Sustainable Urban Living: Green Solar Energy for Food and Biofuels Production - Design with the Desert: Conservation and Sustainable Development - page 410

soils, and fertilizers are diminishing while the demands of urban dwellers for food,
energy, and transportation continue to expand. Additionally, the air, water, and soil pol-
lution caused by fossil resource consumption lowers the quality of life for people living in
both rural and urban areas.
Rural populations pushed out of farming have migrated to urban centers where they
became dependent on others for food. In 1800, only 3% of the world's population lived in
cities but over half live in cities today. In 1950, only 83 cities had populations exceeding
1 million but today 468 cities have populations of more than a million.* The U.N. fore-
casts that the current urban population of 3.2 billion will rise to nearly 5 billion by 2030,
when three out of five people will live in cities. 1 Rural to urban migration results not only
in fewer food producers but more energy consumption because urban dwellers consume
about four times as much energy as their rural relatives. 2
One of the main challenges facing urban designers will be to provide adequate quanti-
ties of nutritious and affordable food for urban inhabitants. People expect food to be read-
ily available and cheap, as it is today. Unless we change the ecological design of our food
supplies and conserve fossil resource inputs, some cities will perish due to insufficient
food and freshwater, while others will find their air and water too polluted for healthy liv-
ing. The following discussions about our freshwater fossil fuel supplies, soils, and climate
change emphasizes the need for a new model for our food production in the future.
24.2 Freshwater Limits
The West holds far too little freshwater to support food production for expanding popula-
tions even before global warming melted 50% of the snowpack and evaporated lakes and
reservoirs. † City faucets and fountains are going dry because farmers are putting far too
many straws in the ground and removing fossil water reserves. The aquifers on which food
production depends are being depleted rapidly and are likely to expire within a generation. 3
Water is the primary limitation to food production from crop plants. Without sufficient
freshwater delivered on time, crops fail and the land reverts to its natural state—which
in much of the West is prairie or desert—and human populations must migrate to more
productive areas.
Therefore, production and yield are directly related to water use. A decrease in applied
water stresses crops and decreases yield. More irrigation has doubled food production
over the last 30 years but at the unsustainable expense of tripling the freshwater con-
sumed. ‡ About 80% of all freshwater use in the West goes to irrigation and much of that
water is lost to evaporation and plant transpiration. Much of the 300% increase in water
consumption occurred because new croplands were expanded into deserts. Irrigation cre-
ates higher yields but consumes more water, especially in hot sunny regions with high
evaporation rates. Irrigation often loses 50% of the applied water before it reaches the crops
from leaks and evaporation. 3 Over half of the irrigation water comes from groundwater
aquifers which are being depleted at 3-300 times nature's replacement rates. §
* http://www.citypopulation.de/world/Agglomerations.html (accessed August 10, 2011).
† http://www.wcc.nrcs.usda.gov/cgibin/westsnow.pl (accessed August 10, 2011).
‡ http://www.fao.org/nr/water/topics.html (accessed August 10, 2011).
§ http://www.fao.org/nr/water/news/clim-change.html (accessed August 10, 2011).