Desertification

                Complex human-induced process that results in the transformation of arid and semi-arid non-desert areas into desert or harsh desert-like environments. That process involves the progressive destruction or degradation of vegetative cover especially in what previously were transitional, semiarid regions bordering existing deserts. Other elements that are an integral part of the desertification process are accelerated erosion, salinization, loss of soil fertility, soil compaction, and the formation of duricrusts or soil crusts. Natural processes such as intensive and persistent drought can and do slowly cause these transformations, at least in part. But over the past several hundred years human intervention in the form of large-scale landscape alterations has rapidly turned dry but habitable regions like the Sahel in central Africa into non-productive arid wastelands. These human-cultural landscape alteration practices include the removal of natural vegetation for agriculture, overgrazing of rangelands that destroys plant cover, widespread introduction of non-native plant and animal species that dry down already stressed water tables, large-scale harvesting of forests and woodlands, and burning of extensive areas with subsequent water and wind erosion of the fragile dryland soils. The climatic impacts of that destruction include increased albedo leading to decreased precipitation, which in turn leads to decreased vegetation cover; increased atmospheric dust loading could lead to decreased monsoonal rainfall and greater wind erosion and atmospheric pollution with particulates.

A common misconception is that drought causes desertification. By definition, drought or, more accurately, drought cycles are directly associated with arid and semiarid landscapes. However, arid landscapes that are well-managed can and do recover when the rains that are normal for the area return. The single most important factor that increases land degradation in arid and semi-arid regions is the continued abuse of dryland habitats during drought conditions through human agency, specifically poor land management practices. In 1992 the well-known Henri Le Houérou (French botanist, former FAO research scientist, and international consultant on rangeland and arid land development) reworked his definition of ‘desertization’ to state that it is “. . . the irreversible growth of new desert landscapes in arid regions which, not long before, presented no such features.”

Author’s Note: The human suffering that has resulted from those landscape alteration practices is almost incalculable as millions of acres are lost each year, with little realistic hope for reclamation and rehabilitation in the span of human lifetimes. And by suffering I mean hunger, malnutrition, disease, starvation, and increased mortality rates especially in the young and old who are least able to fend for themselves.

Real World Problems: Although no continent except Antarctica is free from the problems of desertification the worst illustrations that can be found are from central Africa in the region known as the Sahel, stretching from Mauritania on the western coast through Mali, Niger, northern Nigeria, Chad, Sudan, Ethiopia, Somalia, and northeastern Kenya. What has happened is something like the following scenario. Typically, long-term drought conditions result in the die-off of already stressed vegetation. Cattle and, much worse, goats begin a desperate search for food and eat anything and everything in sight, effectively killing whatever is left of the vegetative cover as their human owners scrounge the landscape for the few remaining pieces of wood or woody shrubs that are immediately used for fuel. Vast areas become desert or desert-like almost overnight, with up to 30 miles of marginal grasslands being converted to desert year after year in the Sahel. That measurement involved many hundreds and even thousands of square miles since the 30-mile range mentioned above is in essence those 30 miles south of the previous boundary marking the separation of desert from drylands and typically runs from east to west across the entire Sahel.

Once the vegetation is removed by humans and beasts, the denuded landscape has no roots to anchor the weakly consolidated soil, which then blows away with the first sizeable gust of wind. For example, in the U.S., intense lobbying by off-road vehicle enthusiasts in the arid Southwest have succeeded in opening large tracts of federally-owned arid land to a variety of off-road vehicles, which when operated with recklessness break up the surface of fragile soils, opening them to water and wind erosion, and increasing soil loss in the delicate desert environment. In a matter of seconds, soils that took hundreds of years to develop can be destroyed by a motorcycle or ATV racing across what the drivers think of as sterile landscape suitable only for their gratification and amusement.

Once the fragile ecosystem balance has been disrupted, powerful storms commonly associated with arid regions pick up much of the remaining soil and silt, forming enormous dust storms that extend thousands of feet into the atmosphere. In Africa, that trail of human suffering and environmental devastation extends for well more than a thousand miles from the Atlantic to the Indian Oceans and has forced hundreds of thousands of people to leave their ancestral homes and migrate south, to already stressed and marginalized drylands that will likely experience the same fate as the lands they left. The only likely solution is to put in place population controls and training in better agricultural and soil conservation practices that have the potential to turn the situation around in the lifetimes of the indigenous peoples.

Real World Examples: Rather than ranging too far afield, an example in the Southwest seems appropriate, since the last thing I want to do is give the impression that desertification only happens in developing nations. Overgrazing and poor range/land management practices have made the Rio Puerco Basin of central New Mexico one of the most heavily eroded river basins of the American West and have increased the River’s high sediment load. Better also be thinking deforestation and accelerated erosion. If interested readers want a larger scale example, how about nearly the entire countries of Niger and Chad, which since suffering the devastating droughts of the 1970s have basically stopped growing high-value crops. Readers who are interested in a popular but perceptive analysis of desertification and politics in the American Southwest may want to see: Marc Reisner, Cadillac Desert : The American West and Its Disappearing Water, Revised Edition; New York: Penguin, 1993.