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Deserts Play an Important Role in the Global Environment and Economy

Deserts interact strongly with the rest of our planet. Global-scale climate change during the 1976–2000 period has shown increased temperatures in nine out of twelve deserts studied. Average projected changes for 2071–2100 show a temperature increase of between one and seven degrees Celsius in all world deserts. Rainfall, on the other hand, could increase or decrease with climate change: while the Gobi Desert in China will most likely receive more rain, the Sahara and Great Basin deserts could become drier. In general, a warmer planet will bring more rainy pulses to winter-rain deserts and more drought pulses to summer-rain deserts. Large desert rivers originate mostly outside deserts, and many could face declining water flow from climate change.

These changes will, undoubtedly, impact the ecology of deserts. For example, nearly half of the bird, mammal and butterfly species in the Chihuahuan Desert are expected to be replaced by other species by 2055. Annual grasses that are prone to wildfire are likely to extend their coverage in some deserts, invading native scrubs and increasing the risk of soil erosion.

Deserts also have strong linkages to non-desert environments. Decreased rainfall in some deserts as a result of climate change will represent increased emissions of cross-boundary dust storms with, literally, far-reaching consequences. Most dust particles in the global atmosphere originate from the deserts of northern Africa (50–70 per cent) and Asia (10–25 per cent). Nutrients carried by desert dust, such as phosphorus and silicon, enhance growth in oceanic phytoplankton by increasing the productivity of some marine ecosystems, and also of nutrient-poor tropical soils, as observed from Saharan dust deposited in the Amazon basin. Desert-generated dust also reduces visibility, interfering with ground and air traffic away from deserts and increases the incidence of respiratory illnesses.

Deserts provide migratory corridors for many species. Non-desert birds on cross-desert migration across the Sahara compete increasingly with the human population of the region for rare oases that cover only two per cent of the area. The desert locust (Schistocera gregaria) is normally found in 25 countries of the Sahel and the Arabian Peninsula, but during epidemic outbreaks can spread over up to 65 countries, consuming 100 000 tonnes of vegetation a day, from India to Morocco, and even crossing the Atlantic to the Caribbean and Venezuela.

Deserts have provided trade corridors from times immemorial through which goods and cultures travelled. Water-soluble salts, such as gypsum, borates, table salt, sodium and potassium nitrates have been historically a product of deserts. Evaporite minerals, such as soda, boron, and nitrates, are common in deserts and are not found in other ecosystems. A sizeable share (30–60 per cent) of other minerals and fossil energy used globally is exported from deserts, including bauxite, copper, diamonds, gold, phosphate rock, iron ore, uranium ore, oil, and natural gas.

Because of their warm climate, deserts also export agricultural products, produced under irrigation, to non-desert areas. Agriculture and horticulture are already profitable in many deserts, as in Israel and Tunisia, and have great further potential. A new non-conventional desert export is derived from aquaculture, which paradoxically, can be more efficient in water use than desert plants, and can take advantage of the deserts’ mild winter temperatures and low cost of land. Biologically-derived valuable chemicals, produced by micro-algae as well as medicinal plants, are also manufactured in deserts, capitalizing on their high year-round solar radiation, and exported to global markets. Besides the ongoing export of wild plant products from deserts to non-deserts, there is a pharmaceutical potential in desert plants which is yet to be tapped.

The growth of desert cities, clearly evidenced in industrial countries in the mid-twentieth century, has attracted the migration of non-desert people into desert habitats, drawn by new employment opportunities and the availability of cheap housing. In recent years, the influx of tourists to deserts, seeking the dry and sunny climate, has encouraged migration to deserts as well. Finally, in developing countries, specifically in Sub-Saharan Africa, periodic droughts in non-desert drylands draw thousands of rural migrants and nomads to adjacent desert cities in search of food and employment.

Research carried out in deserts has enriched the knowledge of the history of our universe and planet, and of life on earth. Deserts attract scientists of every discipline, ranging from testing grounds for planetary exploration equipment, to research on meteorites (well-preserved due to the slow rate of desert rock weathering), to astronomical observations, and archaeological and geomorphologic studies. Many areas of research benefit from the desert’s clean atmosphere, low human disturbance, dry climate, sparse vegetation cover, minimal cloud cover, and thin soils
— features that contribute to good preservation conditions and high detectability of scientifically-relevant objects and phenomena.

Our understanding of global processes, the development of much of our modern research, our ability to cope with global environmental change, and the preservation of much of our global heritage depend to a large extent on the way we manage and preserve the world’s deserts. What happens in deserts affects every one of us.
© UNEP 2006