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