SOILS ERODING
Chapter 3. Signs of Stress: The Biological Base
Lester R. Brown, Eco-Economy: Building an Economy for the Earth
(W.W. Norton & Co., NY: 2001).
After the earth was created, soil formed
slowly over time from the weathering of rocks. It was this soil
that supported early plant life on land. As plant life spread, the
plants protected the soil from wind and water erosion, permitting
it to accumulate and to support even more plant life. This symbiotic
relationship facilitated an accumulation of topsoil until it could
support a rich diversity not only of plants, but also of the animal
life that depends on plants.
The thin mantle of topsoil, measured in inches over most of the
earth, is the foundation of civilization. When earlier civilizations
lost their productive topsoil from mismanagement and erosion, they
crumbled as their food supply shrank. With an estimated 36 percent
of the world's cropland now losing topsoil at a rate that is undermining
its productivity, our food security is also at risk if this trend
continues.50
As pressures to expand food production have climbed, farmers have
been forced into marginal areas, plowing land that is too dry or
too steeply sloping to sustain cultivation. At some point probably
within the last century, the long-term accumulation of topsoil was
reversed as erosion losses surpassed new soil formation, leading
to a gradual depletion of this basic natural capital.
The United States, the world's breadbasket, has undergone two periods
of extensive overplowing, each of which led to heavy losses of topsoil.
The first occurred in the early 1930s when a severe multiyear drought
led to extensive wind erosion in the southern Great Plains. The
resulting environmental devastation not only gave the era its name,
the Dust Bowl, but it triggered one of the largest internal migrations
in U.S. history as droves of people left the southern Great Plains
and headed west for California.51
After new agricultural practices were adopted in response to the
Dust Bowl, such as planting windbreaks and strip-cropping land,
with alternate-year fallowing, the soil was stabilized. But as demand
for food began to climb rapidly after mid-century, and as grain
prices reached record highs during the 1970s, farmers again began
plowing from "fencerow to fencerow"planting
everything in sight. By 1982, the United States was losing annually
an estimated total of 3.08 billion tons of topsoil from its cropland.52
In contrast to the Dust Bowl, when wind erosion in the Great Plains
was the problem, this time it was mostly water erosion in the Corn
Belt. In states such as Iowa, with its rolling farmland, farmers
were losing almost 20 tons of topsoil per hectare each year from
water erosion. A dozen U.S. studies analyzing the effect of erosion
on land productivity found that losing an inch of topsoil reduced
corn and wheat yields an average of 6 percent. With nature needing
centuries to form an inch of topsoil, current losses are irreversible
if time horizons are measured on a human time-scale.53
One consequence of overplowing is that countries eventually have
to pull back and reduce the harvested area. Some have done this
through carefully designed programs to convert highly erodible cropland
back into grassland or forests. For example, the U.S. Conservation
Reserve Program (CRP) launched in 1985 was designed to simultaneously
control surplus production and conserve soil by retiring the most
erodible land. Initiated and supported by environmental groups,
the program encouraged farmers to take their highly erodible land
out of production by providing government payments under 10-year
contracts to plant the land in grass or trees.54
Within five years, U.S. farmers had converted nearly 15 million
hectares of cropland, roughly 10 percent of the national total,
to grassland. This reduced excessive soil erosion nationwide by
some 40 percent, helping to enhance food security for the entire
world. The nonmarket benefits from soil erosion reduction and the
provision of habitat by the CRP between 1985 and 2000 are estimated
to exceed $1.4 billion.55
The Soviet Union overexpanded its plowing with the Virgin Lands
Project between 1954 and 1960. In an effort to boost farm output
and become an agricultural superpower, the Soviets plowed up vast
areas of grassland in Central Asia, an effort centered in Kazakhstan.
During this period, the increase in wheat area in Kazakhstan was
equal to the entire wheat area of Canada and Australia combined.56
Unfortunately, not all of this land could sustain cultivation. Much
of the wheatland of Kazakhstan, a semiarid country, has eroded to
the point where it can no longer support cropping. After the grain
area reached 25 million hectares by 1960, it held there until 1984
or so, when it started shrinking as productivity fell and the less
productive land was abandoned. By 2001, it had dropped to 12 million
hectares. (See Figure 3-2.) Although this loss may have surprised
the political leaders in Moscow who engineered the expansion in
the 1950s, it did not surprise the soil scientists at the Institute
of Soil Management in Alma Alta, who pointed out in 1994 that grain
cultivation could be sustained on only half the area originally
plowed. Even those estimates may prove to be overly optimistic.57
Whether topsoil loss, declining yields, and the abandonment of cropland
in Kazakhstan can be arrested remains to be seen. Even the grainland
still being farmed yields less than 1 ton of wheat per hectarea
fraction of the 7 tons per hectare in France, the leading wheat
producer in Western Europe.58
If soil erosion proceeds too far, it can convert land to desert,
becoming wasteland. At an intermediate stage of degradation, it
can be returned to grassland, as in Kazakhstan, retaining some productive
value. If the intervention comes early enough in the decline cycle,
the land can be saved by managing it responsibly, as was the case
during the Dust Bowl period. Or the land can be systematically retired
and converted to grassland or woodland. Yet for many developing
countries, where populations have doubled or even tripled over the
last half-century, this is not always an option.
