Agriculture Reference
In-Depth Information
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Demand for food is rising, driven by population growth. Without improve-
ments in productivity, ever-increasing amounts of water will be needed to
grow food.
Demand is growing particularly fast for “water-intensive” products such as
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fresh fruits and vegetables. This demand growth, driven by rising incomes,
will further increase water use in agriculture.
Competition is increasing between agricultural and nonagricultural uses of
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water (direct consumption, hydropower, industry, ecosystem services, and
the environment). Improvements in agricultural water productivity will be
needed to maintain desired levels of food production—more food from less
water.
River basins are “closing,” meaning that the demand for water has come to
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exceed its supply, and rivers at times no longer reach the sea. Examples of
closed basins may be found in Africa (Limpopo), South Asia (Indus), China
(Yellow), North America (Colorado), and Australia (Murray-Darling),
among others.
At the global level, food production from rain-fed and irrigated agriculture cur-
rently uses around 7,130 cubic kilometers of water each year. By the year 2050, this
is expected to increase to around 13,000 cubic kilometers. Annual freshwater with-
drawals from lakes, rivers, and groundwater are presently estimated at about 3,800
cubic kilometers, with around 70% used for agriculture (Comprehensive Assessment
2007). Where such water is scarce, pressures to reduce agricultural uses in favor of
other uses may become irresistible.
The global level, however, is not necessarily the best place to analyze water scar-
city. At the global level, there appears to be adequate water for agriculture, indus-
try, and domestic and other uses. Water scarcity is in fact highly concentrated. The
most severe problems are found in such regions as southeastern Australia, northern
and western China, central India, central and western Asia, North Africa, south-
ern Africa and the Sahelian zone of West Africa, northeast Brazil, and northern
Mexico and contiguous areas of the southwest of the United States (Comprehensive
Assessment 2007).
In terms of human needs, a “water-stress threshold” may be said to have been
reached when per capita water availability is less than 1700 cubic meters per year.
At present, around 700 million people live below this threshold, and by 2025 this
number may reach 3 billion. Even when water is not physically scarce, many people
may not have access to adequate water supplies. People may be excluded by their
poverty, their lack of legal rights to water, or simply by a lack of water collection
and distribution infrastructure. Some analysts have concluded that water scarcity is
in many instances an artifact of political processes and institutions that discriminate
against the poor (UNDP 2006).
Water scarcity is not the only water-related problem that threatens sustainable food
production. Floods are an extreme form of water insecurity. So are droughts, which
can occur even where annual rainfall is on average adequate to support agriculture.
As water becomes scarce, further problems emerge. Food production may suffer
as water is diverted from agricultural to nonagricultural uses. Irrigated lands may
