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10 10Desertification A l o n Ta l •Desertification is among the most misunderstood— and the most neglected—of the world’s global environmental challenges. Images of irrepressible waves of sands overwhelming civilization are not entirely fictitious . Indeed, the spectacle can be witnessed every day from the Sahara to China; frequently, natural phenomena can lead to desertification.1 For the most part, however, desertification refers to the much less dramatic but far more pernicious steady decrease in land productivity that takes place in drylands. It is important to emphasize another misconception. Although they may contain productive oases or river valleys, true deserts (arid and hyperarid lands) are typically not the areas in which desertification on a large scale takes place. Rather, it is in the semiarid and subhumid drylands that receive low, often seasonable rainfall and support soils with modest organic content, where the relatively low-land productivity may decline even further. When the nations of the world finally negotiated a treaty to “combat” desertification in 1994, they defined the phenomenon as “land degradation in arid, semiarid and dry sub-humid areas resulting from various factors, including climatic variations and human activities.”2 A higher resolution definition put forward by the United Nations Environmental Program (UNEP) characterizes desertification by five processes that damage land productivity: (1) vegetation degradation, (2) water erosion of soils, (3) wind erosion of soils, (4) soil salinization, and (5) soil compaction—in the drylands. Natural shifts in climate or meteorological j . r . m c n e i l l 146 Uekoetter TEXT••1-208.indd 146 9/9/10 1:48:23 PM 147 processes can surely contribute to these processes. For example, geologists believe that the change in wind directions after the Holocene period replaced the plentiful deposition of Sahara loess in Israel’s Negev Desert, with smaller quantities that arrived from Saudi Arabia. With replenishment diminished, loss of soil due to natural erosive processes was inevitable.3 But generally desertification refers to the loss of soil productivity that is driven by such anthropogenic activities as deforestation, overgrazing, or poorly considered water management. There is nothing new about these activities. Farmers have been aware of the vulnerability of their lands to human abuse and of phenomena like irrigation, waterlogging, soil salinization, or riff and gully erosion from time immemorial. And the ancients were not without effective responses. The Old Testament is full of stories that refer to the importance of imposing stock limits in rangelands (as in the pasture distribution between Abraham and Lot) or normative prescriptions , such as the requirement of crop rotation and sabbatical years for soil rejuvenation .4 Their terraces still define the gnarled landscape of Israel. Although it is not clear that the farmers of old were fully cognizant of desertification processes when adopting such practices, and their implementation alone cannot guarantee the prevention of desertification, they can meaningfully contribute to sustainable land management. Jared Diamond, a Pulitzer Prize–winning ecologist, described the process that undermined many a civilization in the ancient Near East: “Because of low rainfall and hence low primary productivity, (proportional to rainfall), regrowth of vegetation could not keep pace with its destruction, especially in the presence of overgrazing by abundant goats. With the tree and grass cover removed, erosion proceeded and valleys silted up, while irrigation agriculture in the low-rainfall environment led to salt accumulation. . . . Thus, Fertile Crescent and eastern Mediterranean societies had the misfortune to arise in an ecologically fragile environment. They committed ecological suicide by destroying their own resource base.”5 But “desertification” only emerged as a salient term of reference and a modern international problem during the second half of the twentieth century. As early as 1927, a French biologist working in Tunisia documented the low productivity of rangelands there.6 Twenty-two years later, the French colonial forester A. Aubreville coined the term “desertification” itself (in French) when he described the grim situation in West Africa: “The closed forests are shrinking and disappearing, like evaporating spots. The trees of the open forests and savannas become more and more spaced out. On all sides, the bare skin of Africa appears as its thin green veil of savanna burns releasing a grey fog of dust into the atmosDesertification Uekoetter TEXT••1-208.indd 147 9/9/10 1:48:23 PM 148 phere. Arable land is carried away by the yellow waters of flood. Slabs of sterile truncated soil, bearing tufts of grass around uprooted bushes, recall a kind of leprosy that is spreading...


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