms prolificate and colonize intertidal and subtidal areas across all latitudes, influencing dissolved silica fluxes from the seafloor to the water column and supporting diatom-dominated phytoplankton (Leynaert et al. 2009). However, coastal defense structures dominated by concrete or asphalt may critically reduce benthic diatom primary production because these materials contain far less silica (SiO2) than natural rocks.

Benthic diatoms require surfaces with high silica content. Natural rocks such as granite typically contains 70–77% silica by weight. In contrast, concrete surfaces provide chemically unsuitable substrates due to their reduced silica composition. This alteration disrupts benthic diatom colonization, leading to collapses of marine food webs. Because benthic diatoms are key components of the silica cycle and support blooms of diatom-dominated phytoplankton (Rousseau et al. 2002; Leynaert et al. 2009, 2011), the widespread use of concrete poses significant ecological risks.  

 

2.3.4.     Coastal and marine engineering to support benthic diatom habitats: A fisheries management perspective

 

Enrichment of silicic acid through the biogenic silica production of benthic diatoms regulates blooms of diatom-dominated phytoplankton—the foundation of aquatic food webs. Because benthic diatoms require surfaces with high silica content, it is urgently necessary to minimize or eliminate negative impacts from construction materials and engineering designs in coastal, marine, stream, and lake environments from the perspective of fisheries-resource management.

In Japanese traditional indigenous engineering, unique designs were developed to create favorable conditions for benthic diatoms. Masonry structures made of natural rocks without cement—such as dry-stone walls and stepped piers (Fig.1-2)—provide high-silica surfaces that promote active benthic-diatom blooms. 

Ancient Japanese architects also constructed man-made mudflats and earthen groynes using nearby sediments composed of sand, silt, and fine organic materials derived from silica-accumulating plants (Fig. 8). These soft sediments, with their numerous small pores, provide extensive high-silica surface area for benthic diatoms. Through direct Si uptake and biogenic silica production, benthic diatoms regulate dissolved silica availability and enhance coastal ecosystem productivity (Rousseau et al. 2002; Leynaert et al. 2009, 2011). Thus, earthen structures such as mudflats and earthen groynes form the foundation of productive coastal fisheries.

Additionally, large areas of salt marshes—dominated by plant species with high silica-accumulation capacity—were strategically incorporated into man-made sandbanks and engineered estuaries (Fig. 8). The silica-rich organic compounds produced in salt marshes create habitats for benthic diatoms, which in turn enrich silicic acid through biogenic silica production. Consequently, extensive salt marshes play an important role in supporting blooms of diatom-dominated phytoplankton and shaping the basis of marine food webs. 

 

2.3.5.     For freshwater fishery resources: Need for selecting appropriate construction materials and engineering design to support benthic diatoms

 

Benthic diatoms occur in almost all aquatic habitats, including streams and lakes (e.g., Kahlert and Gottschalk 2014). In these environments, benthic diatoms attach to surfaces with high silica content to uptake Si for biogenic silica production, supporting blooms of diatom-dominated phytoplankton and serving as the foundational food source for higher trophic levels. Benthic diatoms therefore play a crucial role in the silica cycle of freshwater ecosystems.

However, benthic diatoms face significant negative impacts from human interventions, such as nutrient loading (fertilizer runoff from agriculture, treated sewage discharge, combined sewer overflows, and urban stormwater) and hardened, armored surfaces created by concrete channelization and bank stabilization. These modified surfaces—together with the deposition of human effluent—destroy favorable conditions for benthic diatoms because of their reduced silica content. The collapse of benthic diatoms’ direct Si uptake and biogenic silica production leads to severe disruption of freshwater food webs—the basis of prolific freshwater fishery resources.

In Japanese traditional indigenous engineering, unique designs were advanced to shape favorable conditions for benthic diatoms through a learning-based approach. In Fig. 9-2, Hiroshige depicts classical Japanese river engineering that secured benthic-diatom habitats. The course of the Sumida-gawa River, running along the edge of reclaimed marshland (Figs. 7-1a, 7-2a), was excavated by human design. To stabilize banks against erosion, numerous groynes were built using nearby sediments composed of sand, silt, and fine materials derived from organic compounds of high‑silica plant species. These engineered floodplain marshes provide habitats for benthic diatoms, which in turn support blooms of diatom‑dominated phytoplankton—the foundation of aquatic food webs (Rousseau et al. 2002; Leynaert et al. 2009, 2011). In canal construction, this engineering design to support benthic diatoms was regarded as standard practice (Figs. 8, 11-3, 13-1).

 

3.     Land governance to safeguard sustainable fisheries harvests: Shibaura in Edo

 

3.1. Architecture of reclaimed land: created prolific fishing grounds through urban planning

 

Ieyasu Tokugawa (徳川家康1542–1616) settled in Edo in 1590 and established his Shogunate (military governing dynasty) in 1603. Edo grew into the largest metropolis in the world, with an estimated population exceeding 1,000,000 by 1721 (Sansom 1963; Uspensky 2003). To meet the rapidly increasing demand for residential land, the urban area of Edo expanded through reclamation works employing unique civil-engineering designs and technologies.

Construction of moat system—beginning at the Sumida-gawa River in Asakusa and looping gradually toward the citadel of Edo Castle—was initiated immediately after Ieyasu‘s arrival in 1590. Soil excavated from moat construction was used to fill an inlet near the castle, and the reclaimed land became residential quarters for feudal lords. Beginning in 1603, additional soil was excavated from the plateau near the castle and used to expand the land for commercial districts and housing for merchants and craftsmen, including Nihon-bashi area (Endoh 2004). After the great fire of 1657, the shallow sea area adjacent to earlier reclaimed land was filled in 1658, forming Tsukiji (築地, lit. “constructed land,” Figs. 1-2, 2-2-c). 　

Fishermen from the artificial island, Tsukuda-jima (佃島, completed in 1644, https://harukanoor4.blogspot.com/2023/10/, Fig. 2-2-f), played an active role in these reclamation works. They applied the coastal-engineering knowledge and techniques they had acquired during the construction of Tsukuda-jima. The architectural design of prolific fishing grounds close to the shore—aimed at maximizing long-term fishery productivity—had long been admired by Japanese architects and decision-makers.

Due to its defensive and military strategic importance, the reclaimed inshore area near Edo Castle was assigned to mansions of feudal lords and high-ranking shogunate officials. The estates, including Hama-goten (Figs. 1-1, 2-2-a), featured gardens with seawater-filled ponds and were surrounded by seawater-filled moats (Fig. 2-2). Japanese decision-makers and architects recognized the critical role of nursery habitats in inshore and nearshore fishery management as a core element of food security governance. Therefore, seawater-filled ponds and moats were intentionally designed as protected nurseries for many species of fishes and crustaceans (Fig. 3).

Notably, small shrimp shiba-ebi (芝海老, Metapenaeus joyneri, Fig. 5-1) were abundant and spawned prolifically in these habitats. their mane derives from the inshore district of Shiba (芝), reflecting their ecological and cultural significance (https://harukanoor4.blogspot.com/2022/).

Fig. 5-1. Lobster and Shrimp, from the series Grand Series of Fishes, Hiroshige, originally published 1832–33 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In this print, Hiroshige illustrates the key role of shrimp nurseries in sustaining inshore and nearshore marine food webs in Shibaura. The lobster at the center of this print—rendered with precise observational details—draws the viewer’s attention. Hiroshige emphasizes that the small shrimps (shiba-ebi, 芝海老, Metapenaeus joyneri, 10–15 cm/4–6 inches) depicted on the right are an important of the lobster’s diet, and lobsters were highly valued delicacies in Edo’s markets. Hiroshige further highlights the nursery habitats—seawater-filled moats and garden ponds of gardens—by quoting a poem praising the shrimp nurseries of Shibaura:

“During the hot summer days/

That warm the seawater/

Shrimps proliferating and upwelling in Shibaura!”

The viewer understands that the productivity of highly valued delicacies such as lobster depended on the high abundance of shrimp supported by these carefully engineered nursery habitats.

3.2. Nursery habitats—the basis of fisheries productivity integrated with coastal protection

 

Coastal ecosystems play a critical role in coastal protection and in reducing vulnerability of coastal communities (Temmerman et al. 2013; Spalding et al. 2014). Salt marshes reduce the height and velocity of incoming waves through the buffering effect of vegetation structures (Möller et al. 2014). Vertical accretion of marshlands through sediment capture (Morgen et al. 2009; Barbier et al. 2011) enhances the effectiveness of coastal protection year by year. Underwater seagrass meadows also stabilize sediment through their roots and rhizomes, preventing erosion and thereby contributing to shoreline protection (Duarte 2002). Kelp forests reduce longshore currents and wave energy, promoting sedimentation (Morris et al. 2020).

Coastal ecosystems are also essential nursery habitats. Most marine species of commercial value require more than a single habitat to complete their live cycle. Major industrial offshore fisheries species—such as Alaska (walleye) pollock (介宗鱈, Theragra chalcogramma, the most landed species globally), Atlantic cod (Gadus morhua), Pacific cod (真鱈, Gadus macrocephalus), Atlantic herring (Clupea harengus), and Pacific herring (nishin, 鰊, Clupea pallasii)—spend their adult lives shoaling in deep offshore waters where they live, feed, and spawn. However, juveniles require seagrass meadows as nursery grounds for foraging and shelter during early life stages. Therefore, the loss of seagrass nursery habitats leads to declines in global fisheries productivity (Unsworth et al. 2018).

Salt marshes and mangrove forests also play significant role in supporting fisheries productivity. Intertidal salt marshes in temperate and high-latitude regions serve as nurseries for commercially important fisheries species such as shrimp, oysters, clams, and fishes (Boesch and Turner 1984; Moyle and Cech 2004; MacKenzie and Dionne 2008). Because shrimp constitute a significant component of the diet of almost all commercially important fish species and invertebrates at some stage of their life history (Moyle and Cech 2004), shrimp productivity—supported by extensive vegetated coastal wetlands serving as nursery grounds—plays a critical role in sustaining prolific fisheries (Boesch and Turner 1984; Chesney et al. 2000; Barbier et al. 2011).

Kelp forests support fisheries productivity by providing essential nursery and foraging habitats for juvenile salmonoids, forage fishes, and decapods (crustaceans including many commercially important fishery species such as crabs, lobsters, shrimp, and prawns) in the northeast Pacific nearshore (Shaffer et al. 2020). Their structural complexity provides shelter from predators. In addition, kelp forests serve as spawning zones for Pacific herring.

The importance of nursery restoration for improving fisheries productivity is increasingly recognized (e.g., Gernez et al. 2023). Historically, Japan developed a unique design of coastal protection integrated with marine resources management through the architecture of diverse and productive nursery habitats (https://harukanoor4.blogspot.com/2023/10/).

In the reclaimed coastal land of Shibaura in Edo, nursery habitats were shaped through engineered pathways for the movement of essential nutrients. Hiroshige depicts numerous features of Japanese traditional coastal-engineering in Shibaura, Edo.

 

3.3. Seagrass meadow restoration requires extensive deep coastal forests

 

Hiroshige depicts commercially important species of inshore marine food webs in Shibaura, illustrating the high productivity of these ecosystems (Figs. 5-1,2,3,4,5). Diatom-dominated phytoplankton are consumed by zooplankton (small crustaceans such as copepods and krill, and larvae of fish, squid, shrimps and crabs). Sequentially, larger zooplankton and forage fish (small, schooling, filter-feeding species such as herring, sardines, and anchovies) feed on these smaller herbivorous zooplankton. The planktivorous forage fishes are then consumed by larger predators, including diverse commercially important fish species of (Fig. 4).

Vegetated coastal wetlands play a key nursery role for many fishes and invertebrates. In Shibaura, Edo, extensive vegetated coastal wetlands within the estates of ruling class families were deliberately created (Figs. 1-1, 2-2), reflecting the importance of shrimp as a dietary component of almost all commercially important fisheries species (Moyle and Cech 2004). Shrimp productivity depends strongly on the vegetated wetlands (Boesch and Turner 1984), and prolific fisheries require such wetlands (Chesney et al. 2000).

In traditional Japanese coastal reclamation engineering, extensive deep coastal forests were deliberately integrated with vegetated coastal wetlands as standard practice. Along the coasts of reclaimed land of Shibaura, ancient Japanese decision-makers and architects created extensive deep coastal forests within the estates of ruling class families. Hiroshige depicts a panoramic offshore view of Shibaura’s coastline, showing unbroken deep coastal forests extending over 2 km (1.25 miles) (Fig. 9-3 in https://harukanoor4.blogspot.com/2023/).

These extensive deep coastal forests played an essential role in supplying nutrients—such as Fe‑containing organic compounds in the form of humus, leaf litter, and detritus—for blooms of diatom-dominated phytoplankton in the sea (Kuma and Matsunaga1995).  

The resilience of seagrass ecosystems—serves as critical nurseries—requires connectivity with adjacent ecosystems such as mangroves and/or salt marshes to ensure the availability of essential nutrients (Unsworth et al. 2015). The extensive deep coastal forests supported seagrass meadow productivity by supplying these nutrients.

Blooms of diatom-dominated phytoplankton (Boyce et al. 2010, 2014; Toseland et al. 2013) and the resilience of seagrass ecosystems (Unsworth et al. 2015) require cool water temperatures. In these extensive deep coastal forests, freshwater formed through cellular respiration in forest ecosystems permeates the soil and constitutes substantially to groundwater. Cool groundwater discharge into the sea (Grossman et al. 2025) historically regulated coastal water temperatures (e.g., Fig. 10-2 in https://harukanoor4.blogspot.com/2023/), supporting diatom blooms and the resilience of seagrass ecosystems.

The inshore area of Edo Castle, Shibaura, was protected by the mansions of ruling-class families. The grounds of these mansions, along with urban forests and gardens containing seawater-filled ponds were surrounded by seawater-filled moats (Fig. 2-2). These moats and ponds were intentionally designed as nurseries for many fishes and invertebrates. In particular, the small shrimp, shiba-ebi (芝海老, Metapenaeus joyneri, Fig. 5-1) were abundant (Fig. 3). Abundant shrimp enhanced both the quantity and quality of prolific fisheries resources.

In Fig. 5-1, Hiroshige depicts the small shrimp, shiba-ebi (芝海老) alongside a spiny lobster (ise-ebi, 伊勢海老, Panulirus, a highly praised delicacy in Japanese cuisine), indicating that highly valued species such as lobster fed on the abundant shrimp in Shibaura. In Fig. 5-2, the most valued prawn species (kuruma-ebi, 車海老, Marsupenaeus japonicus, up to 15 cm/6 inches) is depicted with horse mackerels (aji, 鯵, Trachurus japonicus, a staple of the traditional working-class diet). Hiroshige shows that the marine sanctuaries within the ruling-class residential areas of Shibaura contributed to food security for the people: abundant juveniles of highly valued delicacies, connected through food webs, sustained the productivity of inexpensive fish such as Horse Mackerels. 

Fig. 5-2. Horse Mackerel, Prawns, and Tade, from the series Grand Series of Fishes, Hiroshige, originally published 1832–33 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). Hiroshige depicts prawns (kuruma-ebi, 車海老, Marsupenaeus japonicus, up to 15 cm/6 inches, the most valued prawn in Edo) at the upper left. As is common in Japanese fish/shelfish species, the prawn has a juvenile name; its juveniles are called saimaki shrimp. Hiroshige praises the quality of fisheries harvested in Shibaura, by quoting a poem admiring the peak of perfection of kuruma-ebi:

“What a wonderful Kuruma-ebi prawn!/

Juveniles are called saimaki shrimp/

I shall send the kuruma-ebi harvested in Shibaura as a gift.”

The residents of Edo, including Hiroshige, understood that the eggs and juveniles of prawn played an important role in trophic flows in the shore and nearshore marine food webs. Therefore, the artist placed horse mackerels (aji, 鯵, Trachurus japonicus) in the center of this print with the herb tade (蓼, Persicaria hydropiper). As young red sprouts of tade are used to garnish sashimi and sushi, Hiroshige suggests the freshly caught fish from the inshore area of Edo—the world’s largest metropolis—were so fresh and exquisite that they could be served raw. Hiroshige indicates that the exquisite quality and taste of inshore fish species such as horse mackerel were sustained by trophic transfer in marine food webs, particularly shrimp including saimaki shrimp supplied from the coastal wetland sanctuary of Shibaura.

