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The Sahara and Climate
The Sahara Desert, the world’s largest, is central to discussions of climate change both historical and predicted. Six thousand years ago, the region was much lusher than it is today, perhaps owing to a different pattern of monsoon rains. Yet “dead" dunes hundreds of miles south of the present southern limit of the desert suggest periods in the past when the Sahara covered an even greater extent. Such fluctuations suggest the cyclical variability of the Earth’s climatic regime; human activity may today be influencing those climatic swings, thus the Saharan ecology. How then, do animals adapt to the climate change in the Sahara from year to year?
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Some of the mammals presently found in the Sahara Desert demonstrate the adaptations necessary to survive in such an extreme landscape. Few display such impressive adaptability as the addax, one of the so-called “horse antelopes" and the native ungulate most fully at home in the Sahara’s sand wilderness. It relies greatly on plant forage to meet its water needs, and has broad hooves that allow it to travel long distances over sand to take advantage of shifting resources. The aoudad or Barbary sheep, which inhabits the isolate mountains of the Sahara, similarly obtains much of its water from browse. The fennec fox, smallest of the world’s foxes, has proportionately massive ears—not only to listen for rodent and insect prey, but also to help it cool off in the blazing heat of the desert.
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Some experts believe a warming climate will actually result in a shrinkage of the Sahara, as moister grasslands and savanna environments invade its edges. In recent decades, rainfall has increased in parts of the Sahara, which may be due to human influence. Warming temperatures, which many believe are partly caused by increased greenhouse-gas emissions and other effects of human industry, may increase evaporation off the world’s oceans and result in strengthened monsoonal rains over North Africa. Hypothetically, such a diminishment of the Sahara’s dune tracts and other arid habitats might reduce the range of desert-adapted creatures like the addax, while encouraging grassland and savanna species like ostrich, elephants and the like to colonize former desert country.
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Climate Change and Migrants
Many bird species migrate between Eurasia and sub-Saharan Africa, requiring a yearly double-traverse of the vast desert. Should climate change diminish the Sahara’s extent, birds may find more hospitable layover grounds—but, as the United Nations Environmental Programme notes in its “Global Desert Outlook", increased human development in former desert acreage could threaten the migrants with pollution. Conversely, an expanding desert—which some models still predict for North Africa—could make for a much costlier journey for the traveling birds across treacherous, arid wilderness. Such issues suggest the complexity of predicting animal adaptations to climate change in the Sahara.
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(1) Sahara Desert Greening Due to Climate Change?; James Owen; National Geographic News; July 2009
(2) Dury, G.H.; An Introduction to Environmental Systems; 1981
(3) Estes, R.D.; The Behavior Guide to African Mammals; 1991
(4) Alden et al.; The National Audubon Society Field Guide to African Wildlife; 1995
(5) United Nations Environment Programme: Global Deserts Outlook - Cross-Desert Animal Migration