Haruka Yoshimura, Ph.D.
 |
| Fig. 1 Strategic placement of high LAI (Leaf area index) vegetation associated with human-made wetlands that support the biological process with sufficient supply of available water. In terms of the global hydrological cycle, water is considered a renewable resource because it is replenished by precipitation (rainfall) (e.g., Postel et al. 1996; Pimentel et al. 2004). Significant portion of precipitation to land is formed in rain-cloud development pathways of regional hydrological cycle via vegetation/atmosphere interaction (http://harukanoor4.blogspot.jp/2016/). Biological process of terrestrial vegetation, which is harnessed by solar radiation energy, plays an essential role in the renewability of water resources. Shaping lush landscapes to maintain the rain-cloud development pathways in agricultural lands is vital, as approximately 40% of the world’s surface area has been covered croplands and pastures (Foley et al. 2005, 2011; Rumankutty et al. 2008). |
Globally, irrigation is the most
important water use sector accounting for about 70% of the freshwater
withdrawals and for more than 90% of consumptive water use (not returned to the
watershed). A significant share of consumptive water use for irrigation is
derived from groundwater. Currently, groundwater supplies over 40% of
irrigation water globally (Siebert et al. 2010; Dӧll et al. 2012). The countries with the
largest extent of areas equipped for irrigation with groundwater are India (39
million ha), China (19 million ha) and USA (17 million ha) (Siebert et al.
2010). The irrigation expansion during the last half of the 20th century has
played a central role in tripling world grain harvest over the last six
decades.
Excessive abstraction from aquifers for
irrigation is leading alarming rates of groundwater depletion in the important
food-producing regions around the world such as northwestern India, the North
China Plain, central
USA and California. (Aeschbach-Hertig and Gleeson 2012; Famiglietti 2014). As resource
of groundwater is critically important for irrigated agriculture, therefore
groundwater depletion in the key food-producing regions threatens food
security, not only locally, but also globally via international food trade
(Famiglietti 2014; Dalin et al. 2017).
To avoid catastrophic risks from
unsustainable groundwater irrigation, new paradigms in land planning and
management with a strategic vision aiming to maintain vegetation/atmosphere
interaction are urgently needed (http://harukanoor4.blogspot.jp/2017/04/returning-precipitation-integrated-with_7.html).
Water is a renewable resource in the sense that evaporated water from oceans,
seas, lakes, and rivers returns on land as rainfall (precipitation) via
regional hydrological cycle. Biological process of the terrestrial vegetation,
which is harnessed by solar radiation energy, plays an essential role in the
renewability of water resources through the natural water cycle (http://harukanoor4.blogspot.jp/2016/).
There is a pressing need to highlight
practical solutions of land planning and management in agricultural lands,
taking into account the integrity of the natural water cycle and ecological
systems that support it.
2. Fast-growing
groundwater exploitation in India and China
2.1. Groundwater depletion threatens Asian Giants’ food security
Although the Asian giant countries of India and China
have long histories of irrigation by
surface water over millennia, the advent of unprecedented groundwater-fed
irrigation during the last half of the 20th century has fundamentally changed
the agricultural landscapes. In the Asian giants, the fast-growing groundwater
exploitation has facilitated social development and economic growth via the
outstanding gains in agricultural production. However, the sustainability of
the agricultural production appears threatened by rapid rates of groundwater depletion (Aeschbach-Hertig
and Gleeson 2012; Famiglietti 2014).
2.2. India’s
fast-growing groundwater exploitation during the last half of the 20th century
In India, agriculture is intense and
irrigation by surface water has been practiced for millennia. A network of canals diverting and managing monsoon floodwaters of
rivers has underpinned the civilization of India over millennia. Until around
1960, India was a relatively minor user of groundwater in agriculture.
Although northwestern India had seen some well irrigation even during colonial
times, the availability of small mechanical pumps and well-drilling equipment
profoundly changed the irrigation system in the country. India’s groundwater-fed irrigation expanded in the early
1970s (Shah 2009).
In India, the number of irrigation wells
equipped with diesel or electric pumps increased from some 150,000 in 1950 to nearly 19milliion
by 2000 (Shah 2009). The net irrigated area tripled from 21 million hectares in 1950-1 to 63 million hectares in 2008-9; the share of groundwater
irrigation through wells rose substantially from 28% to 61% (Gandhi and
Bhamoriya 2011).
The largest rates of depletion currently
occur in the Indo-Gangetic Plain, encompassing northern India and Bangladesh as
well as parts of Pakistan and Nepal (Aeschbach-Hertig and Gleeson 2012).
