Desertification and Climate Change

Deserts cyclically expand and contract, reflecting global environmental changes. Many civilizations on the planet are thought to have met their demise because of desertification of the lands they inhabited, and their inability to move with the shifting climate zones. Desertification is defined as the degradation of formerly productive land, and it is a complex process involving many causes, including climate change and misuse of the land. Climates may change, and land use on desert fringes may make fragile ecosystems more susceptible to becoming desert. Among civilizations thought to have been lost to the sands of encroaching deserts are several Indian cultures of the American southwest such as the Anasazi, and many peoples of the Sahel, where up to 250,000 people are thought to have perished in droughts in the late 1960s. Expanding deserts are associated with shifts in other global climate belts, and these shifts too are thought to have contributed to the downfall of several societies, including the Mycenaean civilization of Greece and Crete, the Mill Creek Indians of North America, and the Viking colony in Greenland. Many deserts are presently expanding into previously productive lands creating enormous drought and famine conditions. For instance, Ethiopia, Sudan, and other countries in the horn of Africa have suffered immensely in the past few decades with the expansion of the Sahara desert into their farmlands.

   Desertification is the invasion of a desert into nondesert areas, and it is an increasing problem in the southwestern United States, in part due to human activities. Most notably, water is being moved in huge quantities into California, and people are moving into desert areas in vast numbers, all seeking water from limited groundwater supplies. This decreases water supply, vegetation, and land productivity, with the result being that about 10 percent of the lands in this country have been converted to desert in the last 100 years, while nearly 40 percent are well on the way. Desertification is also a major global problem, costing hundreds of billions of dollars per year. China estimates that the Gobi Desert alone is expanding at a rate of 950 square miles per year (2,460 km2/yr), an alarming increase since the 1950s when the desert was expanding at less than 400 square miles per year (1,035 km2/yr). The expansion of the Gobi is estimated to cost $6.7 billion a year in China and affects the livelihood of more than 400 million people through decreased crop yields and forced migrations of people from formerly productive areas to cities.