3.4. Inshore/nearshore marine food webs in Shibaura

 

In Fig. 1-3 (lower left), Hiroshige depicts low-trophic-level fish species—small, schooling, filter-feeding fishes such as anchovies, sardines, and herrings—in his print of assorted Edo-mae sushi (江戸前寿司). Vinegared fillets of forage fish species such as konoshiro (鰶, Konosirus punctatus, up to 25 cm/10 inches, Fig. 4) and sappa (鯯, Sardinella zunasi, up to 20 cm/8 inches), both belonging to the herring/sardine family, are popular ingredients for Edo-style sushi.

Low-trophic-level fish species account for more than 30% of global fisheries production and play an important role in trophic flows within the marine food webs (Smith et al. 2011). Species such as anchovy, sardine, and herring—as well as invertebrates such as shrimp—serve as key trophic links, transferring phytoplankton production to larger predators (Smith et al. 2011).

The placement of prolific conservation areas to enhance trophic transfer in inshore/nearshore marine food webs was a unique concept of marine resource management in Edo. In the marine sanctuaries located within the ruling-class residential areas of Shibaura (Figs. 1-1, 2-2), large quantities of low-trophic-level species—highly connected within the food webs—prolificated actively. Their high abundance, released from the sanctuary, effectively provided diverse pathways and transfer steps within the food webs, forming a complex and prolific marine ecosystem in dynamic equilibrium in the inshore/nearshore waters in front of Edo Castle (Fig. 4).

The placement of the marine sanctuary in Edo—productive vegetated coastal wetlands where forage fish species and shrimp prolificated, was unique in maintaining the productivity and stock of commercially important fisheries resources, preventing severe declines in stock abundance. In Figs. 5-1,2,3,4,5, Hiroshige depicts species richness and composition that shaped the complex food webs in Shibaura.

The presence of large predatory fish such as red seabream (鯛), with their vivid red coloration swimming in the seawater-filled ponds and moats, signified the well-structured food web in Shibaura (Fig. 5-3). The diverse commercially important species depicted by Hiroshige (Figs. 5-1,2,3,4,5) indicate that the Japanese architects constructed inshore/nearshore marine food webs of significant ecological and economic value, maintained in a state of equilibrium. 

Fig. 5-3. Red Seabream and Sansho Pepper, from the series Grand Series of Fishes, Hiroshige, originally published 1832–33 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In Japan, red seabream (tai, 鯛, Pagrus major, up to 1 m/3.3 ft, highly praised for sashimi/sushi) is regarded as an auspicious fish. The color red has long been believed to ward off evil spirits and bring good fortune. Hiroshige admires the color and quality of red seabream caught in Shibaura by quoting a poem:

“The red-colored fish swimming in Shibaura/

Glows brilliantly/

Even brighter than the sunset at the legendary Nago seashore.”

(Nago: a legendary beach famed for the unparalleled sunsets)

The residential area of ruling-class families of Shibaura was elaborately shaped with seawater-filled ponds and intricate moat system (Fig. 2-2), protected as a coastal marine sanctuary. Shibaura was noted for the proliferating and upwelling of shrimp, as described in the poem quoted in Fig. 5-1. Low-trophic-level species such as anchovy, sardine, and herring, as well as invertebrates such as shrimp, play key roles in transferring primary production by phytoplankton to larger predators (Smith et al. 2011). The abundant large predator fish—red seabream with vivid red coloration—swimming in the seawater-filled ponds and moats of the sanctuary indicate that the architecture of coastal wetlands and the associated marine resource management provided a successful ecosystem-based approach, forming pathways and transfer steps for complex food webs. In the constructed vegetated coastal wetland sanctuary in Shibaura, low-trophic-level species prolificated actively. Abundant fish and shrimp were released through water gates, leading to the formation of a complex and prolific marine ecosystem in the inshore/nearshore of Edo, the world’s largest metropolis. To safeguard sustainable fish and shellfish harvests, Japanese architects created a complex and prolific marine ecosystem in a state of equilibrium through the construction of elaborately shaped urban forests and vegetated coastal wetlands (Fig. 3), combined with unique marine resource management through the placement of protected areas for low-trophic-level species. 

3.5. Unique architecture of reclaimed land: constructed fishing community in front of Edo Castle together with prolific fishing grounds

 

3.5.1.     Engineered passways of dissolved silica for blooms of diatom-dominated phytoplankton

 

The architecture of reclaimed land in Japan was unique in shaping prolific fishing grounds in inshore areas. The reclaimed land of Tsukiji (築地, Figs. 1-2, 2-2-c) constructed by villagers from Tsukuda-jima in front of Edo Castle is a typical example of how prolific inshore fishing grounds were created alongside a fishing community.

Biogeochemical cycles—the movement of essential nutrients—are crucial for supporting fisheries. Japanese architects carefully engineered the pathways of the essential nutrients.

Silica-shelled diatoms are a major phytoplankton group forming the basis of marine food webs (Armbrust 2009; Tréguer et al. 2018). Blooms of diatom-dominated phytoplankton have an absolute requirement for dissolved silica (e.g., Smetacek 1998). Limited availability of silicic acid can restrict diatom growth and lead to shifts in phytoplankton composition from siliceous diatoms to non-siliceous groups such as dinoflagellates (Humorg et al. 1997; Milliman 1997).

Rivers transport significant amounts of dissolved silica to coastal seas (Milliman 1997; Conley 2002; Katz et al. 2024). Therefore, the location of constructed fishing community and its prolific fishing grounds was carefully selected. Tsukiji was placed at the estuary of Sumida-gawa River (Fig. 2-2-e), where large loads of essential nutrients—including silicic acid—were supplied.

The Sumida-gawa River was carefully engineered as a transport corridor for essential nutrients (Fig. 9-2). In its floodplain, irregularly shaped earthen groynes covered with riparian forests and plant species with high silica-accumulation capacity were constructed, actively producing essential nutrients such as Fe‑containing organic compounds and dissolved silica.

As shown in Fig. 1-2, the shoreline of the reclaimed land was reinforced with dry-stone walls equipped with stepped piers where small fishing boats were moored. Two irregularly shaped long bars of rocky reefs were placed as coastal defense structure in front of the dry-stone walls. These walls and reefs stabilized the shoreline, as the spaces between rocks dissipated wave energy and minimized reflective waves, providing safe harborage for moored fishing boats.

The dry-stone walls and rocky reefs were often made of granite or andesite. Silica (SiO2) is a key component of natural rocks such as granite and andesite; for instance, granite typically contains 70–77% silica by weight. These rocks break down through weathering by ultraviolet radiation, crashing surf, and strong currents. The resulting fragments deposit as sediments. Structures made of natural rocks—and the sediment particles derived from them—provide surfaces of high Si content for benthic diatoms to attach and to take up Si for biogenic silica production. Enrichment of silicic acid through benthic diatoms’ biogenic silica production promotes the blooms of diatom-dominated phytoplankton—the basis of aquatic food webs (Rousseau et al. 2002; Leynaert et al. 2009, 2011).

The Japanese architects carefully engineered the constructed prolific fishing grounds of Tsukiji by constructing pathways for the movement of essential nutrients.

 

3.5.2.     Constructed rocky reef: port protection integrated with prolific fishing grounds

 

In traditional Japanese port engineering, constructed rocky reefs were commonly designed to integrate port protection with the creation of prolific fishing grounds (Fig. 1-2).

Rocky intertidal areas and nearshore rocky bottoms are important coastal habitats, providing refuges for juveniles and supporting large numbers of fish species (Moyle and Cech 2004; Sala et al. 2012). At rocky reefs, the upward movement of deep, cooler water, containing larger amounts of essential nutrients such as Fe- and Si-containing compounds—known as upwelling—promotes the growth of diatom-dominated phytoplankton, the basis of marine food webs. Blooms of diatom-dominated phytoplankton lead to abundant and diverse fisheries resources, forming excellent fishing grounds (Eisele et al. 2021; Silva et al. 2021; Pulgar et al. 2022). In Fig. 1-2, fishing boats casting nets and anglers visiting in a cruise boat in the middle distance imply that the placement of constructed rocky reefs successfully created prolific fishing grounds at Tsukiji.

 

3.5.3.     Oyster reef on constructed rocky reef: increasing effectiveness through yearly vertical growth

 

On dry-stone walls and man-made rocky reefs, oysters grow vertically and in dense assemblages, forming oyster reefs. Oyster reefs provide habitats to mollusks (in addition to oysters), crustaceans, and other invertebrates. These forage species are consumed by juvenile fishes and commercially valuable crustaceans. By providing foraging opportunities and refuge from predators, oyster reefs enhance the productivity of commercially important fisheries resources.

Furthermore, oyster reefs contribute to coastal protection by buffering waves and increasing sedimentation. Their shoreline protection becomes increasingly effective each year due to the accumulating vertical growth of the reef (e.g., Grabowski et al. 2012). Oyster reef growth depends on the abundance of filter-feeding oysters, which require diatom-dominated marine phytoplankton. Blooms of diatom-dominated marine phytoplankton occur in cool, clear, clean, and oxygen-rich seawaters supplied with large amounts of essential nutrients such as Si-containing compounds by rivers and streams, and Fe-containing compounds in the form of humus, leaf litter and detritus from forests (https://harukanoor4.blogspot.com/2022/). Thus, the placement of deep coastal forests is a fundamental requirement for shaping prolific fishing grounds.

Commercially valuable species, such as spiny lobsters (ise-ebi, 伊勢海老, Panulirus, highly praised in Japanese cuisine; Fig. 5-1) and abalone (awabi, 鮑, Haliotis, an edible herbivorous sea snail highly valued for sashimi and Edo-style sushi; Fig. 5-4) were harvested at the rocky reefs where oyster reefs accumulated. Japanese architects created prolific fishing grounds close to the shore by engineering coastal structures. As shown in Hiroshige’s print of Tsukiji (Fig. 1-2), these prolific fishing grounds were protected by fishing communities and moats to prevent open access to commercially valuable marine resources, thereby avoiding the well-known “Tragedy of Commons” (Hardin 1968).

 

3.5.4.     Oyster reefs create favorable conditions for flourishing seagrass meadows

 

Seagrass meadows play a critical role in supporting fisheries productivity, because they serve as nursery and foraging grounds. Seagrasses are flowering plants (angiosperms) that rely on sufficient light availability for photosynthesis.  Therefore, flourishing seagrass meadows require calm, shallow, and clear seawaters with adequate supplies of essential nutrients, including slowly decomposing leaf litter from forests. In contrast, excess nutrients and turbid conditions lead to seagrass losses (Orth et al. 2006; Waycott et al. 2009; Jones and Unsworth 2016).

Oysters grow on older shells in a nonuniform manner, forming many crevices. These crevices dissipate wave energy and minimize reflective waves, stabilizing sediments. The structure of oyster reefs enhances sediment deposition and increases bed elevation. As the bed level rises, shallow sea waters expand.   

Although disposal of any kind of waste into urban areas and water bodies (rivers/streams, lakes, and seas) was prohibited in Edo in 1655 (Endoh 2004), estuarine and coastal waters were still affected to some degree by untreated or inadequately treated domestic wastewater. Ancient Japanese decision-makers and architects understood that bivalves such as Pacific oyster (Magallana gigas) thrive in brackish and coastal waters with moderate nutrient loading, and that oyster reefs can remove excess nutrients improve water clarity.

Excessive nitrogen (N) loading leading to eutrophication is a major global challenge in coastal management (Smith et al. 2006). Bivalves can remove nitrogen from nutrient loaded waters by enhancing denitrification—the microbial conversion of reactive nitrogen (e.g., nitrate) into unreactive nitrogen gas (N2) (Piehler and Smyth 2011; Ayvazian et al. 2021).

Oyster reefs reduce turbidity through their filtration capacity, improving water clarity. Bivalves filter nutrients by consuming phytoplankton and particulate organic matter, then excrete metabolic waste that becomes buried in sediments. Through this process, known as bioextraction, bivalves reduce nutrient concentrations (Ayvazian et al. 2021). The calm, shallow, and clear waters created oyster reefs promote the growth of seagrasses.

In Fig. 1-2, oyster reefs on constructed rocky reefs grow vertically and laterally, extending seaward. The ecosystem service of water-quality improvement provided by oyster reefs increases each year as the reefs expand. Their seaward growth leads to the expansion of valuable seagrass meadows, essential for fisheries productivity. Hiroshige illustrates a successful example of created prolific fishing grounds in the inshore zone of the reclaimed land of Ttsukiji by showcasing abundant and diverse fisheries resources (Figs. 5-1,2,3,4,5). 

Fig. 5-4. Abalone, Needlefish, and Peach Blossome, from the series Grand Series of Fishes, Hiroshige, originally published 1832–33 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). Hiroshige depicts fish and shellfish harvested close to the seashore of Edo. Sajori (鱵, Hyporhamphus sajori, up to 40 cm/16 inches), a popular inshore fish in Japanese cuisine including sashimi and Edo-style sushi, is harvested in coastal areas close to the shoreline, though it requires seagrass meadows for spawning and nursery/foraging grounds. Hiroshige depicts freshly caught abalone (awabi, 鮑, Haliotis discus discus), harvested at the constructed rocky reefs in the inshore area in front of Edo Castle (Fig.1-2). The poem quoted in this print indicates that abalone inhabit rocky reef habitats close to the coastline:

“Washed by crashing surf/

Abalone clinging to the solid coastal reef/

Polished as it were a precious jade.”

In Japan, abalone meat is highly valued for Edo-style sushi and sashimi, and freshness is essential. This freshness was made possible by the unique supply system in which prolific fishing grounds were placed directly in front of the fishing community, close to the city center (Fig.2-2).

Thus, Japanese culinary culture—such as sashimi and Edo-style sushi—was supported by the elaborately shaped fishing community and nearby fertile fishing grounds created through engineering coastal structures.   

 

3.6. Architecture and management of productive marine benthic habitats in Edo

 

In Fig. 5-5, Hiroshige depicts abundant and diverse benthic fish resources. Urban planning and management practice that closed the nutrient cycle prevented the formation of “dead zones” and the consequent loss of benthic fauna.  

Marine benthic fauna plays an important role in trophic flows, transferring primary production by marine phytoplankton (first trophic level) to larger predators, including commercially important fisheries species (Diaz and Rosenberg 2008). However, effluents from cities have significant impacts on the productivity of commercially valuable species. Harmful algal blooms caused by excessive nutrient inputs (fertilizer runoff from agriculture, treated sewage discharge, combined sewer overflows, and urban stormwater) create “dead zones”—coastal waters too low in oxygen to sustain life—which reduce abundance and diversity of fisheries resources and typically eliminate benthic fauna (Moyle and Cech 2004; Diaz and Rosenberg 2008; do Rosário Gomes et al. 2014).

The key to solving the excessive nutrient inputs to the sea is to keep large quantities of undesirable nutrients on the land and out of coastal waters. Comprehensive land-use planning and management that close land-ocean biogeochemical cycles are essential (Tilman et al. 2001; Diaz and Rosenberg 2008).

The clean seawater policy of Edo (and throughout Japan), established to maintain high standards of hygiene for seafood, was effective in preventing the creation of dead zones. Disposal of any kind of waste into urban areas and water bodies (rivers/streams and seas) was strictly prohibited in 1655 (Endoh 2004). Human excreta and livestock manure were used as fertilizer and soil amendments, closing the biogeochemical cycle by returning nutrients to agricultural land.

Flourishing photosynthesis in the benthic zone—by diatom-dominated marine phytoplankton, seagrasses, and macroalgae such as kelps—requires a steady supply of essential nutrients. Carefully engineered pathways for nutrient movement, including extensive deep coastal forests (Figs. 1-1,2) and river-engineering designed as transport corridors for essential nutrients (Fig. 9-2), played essential roles in supplying Fe‑containing organic compounds and dissolved silica. Linkages between terrestrial ecosystems and coastal marine photosynthesis are critical for closing biogeochemical cycle between land and sea.

Additionally, the formation of continuous (non-fragmented) habitats facilitated nursery and foraging use by fish and invertebrates, as most commercially important marine species require more than a single habitat to complete their live cycle (Unsworth et al. 2018). In the context of nutrient movement, shaping continuous habitats was crucial.

In Fig. 1-2, ancient Japanese architects constructed coastal structures using natural rocks and nearby sediments (containing silica as a basic component), enabling benthic diatoms to attach and actively produce biogenic silica. Because benthic diatoms are key components of the biogeochemical silica cycle and support blooms of diatom-dominated phytoplankton (Rousseau et al. 2002; Leynaert et al. 2009, 2011), productive benthic fauna such as oyster-reefs grow vertically and laterally. Seaward extension through sedimentation led to the yearly expansion of productive benthic fauna, including commercially important fisheries resources (Fig. 5-5). Thus, prolific benthic fauna were shaped by human design in Shibaura, Edo, demonstrating that engineered pathways of essential nutrient movement, coastal structures that connected terrestrial and marine ecosystems, and continuous marine habitats successfully supported productive benthic ecosystems.     