Northern India and its surroundings, home to roughly 600 million people, is
probably the most heavily irrigated region in the world. Data from NASA’s GRACE satellites
indicate decreasing groundwater storage in the entire Indo-Gangetic basin
(Tiwari et al. 2009). Likewise, GRACE-based estimates show the groundwater
depletion due to unsustainable consumption of groundwater for irrigation and
other anthropogenic use over the Indian states of Rajasthan, Punjab and Haryana
(including Delhi), where are home of 114 million people (Rodell et al. 2009).
2.3. China’s food security threatened by groundwater
depletion
2.3.1.
China’s fast-growing groundwater exploitation
Although China’s recorded irrigation history dates back
to 598 B.C., until recently irrigation was never important on most of the North China Plain.
The North China Plain, 320,000 km2
in extent, is home to more than 200 million people. The deep fossil aquifer
system of the North China Plain plays a dominant role in China’s food production,
as the region produces more than 61 % of the nation’s wheat and 45% of
the maize (Yang et al. 2015
form National Bureau of Statics of China, 2008). Agricultural production in the
North China Plain has increased outstandingly since the 1950s owing to
fast-growing groundwater exploitation (e.g., Wang et
al. 2006).
In the North China Plain, agricultural
production relies heavily on irrigation from groundwater, as almost all rivers
are dammed and nearly all usable surface waters are stored in reservoirs for
transport to domestic and industrial users in the metropolitan areas (Fang et al. 2010, Moiwo et al. 2010). In the early
1950s, groundwater irrigation was almost non-existent in Northern China; in the
1970s, it rose to 30% of the total irrigation water. After the economic reforms in the late
1970s, groundwater irrigation continued to expand, reaching 58% in 1995. In 2004,
most irrigation in northern China came from groundwater resources, and the
share of groundwater irrigated areas increased to nearly 70% (Wang et al. 2008). Groundwater levels in the North
China Plain have dropped more than one meter per year over the last 40years
since the 1970s (e.g., Kendy et al. 2004, Cao et al.
2013, van Oort et al. 2016), indicating that the water use exceeds natural
replenishment rate.
2.3.2.
Implication of China’s
pursuit for improvement of irrigation efficiency
As a solution to declining groundwater
resources, technical approaches of increasing agricultural water use efficiency
is a major focus: lining irrigation canals and ditches; replacing irrigation
ditches with underground pipes; replacing flood irrigation with sprinkler and
drip systems. These practices improved irrigation efficiency, as a result,
total groundwater pumping for irrigation has decreased by more than half. Yet,
despite significant achievements in irrigation efficiency, groundwater levels
have continued to decline (Kendy et al. 2007). Kendy et al. (2004) suggest that
the increasing efficiency with technology is not a sufficient solution to the
problem of declining groundwater resources, because these “water saving” technologies are
likely to increase water loss via evapotranspiration and decrease groundwater
recharge. For example, canal lining and underground pipes reduce seepage, and
therefore, can save water via declined transmission losses. However, they
simultaneously decrease groundwater recharge. Likewise, sprinkler which sprays
fine droplets into the dry, windy air may increase evaporation compared to
traditional flood irrigation.
Current practice of improvement of
irrigation efficiency potentially undermines the integrity of groundwater
systems to sustain food production, therefore, a
viewpoint to increase
groundwater recharge and decrease water loss via evaporation/transpiration is required in a
solution to the problem of declining groundwater resources.
2.4. Need for a paradigm change in land and water governance
Unsustainable groundwater irrigation in India
and China. Both aquifers beneath the Indo-Gangetic Plain and beneath the North
China Plain have storage in part of palaeo-groundwater (Foster and Chilton
2003). The current practice of groundwater irrigation in the Asian giants is
not sustainable. Although it is unclear how long the current practice of
overexploitation can continue, paradigm changes in land and water governance
are required to avoid catastrophic risks (Fig. 1).
3.
Ancient lush landscapes that brought sufficient
precipitation
3.1. Role of precipitation in the global hydrological
cycle
In terms of the global hydrological
cycle, water is considered a renewable resource because it is replenished by
precipitation (rainfall). (e.g., Postel et al. 1996; Pimentel et al. 2004).
Solar radiation energy causes evaporation. Water moves from Earth’s surface into the
atmosphere via evaporation. Evaporation from the oceans constitutes 86% of
evaporated water from the Earth. Although only 14% of the water evaporation is
from land, about 20% of the world’s precipitation
falls on land, with the surplus water returning to the oceans through rivers
(Shiklomanov 1993). Thus, solar
radiation energy transfers a significant portion of water from oceans to land
areas. This aspect of the global hydrological cycle is vital to our water and
food security (e.g., Pimentel et al. 2004).
