The Earth Policy Reader


Lester R. Brown, Janet Larsen, and Bernie Fischlowitz-Roberts

Part 1. Assessing the Food Prospect: Soil: Surplus to Deficit

In some ways, the most fundamental ecological deficit the world faces is the loss of soil through wind and water erosion. This loss of an invaluable natural capital asset and the associated loss of land productivity are spreading as pressure on the land intensifies.

Soil erosion is not only widespread, but it is not reversible in any meaningful human time frame. Once nutrient-rich topsoil is lost, the capacity of the land to store the nutrients and the water that plants need to sustain growth is greatly diminished.

Soil scientists have assessed the risk of human-induced desertification—land that is losing its productivity as a result of human activity—and the number of people affected by it. Using four categories of risk of desertification—low, moderate, high, and very high—they estimate that 11.9 million square kilometers are at very high risk. (See Table 1–3.) They argue that the land in the very high risk category should be the focus of policymakers because if measures are not taken to protect it soon, its productivity may be lost forever. 6

The researchers call each of these categories a “desertification tension zone,” and they are particularly concerned with the very high risk zone both because this area could turn to desert so quickly and because 1.4 billion people live there. For many of these people, their land is their livelihood. 7

The Sahelian region of Africa, the broad band that stretches across the continent between the Sahara and the rainforest to the south, is one of the areas in serious trouble, slowly turning into desert. U.N. Secretary-General Kofi Annan reports that unless the desertification of this region is halted, within the next 20 years some 60 million people will be leaving the region—refugees from the desert. 8

Soil erosion is not new. What is new is the rate of erosion. New soil forms when the weathering of rock exceeds losses from erosion. Throughout most of the earth’s geological history, the result was a gradual, long-term buildup of soil that could support vegetation. The vegetation in turn reduced erosion and facilitated the accumulation of topsoil. At some recent point in history, probably within the last century or two, this relationship was reversed—with soil losses from wind and water erosion exceeding new soil formation. The world now is running a soil deficit, one that is measured in billions of tons per year and that is reducing the earth’s productivity. In China, as noted earlier, and in scores of other countries, the loss of soil is draining the land of its productivity.

In some areas, such as the flat fertile plains of Western Europe and the rice paddies of Asia, soils are stable. In others, including arid and semiarid regions, such as the Great Plains of the United States, most of Africa, Central Asia, and parts of northwestern China, land is vulnerable to wind erosion. Wherever there is sloping land, water erosion is a potential and often increasingly serious problem. In mountainous countries, such as Indonesia, Nepal, and Peru, sloping land can quickly lose its topsoil to water erosion.

In the early 1990s, some 250 scientists from 21 ecological regions concluded that 2 billion hectares of land, including cropland, rangeland, and woodland, had been degraded to some degree. This is roughly three times the 700 million hectares planted to grain worldwide. The overwhelming share of this land—84 percent—suffered from the erosion of soil, either by wind or by water. 9

Scores of countries, mostly developing ones, are suffering a decline in inherent land productivity because of erosion. This does not necessarily mean that the harvest is declining, because in many situations advances in technology are more than offsetting the gradual loss of topsoil. But the cultivation of land that is losing its topsoil eventually becomes uneconomic, regardless of the level of technology.

As soil erodes, the land initially suffers from declining productivity, and eventually it may be abandoned. A dozen or so U.S. studies analyzing the effect of soil erosion on corn and wheat yields found that the loss of an inch of topsoil typically lowered yields by 6 percent. If the erosion continues indefinitely, it will eventually reduce the productivity of the land to the point where it can no longer be economically farmed. When the cost of producing food exceeds its value, the land is abandoned. For farmers, the cost of this ecological deficit is abandonment of their farms. For society, it represents a loss of natural capital that cannot be replaced in any meaningful time frame. 10

Ohio State University agronomist Rattan Lal estimates that soil erosion has reduced Africa’s grain harvest by 8 million tons, or roughly 8 percent. He projects this loss will double to 16 million tons by 2020 if soil erosion is not reduced. So Africa is projected to lose, in effect, the capacity to feed 80 million people at African levels of consumption during a period when its population is projected to increase by 288 million. 11

