Because grain production has not kept up with food demand, the world has consumed half its grain reserves since 1987, dropping them to the lowest level on record. Yet government leaders in nearly every country allow land that could produce grain to be paved over or degraded by erosion. In this new Worldwatch Paper, Shrinking Fields: Cropland Loss in a World of Eight Billion, Research Associate Gary Gardner reports that the area of grainland supporting each person has fallen to less than one sixth the size of a soccer field -- yet most governments make little effort to preserve this basic agricultural resource.

"In effect," Gardner said, "policymakers are gambling that increases in grain yields equal to the dramatic gains of the last generation will continue indefinitely. But with a decade of faltering yields behind us, this is risky policy."

With grain reserves now at an all time low of 48 days of consumption -- barely pipeline supplies -- Shrinking Fields argues that if we fail to halt heavy losses of cropland, it is unlikely that we will be able to feed a world population that will increase by more than 400 million people in just five years. Cropland losses are occurring on every continent, including these examples:

• At least five percent of China's cropland was lost in only six years (1986- 1992), in part to urban expansion and industrialization. Yet Chinese officials hope to establish 600 new cities in the next 14 years -- virtually ensuring more heavy losses of productive land.
• In the United States, net losses of cropland between 1982 and 1992 covered an area the size of New Jersey.
• Erosion and retirement of marginal lands have pulled more than 24 percent of Kazakstan's grainland from production since the mid-1980s.

The three principal sources of grainland loss are:

• Expanding cities. Urbanization is appropriating cropland nearly everywhere cities are growing. And because many cities started on good farmland, the spread of roads, buildings, and industrial parks inevitably eats up some of the most productive remaining land. In the most crowded regions, especially Asia, such losses cannot be replaced, because little room for cropland expansion exists. As urban populations swell from less than 50 percent of world population to more than 60 percent in the next 30 years, the problem will become more acute.

  EXAMPLE: On the Indonesian island of Java , more than 20,000 hectares of land -- an area large enough to supply rice to 330,000 Indonesians -- were lost to urban and industrial expansion in 1994 alone.

  EXAMPLE: More than 125,000 hectares of cropland in California -- some 3 percent of the state's total cropped area -- were converted to urban or other non-farm uses between 1984 and 1992. More than one third of this land was prime farmland.

• Depletion or diversion of irrigation water. In many critically water-scarce regions, such as the Arabian peninsula, North Africa, northern China, northwest India, and the Great Plains of the United States, water from aquifers is applied to crops faster than it is replaced by rainfall. If farmers deplete that water, or if it becomes too expensive to pump, they will abandon their cropland, or it will revert to less productive rainfed land. In addition, available water that farmers need for crops is being appropriated by cities including Tucson, Los Angeles, and Beijing, forcing irrigated cropland out of use. Irrigated land, just 16 percent of total cropland, supplies 40 percent of grain, so each hectare of irrigated land lost is of particular concern.

  EXAMPLE: On the Arabian peninsula, 75 percent of the agricultural water -- much of it from deep aquifers -- is not renewable. When this water is depleted or becomes uneconomical to pump, the bulk of Arabian agriculture will be lost.

• Degradation of agricultural land. Since World War II, and partly as a result of land mismanagement and over-expansion, severe erosion and salination have taken an area equal to the cropland of two Canadas out of production. That lost area could be producing enough grain for 13 percent of today's population.

  EXAMPLE: Nearly all -- 94 percent -- of Iran's agricultural land is estimated to be degraded from erosion or salination, the bulk of it to a moderate or strong degree.

"Replacing lost land is likely to be more difficult than many officials think," Gardner said. "Optimistic officials often overestimate the potential for expansion by including marginal land, where cultivation may not be sustainable. Indeed, the world's major grain producers have all overexpanded into marginal land in recent years, damaging large areas of land in the process. Many are now pulling back to the land that can be cultivated, with a resulting loss of grain production."

The shrinking supply of quality cropland and lethargic growth in yields comes on the brink of the largest projected increase in food demand in history. In 25 years, farmers will be asked to feed 7.9 billion people -- 2.2 billion more than they do today. Nine out of ten new births will occur in developing countries, where grain self-sufficiency has fallen from 96 percent in 1969/71 to 88 percent in 1993/95. In addition, economic expansion is allowing hundreds of millions to move from a monotonous starchy diet to meals that include meat, fruits and vegetables, and vegetable oil. While these foods offer benefits to consumers and farmers, they also require more land to produce.

There is little room for large-scale expansion of grainland, and a large increase in food demand is just around the corner. Although yields could conceivably regain their robust growth of past decades, banking on such gains is risky. Key contributions to the earlier surge in yields, such as expanding irrigation, are no longer available on the same scale, or they may be environmentally or socially unacceptable, such as increased use of pesticides. If that is the case, continued tolerance of unjustified losses of cropland will increase the pressure on yields, and with it, the risk of supply failures.

If policymakers do not see cropland as a key strategic resource -- no less important than oil reserves or armed forces -- then they will not take steps to halt these losses or protect the quality of remaining farmland. Yet preservation programs in Europe and in the United States have saved millions of hectares of prime farmland from the bulldozer. And proven technologies for reducing erosion on all kinds of agricultural fields can be more widely implemented. In addition, increased funding for technologies to make agriculture more sustainable -- as well as productive -- can help reduce the pressures on remaining agricultural land. The author concludes,

"But the challenge is pressing. By 2020, if current trends continue, each of the world's people will rely on an average of just one eighth of a soccer field to meet his or her grain needs. Despite the past successes in raising land productivity, this small area leaves no room for error. If we do not preserve our farmland, the next generation could pay for the cropland we lose with higher food prices or hunger."

Fonte: Worldwatch Institute