The Need for Sustainable Food Production Systems - Agroecology: The Ecology of Sustainable Food Systems - page 10

O VERUSE OF W ATER AND D AMAGE TO
H YDROLOGICAL S YSTEMS

this water either evaporates or drains out of fields. Some
wastage of water is inevitable, but a great deal of waste
could be eliminated if agricultural practices were oriented
toward conservation of water rather than maximization of
production. For example, crop plants could be watered
with drip irrigation systems, and production of water-
intensive crops such as rice could be shifted away from
regions with limited water supplies.
The increasing importance of meat in human diets
worldwide is another factor in agriculture's rising demand
for water, as is the trend toward concentrated grain feeding
of livestock. Animal factories use prodigious amounts of
water for cooling the animals and flushing their wastes,
and many animals drink large amounts of water. Hogs,
for example, can consume up to 8 gallons per animal per
day (Marks and Knuffke, 1998). And these are just the
direct uses of water for raising livestock. Factoring in the
water needed to grow the biomass fed to animals, animal-
derived food requires at least twice as much water to
produce as plant-derived food, and usually much more.

Fresh water is becoming increasingly scarce in many parts
of the world as industry, expanding cities, and agriculture
compete for limited supplies. Some countries have too
little water for any additional agricultural or industrial
development to occur. To meet demands for water in many
other places, water is being drawn from underground
aquifers much faster than it can be replenished by rainfall,
and rivers are being drained of their water to the detriment
of aquatic and riparian ecosystems and their dependent
wildlife. Many of the world's major rivers — including
the Colorado, Ganges, and Yellow — now run dry for part
of the year as a result.
Agriculture accounts for more than two thirds of glo-
bal water use. For every person on the planet, there are
more than 0.04 ha of irrigated land. Agriculture uses so
much water in part because it uses water wastefully. More
than half of the water applied to crops is never taken up
by the plants it is intended for (Van Tuijl, 1993). Instead,

FIGURE 1.6 The San Luis Dam in California. Built in part to hold irrigation water for farms on the west side of the San Joaquin
Valley, it is one of an estimated 800,000 dams in the world that trap life-giving silt, destroy riverine and riparian ecosystems, and
completely alter natural hydrological functioning.