- Dust storms emanating from the Sahara have increased
tenfold in 50 years, contributing to climate change as well as threatening
human health and destroying coral reefs thousands of miles away.
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- And one major cause is the replacement of the camel by
four-wheel drive vehicles as the desert vehicle of choice.
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- Andrew Goudie, professor of geography at Oxford University,
blames the process of Toyotarisation - a coinage reflecting the near-ubiquitous
desert use of Toyota Land Cruisers - for destroying a thin crust of lichen
and stones that has protected vast areas of the Sahara from the wind for
centuries.
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- Four-wheel drive use, along with overgrazing and deforestation,
were the major causes of the world's growing dust storm problem, the scale
of which was much bigger than previously realised, Prof Goudie, master
of St Cross College, told the International Geographical Congress in Glasgow
yesterday.
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- "I am quite serious, you should look at deserts
from the air, scarred all over by wheel tracks, people driving indiscriminately
over the surface breaking it up. Toyotarisation is a major cause of dust
storms. If I had my way I would ban them from driving off-road."
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- The problem has become so serious that an estimated 2-3bn
tonnes of dust is carried away on the wind each year. Storms in the Sahara
transport dust high into the atmosphere and deposit it as far away as Greenland
and the US.
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- Britain was seeing increasing levels of "blood rain"
in spring that came direct from the Sahara, Prof Goudie said. From an aircraft
over the Alps in summer it was possible to see the telltale colour of red
dust on the mountains.
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- Although the storms are mainly particles of quartz, smaller
than grains of sand, they also contain salt and quantities of pesticide
and herbicide which can cause serious health problems. Microbe-laden dust
from storms is also credited with carrying cattle diseases such as foot
and mouth.
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- The world's largest single dust source is the BodÈlÈ
depression in Chad, between an ever-shrinking Lake Chad (now a twentieth
of its size in the 1960s) and the Sahara. The depression releases 1,270m
tonnes of dust a year, 10 times more than when measurements began in 1947,
according to Prof Goudie's research.
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- Taking the whole Sahara, and the Sahel to the south,
dust volumes had increased four to sixfold since the 1960s. Countries worst
affected were Niger, Chad, northern Nigeria, Burkina Faso, and Mauritania,
the research found.
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- Smothering of coral reefs
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- But the effects went far beyond. In the Caribbean, scientists
had directly linked the death of coral reefs to smothering by dust which
had travelled 3,000 miles.
-
- African dust had also found its way to Greenland, Prof
Goudie said. While white ice reflected sunlight and remains frozen, the
dark dust on top absorbed the sun's heat, causing the ice to melt and accelerating
the raising of sea levels.
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- Prof Goudie said it was as yet uncertain what other effects
the dust was having on the climate. The airborne dust both reflected sunlight
back into space and blanketed the earth holding the heat in. When it dropped
in the sea it fertilised the plankton which absorbed carbon dioxide and
cooled the ocean surface, creating fewer clouds and less rain - a vicious
circle which made the dust problem worse.
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- Where the dust source was the dried-up bed of a salt
lake or sea, salt deposited from the storms could ruin agricultural land,
leading to more deserts and more dust. There might be more serious consequences
for human health emerging elsewhere in the world.
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- The Aral Sea in central Asia had almost dried up, according
to the research. Its inflowing rivers were used for irrigating cotton,
causing the seabed to be contaminated by pesticide toxins which were now
being blown about in the dust. People who have breathed in the dust have
serious allergic reactions.
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- Prof Goudie also warned that climate change might cause
dust problems to return to the US prairies. While improved agricultural
practices, wind breaks and higher rainfall had cured the Dust Bowl of the
1930s (immortalised in John Steinbeck's novel the Grapes of Wrath), the
conditions were once again similar. Dust storms were now common in the
US and could lead to a disease, Valley Fever, an allergic reaction to pesticides
in the dust which caused inflammation of the nose and throat, killing several
people a year.
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- In China, extensive efforts had been made to plant trees
to hold back the dust, and increases in rainfall had also helped, the study
found. However, large dust storms were still emanating from the vast deserts
in the north, which included the Lopnor nuclear test site - raising fears
that storms could interfere with the 2008 Olympics in Beijing and might
contain radioactive particles. The Chinese have said they were confident
this would not happen.
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- Choking storms hit far and wide
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- * Dust storms are typically 200km (125 miles) wide and
carry 20 to 30m tonnes of dust. Some carry up to 100m tonnes
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- * Worldwide dust in the atmosphere is predicted to be
2bn-3bn tonnes this year
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- * Florida receives more than 50% of the African dust
that hits the US, causing increased respiratory problems
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- * Mauritania, which had two dust storms a year in the
early 1960s, now has 80 a year
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- * The worst dust storm to reach Britain was in 1903 when
an estimated 10m tonnes landed from the Sahara
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- Guardian Unlimited © Guardian Newspapers Limited
2004
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- http://www.guardian.co.uk/climatechange/story/0,12374,1287212,00.html
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