Significant portion
of the freshwater from oceans to land areas is recurring by rain-cloud
formation pathway of regional hydrological cycle via vegetation/atmosphere
interaction (http://harukanoor4.blogspot.jp/2016/).
3.2. Fossil
aquifer recharge under ancient wetter climate
The groundwater systems exist closely
linked with regional climate, the landscape above and the biosphere (Alley et
al. 2002; Scanlon et al. 2006; Edmunds 2009, 2012; Taylor et al. 2013).
The main source of
groundwater recharge originates from precipitation. The rapidly depleting
groundwater resources in the aquifers beneath northwestern India and the North
China Plain are stored in fossil
aquifers (Aeschbach-Hertig
and Gleeson 2012). Global in scope, some of the fossil aquifers were most
recently replenished under wetter climates during the late Pleistocene and
early Holocene, e.g., up to 13,000 years ago in the central High Plains aquifer
in USA (McMahon et al. 2004, 2011) or even one million years ago in the Sahara
of North Africa (Sturchio et al. 2004).
The sufficient precipitation under ancient wetter climates played an
essential role in the fossil groundwater recharge (Edmunds 2009,
2012).
3.3. Essential role of transpiration from
terrestrial vegetation in rain-cloud formation
The rain-cloud formation via the
vegetation/atmosphere interaction has seasonality. A phenomenon of cumulonimbus
cloud formation in the summer sky along mountain slope that brings summer convective
storm is a prominent case of precipitation (rainfall) via the
vegetation/atmosphere interaction. The formation process of the cumulonimbus
cloud is a visible indicator of the active vegetation/atmosphere interaction (http://harukanoor4.blogspot.jp/2016/).
In this manuscript, I discuss the vegetation/atmosphere interaction focusing on
summer cumulonimbus cloud formation.
In cumulonimbus cloud formation, the
primary pathway in which evaporated water returns to the regional
hydrological cycle starts with the condensation process at ocean waterfront
through interaction between warm moisture evaporated from the ocean and cool moisture
released from vegetation by transpiration. The temperature
of a developing cloud is warmer, as condensation releases latent heat. The
following pathway occurs in vast tracts of land from the ocean waterfront to
mountain slopes. The moisture condensed at the
waterfront travels by atmosphere to mountain slopes where small water droplets
grow into large droplets heavy enough to fall as rain. The conveyance by
atmosphere over the inland is maintained by continuous supply of cool
moisture via transpiration from terrestrial vegetation. While
traveling over land from waterfronts to mountain slopes, the warm air containing abundant small
water droplets grows massive as adding moisture via the occurrence of steady
condensation between two moistures of different temperatures: the warm developing
cloud and cool transpiration (colder than the dew-point of the warm moisture
from the waterfront). In addition, the developing cloud grows dense and heavy as
coalescence of droplets makes each droplet larger and heavier.
3.4. Ancient
forests for wetter climate control
Groundwater is an active part of the
regional hydrological cycle, often closely linked to surface water
landscapes (Alley et al. 2002; Scanlon et al. 2006; Taylor et al. 2013).
The sufficient precipitation under
ancient wetter climates played an essential role in the fossil groundwater
recharge. In the temperate zone of the Northern Hemisphere, the ancient wetter
climates were maintained by the ancient deep angiosperm-dominated forests mixed
with coniferous trees such as fir (Abies) (http://harukanoor4.blogspot.jp/2017/04/specific-structure-of-primordial.html).
The crucial crop-producing areas in the
Asian giants are mostly located in the temperate zone of the Northern
Hemisphere. The North China Plain is located latitudes between 34°N and 41°N, and longitudes
between 113°E and 121°E in the eastern
part of China. The Indo-Gangetic Plain encompasses northern India and
Bangladesh as well as parts of Pakistan and Nepal. Although it is not fully
possible to define the Indo-Gangetic Plain, it roughly has a geographical
extent of 22°–35° North latitude and
66°–93° East longitude.
Thus, the Indo-Gangetic Plain is mostly located in the temperate zone, except
for the lower reaches
of the combined delta of the Brahmaputra River and the Ganges River (the
part of Bangladesh located in the tropical zone).
During the Jurassic Period (145–201 million years ago) of the Mesozoic Era, the “Age of Dinosaurs,” the Earth was
covered with non-flowering plants such as ferns, horsetails, and gymnosperms
(seed-producing non-flowering plants). Jurassic gymnosperms included seed-bearing trees: Cycas,
Ginkgo and conifers such as yew (Taxus), the monkey puzzle tree (Araucaria),
and cypress (Cupressus). The rapid diversification of angiosperms
(flowering plants) in the early Cretaceous led to fundamental changes of
terrestrial landscapes to angiosperm-dominated ecosystems of the Cenozoic Era
(e.g., Crane et al. 1995).