In the majority of developing countries, the growing demand for
food has forced agriculture onto marginal lands. In China, for instance,
a doubling of population since 1950 combined with record rises in
income since 1980 have nearly tripled the demand for grain.59
China's loss of cropland to the construction of factories, roads,
and expanding cities, particularly in the prosperous coastal provinces,
led to mounting concern in Beijing about the country's shrinking
cropland area. The result was an attempt to offset these losses
by plowing more land in the semiarid northwest. But the newly plowed
land, much less productive, was highly vulnerable to wind erosion.60
As described at the beginning of this chapter, in recent years dust
storms in China have become more frequent and more intense, often
covering cities in the northeast with layers of dust. In May 2000,
the China Daily reported, "Disastrous sand storms that hit
several major cities recently in North China have alarmed the nation
about the devastating consequences of the development strategy that
turned a blind eye on the environment." The desertification now
under way in northwest China aroused public concern as "dust-laden
blasts began to bury villages, blow into cities, and suffocate residents."61
These new reports, coupled with scientific studies, indicate that
a dust bowl is forming in northern China. The April 2001 dust storm
mentioned earlier was one of the largest ever recorded. U.S. scientists
in Colorado measured the dust in this storm above them in Boulder
at altitudes up to 10,700 meters (35,000 feet). China is losing
millions of tons of topsoil, a depletion of its natural capital
that it can ill afford.62
In Africa, population growth and the degradation of cropland are
also on a collision course. Rattan Lal, an internationally noted
agronomist at Ohio State University's School of Natural Resources,
has made the first estimate of yield losses due to soil erosion
for the continent. Lal concluded that soil erosion and other forms
of land degradation have reduced Africa's grain harvest by 8 million
tons, or roughly 8 percent. Further, he expects the loss to climb
to 16 million tons by 2020 if soil erosion continues unabated.63
Among the countries experiencing unusually heavy soil losses are
Nigeria, Rwanda, and Zimbabwe. Nigeria, Africa's most populous nation,
is suffering from extreme gully erosion. Lal reports gullies 5-10
meters deep and 10-100 meters wide. In January 2001, Alhaji Sanni
Daura, Nigeria's Minister of Environment, announced that the country
was losing some 500 square kilometers of cropland to desertification
each year. Daura is concerned that unless this desert encroachment
can be reversed, Nigeria may soon face severe food shortages.64
On the northern edge of the Sahara, Algeria is also faced with the
desertification of cropland. In December 2000, the agriculture ministry
announced a four-year plan to halt the advancing desertification
that they fear will soon threaten the fertile northern areas of
the country. The plan is to convert the southernmost 20 percent
of its grainland into tree crops, including fruit and olive orchards
and vineyards. The government hopes that this barrier of permanent
vegetation will halt the northward march of the Sahara. Out of desperation,
Algeria, a country already dependent on imports for 40 percent of
its grain, is willing to convert one fifth of its grain-producing
land to tree crops in an attempt to protect the remaining four fifths.65
In East Africa, governments are facing a similar situation. Countries
such as Ethiopia, Kenya, and Somalia are experiencing land degradation
and cropland abandonment. Kenya's 1950 population of 6 million has
increased to 31 million, putting unsustainable pressure on local
forests, rangelands, and croplands. During the severe drought of
2000, the Masai, in an act of desperation, drove their cattle into
Nairobi to feed on the grass in well-watered parks and residential
lawns.66 The failure of Africa's governments to address the soil
erosion threat effectively is depleting Africa's most essential
natural capitalits
soil. The next generation of farmers in Africa must try to feed
not the 800 million people of today, but the projected 2 billion
in the year 2025and
with far less topsoil.67
In Mexico, many of the 900,000 migrants who leave rural communities
in arid and semiarid regions of the country each year are doing
so because of desertification. Some of these environmental refugees
end up in Mexican cities, others cross the northern border into
the United States. U.S. analysts estimate that Mexico is forced
to abandon 1,036 square kilometers (400 square miles) of farmland
to desertification each year.68
The World Bank, citing studies for Costa Rica, Malawi, Mali, and
Mexico, concludes that the gradual losses of agricultural productivity
from soil erosion now translate into annual losses in farm output
equal to 0.5-1.5 percent of these countries' gross domestic products.