Given the fastest population growth of any continent and some of the world’s worst soil erosion, it comes as no surprise that grain production per person in Africa has been declining for the last few decades. While grain output per person in Europe, where population has stabilized and soil erosion is minimal by comparison, has nearly doubled over the last 40 years, in Africa it has fallen by nearly one fifth. (See Figure 1–2.) Of even more concern, there are no shifts in national population and agricultural policies currently in prospect in Africa to reverse this deteriorating food situation. 12

U.S. farmers have also suffered from land mismanagement. Despite their experience with the Dust Bowl in the 1930s, a new generation of farmers was again overplowing in the 1970s in response to record high world grain prices. As a result, soil erosion increased sharply. By the early 1980s, the United States was losing over 3 billion tons of topsoil a year, an amount equal to the topsoil on 1.2 million hectares (3 million acres). This would produce 7 million tons of grain, enough, at average world consumption levels, to supply 21 million people. 13

The erosion in the 1980s, mostly from water, was concentrated in the midwestern Corn Belt, whereas the earlier erosion of the Dust Bowl in the 1930s, mostly from wind, was concentrated in the Great Plains. In 1985, the Congress, with strong support from environmental groups, created the U.S. Conservation Reserve Program (CRP), which paid farmers to plant highly erodible cropland with grass or trees under 10-year contracts (most of which have been renewed). Within a few years, the CRP had removed some 14 million hectares (35 million acres) of cropland, nearly one tenth of the U.S. cropland total, from production. Of this land, roughly half should never have been plowed in the first place because it was so erodible. The other half could be brought back into production, if needed, with the proper soil management techniques. (Interestingly, the one tenth of cropland being converted to grass or trees is roughly the same as the share of China’s cropland that is slated for conversion to trees during this decade.) 14

Other countries that are also pulling back include Algeria, which is fighting a losing battle to protect its grainland as the desert moves northward. As a result, it has decided to convert the southernmost 20 percent of its grainland to permanent crops, either orchards or vineyards, as it tries to maintain agriculture and halt the advance of the desert. Whether or not this will succeed remains to be seen. 15

There are few opportunities to expand production to new cropland to offset these losses. As the world demand for food has tripled over the last half-century, it has forced agriculture into areas that should not be plowed. Perhaps the most dramatic example of this is Kazakhstan. This former Soviet republic was the site of the vast Virgin Lands project during the 1950s, an initiative its supporters promised would expand grain production sufficiently to make the Soviet Union an agricultural superpower. Within a matter of years, the expanding area of grassland plowed and planted to wheat in Kazakhstan surpassed the wheat-growing area of Canada and Australia combined. It was a massive effort, but one that was destined to fail. From roughly 1960 to 1980, Kazakh farmers cultivated some 26 million hectares of grain. But by 1980 wind erosion was reducing yields to where farmers were abandoning their land because it was no longer economic to farm. By 2000, the area in grain had fallen to less than 13 million hectares. Within two decades, Kazakhstan had abandoned half of its grainland, an area equal to Canada’s wheatland. Wheat yields on the remaining land average scarcely 1 ton per hectare, only a fraction of the 7 tons per hectare of France, Western Europe’s largest wheat producer. 16

Despite the history of overplowing experience in key countries, there are still a few high-risk expansion efforts under way. One consists of replacing tropical rainforests in Indonesia and Malaysia with palm oil plantations. Although this is producing cheap palm oil, it is devastating the biological diversity of the region, and without any assurance that these exposed tropical soils will sustain cultivation over the long term. 17

A far more ambitious effort is under way in Brazil as farmers plow the cerrado—a vast, semiarid savannah that is to the south and west of the Amazon basin. This land has helped Brazil become the world’s second-ranking soybean producer, after the United States. The excitement within Brazil at this region’s potential is remarkably similar to that displayed by the Soviets during the Virgin Lands Project in Kazakhstan some 45 years ago. Only time will tell whether the newly plowed cerrado will sustain cultivation over the long term. 18 

Table 1-3. Land at Risk of Human-Induced Desertification
Degree of Risk
Area at Risk
(million square kilometers)
Low risk
Moderate risk
High risk


Very high risk
Source: Hari Eswaran, Paul Reich, and Fred Beinroth, "Global Desertification Tension Zones," in D.E. Stott, R.H. Mohtar, and G.C. Steinhardt (eds.), Sustaining the Global Farm (2001), pp 24-28.



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