During the Tertiary Period (2.6–66 million years ago) of the Cenozoic Era, a mostly
continuously distributed angiosperm-dominated forest formed. Later, human
evolution began in the Quaternary Period (2.6 million years ago
and continuing to present day) of the Cenozoic Era.
3.5. Contribution
of deep ancient forests on sufficient precipitation
Terrestrial biomes
have spatial variation in structure, depending on leaf area index (LAI). LAI is
generally defined as one-sided green leaf area per unit ground area in
broadleaf canopies, and variously defined (projected or total) in needle
canopies. A high LAI of over 8 is the level found in mature forests such as
ancient temperate forests, having highly stratified structure of canopy foliage
composed of mixture of conifers, broad-leaved evergreen and broad-leaved
deciduous trees with understory vegetation of diverse vascular plants
(flowering plants, conifers, ferns, horsetails and clubmosses) (Fig. 2c).
Whereas the LAI is low in grasslands and crop lands, as the leaf stratified
structure is thinner and simpler (Fig. 2b). The LAI is zero on bare soil, farm
land prior to crop emergence and urban surfaces (Fig. 2a).
LAI, indicating effectiveness of solar
radiation interception, is used as the principal variable for estimation of
photosynthetic primary productivity (e.g., Nemani et al. 2003). Under a
condition with a constant supply of water, transpiration is positively
correlated with LAI (e.g., Running and Coughlan 1988, Santiago 2000), as the
process of photosynthesis synchronizes with transpiration. Massive
transpiration from the ancient temperate forests of high LAI under wetter
climates played a crucial role in natural water cycle that evaporated water
from the oceans, seas, lakes and rivers returns on land as sufficient
precipitation.
 |
| Fig. 2 Land cover
influences rain-cloud formation mainly via two factors: humidity from land and
temperature of the moisture. Highly stratified canopy foliage of ancient
temperate forest (having high LAI) effectively shields solar radiation, which
in turn keeps soil and soil moisture cool. Deep root systems of the dense
forests uptake cool moisture from the soil and extract cold groundwater,
accordingly cool moisture releases to the atmosphere via transpiration (c). In
cropland and pasture areas (b), foliage of thinner and simpler leaf stratified
structure shields solar radiation partly; consequently, rest of solar radiation
warms soil and soil moisture. Shallow root systems of the low LAI vegetation
uptake the warm moisture, consequently warm moisture releases to the atmosphere
via transpiration. Absorbed solar radiation by the land surface is portioned to
sensible heat flux, longwave radiation (long wave flux or the storage), and warm evaporation (latent
heat). (a): The
incoming solar radiation is absorbed by dry urban surface covered by
impenetrable materials such as asphalt and concrete. The absorbed solar
radiation energy is almost exclusively transferred to heat (sensible heat flux
and longwave radiation), eliminating evapotranspiration. |
3.6. Historical unforeseen disruption in regional hydrological cycle due to vegetation loss
Historically, populations have preferred
to live within the near coastal-zone, near major rivers (Small and Nicholls
2003) and near lakes. By the human activity for agriculture or settlement,
original forests within the near coastal-zone and near major rivers/lakes have been
cleared during the human evolution.
Loss of forests in large area probably
caused unforeseen changes in regional hydrological cycle. Loss of forests at
waterfront causes to cease of the primary pathway of condensation. In the
inland areas from the waterfronts to mountain slopes, loss or fragmented supply
of cool moisture via transpiration hampers the conveyance
of rain-cloud
source by atmosphere. These factors lead to local decreases in precipitation (rainfall) due to loss or
fragmented vegetation/atmosphere interaction in rain-cloud formation. Subsequent disruption
of natural water cycle induced the vast tracts of forest degradation even in
remote mountainous areas from the coastal zones, as forests of high LAI are
unable to survive without a sufficient and constant supply of available water.
The large-scale forest degradation adversely affected regional hydrological
cycle, which in turn may have magnified drying.
4.
How the integrity of regional hydrological cycle may have been lost
4.1. Massive cool transpiration from high LAI
vegetation returns via rainfall
Land cover, the large-scale character of
the vegetation covering the landscape, contributes regional hydrological
functioning. Canopy foliage of forest of high LAI effectively shields solar
radiation (e.g., Yoshimura et al. 2010), which in turn keeps soil and soil
moisture cool underneath the canopy foliage (e.g., Jones et al. 2003). Deep
root systems of the dense forests uptake cool water from the soil and extract
cold groundwater (Fig. 2c). Tall trees transport the water of low temperature
from the root systems to leaves; subsequently transported water returns as cool
moisture to the atmosphere from stomata of leaves via transpiration. Active
condensation occurs between the massive cool transpiration from forest
and the developing
cloud (moisture condensed at waterfront). During the conveyance by atmosphere,
the developing cloud continues to grow, as small water droplets accumulates by
active condensation between cool transpiration and the moving warm air mass
from the waterfronts. Subsequently, massive cool transpiration from high LAI
forests backs into the regional hydrological cycle via the
vegetation/atmosphere interaction and returns as rainfall.