Fig. 5-5. Gurnards, Flatfish, and Bamboo Grass, from the series Grand Series of Fishes, Hiroshige, originally published 1832–33 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In this print, Hiroshige depicts abundant commercially valuable benthic fish species that live on or near sea bottom: konoha-karei (木の葉鰈, lit., tree-leaf flounder, Pleuronichthys cornutus, up to 30 cm/12 inches, one of many species in the flounder family) and kanagashira (金頭, Lepidotrigla microptera, up to 30cm/12 inches, belonging to the family Triglidae, the gurnards and sea robins). Both were popular staples in the daily meals of working-class people. Japan has a long history of dried fish production. To preserve abundant catches, fish were salted and dried. Dried fish formed a significant part in the daily diet. A poem quoted in this print shows the popularity of dried fish in Edo:

“At the entrance/

Dried fish, konoha-karei, are already turning/

The hues of autumn leaves in back-garden trees of working-class cottage shine brilliantly!”

This poem indicates that working-class people lived in cottages with gardens, where they spent considerable time using the space practical purposes such as drying fish and admiring autumn foliage. Effluents from cities have significant impacts on the productivity of commercially valuable fisheries species. Harmful algal blooms caused by excessive nutrient inputs (fertilizer runoff, treated sewage discharge, combined sewer outfalls, and urban stormwater) create dead zones—coastal waters too low in oxygen to sustain life—which reduce abundance and diversity of fisheries resources and eliminate benthic fauna (Moyle and Cech 2004; Diaz and Rosenberg 2008). The clean seawater policy of Edo, established to maintain high standards of seafood hygiene, was effective in preventing the formation of dead zones. Disposal of any kind of waste into urban areas and water bodies was strictly prohibited in 1655 (Endoh 2004). Human excreta and livestock manure were used as fertilizer and soil amendments, closing the biogeochemical cycle (https://harukanoor4.blogspot.com/2022/). Photosynthesis in the benthic zone—by diatom-dominated marine phytoplankton, seagrasses, and macroalgae such as kelps—requires essential nutrients. Extensive deep coastal forests (Figs. 1-1,2) and engineered rivers designed to close the biogeochemical cycle (Fig. 9-2) were standard practices for supplying these nutrients. Furthermore, coastal structures using natural rocks and nearby sediments (containing Si as a basic component) were designed to form continuous (non-fragmented) marine ecosystems (Fig. 1-2). In this print, Hiroshige depicts the resulting abundant and diverse benthic fish resources. In Shibaura, Edo, prolific benthic fauna were successfully shaped by human design, demonstrating the effectiveness of engineered nutrient pathways and constructed coastal structures.

  

4.      Watershed management for microclimate stabilization to safeguard agricultural productivity in summer months

 

4.1. High-temperature stress threatens global food security

 

Because agriculture is inherently sensitive to climate variability and change, climate change poses a major threat to global food security (Wheeler and von Braun 2013). A rapidly warming climate reduces crop productivity, thereby undermining food security (Hasanuzzaman et al. 2013: Khan et al. 2023).  

Rice (Oryza sativa), a major staple crop supporting more than half of the global population, is highly susceptible to heat stress. High-temperature stress significantly reduces both yield and grain quality (Xu et al. 2021; Shrestha et al. 2022). Rice is widely cultivated in irrigated cropping systems during the warmer, high-radiation months following the monsoon and throughout the summer.

The optimum daytime temperature for rice growth is approximately 28°C (Prasad et al. 2006; Su et al. 2023). During the flowering period, exposure to temperatures exceeding >34°C induces spikelet (a set of floral parts) sterility (Jagadish et al. 2007), resulting in failure to set seed. Sterility is caused by poor anther dehiscence and low pollen production (Matsui et al. 2000, 2001; Prasad et al. 2006).

The optimum nighttime temperature for grain filling is around 22°C (Prasad et al. 2006; Su et al. 2023). Daytime and nighttime temperatures jointly influence grain filling, although their absolute thresholds differ during the ripening phase (Welch et al. 2010). Increasing nighttime temperatures during the critical grain-filling stage reduce rice yield (Peng et al. 2004; Welch et al. 2010; Su et al. 2023) and grain quality (Ambardekar et al. 2011). These damaging effects occur through spikelet sterility, elevated respiration rates (Mohammed and Tarpley 2009), and reduced assimilate accumulation (Morita et al. 2005).

In major Asian rice-producing countries, the nighttime temperatures have increased faster than the daytime temperatures (Peng et al. 2004; Padma Kumari et al. 2007), leading to detrimental impacts on rice yields and grain quality (Su et al. 2023). Any further increase beyond the optimum temperatures (28° C/22° C) could have devastating consequences for food security.

 

4.2. Role of forests in the local climate and the surface energy balance

 

Changes in vegetation cover alter both radiative and non-radiative biophysical properties, thereby influencing the local climate  (Bonan 2008) and the surface energy balance (Duveiller et al. 2018). Terrestrial vegetation has adapted to the solar radiation environment through long evolutionary processes. On a clear day, radiant energy reaching Earth's surface consists of approximately 5% ultraviolet, 40–45% visible, and 50–55% infrared radiation (Monteith and Unsworth 1990).

Leaves absorb visible solar radiation through photosynthetic pigments (Gates et al. 1965; Yoshimura et al. 1994; Yoshimura 2001). Most of this absorbed energy is consumed in the biochemical processes of photosynthesis (Blackburn 2007). Because leaves are the fundamental units of photosynthesis, higher primary productivity requires greater leaf abundance. The leaf area index (LAI) —the one-sided green leaf area per unit ground area—is therefore widely used as a principal variable for estimating photosynthetic primary productivity (Odum 1971; Whittaker and Likens 1973; Nemani et al. 2003).

To maximize photosynthetic productivity, terrestrial biomes have evolved diverse canopy architectures, including tall, spreading canopies and highly stratified foliage layers characteristic of old-growth forests (Fig. 6c). The highly stratified canopies of old-growth temperate forests (with high LAI) efficiently absorb visible solar radiation for photosynthesis.

In the near-infrared wavelengths, leaves strongly reflect incoming solar radiation, and this reflectivity increases with greater canopy stratification (Yoshimura 1998). Thus, in highly stratified canopies such as old-growth forests (Fig. 6c), much of the near-infrared radiation is reflected back into space, helping regulate the surface energy balance by rejecting near-infrared solar energy.

Leaves also absorb most ultraviolet radiation, reflecting only about 5% and transmitting almost none (Yoshimura et al. 2010). This strong absorption further contributes to surface energy balance regulation.

Overall, terrestrial vegetation—particularly old-growth forests with high LAI —plays a key role in modulating the surface energy balance through high absorptance of visible radiation for photosynthesis, pronounced reflectivity of near-infrared radiation, and strong absorption of the ultraviolet wavelengths. The resulting cool, deep shade beneath forest canopies alters surface energy fluxes and influences the local climate.    

 

4.3. Excess heat and increasing nighttime temperatures

 

Tall, dense forests such as old-growth forests have evolved to buffer against lethal high temperatures during summer. Consequently, human-induced alterations of vegetation cover have driven regional climate change. Vegetation removal modifies the surface energy balance, increasing heat fluxes and elevating both air and surface temperatures.

On bare soil (LAI = 0), part of the incoming solar radiation is reflected, while the remainder is absorbed and partitioned into sensible heat flux, longwave radiation (heat storage), and warm evaporation (latent heat). In contrast, dry urban surfaces (LAI = 0; Fig. 6a) composed of impervious materials such as asphalt and concrete reflect some solar radiation, but most absorbed energy is converted directly into heat (sensible heat flux and longwave radiation), with evapotranspiration effectively eliminated.

Urbanization is now the dominant driver of land transformation, expanding impervious surfaces such as paved roads, parking lots, and buildings (Seto and Ramankutty 2016). At the same time, the increasing agricultural demand to support a growing population has accelerated land conversion for infrastructure—including rural housing, commercial facilities, highways, and roads—thereby increasing impervious coverage even in agricultural regions (Hooke et al., 2012).

Rising nighttime temperatures are primarily driven by changes in the surface energy balance. During the day, impervious surfaces absorb large amounts of solar radiation, storing heat. At night, buildings and streets release this stored energy as longwave radiation, contributing to elevated nighttime temperatures (Oke 1982; Kalnay and Cai 2003).

Fig. 6. Terrestrial vegetation—particularly old-growth forests with high LAI (c)—regulates the surface energy balance by absorbing visible light for photosynthesis (Yoshimura et al. 1994; Yoshimura 2001; Blackburn 2007), reflecting near-infrared radiation (Yoshimura 1998), and absorbing the ultraviolet wavelengths (Yoshimura et al. 2010). Urban surfaces (LAI = 0) composed of impervious materials such as asphalt and concrete reflect some solar radiation, but most absorbed energy is converted into heat (sensible heat flux and longwave radiation). Increased nighttime temperatures arise mainly from altered surface energy balance: during the day, impervious surfaces store absorbed solar energy; at night, buildings and streets release this stored heat as longwave radiation, elevating nighttime temperatures (Oke 1982; Kalnay and Cai 2003).

4.4. Strategic placement of man-made forests to regulate local climate for optimal summer crop temperatures (28° C/22° C): Regional planning for agricultural productivity in reclaimed marshland in Edo

 

4.4.1.     Nature-based soil amendment approaches integrated with local climate stabilization for optimal summer crop temperatures (28° C/22° C)

 

The land governance of reclaimed marshland on the east bank of the Sumida-gawa River was distinctive. Because reclaimed marshlands naturally exhibit high soil salinity, most crops cannot grow in soils with elevated salt levels. Effective soil amendments were planned and implemented through nature-based approaches, simultaneously addressing interconnected challenges. To reduce soil salinity, large-scale water bodies—canals and ponds—were excavated, serving the function of leaching salts with water. At the same time, vast areas of man-made deep forests were strategically established. The creation of these extensive forests contributed to a local climate with optimum summer temperatures for crop growth (28° C/22° C), as the cool, deep shade beneath forest canopies modified surface energy fluxes and thereby influenced local climate conditions.

 

4.4.2.     Flood management in reclaimed marshland in Edo: A canal along the coastline serving as a sea levee

 

When Ieyasu established his residence in Edo Castle in 1590, the eastern edge of the city was a coastline facing Edo Bay, with extensive salt marshes stretching along the shore. The growing demand for agricultural production to support Edo’s expanding population accelerated the reclamation of these marshlands.

Within this salt‑marsh zone, the Onagi‑gawa Canal (小名木川; Figs. 7-1c, 8) was constructed along the coastline by order of Ieyasu between 1596 and 1615. Soil excavated during construction was used to fill low‑lying areas on the eastern side of the Sumida‑gawa River (Endoh 2004). The Onagi‑gawa Canal (length: 5 km/3.1 miles; width: 36 m/118 ft; water depth: 1.8 m/5.9 ft) served as a major route for transporting salt produced at Gyotoku, near the mouth of the newly constructed Edo‑gawa River (Figs. 8‑1, 8-2 in https://harukanoor4.blogspot.com/2022/). It played a vital role in Edo’s waterborne transport system.

In Fig. 8, Hiroshige depicts an important junction within this complex network of waterways: the Naka‑gawa River (Fig. 7-1d), the Onagi‑gawa Canal (Fig. 7-1c) and the Shin‑kawa Canal. The Naka‑gawa River (lit., “intermediate river”, an arm of the Tone‑gawa River system, flows into Edo Bay. In the print, it runs horizontally from left to right between the Sumida‑gawa River and the constructed Edo‑gawa River. Two passenger boats in the foreground travel in opposite directions along the Onagi‑gawa Canal. The boat whose bow points upward is heading toward Gyotoku, located in the upper area of the print. The waterway connecting this junction to Gyotoku is known as the Shin‑kawa Canal.

In the context of the reclamation project, the Onagi‑gawa Canal—together with the dikes built along both sides—functioned as a kind of sea levee, protecting the reclaimed land from high‑tide flooding and coastal hazards.

Fig. 7-1. Intricate canal networks along with strategically placed mansions of feudal lords and temples/shrines in the reclaimed marshland of Edo. The mansions of feudal lords and temples/shrines—featuring distinctive large‑scale naturalized forested landscape gardens with ponds and streams drawing water from the canals—were strategically placed. These mansions were arranged along the Onagi‑gawa Canal (c), the Tate‑kawa Canal (k), and other waterways. Data from Reproduced 1856 Edo Map Verified by Actual Measurement in the Encyclopedia of EDO‑MEIJI‑TOKYO, edited by Keiji Nakagawa, APP Co., Ltd., 2004 (ISBN: 4-901441-30-2); processed by Dr. Sotaro Tanaka (Remote Sensing). Legend: a: Sumida‑gawa River b: Nihon‑bashi district c: Onagi‑gawa Canal (小名木川, excavated 1596–1615) d: Naka‑gawa River (arm of the Tone‑gawa River system) e: Sumida‑gawa River Embankment (completed around 1616) f: Nihon‑zutsumi Dyke (constructed 1620) g: Ryogoku‑bashi Bridge (built 1657) h: Hikifune‑gawa Canal (drinking‑water aqueduct, approx. 60 km/37 miles from the upper Tone‑gawa River, excavated 1660) i: Akiba Shrine (23,141 m²/6 acres; noted for a naturalized forested landscape garden with pond/stream fed by the Hikifune‑gawa Canal) j: Mito Mansion (76,396 m²/18.9 acres) k: Tate‑kawa Canal (堅川, excavated 1659) l: Yoko‑jikken‑gawa Canal (横十間川, excavated 1659) m: Kita‑jikken‑gawa Canal (北十間川, constructed 1663) n: Yanagi‑shima amusement quarter o: Kameido Tenjin Shrine p: Bush‑clover Temple (Ryugen‑ji, “Temple of the Dragon’s Eye”) q: Tsugaru Mansion (54,700 m²/13.65 acres) r: Kuki Mansion s: Koume Village t: Ogura-an Restaurant.

Fig. 7-2. A close‑up view of the map highlights the unique structure of the gardens and their highly planned placement integrated with the canal system. In the Mito mansion (j), streams and irregularly shaped ponds within the large‑scale garden are connected to the Sumida‑gawa River (a) and the Kita‑jikken‑gawa Canal (m). The stream and pond at Akiba Shrine (i) are engineered to draw water from the Hikifune‑gawa Canal (h). The grounds of these gardens were often enclosed by moats and dikes, as seen at the Mito Mansion (j). Fire‑resistant, tall tree species—such as itajii (Castanopsis sieboldii, Fagaceae), Japanese bay tree (Machilus thunbergii, Lauraceae), and ginkgo (Ginkgo biloba)—were planted on the dikes. Along both sides of the Yoko‑jikken‑gawa Canal (l), Kameido Tenjin Shrine (o), Bush‑clover Temple (p), and the mansions of feudal lords, including the Tsugaru Mansion (q), were arranged. These successful ecosystem‑based infrastructures within the city supported natural resource management—enhancing water‑resource resilience and sustaining prolific freshwater fisheries—and offer valuable insights for contemporary policy and practice addressing the interdependent challenges of climate change.

Fig. 8. Naka-gawa River Mouth, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In the salt marshes zone, the Onagi-gawa Canal (小名木川, Fig. 7-1c) was constructed along the coastline by order of Ieyasu Tokugawa (徳川家康1542–1616) between 1596 and 1615. The Onagi-gawa Canal (length: 5 km/3.1 miles, width: 36 m/118 ft, water depth: 1.8 m/5.9 ft) was used to transport salt produced at Gyotoku, located at the mouth of the man-made Edo-gawa River. In addition, the canal played an important role in Edo’s waterborne transport system, linking the city center in the foreground with Gyotoku in the upper part of the print. In this print, Hiroshige depicts the junction of the Onagi-gawa Canal and the Naka-gawa River (中川, lit. “Intermediate river,” Fig.7-1d), an arm of the Tone-gawa River system situated between the Sumida-gawa River and the constructed Edo-gawa River. The Naka-gawa River flows into Edo Bay here, on the right side of this print. For flood management in the low-lying reclaimed marshland, the Onagigawa Canal together with dikes on either side, functioned as a kind sea levee, protecting from high tides and coastal hazards. The Onagi-gawa Canal and the Naka-gawa were noted for their abundant and diverse fisheries resources. Estuarine wetlands formed by irregularly shaped earthen groynes (groins) covered with salt-tolerant plants such as Poaceae (grasses) provided nursery and feeding habitats (Fig. 3) for low-trophic-level species that support complex food webs (Smith et al. 2011). At the center of the print, anglers in two boats are shown enjoying fishing. Along the shoreline, earthen groynes constructed from nearby sediments—composed of sand, silt, and fine materials derived from organic compounds of the high-silica plant species— create habitats for benthic diatoms. These, in turn, support blooms of diatoms-dominated phytoplankton, the foundation of aquatic food webs (Rousseau et al. 2002; Leynaert et al. 2009, 2011).  

