was commonly known as the “Great American Desert.” With time, settlement
accrued in this grassland realm. Three technological innovations played a key role:
the invention of the steel plow, the invention of barbwire fence, and the building of
railroads. As these innovations became widespread the vast grasslands were subdi-
vided by farms and ranches and the crops and cattle could be shipped by rail to dis-
tant markets.
The Great Plains of the United States has a cautionary history that is mirrored in
other places around the world. Grasslands are the climatic result of repeated mois-
ture stress punctuated by relatively wet times. Grasslands usually exist between
the deserts and the forests; people are tempted to use them as if they had depend-
able precipitation like the forests. As the Great Plains were fully settled, much
grass cover was removed to grow dryland (unirrigated) crops like winter wheat.
World War I saw rapid expansion of wheat agriculture as crop prices soared. Ironi-
cally, when wheat prices collapsed after the war, farmers opened up even more
grassland to make enough money to pay mortgages. When the droughts of the
1930s arrived with the driest series of years in a century and a half in some places,
the soil became so dry that much of it blew away, creating the Dust Bowl. The
Dust Bowl’s droughts had a natural cause, but the social effects were staggering,
depopulating entire areas by half or more. The ecological effects were also devas-
tating, ruining grassland areas for centuries to come.Green Belt
Green belts arebuffer zonesof undeveloped land that are found around urban
areas. Sometimes these zones form true belts that completely surround the urban
region; in other cases the green areas are not contiguous but are separated into sec-
tions, often dividing the city proper from suburbs and satellite towns. The concept
of preserving a natural space around urban development first appeared as a compo-
nent of urban planning in the United Kingdom, just before World War II, as a
response to urban sprawl and the decline of farmland and natural areas around the
larger cities. Legislation passed after the war enabled city planners to incorporate
the concept of undeveloped spaces into the larger urban structure, and green belts
became a common feature of many towns and cities in England. The establishment
of green belts and other “green spaces” in urban areas in the developed world has
become a mainstay in the idea ofsustainable development. Today it is estimated
that about 13 percent of the total area of England is protected in the form of green
belts, and some of these are quite large. The green belt that surrounds the greater
London metropolitan area, for example, is more than 5,000 sq km in area—one of162 Green Belt