4.2. Less active interaction of warm
transpiration/evaporation from cropland and pasture in rain-cloud formation
Warm transpiration/evaporation from agricultural
land. In cropland and
pasture areas, foliage of thinner and simpler leaf stratified structure with
short vegetation heights (having low values of LAI)
shields solar radiation partly (Fig. 2 b). Rest of solar radiation warms soil
and soil moisture, and the part of absorbed solar radiation energy is
partitioned to evaporate from land surface. Crops uptake the warm water from
the soil by shallow root systems and transport the water to leaves,
subsequently release the warm moisture to the atmosphere from stomata of leaves
via transpiration. Crops, having low values of LAI, release less amount of
transpiration than from the high LAI vegetation. Likewise, pasture releases
less amounts of the fluxes of warm moisture through transpiration.
Amount of the warm moisture through evaporation in agricultural land may be
rather huge, mainly via two factors: increase in bare soils resulting from widespread
use of herbicides (weed-killers) and current trend in increase in temperature.
Use of herbicides in agriculture contributes remarkable gains in agricultural
production from the time when the first modern herbicide, 2,4-D was
commercially released in 1946. However, negative effect of herbicide use to
hydrological cycle through the alteration of surface energy balance by
vegetation removal may not be negligible. Current practice of widespread use of
herbicides over large areas increases the area of bare soil of zero LAI. On the
bare soil, a part of the incoming solar radiation reflects back, and the rest
of solar radiation is absorbed and partitioned to sensible heat flux, longwave
radiation (long wave flux or the storage), and warm evaporation (latent heat). Warm evaporation from
bare soil may be rather outstanding, as large bare areas act as deserts. In
addition, current trend of increased temperature accelerates evaporation from
the bare soil.
In croplands and pastures, these fluxes of warm moisture through
transpiration/evaporation may interact less active in producing condensation
with the developing clouds. Warm evaporation/transpiration released from
cropland and pasture areas is not sufficient in keeping sequential pathway of
the moisture conveyance by atmosphere in rain-cloud formation.
Historical expansion of agricultural land. Forest clearance
for grain agriculture occurred more than 10,000 years ago in the historical
region of Fertile Crescent in the Tigris-Euphrates river basin, often referred
to as the ‘cradle of
civilization,’ (in present-day
Iraq, Jordan, Lebanon, Syria and Iran) (Ruddiman 2003). In China, agriculture
appeared in the forested regions by 9,400 years ago. In western India, grain
agriculture similar to the Fertile Crescent appeared by 8,500 years ago
(Ruddiman 2003).
In 1700, the Indo-Gangetic Plain and China
already have extensive croplands owing to a long history of agricultural
practice. Over the next three hundred years, from 1700 to 1992, croplands
expanded and intensified into areas of forests /woodlands (Ramankutty and
Foley 1999).
The large geographical areas of
non-negligible forest clearance for grain agriculture may have affected
regional hydrological cycle through changes in temperature and
amount of moisture fluxes via transpiration/evaporation. Warm moistures from
croplands are not sufficient in keeping the continuous rain-cloud formation
pathways. Consequently, land-cover changes in turn resulted in disruptions of
the natural water cycle.
Human–induced land cover changes, forest
clearance for grain agriculture, may have changed the natural water cycle as
early as the middle Holocene, ca., 5000 years ago. In southern Arabian Peninsula (present day Yemen), unique
irrigation agriculture system (date-palm gardens and cereal cultivation)
adapted to scarce water resource conditions has been seen in
many archaeological sites of 5,000 years ago (e.g., Lezine et al. 2010). The widespread use of irrigation agriculture adapted to arid or semi-arid
conditions suggests that the regional hydrological cycle had already been disrupted
around 5,000 years ago.
4.3. Warm or hot evaporation from land may not
return as rainfall
Two factors, humidity from land and the
temperature (cooler than the dew-point of the moisture of the developing cloud),
are necessary in order for condensation to occur in the vegetation/atmosphere
interaction. On the soil surface of zero LAI (on bare soil, or farm land prior
to crop emergence), solar radiation warms soil (e.g., Jones et al. 2003) and
soil moisture, which causes evaporating water from land surface. The moisture
via evaporation may be not cooler than the dew-point of the moisture of the
developing cloud. Therefore, condensation does not occur between the warm water
vapour via evaporation and the warm air mass containing moisture.