 

4.4.3.     V-shaped embankment on either side of the Sumida-gawa River: served as a sort of “dam” not to block river

 

In traditional river engineering, Japanese architects developed a discontinuous levee system designed to diffuse and capture floodwaters within designated areas (e.g., Okuma 1981). To reduce the risk of flooding in urban districts, extensive flood‑retention zones were strategically allocated on either side of the upper reaches of the Sumida‑gawa River in the outskirts of Edo (Fig. 6 in https://harukanoor4.blogspot.com/2022/).

To protect the low‑lying reclaimed marshland from inundation by the Sumida‑gawa River, a long embankment angled obliquely to the river flow was constructed, connecting to an already existing dyke from Kumagaya (about 60 km/37 miles upstream) by around 1616. Hiroshige depicts the starting point of the Sumida Embankment in Fig. 9‑1 (Fig. 7-1e). The Sumida Embankment (3.8 km/2.4 miles) was designed to create large flood‑retention areas that were intentionally allowed to flood during storms (Fig. 9‑2).

On the opposite side of the river, an embankment (length: 1400 m/0.87 miles; height: 3 m/9.8 ft; levee‑crown width: 7.2 m/24 ft), oriented almost perpendicular to the river flow, was constructed in 1620, connecting to the Musashino Plateau. This embankment, named the Nihon‑zutsumi (Fig. 7-1f), played a significant role in preventing flooding in the city center. At the downstream end of the dyke, the famous amusement quarters of New Yoshiwara were established (Fig. 9‑3).

Together, the Sumida Embankment (Fig. 9‑1) and the Nihon‑zutsumi Dyke (Fig. 9‑3) formed a V‑shaped embankment system on either side of the Sumida‑gawa River, functioning as a kind of “dam” without obstructing the river’s flow. In Fig. 9‑2, Hiroshige depicts a broad expanse of the flood‑retention zone spreading across both sides of the Sumida‑gawa River, along with the persistent flow of water originating from distant Mount Buko.

Fig. 9-1. Cherry-blossom Viewing on the Sumida-gawa River Embankment, from the series Famous Places in the Eastern Capital, Hiroshige, originally published 1839–42 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In traditional river engineering, Japanese architects developed unique flood‑management systems using engineered flood‑retention areas intentionally allowed to inundate during high‑water events. To protect the low‑lying reclaimed marshland from flooding by the Sumida‑gawa River, a long embankment angled obliquely to the river flow was constructed by around 1616. Hiroshige depicts the starting point of the Sumida Embankment (3.8 km/2.4 miles; Fig. 7-1e), which connects to an existing dyke from Kumagaya (about 60 km/37 miles upstream). On the opposite side of the river, the sacred forest of Matsuchiyama—seen as a dark mass in the upper left of the print—marks the starting point of the Nihon‑zutsumi Dyke (Figs. 7-1f, 9-3).

Fig. 9-2. Cherry-blossoms in Full Bloom along the Sumida-gawa River, from the series Famous Places in the Eastern Capital, Hiroshige, originally published 1839–42 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). The Sumida Embankment in the foreground and the Nihon‑zutsumi Dyke (Fig. 9‑3) together formed a V‑shaped embankment system on either side of the Sumida‑gawa River, functioning as a kind of “dam” without obstructing the river’s flow. Hiroshige depicts the engineered flood‑retention zones extending across both sides of the Sumida‑gawa River, along with the persistent flow of water from distant Mount Buko. The eighth shogun, Yoshimune Tokugawa (徳川吉宗, ruled 1716–1745), ordered the planting of hundreds of cherry trees, along with pines (Pinus) and willows (Salix), on the embankment, making it one of the most popular places to visit during the cherry‑blossom season. Along the embankment, irregularly shaped earthen groynes were constructed, forming floodplain marshes. These groynes, covered with riparian forests and plant species with high silica‑accumulation capacity such as Poaceae (grasses), play an important role in supplying essential nutrients—including dissolved silica compounds and iron‑containing organic compounds—to the sea. The resulting wetlands simultaneously create continuous nursery and feeding habitats for abundant fishery resources. Moreover, these groynes, built from nearby sediments composed of sand, silt, and fine materials derived from organic compounds of high‑silica plant species, provide habitats for benthic diatoms, which in turn support blooms of diatom‑dominated phytoplankton—the foundation of aquatic food webs (Rousseau et al. 2002; Leynaert et al. 2009, 2011).

Fig. 9-3. Dawn over Nihon-zutsumi Embankment at Emonzaka in the New Yoshiwara, from the series Famous Places in the Eastern Capital, Hiroshige, originally published 1839–42 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). The Nihon‑zutsumi Dyke (length: 1400 m/0.87 miles; height: 3 m/9.8 ft; levee‑crown width: 7.2 m/24 ft), oriented almost perpendicular to the flow of the Sumida‑gawa River, was constructed in 1620, connecting to the Musashino Plateau. The dyke played a crucial role in preventing flooding in the city center of Edo, located to the right of this print. The flood‑retention zones behind the dyke, on the left side of the print, were designed to accept and store floodwaters during high‑water events. At the downstream end of the dyke, the famous amusement quarters of New Yoshiwara—renowned for their beautiful courtesans—were established. Hiroshige depicts the Nihon‑zutsumi Dyke as viewed from the main gate of New Yoshiwara, shown in the lower right‑hand corner. In the early morning, visitors are seen leaving the amusement quarters and heading home. The Matsuchiyama at the Sumida‑gawa River (Fig. 7-1f) lies beyond the horizon.

 4.5. Flood management in low-lying reclaimed marshland: Land governance after the great fire of 1657

 

Extensive forests were strategically established to safeguard sustainable agricultural productivity in the reclaimed marshland. Land governance in these areas was distinctive in its integrated approach to multiple interdependent challenges.

After the Great Fire of 1657, large-scale infrastructure development began in the low-lying reclaimed marshland on the east bank of the Sumida-gawa River. These projects were directed by the fourth shogun, Ietsuna Tokugawa (徳川家綱, ruled 1651–1680). The Ryogoku-bashi Bridge (Fig. 7-1g) was constructed immediately after the fire to connect the already populated Nihon-bashi district with the Honjo district in the reclaimed marshland (Fig. 10). In the upper left portion of Fig. 10, extensive urban forests can be seen along the riverside zone of Honjo.   

As Edo expanded and demand for residential land increased, the riverside zone in Honjo was allocated to the mansions of ruling-class families and to shogunate facilities (Fig. 7-1). Their estates, with gardens incorporating extensive urban forests and ponds connected to the Sumida‑gawa River were designed to buffer river flooding. Earthen dykes and moats surrounded these estates, and their sophisticated gardens—featuring hills and ponds/streams supplied by the Sumida-gawa River—functioned as multi-layered flood-buffering system, a kind of discontinuous levee system.

Fig. 10. Ryogoku-bashi Bridge and the Great Riverbank, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). The Ryogoku-bashi Bridge (length: 175 m / 574 ft) was constructed immediately after the devastating fire of 1657 to link the Nihon-bashi district with the Honjo district in the reclaimed marshland (Fig. 7-1g). In the upper left of this print, extensive urban forests are visible along the Sumida‑gawa River. These forests belonged to estates of ruling-class families and shogunate facilities. Their sophisticated gardens, incorporating hills and ponds/streams supplied by the Sumida-gawa River, were designed as a multi-buffering system against floods—a form of discontinuous levee system. Fire risk reduction was also a deliberate element of early urban planning; the open space at the end of the bridge, in the foreground, was intentionally placed to prevent the spread of fire.

 

4.5.1.     Unique flood-water retention system: the distinctive Japanese garden style rinsen (林泉)

 

Although the reclaimed marshland on the east bank of the Sumida-gawa River was protected from river overflow by the Sumida Embankment (Figs. 7-1e, 9‑1, 9-2), and from high-tide flooding by the Onagi-gawa Canal (Figs. 7-1c, 8), it remained highly susceptible to “inland flooding” due to its low elevation.

Unique flood-water retention systems were therefore strategically developed to prevent inundation within the levee-protected areas. Hiroshige depicts a typical flood-retention device in Fig.11-1: the garden of the Akiba Shrine (Figs. 7-1i, 7-2i), which incorporates a pond and stream constructed using water drawn from the Hikifune-gawa Canal excavated 1660 (Figs. 7-1h, 7-2h, 11-2). Landscape gardens in the low-lying reclaimed marshland were intentionally designed to accept and store floodwaters during rainfall or flood events, thereby increasing the overall flood-storage capacity of the system. By holding water long enough to reduce peak discharge, these gardens significantly reduced flood damage.

The  the  were constructed in the distinctive style of rinsen (林泉): rin (林) meaning “man-made forest,” and sen (泉) meaning “spring water.”

The Hikifune-gawa Canal (曳舟川, hikifune meaning “towboats pulled by human traction”), approximately 60 km (37 miles) long from the upper reaches of the Tone-gawa River, was constructed in 1660 to supply drinking water to the Honjo and Fukagawa districts.

 

Fig. 11-1. In the Precincts of the Akiba Shrine at Ukeji, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum). The reclaimed marshland was protected from river overflow by the Sumida Embankment (Figs. 7-1e, 9‑1, 9-2) and from coastal hazards by the Onagi-gawa Canal (Figs. 7-1c, 8). However, due to its low elevation, the area remained highly susceptible to inland flooding. To prevent inundation within these levee-protected lowlands, numerous naturalized forested landscape gardens with ponds and streams were created to accept and store floodwaters during rainfall or flood events. The garden of the Akiba Shrine, designed in a distinctive rinsen (林泉) style, covered a large area of 23,141 m² (6 acres). It incorporated a pond and stream supplied with water drawn from the Hikifune-gawa Canal (Figs. 7h, 11-2, 13-1), completed in 1660. A reliable supply of high-quality freshwater in this water-scarce reclaimed marshland was another deliberate element of regional and urban planning. For this reason, ancient Japanese architects constructed large-scale water bodies—canals and ponds—in combination of extensive areas of man-made forests. Continuous inputs of freshwater from these canals and ponds, together with freshwater generated through the cellular respiration of deep forests, gradually contributed to the formation of freshwater-filled groundwater aquifers. As a result, artesian springs often emerged within the gardens. At the Akiba Shrine, the spring water was reputed to possess curative properties for various ailments.

Fig. 11-2. Towboats along the Yotsugi-dōri Canal, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). The Hikifune-gawa Canal (Figs. 7-1h, 7-2h, 13-1) was constructed in 1660 to supply the Honjo and Fukagawa districts with drinking water. Extending approximately 60 km (37miles) from the upper reaches of the Tone-gawa River, the aqueduct was abandoned in 1722. Thereafter, its course was used solely for irrigation and for conveying freight. Over time, pleasure boats also appeared. The hikifune (曳舟) —small barges carrying two or three passengers and pulled by men walking along the bank—became a popular leisure activity and attracted inhabitants of Edo. 

4.5.2.     Intricate canal networks together with large-scale naturalized forested landscape gardens connected to canals

 

In the levee-protected low lands, intricate canal networks were constructed for irrigation and for the Edo’s waterborne transport system. These canals were also intended to accept and store floodwaters during high water events. The Tate-kawa Canal (堅川, Fig. 7-1k), running perpendicular (tate, 縦or 堅) to Edo Castle, was excavated in 1659 to link the city center of Nihon-bashi with the Naka-gawa River (Fig. 7-1d). The Yoko-jikken-gawa Canal (横十間川, “Parallel Sixty-Foot River,” Figs. 7-1l, 7-2l, 11-3), running parallel (yoko, 横) to Edo Castle, was also excavated in 1659: its width was 18 m (60 feet), The ken (間) is a traditional Japanese unit of length, approximately 1.82 m (6 feet) in civil engineering. The Kita-jikken-gawa Canal (北十間川, “Northern Sixty-Foot River,” Figs. 7-1m, 7-2m, 11-3) was constructed in 1663.

At the same time, placement of feudal lords’ mansions was strategically planned. All mansions in the low-lying reclaimed marshland were equipped with gardens created in the distinctive rinsen (林泉) style. This garden style (Fig. 11-1)—a large-scale naturalized forested landscape garden with a pond and stream supplied by water drawn from nearby rivers or canals—functioned effectively as a flood-water retention system. Similarly, shrines and temples (Figs.11-4, 11-5, 11-6) were constructed with rinsen-style gardens designed to capture and store floodwaters during high-water events.

Fig. 11-3. Yanagi-shima, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). Hiroshige depicts a popular amusement center at the junction of two major canals. The Yoko-jikken-gawa Canal (横十間川, “Parallel Sixty-Foot River,” Figs. 7-1l, 7-2l, excavated in 1659), running from the lower left to the upper right, is crossed at right-angles by the Kita-jikken-gawa Canal (北十間川, “Northern Sixty-Foot River,” Figs. 7-1m, 7-2m, constructed in 1663). On either side of the Yoko-jikken-gawa Canal, mansions of feudal lords and temples/shrines with gardens were laid out. The naturalized forested landscape gardens, with ponds and streams fed by water drawn from the canal, were also intended to serve as fire-resistant barriers. Together, the canal and the large-scale gardens formed a highly advanced protective zone designed to prevent the spread of fire. The brightly lit building at the center of this print is the restaurant Hashimoto-ya, renowned for its cuisine featuring ayu (鮎, Plecoglossus altivelis, river trout). Despite being located in the built-up area of the Eastern Capital, the reclaimed marshland supported abundant freshwater fishery resources. The large-scale, naturalized forested landscape gardens—with ponds and streams connected to the canals—were designed as nursery and feeding habitats for many species of freshwater fish and crustaceans. Gardens within mansions of feudal lords and the grounds of temples/shrines were protected as riverine sanctuaries, which contributed to the abundance and diversity of freshwater fishery resources.

Fig. 11-4. Kameido Tenmangu Shrine, from the series Famous Places in Edo, Hiroshige, originally published 1848–49 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). The fourth shogun, Ietsuna Tokugawa (徳川家綱, ruled 1651–1680), donated land for the construction of the Tenjin Shrine (亀戸天神, Figs. 7-1o, 7-2o), which was completed in 1662 and celebrated for its garden. A pond, connected to the Yoko-jikken-gawa Canal (excavated in 1659), was designed in the shape of the character kokoro (心, meaning “heart” or “soul”), with the two high-arched bridges leading to the main building (shinden, 神殿). 

Fig. 11-5. In the Precincts of the Tenjin Shrine at Kamaido, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In the foreground, Hiroshige presents the close-up of purple wisteria, with a high-arched bridge beyond. In the middle ground, a young mother and her son cross the high-arched bridge. In the background, visitors spend their time admiring the violet blooms beneath a pergola entwined with wisteria. In the far distance, the deep sacred forests are described. The canal networks, connected with large-scale gardens containing ponds and streams, were designed to enhance interdependent ecosystem functions: floodwater retention, fire-barrier structures, groundwater recharge and formation, and nursery/feeding habitats for resilient freshwater fisheries. In this print, Hiroshige also conveys that the garden was intended to provide the population with a place of relaxation and seasonal enjoyment.

Fig. 11-6. Bush-clover Temple, from the series Famous Places in the Suburbs of Edo, Hiroshige, originally published 1839 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In the vicinity of the Tenjin Shrine, a naturalized forested landscape garden with a pond connected to the Yoko-jikken-gawa Canal (excavated in 1659) was newly constructed within the temple precincts (Fig. 7p). The arrangement of numerous planted species of bush clovers gained popularity and attracted the inhabitants of Edo. An artesian spring emerged within the garden through the gradual process of groundwater recharge and formation, sustained by the water bodies and the freshwater generated over years through the cellular respiration of the deep forests. The spring water became renowned for its curative properties in treating eye ailments, leading the temple to change its name to 龍眼寺 (Ryugen-ji, Temple of the Dragon’s Eye). The constructed pond was fringed with man-made sandbanks composed of nearby sediments consisting of sand, silt, and fine materials derived from organic compounds with high silica content, thereby creating habitats for benthic diatoms. Through silica uptake and biogenic silica production, these benthic diatoms played a key role in enhancing the productivity of aquatic ecosystems (Rousseau et al. 2002; Leynaert et al. 2009, 2011). Hiroshige depicts the pond as carefully engineered to provide nursery and feeding habitats that supported the abundance and diversity of freshwater fishery resources.

