Holding back the desert sands

Press, 2 June 1984, Page 18

Holding back the desert sands

From “The Economist,” London

Tutored by grim pictures of the Sahel succumbing to the Sahara, most people have learned to think that the advance of deserts is simple and relentless. The statistics add to the sense of the desert’s invincibility: when the United Nations Environment Programme (U.N.E.P.) opened its twelfth governing council in Nairobi earlier this month, it was duly reported that the Sahara is now growing by 1.5 million hectares a year. The truth about the encroaching deserts, even in the Sahel, is more complicated. For a start, many experts are now sceptical about grand figures like the 1.5 million hectares U.N.E.P. arrived at. Not only are they wild guesses, but they give a misleading impression of the problem. The image of devouring dunes applies to only a tiny area of land; the rest is exhausted or droughtstricken land, some of it far from the desert itself. Even proving that agricultural production has been depressed is tricky. An analysis of millet yields in Niger found that they varied by a factor of 10 from farm to farm and bore little resemblance to published estimates. This does not mean there is nothing to be frightened of: most people agree that something bad has happened to agriculture in many of the world’s arid areas and that this is having serious consequences. There is also general agreement about the four immediate causes: overcultivation, overgrazing, deforestation and bad irrigation. Lump them together and call them “desertification,” but there the agreement ends. Who are the real culprits? Droughts, planners, expanding pop ulations, greedy nomads, or even United Nations agencies? Is the damage permanent or can it be reversed? Consider each of the causes. • Overcultivation. American farmers created a dustbowl in the 1930 s by ploughing land that, in dry years, could not support crops; the wind took the unprotected soil. The mistake is now being repeated in many dry parts of the world. In Niger, cultivation still creeps north into areas with less than 350 millimetres of rain a year, where crops fail more often than not. In the Indian state of Rajasthan, the area under cultivation doubled to more than 60 per cent of the available land between independence and the 19705.

More worrying is the evidence that farmland in well watered areas is becoming exhausted: land is left fallow for shorter periods and yields are falling. • Overgrazing. Nomadic and settled grazers have steadily increased their herd sizes at the same time that the spread of cultivation has squeezed their pastures. In spite of the drought, most Sahel countries have as many cattle and more goats now than in the 19605. As a result, the Sahel is disfigured in the dry season with broad blotches of desert around each water hole, but even these areas may not be permanently damaged. African pasture — unlike, for example, North American range land — consists largely of grasses and other annual plants. Each year, a fresh crop regenerates from seeds left in the soil. This means that the grass can be grazed into the ground this year without affecting next year’s productivity. In much of the Sahel, the soil is astonishingly resilient. It is comparatively rich in nutrients, especially in the most heavily grazed (and therefore manured) spots; it is sandy, which means that it holds water rather than letting it run off; and the seeds of grasses can survive for years. One rain shower, or a fence to exclude stock, and the dust can turn green. • Deforestation. In most arid regions, people depend on wood for fuel. Driven by growing populations, demand has expanded at the same time that regeneration has slowed. Africa is probably losing more than two million hectares of dry woodland each year. Round each town, the distance people have to travel to get wood steadily increases: in many parts of the Sahel it is 50 kilometres or more. Without trees, the soil is open to the desiccating effects of wind and sun. Deforestation is especially damaging in hilly regions, like those in Ethiopia or Nepal, where it leads to erosion. The silver lining, for those in the plains below, is the arrival of rich alluvial silt for agriculture. • Salinisation. Poor irrigation practices have been responsible for turning huge areas of land into desert. Either the water used in irrigation raises the (already salty) underground water table, or it leaves salts behind in the soil when

it dries out. One of the worst-hit countries is Pakistan, where half the soil is now too saline. Irrigation has another damaging effect: it encourages cultivation, which further encroaches on pasture land. Policy-makers who want to stop the encroaching deserts should begin by recognising that desertification is usually a political problem. The Soviet Union’s policy of opening up “virgin lands” with irrigation has created more than 7 million hectares of near-desert. Desertification in the Sahel is variously blamed on the declining power of Tuareg nomads (which allowed cultivators to move north into drier areas), the colonial emphasis on settlement or the demand for meat and firewood created by urbanisation. Even more idiosyncratic factors sometimes emerge: overgrazing in Somalia has probably been encouraged by the growth of mutton exports to Saudi Arabia. The technical problems of curing desertification are not insuperable. Except where the soil has

been lost by erosion, the process can usually be reversed. Many of the solutions, however, would be painful: reducing the number of cattle, restricting cultivation to wetter regions, or leaching salt from the soil with more irrigation water, are not easy steps for a poor country to take. One of the most promising strategies, which should be within the reach of every country, is to plant special trees to protect the soil, improve fertility and provide firewood. Some trees, like Acacia tortilis from the Middle East, can actually stabilise sand dunes. About 60,000 hectares of Rajasthan have already been reclaimed with it. Others, like the African kad tree, Acacia albida, seem ideal for exhausted cropland or pasture. The kad tree has leaves only during the dry season; it thus offers shade when the ground most needs it and not when sun-loving grass or millet is growing. The kad tree also breaks the wind, fixes nitrogen from the air (which increases the yield of crops around it), and provides firewood. Its seed

pods and leaves are protein-rich food for cattle and goats. So why is West Africa not covered with kad trees? Local people have known their value for generations. The obstacle, again, is political. Too often, governments plant trees and, in a misguided effort to protect them, fine the people whose goats nibble the leaves. One anti-desert plan has been remarkably successful in India. The state government of Gujarat encouraged shelter belts of trees by sharing the profits from firewood and grass among the local villagers. Many aid agencies, including U.N.E.P., seem to have taken the lesson. Local people understand how and where to graze their livestock without the help of scientists. A new programme to rehabilitate pasture in Niger is modelled on one drawn up by a tribal chief in the early nineteenth century. Give local people responsibility for their pasture, water, or firewood and they can roll back the desert. — Copyright, “The Economist.”