Drylands in arid or hyper-arid zones are
characterized by lack of precipitation coupled with high evaporation rate
(e.g., Sharaf and Hussein 1996; Edmunds 2009). These characteristics suggest
that warm or hot water vapour via evaporation from land does not return
to the regional
hydrological cycle and therefore does not return as rainfall. Neither condensation nor
coalescence occurs between two fluxes of evaporation: warm or hot fluxes of
evaporation from land and fluxes of evaporation from the water bodies.
4.4. Fragmented
pathway of rain-cloud formation due to expansion of impervious
surface area of zero LAI
4.4.1. Collapse
of pathway due to large geographic area of urbanization
Expansion of impervious surface area of zero
LAI. Vitousek (1997)
remarks that growing land transformation is a significant element that
contributes to local and regional climate change. Currently, land
transformation by anthropogenic land-use activities is becoming a force of
global importance on human food production and climate change (Foley et
al. 2005).
Globally, urbanization is the primary process of
land transformation (Seto and Ramankutty 2016). Urban land expansion—creating
human-dominated form of land use for housing and activities of urban
populations—has increased
impervious areas: paved road, parking lots, and buildings. The dry urban
surfaces covered by impenetrable materials such as asphalt and concrete
directly influence surface energy balance (Oke 1982). The incoming solar
radiation is absorbed by the dry impervious surface that rainwater does not infiltrate
into it. This solar radiation
energy is almost exclusively transferred to heat: sensible heat flux and
longwave radiation flux (storage), eliminating evapotranspiration (latent heat
flux). The excessive heat greatly alters urban airflow by heat convection and
forms a dry and hot air
layer over the entire city caused by complex air movement of upward sensible
heat flux and downward heat flux (Oke 1982).
Neither condensation nor coalescence
occurs over the large areas of hot dry urban surfaces, due to the lack of two necessary
factors: humidity from land and the cooler temperature. Thus, pathways of the
development of cumulonimbus convective rainfall are collapsed due to urban land
expansion.
4.4.2. Fragmented
pathway due to land transformation in agricultural areas
Increasing impervious area in agricultural land. The expansion of
infrastructure and agricultural need to support an ever-growing population has
quickened the pace of land transformation of agricultural land in recent
decades (Hooke et al. 2012). Conversion of land for infrastructural purposes
(e.g., rural housing and businesses, highways and roads in rural
areas) has increased impervious areas. The dry surfaces covered by impenetrable
materials such as asphalt and concrete directly influence surface energy balance.
The incoming solar radiation is absorbed by the dry impervious surfaces and the
solar radiation energy is exclusively transferred to heat: sensible heat flux
and the long wave radiation flux (storage), which in turn has resulted in
unforeseen fragmentation of pathways of rain-cloud formation.
In addition, construction of engineering
works such as lining canals for improvement of irrigation efficiency has
increased dry surfaced networks covered by impenetrable materials such as
asphalt and concrete. The dry surfaced networks also directly influence surface
energy balance, causing of fragmented pathways of rain-cloud formation.
4.5. Deterioration of biological process of
terrestrial vegetation
4.5.1. Critically
important role of ocean waterfront in rain-cloud formation
Globally, evaporation from the oceans
constitutes 86% of evaporated water from the Earth (Shiklomanov 1993).
Biological process of the coastal vegetation (in particular high LAI) plays a
critical role as the primary pathway in which evaporated water from
the oceans return to the regional hydrological cycle (Fig. 3).
Disrupted functioning of the primary pathway of
marine shorelines. There is a long history of estuarine and coastal ecosystems disruption by human activities such as
habitat transformation, land reclamation, coastal development (Lotze et al.
2006; Barbier et al. 2011). To reduce storm surges or mitigate erosion, humans
fortify marine shorelines with coastal defense structures such as jetties and
sea walls. In Europe alone, 22,000 km2 of the coastline is
artificially covered with concrete and asphalt. The greatest urban development
occurs in the Euro-Mediterranean coasts and about two thirds of the coastline
is urbanized (Airoldi and Beck 2007).