 4.6. Gardens with ponds and streams connected to canals to address interdependent challenges in urban and regional planning

 

4.6.1.     Urban fire-risk reduction: constructed structures

 

Fire risk reduction was a principal issue in the urban planning of reclaimed marshland, owing to the bitter experience of the devastating fire of 1657, which destroyed 60–70% of Edo and caused the deaths of more than 100,000 people.

Through a learning-based approach, ancient Japanese architects and decision-makers recognized that deep forests associated with rivers, streams, and lakes could serve as barriers to prevent the spread of fire. Thus, they advanced a garden style designed as a fire-barrier structure that replicated natural systems.

This garden style—a naturalized forested landscape with ponds and streams—was conceived as a fire‑resistant barrier. The grounds were often enclosed by moats and earthen dikes. On these dikes, tall fire-resistant structures were created by planting fire‑resistant tree species such as itajii (Castanopsis sieboldii, Fagaceae; evergreen tree up to 30 m/98 ft high), Japanese bay tree (Machilus thunbergii, Lauraceae; evergreen tree up to 20 m/70 ft), and ginkgo (Ginkgo biloba; deciduous, dioecious tree up to 35 m/115 ft, regarded as a living fossil). A distant view of the fire‑resistant barrier at the Akiba Shrine can be seen on the horizon in Fig. 13-1, resembling ancient lush woods. These constructed fire-resistant zones were historically effective in preventing the spread of fire and provided large areas of safe evacuation sites within the wooded barrier structures.

In Fig. 11-1, Hiroshige depicts the precincts of the Akiba Shrine, with its naturalized forested landscape garden containing a pond and stream, situated in reclaimed marshland (Figs. 7-1i,7-2i). Because forests with high leaf area index (LAI) require a sufficient and constant supply of water, the installation of water features such as ponds and streams played an essential role in this garden style. Within the precincts, a pond and stream were constructed using water drawn from the Hikifune-gawa Canal (Figs. 7-1h, 7-2h, 11-2, 13-1; constructed in 1660). This suggests that the scheme of the landscape garden—hills, pond, and stream—was created simultaneously with the construction of the Hikifune-gawa Canal. In 1702, the main building of the shrine was erected with funds provided by Masanaga Honda (本多正永, 1645–1711), a high-ranking shogunate official.

The shrine was dedicated to the Japanese Shinto deity Akiba-daigongen, who was believed to offer protection against fire. It was visited by many inhabitants of Edo seeking such protection, as the city was highly susceptible to fires due to its wooden and paper-built structures. The shrine was particularly venerated by the women of Ōoku (大奥, the women’s quarters of Edo Castle) and by high-ranking families. The restaurants adjoining the Akiba Shrine were famous for their cuisine featuring carp (Cyprinus carpio, freshwater fish, average size: 40–80 cm/16–31 in)

Under Ietsuna, the fourth shogun, shrines and temples with gardens designed as fire-barrier structures were established along the canals that played a substantial role in Edo’s transport system. In Fig. 11-3, Hiroshige depicts the junction of two major canals. The Yoko-jikken-gawa Canal (横十間川, “Parallel Sixty-Foot River,” Figs. 7-1l, 7-2l, excavated in 1659), running from the lower left to the upper right, is crossed at right angles by the Kita-jikken-gawa Canal (北十間川, “Northern Sixty-Foot River,” Fig. 7-1m, 7-2m, constructed in 1663). With the construction of the Yanagi-shima Bridge (Willow-Islet Bridge) in 1718, the area surrounding the bridge developed one of the liveliest amusement centers in Edo.

The brightly lit building at the center of the print is the restaurant Hashimoto-ya, a first-class establishment intended primarily for large banquets. The restaurant was renowned for its cuisine featuring ayu (鮎, Plecoglossus altivelis; typical maximum size: 30 cm/1 ft), an amphidromous fish that migrates between coastal seawaters and freshwater rivers. Two roofed pleasure boats in the foreground of the Yoko-jikken-gawa Canal indicate that waterborne amusements were popular here. Passengers were entertained by geishas, who served wine and food and performed songs accompanied by the shamisen, a three-stringed traditional Japanese instrument.

The deep sacred forests at the left center of Fig. 11-3 belonged to the Myōken-dō, a temple of the Nichiren (日蓮) monastery. This temple was dedicated to the bodhisattva Myōken (妙見), a Buddhist deity believed to provide protection from fire and revered as a god of war who defends the nation.

On the opposite side of the Yoko-jikken-gawa Canal, the Tenjin (天神) Shrine—celebrated for its garden—was constructed (Figs. 7-1o, 7-2o, 11-4, 11-5). The shrine was dedicated to Sugawara no Michizane (菅原道真, 845–903), a minister and scholar of the Heian period (794–1185), who was deified after his death as the patron saint of learning and calligraphy. Michizane died in exile, far from the capital, in profound despair.

Shogun Ietsuna, a devoted adherent of the Tenjin cult, donated land for the construction of the Tenjin Shrine, which was completed in 1662 and became renowned for its garden. A pond, fed by water drawn from the Yoko-jikken-gawa Canal, is formed in the shape of the character kokoro (心, meaning “heart” or “soul”), with two high-arched bridges leading to the main building (shinden, 神殿) (Fig. 11-4).

In the foreground of Fig. 11-5, Hiroshige presents the violet blossoms of wisteria (fuji, 藤) on a large scale, while visitors in the background admire the flowers, which bloom in May. In this print, Hiroshige suggests that the garden was intended to provide the population with a place of relaxation and seasonal enjoyment.

In the vicinity of the Tenjin Shrine, a naturalized landscape garden with a pond was newly constructed within the temple precincts (Figs. 7-1p, 7-2p, 11-6). According to legend, this area had originally formed a small islet known as Yanagi-shima Island. A small temple was established there by a monk in 1395. The garden, created following the construction of the Yoko-jikken-gawa Canal (‘Parallel Sixty-Foot River,’ excavated in 1659), was celebrated for its autumn display of bush clover blossoms. Numerous species of bush clover, with flowers in shades of white, pink, red, and purple, attracted the inhabitants of Edo, including writers and artists.

In Fig. 11-6, visitors are shown strolling through the constructed hills and along the irregularly shaped pond connected to the Yoko-jikken-gawa Canal, admiring the blooms of bush clovers. In the background, the deep sacred forests are depicted. Within the precincts, monuments were erected to entertain the public. Some of these monuments have survived, including a stone plaque inscribed with a poem by Basho Matsuo (松尾芭蕉, 1644–1694), one of the most celebrated poets of the Edo period.

 

4.6.2.     Structure of wooded gardens imitating natural systems: designs to enhance interdependent ecosystem functions

 

The mansions of feudal lords (provincial governors) were laid out along the Onagi-gawa Canal (小名木川), the Tate-kawa Canal (堅川), and other waterways (Figs. 7-1,7-2). Within these estates, naturalized forested landscape gardens with ponds and streams fed by canal water were constructed, serving as effective barriers against the spread of fire.

A mansion belonging to the Mito clan, a side branch of the Tokugawa house, was located at the junction of the Sumida-gawa River and the Kita-jikken-gawa Canal (Fig. 7-1j, 7-2j). The grounds of the Mito mansion, occupying a vast area of 76,396 m² (18.9 acres), were granted by the shogunate in 1693. Because the estate adjoined the Sumida Embankment, it was vulnerable to flooding from the Sumida-gawa River. As shown clearly in Fig. 7-2, the grounds of the Mito mansion were designed as a multi-buffering system to mitigate this risk: earthen dykes and moats surrounding the estate formed multiple protective structures, while the magnificent landscape garden—with hills and ponds/streams connected to both the Sumida-gawa River and the Kita-jikken-gawa Canal—functioned as a multi-layered flood-buffering system, a kind of discontinuous levee system protecting the low-lying reclaimed marshland. The Mito mansion served as a villa, accommodation for noble guests, and a warehouse. Although greatly modified, the garden still exists today as Sumida Park (35°43′ N, 139°48′ E).

In the built-up area along the Onagi-gawa Canal, mansions of feudal lords were arranged on both sides of the waterway (Fig. 7-1). Each mansion contained naturalized forested landscape gardens with ponds and streams, which effectively served as fire-barrier structures. In Fig. 12, Hiroshige depicts one such mansion (Fig. 7-1r). The unusual shape of the old pine tree, growing within the grounds of the mansion of the Kuki (九鬼) family from Ayabe Province near Kyoto, was a well-known landmark.

These gardens, maintaining connectivity among aquatic habitats within the built‑up areas, provided nursery and feeding habitats for freshwater fishery resources. Despite being largely occupied by urban development, the reclaimed marshland supported abundant and diverse fishery resources.

Large-scale gardens connected to canal networks imitated natural systems and were deliberately designed to enhance interdependent ecosystem functions, including regional climate stabilization, fire-risk reduction, flood-water management, and the provision of nursery and feeding habitats for freshwater fishery resources. 

Fig. 12. Five Pines, Onagi-gawa Canal, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In the built-up areas along the canals, the mansions of feudal lords with naturalized forested landscape gardens were strategically laid out (Fig. 7-1). These gardens served as barriers to prevent the spread of fire. In this print, Hiroshige depicts a built-up area along the Onagi-gawa Canal (Fig. 7-1r). The unusual shape of the old pine tree, which grew within the grounds of the mansion of the Kuki (九鬼) family from Ayabe Province near Kyoto, was a renowned landmark. Passengers on the boat providing regular connections between the city center and Gyotoku are shown admiring the pine tree, whose exceptionally long, wide-spreading branches extended over both the road and the canal. These gardens played a critical role in maintaining connectivity among aquatic habitats within the built-up areas. Hiroshige emphasizes the importance of public awareness that gardens in built-up areas play a crucial role in natural resource management: the quantitative renewal and qualitative restoration of freshwater resources, as well as the support of resilient freshwater fisheries. 

 4.7. Deliberate placement of village woodlands in damp, low-lying reclaimed marshland for enhanced interdependent ecosystem functions

 

In Fig. 13‑1, Hiroshige depicts the village of Koume (小梅, Fig. 7s), adjoining the Mito mansion, as a typical agricultural settlement in the reclaimed marshland. The name Koume (小梅) derives from the large numbers of plum trees (ume, 梅, Prunus mume) planted in the village and its surrounding area. Several celebrated plum orchards were established here. In Koume Village, one renowned orchard—covering approximately 8,000 m² (2 acres)—was created. The beauty of the plum blossoms in mid‑winter, together with their fragrant scent, was widely appreciated by the inhabitants of Edo (Fig. 13‑2). Pickled plums prepared with coarse salt—a Japanese specialty highly valued for their medicinal properties—were sold in the capital’s markets.

The canal depicted in Fig. 13‑1 was constructed in 1660 to supply the Honjo and Fukagawa districts with drinking water. Extending about 60 km (37 miles) from the upper reaches of the Tone‑gawa River, the aqueduct was abandoned in 1722 following the shift to a new water‑supply system. Thereafter, its course was used solely for irrigation and the transport of freight. Over time, pleasure boats appeared. Hikifune (曳舟)—small barges carrying two or three passengers and pulled by men walking along the bank—became a popular attraction among Edo residents (Fig. 11‑2).

The canals were also designed as nursery and feeding habitats for many species of freshwater fish and crustaceans. Irregularly shaped earthen groynes along the Hikifune Canal were formed by driving numerous wooden piles into the canal bed (Figs. 11-2, 13‑1). The resulting wetlands along the shoreline provided abundant food and refuge from predators, supporting prolific inland fishery resources.

The deciduous trees in the foreground of Fig. 13‑1—under which children are playing with puppies—and those in the distance are Japanese alders (Alnus japonica). Japanese alders grew widely in the damp, low‑lying areas and were valued for producing high‑quality charcoal. Highly tolerant of salt and capable of fixing nitrogen, alders improve soil quality. Owing to these attributes, they were selected for soil enhancement in the reclaimed land.

In Fig. 13‑1, the farmhouses along the canal are surrounded by tall, dense woods. Small‑scale naturalized landscape gardens with ponds and/or streams were often constructed at farmers’ cottages and village officials’ residences. A typical distant view of an agricultural village in reclaimed marshland is shown in Fig. 11‑3 in the background. Hiroshige depicts an expanse of rice paddies with a village largely concealed beneath the tree crowns.

The deliberately placed woods in the agricultural village contributed to a local climate with optimum summer temperatures for crop growth (28 ° C / 22 ° C), as the tree crowns altered surface energy fluxes and thereby influenced local climatic conditions (Fig. 6).

Land governance encompasses all activities associated with the management of land and natural resources. Deliberate placement of woods in regional planning requires recognition that each person’s nearby space—such as a garden—forms part of functional ecosystems that underpin regional climate stabilization and natural resource management. Public awareness and active participation are therefore essential for effective land‑governance practices.

Koume Village lies along the route to the Akiba Shrine (Fig. 11‑1), whose location is indicated by the sacred grove of evergreen tree species on the horizon in Fig. 13‑1. Situated about 4 km (2.5 miles) from the city center, the village became a popular destination for excursions. Teahouses and restaurants soon appeared. Hiroshige depicts the upscale Ogura‑an Restaurant (Figs. 7-1t, 7-2t), a well‑known dining establishment in the Koume area (Fig. 13‑3). Its dining rooms overlook the canal and are set within a beautiful garden. 

Fig. 13-1. Koume Embankment, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Brooklyn Museum via Wikipedia). In the agricultural village within the reclaimed marshland, woods were deliberately placed to regulate surface energy fluxes and create optimum summer temperatures for crop growth (28 ° C / 22 ° C). The deciduous trees in the foreground—under which children play with puppies—and those in the distance are Japanese alders (Alnus japonica). Pines and Japanese alders are planted along the embankment. The farmhouses beside the canal are surrounded by tall, dense woods. Small‑scale naturalized landscape gardens with ponds and/or streams were commonly constructed at farmers’ cottages and village officials’ residences. The canals were designed as nursery and feeding habitats for many species of freshwater fish and crustaceans. Irregularly shaped earthen groynes along the canal bank were formed by driving numerous wooden piles into the canal bed. The resulting wetlands provided abundant food and refuge from predators for freshwater species. These groynes, constructed from nearby sediments rich in silica, created habitats for benthic diatoms and supported blooms of diatom‑dominated phytoplankton—the foundation of aquatic food webs (Rousseau et al. 2002; Leynaert et al. 2009, 2011). Each person’s nearby space—such as a garden—forms part of functional ecosystems that regulate regional climate conditions and support natural resource management, underscoring the importance of public awareness and participation in successful land‑governance practice.  

Fig. 13-2. A Red Plum Branch against the Full Moon, Hiroshige, originally published mid-1840s (Image courtesy of the Art Institute of Chicago). Plums (ume, 梅, Prunus mume) were planted extensively in Koume Village and the surrounding area. Several celebrated plum orchards were established, and the beauty of their mid-winter blossoms, along with their fragrant scent, attracted many inhabitants of Edo. These orchards became popular venues for a variety of leisurely activities. Pickled plums prepared with coarse salt—a Japanese specialty highly valued for their medicinal properties—were sold at the capital’s markets. As part of deliberate landscape planning, tree species were selected to enhance the resilience of local livelihoods, communities, and the broader region.

Fig. 13-3. Koume in Honjo: Ogura-an Restaurant, from the series Famous Restaurants in Edo, Hiroshige, originally published 1838–40. Freshwater fisheries contribute to food security and livelihoods (Tedesco et al. 2017; Fluet‑Chouinard et al. 2018). In the reclaimed marshland, the large‑scale construction of nursery grounds and habitats supported abundant and diverse fishery resources, which in turn provided employment and livelihood opportunities for surrounding communities. Numerous restaurants serving dishes prepared from local catches emerged, and exquisite cuisine featuring freshly caught fish attracted the inhabitants of Edo. Small‑scale naturalized landscape gardens with ponds and/or streams were commonly created at these establishments. The high‑class Ogura‑an Restaurant was located in the vicinity of the Mito Mansion (Figs. 7-1t, 7-2t). Its garden setting includes tall momi fir trees (樅, Abies firma, reaching up to 50 m / 160 ft) visible at the upper left. The restaurant was particularly popular among women as a venue for leisurely activities, offering private dining rooms with views of the canal as well as opportunities for boat cruises. In the foreground of this print, female guests enjoy a boat trip, and one woman is absorbed in fishing—an indication that the canal was an excellent fishing spot.