The toll of soil erosion on the earth's productivity can be seen
in the abandoned villages in Ethiopia, where there is not enough
soil left to support even subsistence-level agriculture. And in
the former Soviet Union, land degradation, mostly from erosion,
helped convert some 20 percent of the land in grain in 1977 either
to soil-conserving forage crops, to alternate-year fallowing, or,
where there was no effort to save the soil, to forest or wasteland
by 1993.69
Unfortunately, many countries have not taken the initiative to reduce
soil erosion and are paying a high price. For example, lost productivity
on Africa's rain-fed cropland, virtually all from soil erosion,
has reduced the annual harvest by an estimated $1.9 billion.70
The challenge is to arrest the excessive loss of topsoil on all
land everywhere, reducing it to or below the level of new soil formation.
The world cannot afford this loss of natural capital. If we cannot
preserve the foundation of civilization, we cannot preserve civilization
itself.
ENDNOTES:
50. Wali et al., op. cit. note 5; WRI, op. cit. note 5.
51. Robert Henson, Steve Horstmeyer, and Eric Pinder, "The 20th
Century's Top Ten U.S. Weather and Climate Events," Weatherwise,
November/December 1999, pp. 14-19.
52. Grain prices from IMF, International Financial Statistics (Washington,
DC: various years); topsoil loss from USDA, Economic Research Service,
Agri-Environmental Policy at the Crossroads: Guideposts on a Changing
Landscape, Agricultural Economic Report No. 794 (Washington, DC:
January 2001), p. 16.
53. Loss of topsoil from water erosion from USDA, Summary Report:
1997 Natural Resources Inventory (Washington, DC: December 1999,
rev. December 2000), pp. 46-51; effect of topsoil loss on yields
in Leon Lyles, "Possible Effects of Wind Erosion on Soil Productivity,"
Journal of Soil and Water Conservation, November/December 1975,
discussed in Lester R. Brown, "Conserving Soils," in Lester R. Brown
et al., State of the World 1984 (New York: W.W. Norton & Company,
1984), pp. 62-65.
54. USDA, op. cit. note 52.
55. Ibid.
56. FAO, The State of Food and Agriculture 1995 (Rome: 1995), pp.
174-95; USDA, op. cit. note 5.
57. Figure 3-2 and Institute of Soil Management from FAO, op. cit.
note 56; USDA, op. cit. note 5.
58. USDA, op. cit. note 5.
59. United Nations, op. cit. note 6; IMF, op. cit. note 49; USDA,
op. cit. note 5.
60. Hong Yang and Xiubin Li, "Cultivated Land and Food Supply in
China," Land Use Policy, vol. 17, no. 2 (2000).
61. "Combating Desertification," China Daily, 25 May 2000.
62. NCAR, op. cit. note 2; "Drought Promotes Sandstorms in North
China," People's Daily, 10 March 2001; "Sandstorms to Increase in
China," Xinhua, 10 April 2000; Gareth Cook, "Massive Dust Cloud
to Travel Over N.E.," Boston Globe, 20 April 2001; Philip P. Pan,
"In Inner Mongolia, Nature Lets Loose a Blizzard of Calamity," Washington
Post, 21 January 2001; Dong Zhibao, Wang Xunming, and Liu Lianyou,
"Wind Erosion in Arid and Semiarid China: An Overview," Journal
of Soil and Water Conservation, vol. 55, no. 4 (2000).
63. Rattan Lal, "Erosion-Crop Productivity Relationships for Soils
of Africa," Soil Science Society of America Journal, May-June 1995.
64. Ibid.; Samuel Ajetunmobi, "Alarm Over Rate of Desertification,"
This Day (Lagos, Nigeria), 23 January 2001.
65. "Algeria to Convert Large Cereal Land to Tree-Planting," Reuters,
8 December 2000.
66. United Nations, op. cit. note 6; Mark Turner, "You Can't Blame
it All on the Weather," Financial Times, 14 October 2000.
67. United Nations, op. cit. note 6.
68. Michelle Leighton Schwartz and Jessica Notini, Desertification
and Migration: Mexico and the United States, U.S. Commission on
Immigration Reform Research Paper (San Francisco: fall 1994).
69. World Bank, World Development Report 1992 (New York: Oxford
University Press, 1992), p. 56; soil erosion in Ethiopia from personal
observation; grain area in the former Soviet Union from USDA, op.
cit. note 5.
70. M. Kassas, "Desertification: A General Review," Journal of Arid
Environments, vol. 30 (1995), p. 118.
Copyright
© 2001 Earth Policy Institute
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