Adverse effects of climate change on soil quality may be due to depletion of soil
organic carbon (SOC) pool, decline in plant available water capacity (AWC),
reduction in soil fertility and use efficiency of nutrients, decline in structure with
attendant adverse impacts on vulnerability to degradation including crusting,
compaction, accelerated erosion, and salinization. Climate change may also
adversely affect water resources through alterations in the hydrologic balance, and
high soil erosion may exacerbate nonpoint source pollution (Lal 2013a).
On the other hand, global warming has been speculated to increase yields due to
the ‘‘fertilizer effect’’ of rising atmospheric carbon, but the impacts are likely to be
net negative for poor countries. For example, global warming will reduce food
production in countries closer to the equator (Droogers and Aerts 2005).
It is believed that climate change will increase water scarcity in the coming
decades. With temperature increasing and precipitation fluctuating, water availability and crop production will decrease in the future. If the irrigated areas are
expanded, the total crop yield will increase; however, food and environmental
quality may degrade. And even if new supplies are added to existing ones, water
might not be sufficient for increased food demand (Kang et al. 2009; Hanjra and
Qureshi 2010).
1.10.2 Diminish in Water Availability
All organisms, including humans, require water for their survival. Although there
is a lot of water on Earth, only a small amount of water is easily accessible (Oki
and Kanae 2006). The Water Atlas reports a volume of 1,386 million Gm
3 of
water on Earth, which consists of 97.5 % saline water and 2.5 % freshwater, most
of which is stored as glaciers or deep groundwater. Out of 35 million Gm
3 of
freshwater on Earth, approximately 30.5 % is available for human use. This
amounts to 10.5 million Gm
3 water as groundwater and 0.13 million Gm
3 in
lakes, soil, wetlands, etc. (Clarke and King 2004). The availability of freshwater
for human use was mapped by the International Water Management Institute
(IWMI). Irregularities in precipitation spatial distribution divide the globe into
water-scarce and water abundant regions. The abundant water locations around the
globe with less than 25 % water withdrawals were grouped by IWMI as regions of
little or no water scarcity. If more than two-thirds of the available water was
withdrawn in a location, this was accounted as physical water scarcity (IWMI
2008). The locations with more than 60 % withdrawals were labeled as
approaching physical water scarcity.
Global demand for water has tripled since the 1950s, but the supply of freshwater has been declining. Half a billion people live in water-stressed or waterscarce countries, and by 2025 that number will grow to 3 billion due to an increase
in population (Hanjra and Qureshi 2010).
Water availability will be one of the limiting constraints for crop production
and food security. It is known that water resources play a vital role in human
22
L. Garcia-Mier et al.
organic carbon (SOC) pool, decline in plant available water capacity (AWC),
reduction in soil fertility and use efficiency of nutrients, decline in structure with
attendant adverse impacts on vulnerability to degradation including crusting,
compaction, accelerated erosion, and salinization. Climate change may also
adversely affect water resources through alterations in the hydrologic balance, and
high soil erosion may exacerbate nonpoint source pollution (Lal 2013a).
On the other hand, global warming has been speculated to increase yields due to
the ‘‘fertilizer effect’’ of rising atmospheric carbon, but the impacts are likely to be
net negative for poor countries. For example, global warming will reduce food
production in countries closer to the equator (Droogers and Aerts 2005).
It is believed that climate change will increase water scarcity in the coming
decades. With temperature increasing and precipitation fluctuating, water availability and crop production will decrease in the future. If the irrigated areas are
expanded, the total crop yield will increase; however, food and environmental
quality may degrade. And even if new supplies are added to existing ones, water
might not be sufficient for increased food demand (Kang et al. 2009; Hanjra and
Qureshi 2010).
1.10.2 Diminish in Water Availability
All organisms, including humans, require water for their survival. Although there
is a lot of water on Earth, only a small amount of water is easily accessible (Oki
and Kanae 2006). The Water Atlas reports a volume of 1,386 million Gm
3 of
water on Earth, which consists of 97.5 % saline water and 2.5 % freshwater, most
of which is stored as glaciers or deep groundwater. Out of 35 million Gm
3 of
freshwater on Earth, approximately 30.5 % is available for human use. This
amounts to 10.5 million Gm
3 water as groundwater and 0.13 million Gm
3 in
lakes, soil, wetlands, etc. (Clarke and King 2004). The availability of freshwater
for human use was mapped by the International Water Management Institute
(IWMI). Irregularities in precipitation spatial distribution divide the globe into
water-scarce and water abundant regions. The abundant water locations around the
globe with less than 25 % water withdrawals were grouped by IWMI as regions of
little or no water scarcity. If more than two-thirds of the available water was
withdrawn in a location, this was accounted as physical water scarcity (IWMI
2008). The locations with more than 60 % withdrawals were labeled as
approaching physical water scarcity.
Global demand for water has tripled since the 1950s, but the supply of freshwater has been declining. Half a billion people live in water-stressed or waterscarce countries, and by 2025 that number will grow to 3 billion due to an increase
in population (Hanjra and Qureshi 2010).
Water availability will be one of the limiting constraints for crop production
and food security. It is known that water resources play a vital role in human
22
L. Garcia-Mier et al.