amako, where my quest to understand these processes began, sprawls unprepossessingly on both sides of the Niger River. Few houses are taller than one story. The city seems more like a big village, an anarchic collection of bougous, or neighborhoods, where Mali's various ethnic groups live in vast extended families -- the Bamana with the Bamana, the Songhai with the Songhai, the Peulh with the Peulh. The women cook on charcoal braziers in the courtyards. The charcoal smoke mingles with diesel fumes and the Sahara dust, so the pall over Bamako is particularly thick.
The latest United Nations Human Development Report, released in 2005, ranks Mali as the 174th-worst country in the world (out of 177) in terms of its annual per capita income ($994), literacy rate (19 percent among adults), average life span (48 years), and infant mortality rate (122 out of 1,000 live births). Yet Mali's art -- particularly its music and wood sculpture -- ranks high among the world's cultural treasures. And perhaps because there is so little to steal, there is very little crime in the country's Sahel region (although there are bandits and Islamic terrorists in the north). Mali's government, though cash-strapped, is one of Africa's most promising new democracies. Many people have a family member in New York or Paris who wires money home, which bolsters the economic picture. But many villages are barely surviving.
There were once two schools of thought about desertification. The "degradation narrative," as it is referred to by one of its critics, attributed it primarily to rampant deforestation, which is still going on: When the trees go, the soil is quickly eroded by runoff from storms and by wind. The more current school of thought, drawing on recent studies of climate data, attributes desertification primarily to "the remote influence" -- a cyclical shift in the world's climate, exacerbated by the accumulation of greenhouse gases warming the earth's atmosphere. In fact, most experts now agree that both factors are involved: The remote influence is the main cause, but it is aggravated by deforestation.
One morning, I went to the Institute of the Sahel, which was founded in 1976, after the first famine took a quarter of a million lives. Its members are eight Sahel countries (Mali, Niger, Burkina Faso, Chad, the Gambia, Mauritania, Guinea-Bissau, and Senegal) as well as Cape Verde, the islands in the Atlantic that are desertifying because the Sahara's dust clouds are suppressing the winds that bring them rain. I was taken down a dark, empty corridor the length of a football field to the office of Boubacar Diallo, the institute's economist and coordinator of food security, who laid out the degradation narrative.
"Malians have always had droughts to contend with," he explained in such calm, measured tones that a listener could be forgiven for not grasping the gravity of the situation. "There were droughts 6,000 years ago and in the thirteenth century that made the Sahel uninhabitable. But now there is also the population problem. The Sahel's population is currently 50 million, and it is growing by 2.7 percent a year. By 2050 it will conservatively hit 100 million. This is because the women continue to have seven children. Before, there was equilibrium because of infant mortality and sickness, but now, with the availability of modern medicine, population growth is unchecked.
"For the people in the villages," Diallo went on, "wood is the main fuel and an important source of income, and the forest also provides traditional plant medicines, the first line of defense against disease. So there is a lot of harvesting. And in Bamako almost everybody cooks with charcoal, which produces only one-third of the energy that raw wood does [though it has the advantage of being lighter and more transportable]. So abandoning the countryside doesn't alleviate deforestation. It actually accelerates it."
The institute tried to "politicize" the villagers: "We showed them pictures of what it was like 30 years ago and now, so they could see the degradation," Diallo explained. "But it hasn't worked. They keep cutting and having lots of children. The same piece of land that used to feed five people now has to feed 20, and it has deteriorated, so farmers are venturing into more marginal, waterless land." The institute is now concentrating on raising the productivity of land already under cultivation by introducing improved strains of millet and other crops, fertilizers, and anti-erosion and water-retention techniques. This has slowed down the clearing for farming but hasn't stopped the clearing for firewood.
"Stopping desertification is impossible," Diallo concluded. "All we can do is try to slow it down. It isn't caused only by local deforestation. Global climate patterns are implicated. The whole world is slowly becoming a desert. That is why everyone should be concerned about what is happening here. This is the future."
According to the United Nations Environment Program, half of the world's land surface -- 28 million of its 57 million square miles -- is "dryland": plains, grasslands, savannas, steppes, or pampas with a modest water supply compared to that of the world's forests. Four million square miles are hyperarid desert, and another 19 million are becoming desert or are threatened with desertification. Desertification is proceeding at a faster rate than perhaps any other time in recorded history, with disastrous implications for vegetative cover, biodiversity, and the existence of 1.5 billion people in more than 100 countries. Twenty-eight percent of China is desert, and the country's deserts, including the Gobi and Taklimakan, are expanding at a rate of 3,800 square miles a year despite the most extensive tree-planting campaign ever undertaken (42 billion trees have been planted since 1982). So what is happening in the Sahel is a frightening model, an advanced case of what much of the earth's land surface is going to become.