UNEP Report - World's Desert Cities Living On Borrowed Time - Guardian

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The 500 million people who live in the world's desert regions can expect to find life increasingly unbearable as already high temperatures soar and the available water is used up or turns salty, according to the United Nations. Dsert cities in the US and Middle East, such as Phoenix and Riyadh, may be living on borrowed time as water tables drop and supplies become undrinkable, says a report coinciding with today's world environment day.

Twentieth-century modernist dreams of greening deserts by diverting rivers and mining underground water are wholly unrealistic, it warns. Bt the report also proposes that deserts become the powerhouses of the next century, capturing the world's solar energy and potentially exporting electricity across continents. For instance, a 310-square mile area of the Sahara could, with today's technology, generate enough electricity for the whole world.

The problem now facing many communities on the fringes of deserts, says the UN environment programme report, is not the physical growth of deserts but that rising water tables beneath irrigated soils are leading to more salinisation - a phenomenon already taking place across large tracts of China, India, Pakistan and Australia. The Tarm river basin in China, it says, has lost more than 5,000 square miles of farmland to salinisation in a period of 30 years. The report suggests that Middle Eastern countries such as Saudi Arabia have used water from the desert very unwisely. Rather than growing staple crops such as wheat or tomatoes, it suggests that precious water should be used only for high value crops such as dates and fish farming. The mining "fossil" water, laid down many millions of years ago, was once believed to have the potential to green deserts, but is now not thought to be a solution - except in Libya, where opinion is divided as to whether supplies may last 100 or 500 years.

But the greatest threat to people and wildlife living anywhere near deserts is climate change, which is already having a greater impact on desert regions than elsewhere. The Dashti Kbir desert in Iran has seen a 16% drop in rainfall in the past 25 years, the Kalahari a 12% decline and Chile's Atacama desert an 8% drop.



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http://www.guardian.co.uk/climatechange/story/0,,1790471,00.html