Sorry for all the posts. I find this interesting and pertinent, even on
a small scale.
Lester R. Brown
In 1938, Walter Lowdermilk, a senior official in the Soil Conservation
Service of the U.S. Department of Agriculture, traveled abroad to look
at lands that had been cultivated for thousands of years, seeking to
learn how these older civilizations had coped with soil erosion. He
found that some had managed their land well, maintaining its fertility
over long stretches of history, and were thriving. Others had failed to
do so and left only remnants of their illustrious pasts.
In a section of his report entitled “The Hundred Dead Cities,” he
described a site in northern Syria, near Aleppo, where ancient
buildings were still standing in stark isolated relief, but they were
on bare rock. During the seventh century, the thriving region had been
invaded, initially by a Persian army and later by nomads out of the
Arabian Desert. In the process, soil and water conservation practices
used for centuries were abandoned. Lowdermilk noted, “Here erosion had
done its worst....if the soils had remained, even though the cities
were destroyed and the populations dispersed, the area might be
re-peopled again and the cities rebuilt, but now that the soils are
gone, all is gone.”
Now fast forward to a trip in 2002 by a United Nations team to assess
the food situation in Lesotho, a small country of 2 million people
imbedded within South Africa. Their finding was straightforward:
“Agriculture in Lesotho faces a catastrophic future; crop production is
declining and could cease altogether over large tracts of the country
if steps are not taken to reverse soil erosion, degradation, and the
decline in soil fertility.” Michael Grunwald reports in the Washington
Post that nearly half of the children under five in Lesotho are stunted
physically. “Many,” he says, “are too weak to walk to school.”
Whether the land is in northern Syria, Lesotho, or elsewhere, the
health of the people living on it cannot be separated from the health
of the land itself. A large share of the world’s 852 million hungry
people live on land with soils worn thin by erosion.
The thin layer of topsoil that covers the planet’s land surface is the
foundation of civilization. This soil, measured in inches over much of
the earth, was formed over long stretches of geological time as new
soil formation exceeded the natural rate of erosion. As soil
accumulated over the eons, it provided a medium in which plants could
grow. In turn, plants protect the soil from erosion. Human activity is
disrupting this relationship.
Sometime within the last century, soil erosion began to exceed new soil
formation in large areas. Perhaps a third or more of all cropland is
losing topsoil faster than new soil is forming, thereby reducing the
land’s inherent productivity. Today the foundation of civilization is
crumbling. The seeds of collapse of some early civilizations, such as
the Mayans, may have originated in soil erosion that undermined the
The accelerating soil erosion over the last century can be seen in the
dust bowls that form as vegetation is destroyed and wind erosion soars
out of control. Among those that stand out are the Dust Bowl in the
U.S. Great Plains during the 1930s, the dust bowls in the Soviet Virgin
Lands in the 1960s, the huge one that is forming today in northwest
China, and the one taking shape in the Sahelian region of Africa. Each
of these is associated with a familiar pattern of overgrazing,
deforestation, and agricultural expansion onto marginal land, followed
by retrenchment as the soil begins to disappear.
Twentieth-century population growth pushed agriculture onto highly
vulnerable land in many countries. The overplowing of the U.S. Great
Plains during the late nineteenth and early twentieth centuries, for
example, led to the 1930s Dust Bowl. This was a tragic era in U.S.
history, one that forced hundreds of thousands of farm families to
leave the Great Plains. Many migrated to California in search of a new
life, a move immortalized in John Steinbeck’s The Grapes of Wrath.
Three decades later, history repeated itself in the Soviet Union. The
Virgin Lands Project between 1954 and 1960 centered on plowing an area
of grassland for wheat that was larger than the wheatland in Canada and
Australia combined. Initially this resulted in an impressive expansion
in Soviet grain production, but the success was short-lived as a dust
bowl developed there as well.
Kazakhstan, at the center of this Virgin Lands Project, saw its
grainland area peak at just over 25 million hectares (44 millions
acres) around 1980, then shrink to 14 million hectares today. Even on
the remaining land, however, the average wheat yield is scarcely 1 ton
per hectare, a far cry from the nearly 8 tons per hectare that farmers
get in France, Western Europe’s leading wheat producer.
A similar situation exists in Mongolia, where over the last 20 years
half the wheatland has been abandoned and wheat yields have also fallen
by half, shrinking the harvest by three fourths. Mongolia—a country
almost three times the size of France with a population of 2.6
million—is now forced to import nearly 60 percent of its wheat.
Dust storms originating in the new dust bowls are now faithfully
recorded in satellite images. In early January 2005, the National
Aeronautics and Space Administration (NASA) released images of a vast
dust storm moving westward out of central Africa. This vast cloud of
tan-colored dust stretched over some 5,300 kilometers (roughly 3,300
miles). NASA noted that if the storm were relocated to the United
States, it would cover the country and extend into the oceans on both
Andrew Goudie, Professor of Geography at Oxford University, reports
that Saharan dust storms—once rare—are now commonplace. He estimates
they have increased 10-fold during the last half-century. Among the
countries in the region most affected by topsoil loss from wind erosion
are Niger, Chad, Mauritania, northern Nigeria, and Burkino Faso. In
Mauritania, in Africa’s far west, the number of dust storms jumped from
2 a year in the early 1960s to 80 a year today.
The Bodélé Depression in Chad is the source of an estimated 1.3 billion
tons of wind-borne soil a year, up 10-fold from 1947 when measurements
began. The 2 to 3 billion tons of fine soil particles that leave Africa
each year in dust storms are slowly draining the continent of its
fertility and, hence, its biological productivity. In addition, dust
storms leaving Africa travel westward across the Atlantic, depositing
so much dust in the Caribbean that they cloud the water and damage
coral reefs there.
In China, plowing excesses became common in several provinces as
agriculture pushed northward and westward into the pastoral zone
between 1987 and 1996. In Inner Mongolia (Nei Monggol), for example,
the cultivated area increased by 1.1 million hectares, or 22 percent,
during this period. Other provinces that expanded their cultivated area
by 3 percent or more during this nine-year span include Heilongjiang,
Hunan, Tibet (Xizang), Qinghai, and Xinjiang. Severe wind erosion of
soil on this newly plowed land made it clear that its only sustainable
use was controlled grazing. As a result, Chinese agriculture is now
engaged in a strategic withdrawal in these provinces, pulling back to
land that can sustain crop production.
Water erosion also takes a toll on soils. This can be seen in the
silting of reservoirs and in muddy, silt-laden rivers flowing into the
sea. Pakistan’s two large reservoirs, Mangla and Tarbela, which store
Indus River water for the country’s vast irrigation network, are losing
roughly 1 percent of their storage capacity each year as they fill with
silt from deforested watersheds.
Ethiopia, a mountainous country with highly erodible soils on steeply
sloping land, is losing an estimated 1 billion tons of topsoil a year,
washed away by rain. This is one reason Ethiopia always seems to be on
the verge of famine, never able to accumulate enough grain reserves to
provide a meaningful measure of food security.
Fortunately there are ways to conserve and rebuild soils. These will be
discussed in the next Earth Policy Institute Book Byte.