Geography Reference
In-Depth Information
The other famous American desert that is not part of the Great Basin is Arizona's
Painted Desert
, a
brightly colored region of mesas and plateaus. Here, centuries of erosion have exposed red, brown, and
purple rock surfaces that give the area its name.
The world's deserts are spreading, extending over more and more land. When the desert encroaches
because of human activity, the process is called
desertification.
People have been creating deserts since the
beginning of settled agriculture, ten thousand years ago. The once-fertile crescent lying between the Tigris
and the Euphrates Rivers is now mostly desert. Yet it once supported tens of thousands of people and nur-
tured some of the world's first true cities. Centuries of overuse, combined with poor irrigation techniques,
sterilized the land and was one of the main causes of the collapse of some of these early civilizations.
The human factors in desertification are simply human attempts at survival. Marginal lands are cleared
and plowed in often futile attempts to plant crops, and trees are removed. Trees and woody plants are also
slashed for fuel, adding to the problems of deforestation. The trees might block the wind that carries away
topsoil. Faulty irrigation sterilizes the earth by introducing salts and alkalis into already depleted soils.
Goats, sheep, cattle, and camels are allowed to overgraze, removing (and flattening) vegetation that would
help keep soil in place.
By some estimates, the expense of rehabilitating the degraded lands, and of halting the spread of
deserts, need be no more than $2.5 billion a year. That is a fraction of the cost of lost agricultural lands
and their yields. But funds provided for these areas are increasingly used for emergency measures. Ironic-
ally, the remedies are not overly exotic, rather as simple as planting trees or preventing overcutting. It has
already worked. Deserts are being turned back.
In northern China, a green wall of trees has been planted to hold off the advancing desert and to stabilize
badly eroded uplands. In Rajasthan, India, imported acacia trees from the Middle East were used to stabil-
ize sixty thousand acres of sand dunes. In Haiti, 35 million trees have been planted. And in parts of West
Africa, selected trees have been used to revitalize exhausted cropland and pasture. The trees have leaves
during the dry season, giving shade when it is most needed. They also act as a windscreen and transfer
nitrogen from the air into the soil, increasing crop yields. The trees' pods and seeds provide protein-rich
fodder for cattle and goats. In Kenya, the Green Belt Movement, started in the 1970s, has created hundreds
of tree nurseries. Farmers—mostly women—have planted more than seven million trees around croplands
to reduce wind erosion. In Niger, where wind is the chief cause of soil erosion, another project has planted
rows of trees, creating a windbreak now over two hundred miles long. There are even simpler methods. In
poor Burkina Faso, in northwestern Africa, farmers use an ancient technique. Lines of stones are placed in
the fields, trapping soil that would otherwise have been washed away, and acting as dams to hold rainwa-
ter. Crop yields there have been raised by 50 percent.
Where Was the Dust Bowl?
Americans savor their football with the same passion that the people of most other nations reserve for
their football, or soccer, as it's called in the United States. They watch the Super Bowl, the Rose Bowl,
the Orange Bowl, the Cotton Bowl, and the Peach, Liberty, Hula, and Blockbuster bowls. They remember
the winners and losers, the tackles and fumbles, and who scored the winning touchdowns. But far fewer
Americans recall the Dust Bowl. It wasn't a game and nobody won.
For those who think desertification is an exotic thing that only happens someplace else, there is a stark
lesson in the experience of the American Great Plains region in the 1930s, the period of the Great Depres-