Although returning fresh water from ocean
to land is vital to our water and food security, the functioning of estuarine
and coastal ecosystems as the primary pathway of rain-cloud formation is
severely degraded.
 |
Fig. 3 Globally,
evaporation from the oceans constitutes 86% of evaporated water from the Earth
(Shiklomanov 1993). Strategic placement of high LAI vegetation in estuarine and
coastal zone is essential in functioning as the primary pathway for
evaporated water from oceans returning back to land as rainfall.
|
4.5.2. Fragmented
pathway due to human impacts on terrestrial vegetation
Lost forests and lost functioning of rain-cloud
formation. Biological processes on land, photosynthesis and transpiration, have a
direct effect on rain-cloud formation. (Gross) primary productivity, the amount
of photosynthetically fixed carbon, increases depending on LAI (e.g., Odum
1971). High LAI terrestrial ecosystems having the highly stratified structure
of canopy foliage (Fig. 2c) have highest quantity of the biological process on
land.
During the Tertiary Period of the
Cenozoic Era prior to human evolution, a mostly continuously distributed temperate forest
covered the temperate zone of the Northern Hemisphere (e.g., Xiang et al.
1998). The ancient temperate forests (having high LAI, Fig. 2c) functioned
as a complete
(unbroken) pathway for the rain-cloud formation.
In many temperate regions, ancient
temperate forests became degraded and were then lost by human activities for
agriculture or settlement. For example, extensive forests once existed in the
Middle East and North Africa are now almost entirely deforested. Consequent
reduction or loss of the biological process on land leads to highly fragmented
pathway of rain-cloud formation.
Ignored functionality of fresh water on land
surface for terrestrial vegetation. In terms of the global hydrological
cycle, the overall quantity of fresh water is only about 2.5% and two-thirds of
this fresh water is locked in glaciers and ice caps (Shiklomanov and Rodda
2003). Approximately 0.3% of the Earth’s fresh water is held in rivers, lakes and reservoirs (Shiklomanov and Rodda 2003; Pimentel et al. 2004).
Water existing on the land surface is “source of life,” as the renewability
of water resources is controlled by active biological process of terrestrial
vegetation. The flow of rivers and streams is the bloodstream of the biosphere,
as the flowing freshwater supports the biological process of terrestrial
vegetation.
However, the water supplying functioning
for terrestrial vegetation is greatly ignored in current practice. To control
rivers/streams for irrigation, hydropower, and flood mitigation, humans have
modified the flows by constructing engineering works (Vörösmarty and Sahagian
2000, Nilsson et al. 2005). In addition, the adjoining riparian zones have been
transformed by wetland reclamation and dredging, and then almost lost (Jansson
et al. 2007). Subsequently, disrupted biosphere dynamics caused by
current water management
undermine the natural cycle of water.
5.
Shaping lush landscapes for stabilization of
water supply
5.1.
Terrestrial renewable fresh water supply:
precipitation on land
Dynamic water resources depending upon
biological process of terrestrial vegetation. Precipitation on
land is the main source of fresh water for all human use and for terrestrial
ecosystems. The terrestrial
renewable fresh water supply equals precipitation on land (Postel et al 1996), significant portion of which is
a dynamic resource controlled by biological process of terrestrial vegetation.
Therefore, stabilization of water supply requires governance of land and water
to shape unbroken pathway of active and massive biological process for
rain-cloud formation.
5.2. Architecture of unbroken pathway of the
rain-cloud formation
5.2.1. Importance
of the first step of rain-cloud formation
Active and massive
biological process of terrestrial vegetation in estuarine and coastal zone is
vital as the primary pathway of rain-cloud formation (Fig. 3). Similarly,
active and massive biological process of vegetation in riparian zones (of
rivers, streams, lakes and wetlands) is essential as the primary pathway of
rain-cloud formation in inland areas. The river restoration (e.g., Bernhardt et
al. 2005) taking into account the strategic viewpoint of shaping unbroken
pathway of the rain-cloud formation can lead to restoration of the natural
water cycle.
5.2.2. Active
pathway of the rain-cloud formation in agricultural area
To fulfil the
required demand for sufficient precipitation for irrigated agriculture and
domestic needs, governance of land and water is one of the oldest activities
practiced in Eastern philosophy (http://harukanoor4.blogspot.jp/2016/).
Acknowledged that the terrestrial renewable fresh water supply is maintained by
massive transpiration released from terrestrial vegetation, lush landscapes
were shaped in agricultural areas (Fig. 1).
While the Ramsar Convention
(www.ramsar.org) is an inter-governmental conservation treaty primarily for the
importance of wetlands as a habitat for migratory birds, human-made wetlands
(irrigation channels, canals, creeks, ponds, and ditches) have utilized for
provision of a low-cost, self-sufficient method of natural irrigation for the
terrestrial vegetation. Sometimes, meandering
irrigation channels were designed to make the residence time of water on land longer. In
turn, this infiltration from
the flows provides vegetation-available soil moisture effectively and for
longer time (Fig. 1).
