[URBANTH-L]NEWS: Desert Cities are Living on Borrowed Time, UN warns

Angela Jancius acjancius at ysu.edu
Mon Jun 12 13:21:41 EDT 2006

Desert cities are living on borrowed time, UN warns

· Climate change threatens conditions for 500 million
· But report points to huge solar energy potential

John Vidal, environment editor
Monday June 5, 2006
The Guardian

[The following correction was printed in the Guardian's Corrections and 
clarifications column, Tuesday June 6 2006: In the article below, we said 
that "a 310-square mile area of the Sahara could ... generate enough 
electricity for the whole world". Alas no. What the UN environment report 
said was that an area of the Sahara 800km x 800km (800km squared, not 800 sq 
km) could do that: 640,000 sq km, or in square miles 250,000 (not 310). The 
total area of the Sahara is more than 9,000,000 sq km.]

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.

Desert 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.

But 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.

Most deserts, says the report, will see temperatures rise by 5-7C by the end 
of the century and rainfall drop 10-20%. This will greatly increase 
evaporation and dust storms, and will move deserts closer to communities 
living on their edges.

The problems of more heat and lower rainfall are being compounded by the 
melting of glaciers in mountainous regions. These waters sustain life in 
deserts but would be perilously close to drying up if global warming 
continued as expected.

The glaciers in the mountains of south Asia are expected to decline by 40% 
to 80% in the next century with profound effects on large populations in 
Bangladesh, Pakistan, India and China.

Much of the water used for farming the south-west US, central Asia and 
around the Andes is drawn from rivers that originate in snow-covered 
mountains, says the report.

Development in the next 100 years is largely contingent on what happens to 
the climate. However, the report envisages that deserts will become more 
popular tourist destinations and that some of the plants that grow there 
could be "crops of the future".

"Deserts are threatened as never before by climate change, overexploitation 
of water and salinisation," said Professor Andrew Warren of University 
College London, one of the report's authors.

"We risk losing not only astounding landscapes and ancient cultures but also 
wild species that may hold keys to our survival." 

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