Niamey, Niger — Across the great sweeps of the Sahel - the thin strip of semiarid land stretching across most of Africa south of the Sahara Desert - little has changed since the devastating drought of 1968-73.
A decade of aid money, a United Nations conference and ''plan of action'' - all have had little effect. Deforestation, overgrazing, and overcultivation continue. Populations grow faster than food production.
In the eight Sahelian countries - Chad, Niger, Mali, Upper Volta, Mauritania, Senegal, Gambia, and Cape Verde - population is increasing at a steady 2.5 percent a year, while food production grows at only 1 percent a year.
Another drought could bring results worse than the one a decade ago.
But the town of Bouza, in southern Niger, shows what can be done to ward off disaster. This town is rapidly being encircled by dense little woods. Peasants are raising trees on their small plots, then giving and selling them to individuals and cooperatives. The World Bank is so encouraged by this and by ''Johnny Appleseed'' nurseries popping up there that it plans to finance more such projects.
In the nearby Majia Valley, an increasing number of richer peasants are switching to raising trees in some of their fields, encouraged by the example of 95 miles of windbreak trees.
The basic idea is that if people raise their trees, they will carefully tend them, instead of letting their goats eat them.
The drought that swept the Sahel was caused by man, a UN Conference on Desertification concluded in Nairobi five years ago. Such ''desertification,'' the conferees said, was caused by deforestation, overgrazing and overcultivation. Too many people pressed too hard on a fragile environment.
Planting trees, as in Bouza, is one step that may help stabilize the environment. But if mass forestry is to be successful in the Sahel, money will be required to train citizens in tree-raising. So far, only 1.4 percent of foreign aid goes to forestry and ecology projects.
The Sahel, due to the last drought and the amount of aid since given to prevent a recurrence, remains the key test case of man's ability to control desertification. But the problem is widespread. Some 19 percent of the Earth's surface and 80 million people who live on that land are threatened by desertification. In the United States, Canada and Mexico alone, an estimated 4 million square miles - an area the size of Canada - are in jeopardy.
In Niger, one of the most critically affected drought areas, even the most optimistic planners say the region is nowhere near coming to grips with the problem. These planners say tree planting must be increased 20 to 30 times in the Sahel. They have come up with two rival approaches to meet this need: huge industrialized plantations and village woodlots. The World Bank is backing both.
Sahelians are accustomed to burning wood for fuel. Even in the capital cities , 90 percent of the population cooks with wood or charcoal. Camel trains laden with wood lurch across the President Kennedy Bridge into Niamey, Niger's capital , each morning as they have done for decades. Ten years ago, as regions near the cities and villages became deforested, planners zeroed in on kerosene as an alternative fuel. But today, high oil prices rule it out for all but the relatively rich.
For these reasons, the World Bank has established a vast irrigated plantation of eucalyptus trees at Namardegongou, 30 miles south of Niamey. The Namardegongou project is on prime agricultural land. It is capital-intensive, expert-intensive, and technology-intensive. In theory at least, such plantations - with their daily water feeds through plastic pipes and diesel-fueled pumps that draw the water - grow firewood 10 times faster than dryland woodlots.
Not everyone is convinced such projects are the answer for the Sahel, however. Niger Forest Service chief Ibrahim Najada says foresters would have act as policemen to keep peasants off of the plantations.
The second cause of desertification - overgrazing - is harder to tackle than deforestation, say forestry experts.
Nomadic herdsmen who graze the sparse pastures on the edge of the desert increase the size of their flocks in good years, the better to survive periods of drought.
Recently this practice has been on a sharp upswing. Nomads who have moved into towns to get government jobs have tended to invest this money in animals in their family's herd. Population growth among the nomads themselves has meant more people and thus more animals. Better veterinary care has resulted in lower animal mortality rates. Drilling of new boreholes has allowed more animals to be watered - more than the rangelands can feed in periods of drought.
Human population growth has created steady pressure for more land. Farmers are encroaching on traditional pasture lands.
The UN's desertification conference proposed to limit herd growth by ''stratification'' - meaning rearing of animals in the arid zone, moving them into the southern semi-arid zone to fatten them, then moving them further south to the cities and coastal towns to be consumed.
But this has not worked. Nomads, analysts conclude, do not want to sell their livestock. They prefer to keep their beasts as ''walking savings'' against hard times.
But local experts say that herders' growing involvement in the cash economy will gradually persuade them to sell the young beasts for meat.
The third cause of desertification - overcultivation - is even more intractable. Agriculture in the Sahel, experts say, is really only possible where the average rainfall exceeds 16 inches a year. Even here, the soil must lie fallow every few seasons.
But populations continually to grow and demand more food. As a result, the fallow period is increasingly being abandoned. And farmers are pushing north into pastoral zones, tilling soil that is too arid to be permanently cropped. Thus the soil is becoming drier, dustier, sandier.
The area under rain-fed cereal production in Niger is more than 40 percent greater than before the drought, but production is only 4 percent higher and per-acre yields average only 75 percent of their 1968 values.
Populations obviously cannot continue to grow beyond the capacity of the land , but there is almost no effort toward population control in the region.