Reedbeds, which naturally occur in
transition zone between land and water, play a valuable role in connecting the
massive transpiration from the sacred groves and riparian forests. The dense
tree foliage shields solar radiation and keeps the water of canals/creeks cool
underneath the canopy. The root systems of reeds uptake the water from the
steady flow of cool water, accordingly cool moisture releases to the atmosphere
via transpiration.
Since ancient times, Japanese highly
praised the functionality of reedbeds, so Japan has been poetically described
as 豊葦原瑞穂国 (Land of eternal
rich harvest of grain along with lush green reedbeds). This poetical
description is seen in Kojiki (古事記, “An Account of
Ancient Matters,” dating from the early 8th century, A.D. 711–712), the oldest extant chronicle in
Japan. The effectiveness of the strategy of shaping the unbroken pathway of
rain-cloud formation has been tested and proofed over a millennium in Japan.
5.2.3. Spatial
design to mitigate the negative effect of impervious area
Increased impervious
areas undermine integrity of the rain-cloud formation due to the change of
surface energy balance. Appropriate spatial design of landscape can mitigate
the negative effect of surface energy balance change (Fig. 4a, b).
Strategic placement of shade trees
associated with human-made wetlands can maintain the
connectivity of the flow of rain-cloud formation pathway. Trees with huge
canopies shield solar radiation, which in turn keeps impervious areas cool
underneath the canopy foliage. Deep root systems of the trees uptake cool water
and releases cool moisture to the atmosphere via transpiration.
High
LAI vegetation can provide the functional effectiveness of keeping the
connectivity of the flow of rain-cloud formation pathway by massive
transpiration. Over geological time, high LAI vegetation such as mature temperate
forests have evolved to maximize the biological process (photosynthesis and
transpiration) forming tall spreading canopies and highly stratified foliage
structure composed of biodiversity (Fig. 2b). In current practice, land use has
caused declines in biodiversity through the loss, modification and
fragmentation of habitats (Pimm and Raven 2000).
As high LAI vegetation requires a
sufficient and constant supply of available water for the active biological
process, appropriate placement of human-made wetlands (e.g., Fig. 4a: ditches
along roads; Fig. 4b: pond/canal) that support the biological process with
sufficient supply of water is essential,
To keep connectivity of the flow of rain-cloud
formation pathway, site-specific spatial design appropriate for biogeographic
history, topographical features and cultures is vital.
 |
| Fig. 4a Land transformation
influences precipitation and the ongoing rapid land conversion can disrupt the
water cycle (Pielke et al. 2007). Strategic placement of shading by tree
canopies over the impervious surfaces associated with human-made wetlands
(e.g., ditches along a road in Fig. 4a; pond/canal in Fig. 4b) that provide
natural irrigation can maintain the connectivity of the flow of rain-cloud
formation pathway. |
 |
| Fig. 4b The terrestrial
renewable fresh water supply equals precipitation on land (Postel et al 1996).
Stabilization of water supply requires the strategy of shaping unbroken pathway
of rain-cloud formation of high LAI vegetation having high photosynthetic
primary productivity composed of biodiversity. |
6.
Governance of land and water for sufficient
precipitation on land
Land transformation influences
precipitation and the ongoing rapid land conversion can disrupt the water cycle
(Pielke et al. 2007). Through the loss, degradation and fragmentation of the pathway
of rain-cloud formation, precipitation on land has changed in its pattern: disruption
of vegetation/atmosphere interaction and consequent disappearance of the summer
convective storms that occur frequently and regularly,
drought, and occasional torrential rain (heavy snow) due to frontal storm that
occur infrequently and irregularly. We humanity face an unprecedented challenge
to produce enough food under the condition that the unstable terrestrial
renewable fresh water supply (precipitation on land) is a major constraint.
This challenge requires a global shift to governance of
land and water to shape unbroken pathway of rain-cloud formation: connectivity
of high photosynthetic primary productivity of terrestrial biomes. As
connectivity of high photosynthetic primary productivity of land vegetation
is essential in the renewability of water resources via vegetation/atmosphere
interaction.
Currently croplands and pastures occupy
approximately 40% of the Earth’s terrestrial
surface (Foley et al. 2005, 2011; Rumankutty et al. 2008). Globally, about 70%
of the freshwater withdrawals is used for agriculture. Acknowledged that the
terrestrial renewable fresh water supply originates precipitation on land, restoration
of the integrity of regional hydrological cycle and the ecological systems in agricultural
lands is urgently required.
To replenish fossil aquifers, governance
of land and water is also required, as groundwater is a dynamic part of the
hydrological cycle closely linked to water landscapes above and regional
climate.
There is an urgent need for
decision-making and policy action to explicitly take into account the role and
functionality of biological process of terrestrial vegetation to sustain our
civilization with water and food security.
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