Dear EarthTalk

Can you explain what “desertification” is and why it is an important environmental issue?

Jay Harris

Nashville, TN

Desertification is the degradation of land in already dry parts of the globe that results from various factors, including natural climate changes as well as human activity. As the name connotes it is the expansion of desert-like conditions which render useless land that was once biologically and/or economically productive. According to the United Nations’ Convention to Combat Desertification, the phenomenon occurs in “drylands” (arid, semi-arid and dry sub-humid areas) on all continents except Antarctica and affects the livelihoods of millions of people, including a large proportion of the world’s poor.

Drylands constitute about 40 percent of the world’s total land area, and are home to some two billion people — a third of human population. Water scarcity in existing drylands makes it difficult for plants, animals and humans to thrive there; desertification makes it impossible, forcing those affected to flee to more hospitable lands, whether they are welcome or not. The United Nations estimates that 10-20 percent of the world’s drylands are already degraded to the point where desertification is an imminent threat.

While global warming — and the resulting intensification of fresh water scarcity — is the most serious factor in converting drylands into deserts, population pressure and lack of proper land use planning only serve to make matters worse. In Sub-Saharan Africa, one of the regions most vulnerable to desertification, severe droughts already lead to major food and health crises once every three decades or so on average; environmentalists and planners worry that human-induced warming and other factors will increase the frequency of such debilitating droughts and lead to even more problems with desertification there. The African Union is working to muster international support for the creation of a “Green Wall” — a forested green belt — to help hold back the Sahara desert.

Other governments are also taking steps to keep desertification in check. China is working to create a 2,800-mile forest belt that will not only block the fast advancing sands of the Gobi desert but serve as a “carbon sink,” as well, to absorb greenhouse gas emissions. And Algerian leaders are optimistic that the recent creation of a 600,000 acre national park will head off a looming desertification crisis there.

Desertification is also a problem right here in the United States, mostly a result of overgrazing by farm animals and poorly designed irrigation schemes across especially vulnerable parts of Texas, New Mexico and Arizona. Some 40 percent of the continental U.S. is dry enough to be at risk for desertification.

Historians point to the Dust Bowl of the 1930s as proof positive of America’s susceptibility to such problems. Lessons learned then led to the creation of the Soil Conservation Service — now called the Natural Resources Conservation Service — to teach farmers and other landowners agricultural practices that reduce soil loss and maintain biological diversity around agricultural operations. In spite of such efforts, desertification still plagues parts of the U.S. today. The hope today is that global warming won’t tip us to the point where have to learn some hard lessons all over again.

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