 

4.8. Emergence of prolific freshwater fisheries by large‑scale construction of nursery grounds and habitats

 

Freshwater constitutes only 2.5% of the total volume of water on Earth, and just about 0.3% of this is contained in rivers, swamps, and lakes (lakes: 0.26%; swamps: 0.03%; rivers: 0.006%) (Shiklomanov 1993). Although freshwater environments account for less than 0.3% of global freshwater, they are vital ecosystems that support approximately 40% of all fish species (Tedesco et al. 2017). Freshwater fisheries play an essential role in food security and livelihoods (Fluet‑Chouinard et al. 2018); however, they are increasingly threatened by human activities, particularly pollution and the loss or fragmentation of habitats.

Despite being largely occupied by built‑up areas, the reclaimed marshland supported abundant and diverse fishery resources. The Onagi-gawa Canal (Figs. 8, 12) was known as the Eel Stream (unagi sawa, 鰻沢) because of its plentiful eel (Anguilla japonica, a catadromous species). Eels primarily inhabit freshwater environments such as rivers and lakes, but migrate to the ocean to spawn. Catadromous fish such as eels depend on estuaries, where they reside for considerable periods during their migrations between saltwater and freshwater. Their tiny, transparent, leaf‑shaped larvae require estuaries as nursery grounds, taking advantage of both abundant food and protection from predators.

Abundant and diverse fishery resources are vital to local economies, providing ample employment and livelihood opportunities for surrounding communities. In the reclaimed marshland, many restaurants serving dishes prepared from local catches emerged. Exquisite cuisine featuring freshly caught fish attracted the inhabitants of Edo. For example, the restaurant Hashimoto‑ya, located along the constructed canals (Fig. 11‑3), was renowned for its dishes featuring ayu (鮎, Plecoglossus altivelis), an amphidromous fish with a life span of only one year. Amphidromous ayu are born in the lower reaches of rivers in autumn, after which the larvae drift into the sea. The larval and early juvenile stages overwinter in coastal waters before migrating back to rivers in spring.

Young ayu depend on estuaries, where they spend noticeable length of time during their migrations. Both the downstream migration of tiny larvae from freshwater to saltwater and the upstream migration of juveniles from saltwater to freshwater require marshy estuarine areas that provide abundant food and refuge from predators (Boesch and Turner 1984; Barbier et al. 2011). In contrast, adult ayu feed on diatom‑dominated freshwater algae that accumulate on rocks and stones in cool, clear streams, particularly in deep mountain valleys. Within the reclaimed marshland, continuous, non-fragmented habitats—linking estuarine nursery grounds to cool, clear streams that emulated deep mountain valleys through an interconnected canal system—were elaborately constructed.

As shown in Fig. 8 of the constructed Onagi-gawa Canal, marshy areas covered with salt‑tolerant plants such as Poaceae (grasses) formed in the estuarine zone, providing nursery grounds rich in food and shelter for migratory fish. Irregularly shaped earthen groynes constructed from nearby sediments—composed of sand, silt, and fine materials derived from organic compounds of the high-silica plant species—create habitats for benthic diatoms. These, in turn, support blooms of diatoms-dominated phytoplankton, the foundation of aquatic food webs (Rousseau et al. 2002; Leynaert et al. 2009, 2011).  

In addition, the gardens within the mansions of feudal lords and the grounds of temples and shrines—designed as nursery and feeding habitats for many species of freshwater fish and crustaceans—played an essential role in maintaining connectivity among aquatic habitats within the built‑up areas.

In the garden architecture of the reclaimed marshland, rocks and stones were often arranged to form the framework of ponds and streams, creating landscapes reminiscent of deep mountain valleys (e.g., the former Mito Mansion at Sumida Park). The ponds and streams were continuously replenished with cool, clear freshwater generated as a by‑product of cellular respiration within the deep man‑made forests. High silica content of rocks and stones created habitats for benthic diatoms. Through silica uptake and biogenic silica production, these benthic diatoms play a key role in regulating dissolved silica availability (Rousseau et al. 2002; Leynaert et al. 2009, 2011). This cool, clear freshwater along with enhanced dissolved silica by benthic diatoms, in turn, supported diatom‑dominated algae. These gardens, protected as riverine sanctuaries, played an important role in securing abundant and diverse freshwater fishery resources, including ayu.

The land governance practices in the reclaimed marshland provide an encouraging example of how large‑scale construction of continuous, non-fragmented nursery grounds and habitats can lead to the emergence of prolific freshwater fisheries.

 

4.9. Emergence of artesian spring water in the reclaimed marshland

 

4.9.1.     Elaborately engineered landscapes that shaped the newly formed groundwater aquifer

 

Water is an essential resource; however, the availability of freshwater is increasingly challenged by climate change and human intervention. Nearly 80% of the world’s population is exposed to high levels of threat to water security (Vörösmarty et al. 2010). Because groundwater and surface water are strongly interconnected, strategies to enhance water-resource resilience require integrated management of both as a single resource (Scanlon et al. 2023).

In terms of the global hydrological cycle, freshwater makes up only 2.5% of the total volume of water on Earth, of which about 0.3% is held in rivers, lakes, and reservoirs (Shiklomanov 1993). Surface freshwater is the main source for all human use, including drinking water.

The history of salt marsh reclamation in Japan dates back to the Nara period (A.D. 710–794), around 1,300 years ago. In traditional indigenous Japanese policy, the supply of reliable, high-quality water was considered one of the core issues of governance. However, providing high-quality freshwater in reclaimed marshland was challenging. Ancient Japanese architects developed a unique system of integrated management, treating groundwater and surface water as a single resource.

Groundwater in reclaimed marshland was inherently non-potable due to seawater intrusion. To ensure the availability of reliable, high-quality freshwater, ancient Japanese architects constructed large-scale water bodies (canals and ponds) together with man-made deep forests. Freshwater generated through the cellular respiration of these forests played a significant role in the formation of freshwater aquifers. The long-term, continuous input of freshwater from canals and ponds, combined with contributions from forest respiration, gradually created groundwater aquifers filled with freshwater.    

In the reclaimed marshland of Edo, artesian spring water often emerged within large-scale, naturalized forested landscape gardens containing ponds and streams. At the Akiba Shrine (Fig.11-1), spring water in the precincts was reputed to cure various ailments. Similarly, the Bush-clover Temple (Fig.11-6) was particularly popular among people suffering from eye disorders, as its waters were believed to have curative effects on eye disease.

In Fig. 11-1, Hiroshige depicts the autumn foliage at the Akiba Shrine as an example of an elaborately engineered landscape garden designed to enhance ecosystem functioning, particularly freshwater formation. The capacity for water generation through cellular respiration depends on the characteristics of tree species.  Deciduous tall trees with deep root systems, such as maple (Acer), typically exhibit a greater ability to contribute to freshwater formation. Constructed ponds and streams, combined with planted maple trees, supply high-quality freshwater that progressively creates freshwater groundwater aquifers. The scarlet leaves of the maples are reflected in the still waters, offering the local population a place of relaxation and seasonal enjoyment, such as admiring the turning hues of autumn.

 

4.9.2.     Critical role of forests in freshwater formation

 

 Forests play critical roles in the hydrological cycle within watersheds. The biochemical processes of cellular respiration in forests directly influence both the quantitative renewal and qualitative restoration of freshwater.   

During autumn, deciduous trees such as maple and oak in temperate forests shed their leaves, adding a newly formed layer to the annual stratification of leaf litter—the thick layer of leaves covering the forest floor. The decomposition of leaf litter, primarily by microorganisms, is a key process in forest biogeochemical cycles (e.g., Bani et al. 2018).

Deciduous forests regulate water loss by transpiration and evaporation. In winter, trees that shed their leaves cease transpiration (water loss through stomata, the tiny pores formed by two guard cells on the leaf surface).

Although deciduous trees cease photosynthesis during the winter, all living cells—including those in deeper roots—continue cellular respiration to acquire biochemical energy for cellular activity. Likewise, microorganisms responsible for leaf-litter decomposition obtain biochemical energy through cellular respiration.

Cellular respiration—a series of metabolic processes within a cell—oxidizes glucose (a monosaccharide sugar) into carbon dioxide and water. During winter, leafless trees cease transpiration; however, all living cells, including deeper roots, produce a considerable amount of water as a by-product of cellular respiration. Trees are protected by thick bark, which reduces water loss via evaporation.

Dead leaves on the forest floor shield the soil from solar radiation (e.g., Yoshimura 1998; Yoshimura et al. 2010), thereby reducing evaporation. Microorganisms in the leaf-litter layer also produce significant amounts of water as a by-product of cellular respiration.

Water formation through cellular respiration in forest trees and microorganisms can also occur at night during the spring and summer growing seasons (Fig. 10-4 in https://harukanoor4.bcoolpot.com/2023/).

Forest ecosystems with deep root systems function as consistent freshwater-supplying systems, maintaining soil moisture reserves and lowering soil temperatures. At the same time, considerable amounts of freshwater produced as a by-product of cellular respiration permeate the soil and constitute an important portion of groundwater. The freshwater produced through cellular respiration in forest ecosystems infiltrates the soil and becomes a significant component of groundwater, forming cool subsurface water that plays an essential role in regulating local summer temperatures—a process examined in the following section.

 

4.9.3.     Cool groundwater containing freshwater produced through cellular respiration by forest ecosystems: regulating local climate for summer temperature (28° C/22° C)    

 

The freshwater produced through cellular respiration in forest ecosystems infiltrates the soil and contributes to the formation of cool groundwater. This cool subsurface water—maintained at approximately 15° C (59° F) throughout the year (e.g., Figs. 10-2, 10-4 in https://harukanoor4.blogspot.com/2023/), exerts an important influence on local summer climate conditions (28° C/22° C). Cool groundwater contributes to streamflow through seepage and discharge, thereby helping maintain cool stream temperatures during summer months. Streams with cool water temperatures can influence the local climate by lowering ambient temperatures.

In the reclaimed marshland of Edo, strategically placed man-made forests and woods functioned as consistent freshwater-yielding systems that actively replenished cool water into groundwater aquifers. Because intricate canal networks deliberately connected these freshwater-yielding systems (Figs. 7-1,7-2), water in the canals contained cool groundwater. Cool stream water effectively cooled ambient temperatures during summer months.

To facilitate active groundwater seepage and discharge into streams, ancient Japanese architects advanced vegetated earthen canal designs (Figs. 8, 11-2, 11-3, 13-1). Ecosystem-based canal construction—stabilizing banks with planted woods and preventing erosion with vegetated marshes and wetlands—was intended to maintain cool stream temperatures through continuous seepage and discharge of cool groundwater. Groundwater flows underground; thus, connectivity between subsurface groundwater flow, invisible to the human eye, and cool stream water plays an important role in regulating local summer temperatures (28° C/22° C).

In addition, the biological process of transpiration—uptake of cool groundwater/soil moisture by deep root systems and release of cool water vapor through tiny leaf pores (stomata)—also influences local climate by lowering ambient temperatures. These cooling effects are particularly prominent in tall trees and forests with deep root systems (Fig. 3 in https://harukanoor4.blogspot.com/2019/).  

 

4.9.4.     For solutions to create/restore groundwater aquifers

 

Global water security is at risk, as water scarcity is emerging as one of the most urgent global challenges (Wada et al. 2010; Vörösmarty et al. 2010; Jasechko et al. 2024). In the freshwater-scarce reclaimed marshland, land-governance practices—engineered canals and ponds combined with deliberately placed forests and woodlands—led to the emergence of artesian springs and newly formed freshwater groundwater aquifers. This historical ecosystem-based achievement offers valuable insights for present-day initiatives aimed at creating new freshwater groundwater aquifers and replenishing existing ones.

 

Fig. 14-1. Ayase-gawa River and Kanegefuchi, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). In this print, Hiroshige depicts Kanegefuchi (鐘ヶ淵), the “Bell Deep,” a unique floodwater management system developed by ancient Japanese architects in reclaimed marshland lying below sea level (Fig. 15f). The junction of two rivers—Sumida-gawa River and Ayase-gawa River (綾瀬川) —formed a flood-prone spot within the engineered flood-retention areas. In ancient times, the Ayase-gawa River (Fig. 15c) originally constituted a main river course of the Tone-gawa River System. After Ieyasu’s settlement in Edo in 1590, the Ayase-gawa River was excavated by human design for irrigation and river transport. At the junction of two rivers, intricate canals and numerous ponds were engineered to store excess water and allow it to recede underground through infiltration (Fig. 15). Kanegefuchi, the “Bell Deep,” was an exceptionally deep pond. Ancient Japanese architects understood that extremely deep ponds could effectively store excess surface runoff and facilitate the recession of floodwaters underground, as their immense hydrostatic pressure naturally shaped subsurface water-receding routes and spaces. Legends highlight its exceptional depth. In the early eighteenth century, a newly cast bell was being transported to the Chōshō-ji Monastery (長昌寺). In the middle of the pond, the boat overturned and the bell sank. All attempts to retrieve it proved futile, and the spot became known as the “Bell Deep.” The replacement bell cast in 1720 after the accident still exists today at Chōshō-ji Monastery near Ueno (上野). Raised grounds—constructed from soils excavated during the creation of the deep pond—provided elevated evacuation areas and causeways during high-water events. At the same time, the area surrounding the “Bell Deep” was designed as a place of relaxation and enjoyment for the public. The pond was adorned with Persian silk trees (Albizia julibrissin), shown in the foreground of this print, whose flowers attracted Edo residents in early summer. The area was also renowned for its rustic scenery and for listening to the chirping of the Japanese bush warblers (Horornis diphone) in early spring. The shogun visited this site to hunt with falcons. Japanese architects and decision-makers recognized that the area surrounding the “Bell Deep” lying below sea level, functioned as a highly resilient flood-water management system. Consequently, these exceptionally deep pond systems—with high water-storage capacity and ability to allow floodwaters to recede underground—were considered as standard practice in traditional Japanese land-governance strategies in low-lying zones across the country.  

Fig. 14-2. Horikiri Iris Garden, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). The Horikiri Iris Garden (Fig. 15e) was created by converting former rice paddies in the early 19th century by a farmer named Izaemon Kodaka (小高伊左衛門) and his son. In this print, Hiroshige depicts the successful engineering of rice paddies and ecosystem-based infrastructure that stabilized high-yield agricultural production in back-swamps. Through the large decorative flowers of the Japanese water iris (Iris ensata) in the foreground, visitors are shown strolling through a vast flower field along the irregularly shaped shoreline of a canal or pond. Intentionally placed woods are scattered throughout the flower field, and deep man-made forests appear in the background. The engineered landscape—constructed large-scale water bodies such as canals and ponds together with strategically placed deep woods—created a natural regional cooling effect in summer. Dense forest canopies altered surface energy fluxes and thereby influenced local climate conditions, maintaining optimum summer temperatures for crop growth (28° C/22° C) (Fig. 6). Freshwater produced as a by-product of cellular respiration by woods and trees contributed to groundwater formation with distinctive thermal properties, remaining at approximately 15° C (59° F) throughout the year. Through active seepage and discharge of cool groundwater into canals and ponds, water temperatures remained cool in a state of dynamic equilibrium. Cool water in these water bodies effectively cooled ambient temperatures in summer (4.9.2; 4.9.3). Hiroshige realistically represents engineered back-swamps designed to create a natural cooling effect in summer.

 

Fig. 15. Engineered extensive flood-retention zones shaped by the Sumida Embankment (b) and Nihon-zutsumi Dyke (Fig. 7-2f) on the upper reaches of the Sumida-gawa River (a), reclaimed after the Ieyasu ‘s settlement in Edo Castle in 1590 (Endoh 2004). These engineered extensive flood-retention zones reduced the risk of flooding in the urban districts of Edo. The Sumida-gawa River (e.g., Fig. 9-2) was constructed by human design in an area originally formed coastal salt marshes. The junction of two rivers (f) —the Sumida-gawa River (a) and the Ayase-gawa River (綾瀬川, c)—formed a flood-prone spot within the engineered flood-retention areas. To slow and store floodwater runoff, intricate canals and numerous ponds were constructed. Kanegefuchi (鐘ヶ淵, f), the “Bell Deep,” was an exceptionally deep pond system with high water-storage capacity, designed to allow floodwaters to recede underground. The Horikiri Iris Garden (e, Fig. 14-2) exemplifies land‑use practices adapted to site conditions—specifically, the poorly drained, low‑lying back-swamps. Data are from the Reproduced 1856 Edo Map Verified by Actual Measurement in the Encyclopedia of EDO–MEIJI–TOKYO, edited by Keiji Nakagawa, APP Co., Ltd., 2004 (ISBN: 4-901441-30-2), processed by Dr. Sotaro Tanaka (Remote Sensing). Legend: a: Sumida-gawa River b: Sumida Embankment (constructed until around 1616) c: Ayase-gawa River d: Hikifune-gawa Canal (曳舟川, excavated in 1660) e: Horikiri Village f: Kanegefuchi (鐘ヶ淵, “Bell Deep”) g: Senjyu Great Bridge (built in 1594) h: Sekiya Village i: Kamon Embankment (掃部堤, constructed 1616). In http://harukanoor4.blogspot.com/2022/, the Senjyu Great Bridge (g) by Hiroshige is shown in Fig. 6-1, Sekiya Village (h) by Hiroshige II is shown in Fig. 6-2, and the Kamon Embankment (i) by Hokusai is shown in Fig. 6-3.

 4.10. Land governance practices in back-swamp zones: enhancing floodwater retention while boosting natural regional cooling effects in summer

 

4.10.1.     Floodwater management system: exceptionally deep pond system that allow stored excess water recede underground

                                                                         

The eastern area of the upper reaches of the Sumida-gawa River (Fig. 15a) including Horikiri Village (Fig. 15e), originally formed coastal salt marshes and was reclaimed after the Ieyasu’s settlement in Edo in 1590 (Endoh 2004). The Sumida-gawa River was excavated by human design in these former coastal marshes (e.g., Fig. 9-2). Construction of the Sumida Embankment (Fig. 15b) by around 1616 created large tracts of low-lying, damp environments resembling natural back-swamps behind the engineered embankment.

Historically, the engineering of rice paddies that utilized back-swamps has been central to establishing and maintaining national food security for over 2,000 years. In Japanese traditional ecosystem-based approaches, floodplains and back-swamps were intentionally designed to enhance floodwater retention—the primary role of these landforms.

Intricate canals and numerous ponds were constructed to slow and store floodwater runoff and then allow it to recede underground through infiltration, while sandbanks and mounds planted with man-made forests were strategically placed to dissipate floodwater energy and diffuse it across the engineered flood-retention areas (Fig. 15). These constructed wetlands and planted woods were intended to enhance interdependent ecosystem functions, including natural regional cooling in summer to stabilize high-yield agricultural production.

Within the engineered flood-retention areas, Japanese architects advanced unique floodwater management systems. In Fig. 14-1, Hiroshige depicts Kanegefuchi (鐘ヶ淵, Fig. 15f), the “Bell Deep,” an exceptionally deep pond. Legends highlight its remarkable depth.　

 Because these engineered flood-retention areas lay below sea level, excess water could not drain away into the sea. Deep ponds were therefore constructed to allow floodwaters to recede underground. Through a learning-based approach, ancient Japanese architects and decision-makers recognized that exceptionally deep ponds constructed in low-lying reclaimed lands effectively stored excess surface runoff and successfully facilitated underground recession of floodwaters. Their immense hydrostatic pressure spontaneously shaped subsurface water-receding routes and spaces in soft, relatively featureless soils composed of sand, silt, broken shells, and other fine materials.

Raised grounds—constructed from soils excavated during the creation of the deep pond—were designed for elevated evacuation areas and causeways during high-water events.

Exceptionally deep pond integrated with engineered evacuation system—elevated evacuation areas and causeways—constituted a ubiquitous floodwater management system in low-lying zones across the country. Rustic scenery was created through site-specific design. This floodwater management system is broadly applicable to low-lying zones across the globe.  

 

 

4.10.2.     Engineering of rice paddies in back-swamp zones: floodwater management integrated with regional cooling strategy in summer

 

Natural back-swamps form on floodplains behind natural river levees where sediments settle. In Japan, the engineering of rice paddies that utilized natural back-swamps has been central to establishing and maintaining national food security for over 2,000 years.  

In Fig. 14, Hiroshige depicts the Japanese water iris (Iris ensata) in large scale in the foreground. This species grows naturally in low-lying, damp environments such as freshwater bogs, marshes, and swamps. According to legend, wild species of water iris from northern Japan were first planted in the ancient reclaimed marshland during the Muromachi period (1336–1573). From Koume Village (Figs. 13-1, 13-3), following the Hikifune-gawa Canal (Figs. 11-2, 13-1) upstream for about 2 km (1.3 miles), lay the village of Horikiri (Fig. 15c), renowned for its iris garden.

The eastern area of the upper reaches of Sumida-gawa River, including Horikiri Village (Fig. 15c), was reclaimed after the Ieyasu ‘s settlement in Edo Castle in 1590 (Endoh 2004). The Sumida-gawa River (e.g., Fig. 9-2) was excavated by human design in an area originally formed coastal salt marshes; construction of the Sumida-gawa River embankment (Fig. 15b) by around 1616 created large tracts of low-lying, damp environments resembling natural back-swamps behind the engineered embankment.

In Japanese traditional ecosystem-based approaches, floodplains and backswamps were intentionally designed to enhance floodwater retention—the primary role of these landforms. Intricate canals and numerous ponds were constructed to slow and store floodwater runoff, while sandbanks and mounds planted with man-made forests were strategically placed to dissipate floodwater energy and diffuse it across the low-lying plain (Figs. 14, 15). Within this framework, the engineering of rice paddies in back-swamps was designed to enhance interdependent ecosystem functions, including regional cooling in summer. 

In Hiroshige’s time, rice and various vegetables were cultivated in the reclaimed marshland. Flowers, including irises sold in the capital’s markets, were also grown. In the early 19th century, a Horikiri farmer named Izaemon Kodaka (小高伊左衛門) and his son created a plantation cultivating numerous iris varieties, converted from rice paddies. Kodaka’s garden eventually contained some 10,000 plants representing more than 200 varieties, becoming a major attraction for Edo residents during the flowering season.

Hiroshige depicts land-governance practices in back-swamp zones in Fig. 14. Through the large decorative flowers of the Japanese water iris (Iris ensata) along the irregularly shaped shoreline of a canal or pond in the foreground, visitors are shown strolling through a vast flower field converted from rice paddies. Intentionally placed woods are scattered throughout the flower field, and deep man-made forests appear in the background.

In Fig. 14, Hiroshige highlights the connectivity between surface water and groundwater. The excavated canals and ponds were unlined, allowing essential interactions between groundwater and surface water to continue. Because strategies to enhance water-resource resilience require integrated management of surface water and groundwater (Scanlon et al. 2023), unlined canals and ponds play a critical role in sustaining water-resource resilience. In contrast, canals and ponds lined with hard surfaces such as concrete restrict this connectivity.

The silica cycle is fundamentally linked to fisheries resources because silica is an essential nutrient for diatoms, which form the base of aquatic food webs (Fig. 4). In particular, biogenic silica production by benthic diatoms plays a key role in aquatic ecosystem productivity (Rousseau et al. 2002; Leynaert et al. 2009, 2011). Benthic diatoms require high-silica surfaces such as rocks (granite/andesite), stones, sediments, and plants capable of accumulating high levels of silica, including Poaceae (grasses), Cyperaceae (sedges), and Equisetaceae (horsetails) (Currie and Perry 2007). To secure prolific freshwater fisheries resources, habitats for benthic diatoms underpin the silica cycle.

However, hardened and armored surfaces such as concrete in streams and lakes destroy favorable conditions for benthic diatoms by reducing the availability of silica (SiO₂). The collapse of benthic diatoms’ direct uptake of Si and the decline in biogenic silica production disrupt aquatic food webs.

Japanese traditional ecosystem-based approaches developed unique designs and techniques that create favorable conditions for benthic diatoms. These approaches offer valuable insights for policies and practices addressing the interdependent challenges of global climate change.

Land governance encompasses all activities associated with managing land and natural resources. Natural resource management—including the quantitative renewal and qualitative restoration of freshwater resources and the support of resilient freshwater fisheries essential for human well-being—is sustained by biological processes governing energy and material flows.

Fig. 16-1. Niijuku Ferry, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). Large tracts of rice paddies with high-yield agricultural production were created by converting former flood-prone, low-lying, damp reclaimed marshland. The distinguished architect Yasobeh Izawa (井沢弥惣兵衛, 1654–1738), invited by the eighth shogun Yoshimune (ruled 1716–1745), developed large-scale infrastructures. To secure water resources for irrigation, a freshwater reservoir replicating a naturally formed oxbow lake was created in 1729. To supply cool, mineral rich water for irrigation, a canal was excavated extending from the upper reaches of the Tone-gawa River, approximately 15 km (9.35 miles) away, to the freshwater reservoir. To distribute this cool, high-quality water throughout the extensive rice paddies, canal networks were constructed. In addition, the Naka‑gawa River was carefully engineered to function as a core drainage system. In 1729, the Naka‑gawa River was straightened and widened form 44 m (144.4 ft) to 144 m (472.4 ft). At the same time, a continuous levee with 3 m (9.84 ft) high was constructed along the east bank to protect the irrigation canal networks and the large tracts of rice paddies. Hiroshige depicts the landing of the Niijyuku ferry crossing the engineered river channel of the Naka‑gawa River, with the continuous 3 m-high levee visible along the east bank in the upper part of the print. Niijyuku was the first station of the Mito-kaidō Highway leading northward to the city of Mito, home of the Mito clan, a branch of the Tokugawa house. In Japan, it was customary to hold a farewell banquet at the first station when seeing someone off on a journey. Restaurants on either side of the ferry were renowned for cuisine featuring freshwater fish such as carp (Cyprinus carpio), because the Naka‑gawa River was noted for its abundant and diverse freshwater fishery resources. The engineered river channel was designed to enhance interdependent ecosystem functions. To prevent scour and erosion, sequential earthen groynes were placed, shaping vegetated marshes and wetlands that functioned as nursery and feeding habitats for prolific freshwater fishery resources. On the levee slope, serial man-made riparian forests were planted to stabilize riverbank through dense root networks and improve water quality through biological assimilation of excess nutrients. The widened river channel of the Naka‑gawa River was designed to slow and store floodwater runoff and then allow it to recede underground through infiltration.

Fig. 16-2. The Ferry Crossing at Sakasai, from the series One Hundred Famous Views of Edo, Hiroshige, originally published 1856–59 (Image courtesy of the Museum of Fine Art, Boston, via the British Museum: https://www.hiroshige.org.uk/ by Chiappa JN). Hiroshige depicts the engineered river channel of the Naka‑gawa River with its continuous 3 m (9.84 ft)-high levee, designed as an ecosystem-based flood alleviation system. The ferry at Sakasai crossed this engineered river channel. In the upper right of the print, the landing at the village of Komatsuisgawa is shown: one ferry boat is moored, while others are just casting off. In the foreground, the presence of the settlement of Sakasai is indicated only by the engineered river marsh, where white egrets (Egretta garzetta) stand among common reed (Phragmites australis). The continuous levee, visible in the upper part of the print, protected the canal networks that irrigated cool, high-quality water and the large tracts of rice paddies. The levee was meticulously designed to suit site-specific conditions. The ferry at Sakasai was located near the junction where the Tate-kawa Canal (Fig. 7-1k) joins the Naka-gawa River (Fig. 7-1d). At high tide, salt water travels upstream to around this point, reversing the direction of the river current. The collision between the river current and the incoming salt water created a high-risk flooding spot. For flood alleviation, the settlement of Komatsugawa village was situated on raised ground built atop the levee. Furthermore, a highly elevated hill planted with riparian forests and fringed with river marshes and wetlands was constructed on the levee slope, visible in the upper left. These man-made riparian forests dissipated flood energy, significantly reduced floodwater velocity, and functioned as an effective flood-management system at this high-risk location. A fisherman’s boat loaded with the catches covered with matting indicates that these structures supported prolific river fisheries. 

 

4.10.3.     Ecosystem-based engineering of rivers flowing through low-lying coastal zones

 

Rivers flowing through low-lying areas play a significant role in floodwater retention because river water cannot drain away into the sea. Instead, seawater travels upstream with the tides, reversing the direction of the river current. In Japanese traditional ecosystem-based river engineering, large areas of brackish water zones integrated with estuarine wetlands were created, providing nursery and feeding habitats for prolific fisheries resources (Figs. 3, 8). In addition, river channels in low-lying areas were deliberately designed to slow and store floodwater runoff and then allow it to recede underground through infiltration.

The Naka‑gawa River (lit., “intermediate river”, Fig. 7-1d), an arm of the Tone‑gawa River system, flows between the Sumida‑gawa River and the constructed Edo‑gawa River (e.g., https://harukanoor4.blogspot.com/2022/) in the reclaimed marshland created after the Ieyasu’s settlement in Edo in 1590 (Endoh 2004).

To develop new rice paddies in the extensive flood-prone, low-lying reclaimed marshland, the eighth shogun Yoshimune (ruled 1716–1745) invited Yasobeh Izawa (井沢弥惣兵衛, 1654–1738), an excellent architect and capable administrator from Kii Province (present-day Wakayama Prefecture). Izawa engineered the extremely meandering course of the Naka‑gawa River.   

To secure water resources for irrigation, a freshwater reservoir replicating a naturally formed oxbow lake was created in 1729. On the upper Naka‑gawa River in the Katsushika district, a wide river meander was cut off by wooden weirs (straight-line distance between the two weirs: 1,200 m/0.75 miles), forming a semi-U-shaped lake named Koai-tamei (小合溜井). At the same time, the Nigouhanryō-yōsui Canal (二郷半領用水) was excavated, extending from the upper reaches of the Tone-gawa River approximately 15 km (9.35 miles) away, to supply cool, mineral rich water to the freshwater reservoir. The reservoir area also functioned as a floodwater-retention zone.     

Furthermore, the Kamishimonowari-yōsui Canal (上下之割用水) was excavated to distribute this cool, high-quality water derived from the Tone-gawa River throughout the large tracts of rice paddies and farmlands, supporting high-yield agricultural productivity.

Rice paddies require structured drainage systems to control water levels, prevent root rot, and ensure soil aeration. In the flood-prone, low-lying reclaimed marshland, the Naka‑gawa River was carefully engineered to function as a core drainage system.  

In 1729, the river channel of the Naka‑gawa River was straightened and widened form 44 m (144.4 ft) to 144 m (472.4 ft). At the same time, a continuous levee 3 m (9.84 ft) high was constructed along the east bank to protect the irrigation canal networks and the extensive rice paddies.

A map from Hiroshige’s time (Fig. 7-1), created 130 years after the river-engineering work of 1729, indicates that the Naka‑gawa River (d) still had a meandering course in the Katsushika district. Meandering flow plays a significant role in flood alleviation: it increases the total length of the river channel, thereby increasing total water-storage capacity; it reduces the speed and energy of the water flow; and by slowing the current, it facilitates underground recession of excess water. Izawa deliberately designed the meandering river channel as a flood-alleviation system.

The widened river channel of the Naka‑gawa River was intended to increase total water-storage capacity. Importantly, the engineered river channel was conceived as ecosystem-based infrastructure.

In Fig. 16-1, Hiroshige depicts the engineered river channel on the upper Naka‑gawa River in the Katsushika district near the freshwater reservoir Koai-tamei (not shown in Fig. 7-1). To prevent scour and erosion, continuous earthen groynes are placed, shaping vegetated marshes and wetlands. On the levee slope, sequential man-made riparian forests were placed.         

In Fig. 16-2, Hiroshige emphasizes the distinctive earthen structures designed as ecosystem-based flood-alleviation systems in the lower reach of the Naka‑gawa River. Deep man-made riparian forests were deliberately placed on a highly raided hill on the levee slope. To prevent scour and erosion, extensive vegetated marshes and wetlands were shaped by earthen groynes. The presence of deep riparian forests and large vegetated wetlands reduced flood water velocity and functioned as effective flood-alleviation measures at the high-risk spot where the river current collided with incoming salt water.

Deliberately placed man-made riparian forests integrated with engineered vegetated wetlands slowed and stored floodwater runoff and then allowed it to recede underground through infiltration. Freshwater produced through cellular respiration by strategically placed riparian forests formed cool subsurface water, remaining at approximately 15° C (59° F) throughout the year (e.g., Fig. 10-2 in https://harukanoor4.blogspot.com/2023/). Through active seepage and discharge of cool subsurface water into the river, water temperatures remained cool in a state of dynamic equilibrium, effectively lowering ambient temperatures in summer. 

Rivers function as silicic acid (dissolved Si‑containing compounds) supplying corridors to coastal waters (e.g., Milliman 1997; Conley 2002; Katz et al. 2024). Silicic acid, a vital nutrient for diatom‑dominated phytoplankton, supports the basis marine food webs (Fig. 4). Engineered continuous river marshes covered with high silica-accumulating plant species such as common reed (Phragmites australis), enhance this silicic-acid-supplying function. Similarly, rivers supply essential nutrients—such as Fe‑containing organic compounds in the form of humus, leaf litter, and detritus—to the sea (Kuma and Matsunaga1995). Sequential man-made deep riparian forests function as corridors supplying these essential nutrients to coastal waters.  

 

4.10.4.     Ecosystem-based infrastructures: application for present-day policies and practices

 

1.1.2..Flood-alleviation measures in low-lying coastal areas

 

Rapidly urbanizing coastal lowlands face severe flood risks (Seto et al. 2011; Neumann et al. 2015; MacManus et al. 2021). In low-lying coastal areas, flood risks are increasing due to the intensification of extreme precipitation events driven by a modified hydrological cycle under climate change (Tabari 2020). Therefore, effective flood-alleviation measures in coastal lowlands are urgently required.

Japanese traditional land governance in coastal lowlands offers practical guidance for present-day initiatives seeking effective flood-alleviation measures. In these traditional approaches, architects advanced unique flood-alleviation systems: numerous gardens with ponds and streams connected to intricate canal networks in urban planning (4.5), and elaborate canals and numerous ponds in regional planning (Fig. 15). These systems were intended to slow and store floodwater runoff and then allow it to recede underground through infiltration.

Exceptionally deep pond systems—such as the “Bell Deep”—with high water-storage capacity and the ability to allow floodwaters to recede underground, were extremely effective floodwater-management systems (Fig. 14-1). Consequently, “Bell Deep”-type floodwater-management systems were ubiquitous in low-lying zones across the country. Due to their rustic appearance, however, the values and functions of these systems were often ignored and abolished during modernization.

In Japanese traditional land governance in coastal lowlands, river engineering was also intended to slow and store floodwater runoff and then allow it to recede underground through infiltration. Distinctive ecosystem-based flood-alleviation systems were incorporated into river engineering (Figs. 16-1, 16-2).

Japanese traditional land governance in coastal lowlands thus offers practical guidance for present-day initiatives seeking effective flood-alleviation measures. It is also noteworthy that engineered landscapes in coastal lowlands—including strategic placement forests and woodlands—contribute to restoring the hydrological cycle over medium- to long-term timescales. Forests are active determinants of the water cycle (Sheil 2018). Japanese traditional indigenous watershed management, including strategic placement of forests and woodlands, was based on an understanding of how forests function as hydrological regulators (https://harukanoor4.blogspot.com/2016/).  

 

1.1.2.  Preventing the catastrophic impacts of drying lands and groundwater depletion

 

Currently, the world is facing an unprecedented loss of freshwater both on land surfaces and in groundwater. Satellite data show rapid expansion of drying lands. Roughly 75 % of the global population in 2020—nearly 6 billion people across 101 countries—has experienced accelerated shrinking freshwater availability over the past 22 years since 2002 (Chandanpurkar et al. 2025).

To prevent the catastrophic impacts of drying lands and groundwater depletion, Japanese traditional ecosystem-based approaches offer practical guidance for contemporary policy and practice aimed at restoring freshwater on land surfaces and in groundwater.

Biological processes of terrestrial vegetation regulate the resilience of freshwater resources both on land surfaces and in groundwater:

 

• increasing freshwater quantity through water produced as a by-product of cellular respiration;

• reducing evaporation loss through natural cooling effects at land surfaces and in water bodies, driven by biologically formed cool freshwater;

• improving water quality through biological assimilation of excess nutrients.

 

The appearance of freshwater artesian springs within large-scale naturalized forested landscape gardens in reclaimed marshland with high soil salinity (Fig. 11-1; 4.9) indicates that cellular respiration by man-made forest ecosystems plays a critical role in the formation of subsurface freshwater. This produced freshwater contributes to the creation of newly-formed groundwater aquifers and/or increases the volume of existing groundwater.

Freshwater produced through cellular respiration by forest ecosystems has distinctive thermal properties, remaining at approximately 15° C (59° F) throughout the year. Forest ecosystems with deep root systems function as consistent cool-freshwater-supplying systems, maintaining soil moisture reserves and lowering soil temperatures. At the same time, groundwater containing produced cool freshwater also remains near 15° C year-around (e.g., Figs. 10-2, 10-4 in https://harukanoor4.blogspot.com/2023/). Through connectivity between cool groundwater and water bodies (rivers, canals and ponds), cool groundwater contributes to cool water temperatures, reducing evaporation losses.  

Strategically placed forests and woods improve water quality through biological assimilation of excess nutrients.

In contrast, severe removal of vegetation (e.g., replacing by concrete or asphalt) leads to degradation of freshwater both on land surfaces and in groundwater:

 

• decreasing freshwater volume due to loss of respiration-derived freshwater production;

• accelerating evaporation losses from land surfaces and water bodies due to increased temperatures; 

• deteriorating water quality due to loss of biological assimilation of excess nutrients.

 

Therefore, ecosystem-based approaches—strategically placed forests and woods integrated with carefully engineered water bodies, including management and design of river flows—form the basis of coherent land governance. The resilience of freshwater resources is supported by biological processes of terrestrial vegetation, particularly forests and woods, and by ecosystem services and functions associated with their connectivity to water bodies. Hiroshige depicts unique, highly planned engineering designs in Japanese traditional watershed management that enhance the resilience of freshwater resources both on land surfaces and in groundwater.

 

 

4.11.Ecosystem-based approaches in regional and global climate stabilization

 

In the reclaimed marshland in Edo, distinctive land-governance practices—constructing large-scale water bodies such as canals and ponds, together with unique river engineering integrated with the strategic placement of deep man-made forests—transformed high-salinity reclaimed marshland into fertile arable land. At the same time, these engineered landscapes generated natural regional cooling effects in summer.

Biological processes and structural attributes of terrestrial vegetation, particularly forests, together with its ecosystem services and functions linked to water bodies produce natural regional cooling effects in summer.

 

• Deliberately placed forests and woods alter the surface energy balance, reducing excess heat in summer and maintaining cool nighttime temperatures. This capacity depends on forest structure, especially high photosynthetic primary productivity and high leaf-rea index (LAI) (Fig. 6).

• Freshwater produced through cellular respiration by forests and woods forms cool subsurface water that remains at approximately 15° C (59° F) throughout the year (Figs. 10-2, 10-4 in https://harukanoor4.blogspot.com/2023/ ). Through transpiration—uptake of cool subsurface water by deep root systems and release of cool water vapor through stomata—forests lower ambient daytime temperatures (4.9.2; 4.9.3).

• Active seepage and discharge of cool groundwater into canals and ponds maintain cool water temperatures in dynamic equilibrium. These cool water bodies effectively lower ambient temperatures in summer (4.9.2; 4.9.3).

 

Engineered intricate water bodies together with intentionally placed forests and woods generated natural regional cooling effects and contributed to local climates with optimum summer temperatures for crop growth (28 ° C / 22 ° C). At the same time, these constructed landscapes enhanced interdependent ecosystem functions, including flood-water management, nursery and feeding habitats for fishery resources, and the quantitative renewal and qualitative restoration of freshwater resources.

From a global perspective, forest ecosystems play a critical role in climate stabilization. Primary production (the synthesis of organic compounds from CO₂ through photosynthesis), freshwater produced as a by-product of cellular respiration, and natural cooling effects are closely interrelated (Fig. 6).

Terrestrial vegetation fixes carbon dioxide (CO₂) as organic compounds through photosynthesis. Fixed carbon at the ecosystem level is known as gross primary production (GPP), the largest global CO₂ flux. Beer et al. (2010) estimate that tropical forests and savannahs account for roughly 60% of toral global GPP.   

Forest GPP increases with age, peaks at maturity, and then gradually declines, whereas cellular respiration increases in response to accumulating wood biomass. Mature forests with high GPP consume large amounts of fixed CO₂ for cellular respiration (Kira and Shidei 1967; Odum 1969; Tang et al. 2014) to maintain the substantial biomass of old-growth forests (e.g., Keith et al. 2009).

High GPP, together with high cellular respiration, is one of the major biological processes controlling the quantity and quality of freshwater resources both on land surfaces and in groundwater. Large volumes of respiration-derived cool, high-quality freshwater produced by mature forest ecosystems generate substantial subsurface water and constitute a vital portion of groundwater.  

In the global hydrological cycle, freshwater makes up only 2.5% of Earth’s total water volume, of which about 0.3% is held in rivers, lakes, and reservoirs—the main source for human use. Meanwhile, 29.9% exists as fresh groundwater (Shiklomanov 1993).

Consistent production of respiration-derived cool freshwater by old-growth forests plays a critical role in regional and global hydrological cycle due to its magnitude. Through connectivity between groundwater and water bodies, biologically-formed freshwater sustains persistent streamflow in volume, temperature, and quality.  

At the same time, forest ecosystems with high GPP create natural cooling effects in summer. Old-growth forests have the greatest capability to alter the surface energy balance away from excess heat and maintain cool nighttime temperatures. Large cool river flows generated by active groundwater seepage and discharge lower ambient temperatures across extensive areas. 

Forest ecosystems such as old-growth forests also exhibit the largest biological process of transpiration—uptake of the cool subsurface water by deep roots and release of cool water vapor through stomata—which lowers ambient daytime temperatures (4.9.2; 4.9.3). Together, the release of large volumes of cool water vapor interacts with atmosphere moisture to sustain constant precipitation. Forests are active determinants of the water cycle (Sheil 2018). Old-growth forests function as the most effective hydrological regulators.    

In contrast, historical loss of old-growth forests has led to extreme summer temperatures and the disappearance rivers and lakes (https://harukanoor4.blogspot.com/2017/04/returning-precipitation-integrated-with_7.html).

Forest ecosystems with high LAI account for a vital component of global CO₂-fixation fluxes (Whittaker and Likens 1973). Old-growth forests with high GPP contribute to climate stabilization through large global CO₂-fixation fluxes, strong capability to alter surface energy balance (Fig. 6), and large volumes of respiration-derived cool freshwater that cool land surfaces and water bodies, thereby lowering ambient temperatures. In contract, loss of old-growth forests leads to extreme summer temperatures, drying lands, and groundwater depletion.

Old-growth forests have been exploited from the early Holocene (about 11,700 to 8,200 years ago) to the present (Mather 1990; Perlin 2005; https://harukanoor4.blogspot.com/2017/04/returning-precipitation-integrated-with_7.html). This means that a substantial component of global CO₂-fixation fluxes, along with large volumes of respiration-derived cool freshwater, has been lost or diminished from the early Holocene to today. Consequently, trends of extreme summer temperatures, drying lands, and groundwater depletion continue.

 For global climate stabilization, large-scale policies and practices restoring forest ecosystems—forming tall canopies and highly stratified foliage structures that replicate primordial forests are—required (https://harukanoor4.blogspot.com/2017/).   

 

5.     Coherent land governance to enhance biological processes of energy and material flow  

 

Biogeochemical cycles are fundamental to human welfare, transforming energy and matter into usable forms that sustain ecosystem functioning. Yet human activities have drastically altered Earth’s biogeochemical cycles.

Through photosynthesis, terrestrial plants convert solar radiation into chemical energy. Terrestrial ecosystems fix carbon dioxide (CO₂) as organic compounds; the total amount of carbon fixed at the ecosystem level is known as gross primary production (GPP). This flow of solar energy into biological systems is fundamental to human well-being.    

Terrestrial forest ecosystems evolved to maximize the synthesis of organic compounds from CO₂, forming complex mixtures of conifers such as ceder, broad-leaved evergreen and deciduous trees, and diverse understory vegetation including shade-tolerant herbs, shrubs, ferns, mosses, liverworts, and liches (Fig. 6). These primordial forests, with high GPP, function as the largest global carbon flux. At the same time, large volumes of respiration-derived freshwater contribute to the formation of cool subsurface water, which plays a critical role in regional and global hydrological cycles.

However, these primordial forests have been exploited from the early Holocene (about 11,700 to 8,200 years ago) to the present (Mather 1990; Perlin 2005; https://harukanoor4.blogspot.com/2017/04/returning-precipitation-integrated-with_7.html). Consequently, the largest global carbon flux has shrank. Simultaneously, dramatic declines in respiration-derived freshwater production have disrupted regional and global hydrological cycles. To avoid catastrophic disruption, massive restoration of forest ecosystems with high GPP—replicating primordial forests—is an urgent challenge, because water is an irreplaceable resource.

Marine fisheries are crucial to global food security. Ocean net primary production (NPP)—the amount of photosynthetically fixed carbon after subtracting respiration—is a key regulator of ecological processes, forming the base of marine food webs (Field et al. 1998). Ocean NPP contributes approximately half of total global NPP (Field et al. 1998) and is dominated by phytoplankton, mainly diatoms (Armbrust 2009; Tréguer et al. 2017). Blooms of diatom-dominated phytoplankton are highly sensitive to anthropogenic alteration of the silica cycle. Because diatoms are single-celled microalgae protected by silica shells (frustules), their blooms require dissolved silica. Rivers transport significant amounts of dissolved silica to coastal seas (Milliman 1997; Conley 2002; Katz et al. 2024). Limited availability of silicic acid due to damming restricts diatom growth and shifts phytoplankton composition toward non-siliceous groups such as dinoflagellates (Humborg et al. 1997; Milliman 1997). Thus, the architecture of land-sea interactions is critical.

In addition, benthic diatoms play a key role in aquatic silica cycling, supporting blooms of diatom-dominated phytoplankton by increasing dissolved silica concentrations through biogenic silica production (Rousseau et al. 2002; Leynaert et al. 2009, 2011). Habitat architecture for benthic diatoms is therefore essential.

Iron (Fe) biogeochemical cycling is also crucial to ocean productivity. In successful Japanese traditional ecosystem‑based approaches, extensive deep coastal forests were deliberately placed as standard practice for prolific fisheries. Fe-containing compounds in the form of humus, leaf litter and detritus from forests are essential nutrients for ocean productivity (e.g., Kuma and Matsunaga 1995).

Linkages between terrestrial ecosystems and marine photosynthesis are critical for closing biogeochemical cycle between land and sea. Rivers and streams function as transport corridors for essential nutrients such as dissolved silica and Fe-containing organic compounds. Japanese traditional river-engineering—designed as nutrient-transport corridors integrated with land-sea interactions (e.g., Figs. 9-2, 16-1,16-2)—demonstrates successful historical ecosystem-based approaches. These historical designs offer practical guidance for practical guidance for contemporary site-specific applications.

Excess nutrient inputs to water bodies (fertilizer runoff, treated sewage discharge, combined sewer overflows, urban stormwater) cause harmful algal blooms (e.g., Anderson et al. 2008; Heisler et al. 2008) and create “dead zones” (Moyle and Cech 2004; Diaz and Rosenberg 2008; do Rosário Gomes et al. 2014). Preventing excessive nutrient inputs requires keeping large quantities of undesirable nutrients on land and out of the water bodies (Tilman et al. 2001; Diaz and Rosenberg 2008). Therefore, strategic placement of terrestrial ecosystems with high biological assimilation capacity, together with management systems that recycle human and animal waste for fertilization and soil improvement, is essential.

Climate change is inextricably linked to the anthropogenic alteration of biogeochemical cycles. Coherent land governance that closes biogeochemical cycles is therefore essential for addressing the interdependent challenges of climate change. This article highlights ecosystem-based regional climate stabilization and natural-resource management—enhancing water‑resource resilience and sustaining prolific fisheries—integrated with local community resilience, as practical guidance for contemporary policies and practice.

 

Acknowledgements

 

I would like to express my sincere gratitude to the Internet pioneer J. Noel Chiappa for his excellent website on Hiroshige’s prints, which provides invaluable site-specific designs illustrating how biogeochemical cycles can be closed. I am also deeply thankful to Dr. Sotaro Tanaka (Remote Sensing) for processing the digital maps that demonstrate successful historical ecosystem-based land planning.

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