30 years ago, spin eco-doctors were crying wolf about the "creeping deserts" that threathened the livelihoods of millions in Africa, Central Asia,...:
Monday, Sep. 12, 1977
Earth's Creeping Deserts
A tide of ecological refugees from land turning to sand
Outside the great conference hall in Nairobi, 16 fountains sent up sparkling plumes of water, and black Mercedes limousines glistened in the bright East African sun. Inside, some 1,500 delegates from 110 nations sat in air-conditioned comfort. The splendid setting of the meeting could hardly have clashed more jarringly with its purpose. At the U.N.'s invitation, the representatives had gathered in the Kenyan capital last week to discuss and devise ways of containing what an increasing number of experts regard as a major environmental danger: the creeping, seemingly relentless spread of the earth's deserts.
More than a third of the earth's land mass is desert or desert-like, and one put of seven people—some 630 million—dwell in these parched regions. In the past, they have been able to scratch out a livelihood—barely. Now, largely through man's own folly, their fragile existence is threatened by a deadly disease of the land called, awkwardly but accurately, "desertification."
In only half a century, an estimated 251,000 sq. mi. (650,000 sq. km.) of farming and grazing land has been swallowed up by the Sahara along that great desert's southern fringe. In one part of India's Rajasthan region, often called the dustiest place in the world, sand cover has increased by about 8% in only 18 years. In the U.S., so much once fertile farm land has been abandoned for lack of water along Interstate 10 between Tucson and Phoenix that dust storms now often sweep the highway.
For most Americans, desertification is not a problem. But for many of the 78 million people who in recent years have had the ground under them turn to dust or sand, there is no easy escape. Washington's Worldwatch Institute estimates that the lives of perhaps 50 million people are jeopardized. As their fields and pastures become no man's lands, the dispossessed add to the tide of ecological refugees who have already swollen the Third World's ranks of unemployed and destitute. Unable to feed themselves, they place new strains on the food supply and create a tinderbox for social unrest. Warns U.N. Secretary General Kurt Waldheim: "We risk destroying whole peoples in the afflicted area."
The deserts' cancerous growth came to worldwide attention in the early 1970s with the great drought and famine in Africa's Sahel, the band of impoverished land across the Sahara's southern flank. More than 100,000 people perished before the rains finally came in 1974, and that was not the end of the tragedy. Hundreds of thousands of tribesmen remain in camps, and the desert's encroachment has not halted. Senegal told the U.N. meeting that it feared its coastal capital, Dakar, would soon be engulfed.
Droughts and crop failures have always been a harsh fact of life in arid regions. But the Sahel's calamity was worsened by distinctly modern factors. Improvements in public health had vastly expanded population. New wells lulled the Africans into thinking they were no longer so completely dependent on the slim rainfall. They enlarged their herds and planted more cash crops like cotton and peanuts. For a while, the land withstood the strains. But when the rains ceased, the crops failed and the cattle stripped the fields of virtually every blade of grass around the overworked wells. Soon the thin layer of topsoil vanished, and there was nothing but rock, sand and dust. The Sahara had won.
Other countries have committed the same sad mistakes. In the Sudan, which could be turned into the pita basket of the Arab world, traditional crop rotation has been all but abandoned—with disastrous reductions in yields. In Tunisia, mechanized plowing cut so deeply into the thin layer of topsoil that much of it loosened and blew away.
Land erosion has also been accelerated by the cutting of trees for firewood and farming of marginal lands, leaving the soil unprotected against winds or heavy rains. In Peru and Chile, some hillside terraces now look as barren as the moon, and clear-cutting of Brazil's Amazon rain forests has left great swaths of worthless sunbaked earth. In the foothills of the Himalayas, the watershed has been so badly damaged by the quest for firewood and farm land that mud is now sliding into the major rivers—the Indus, Ganges and Brahmaputra. Because the uplands are no longer able to retain much water, the entire region is threatened with what British Economist Barbara Ward calls "a fatal alternation of drought and flood."
Another factor has been overgrazing, and the goat—valued and bred in great numbers by desert people for its milk and meat—has probably been the greatest villain. Watching this hardy animal tear up almost every shrub or blade of grass in sight, some observers have suggested, only jokingly, that desertification could be quickly stopped in much of Africa or the Middle East if the goat were to suddenly disappear.
The new wastelands created by man may be self-perpetuating. Climatologist Reid Bryson of the University of Wisconsin notes, for example, that the winds that sweep over India's Rajputana desert are rich in moisture; yet little, if any, rain ever falls. Why? According to Bryson and his Indian colleagues, the dust—much of it created by man-caused erosion—is so thick that it acts like a lid, preventing the formation of warming updrafts that would turn the overhanging moisture into rainfall.
There are still many gaps in scientific understanding of the complex desert ecology. But there has been no shortage of ideas for saving productive land. Using its oil wealth to good advantage, Saudi Arabia has planted some 10 million tamarisk, acacia and eucalyptus trees to help keep the dunes from overwhelming its al-Hasa oasis near Hofuf. Taking a cue from the cattle drives of the old American West, seven Sahel nations are involved in a scheme, dubbed Solar, that would allow nomads to continue to raise cattle on marginal Sahelian rangeland. But when it comes time for fattening before marketing, the time when the cattle make their greatest inroads on pastureland vegetation, they will be marched to the wetter and hardier lands in the south.
Another idea, already acted on by Algeria, would create pockets of trees, shrubs and other barriers against the Sahara in a so-called green belt across the breadth of North Africa from Morocco to Egypt. The Sahel nations are talking of a similar desert project in the south.
The Israelis not only have restored some of the water collection systems left by the ancient Nabateans in the Negev desert, but are letting the runoff nourish flourishing orchards of almond and pistachio trees. Another strategy for making the Negev bloom: drip irrigation systems that feed small amounts of water directly to the roots of plants with the help of computer monitors.
Though the U.N. conference featured an Arab-led walkout during the Israeli delegate's Negev report and other outbursts of rudeness and rancor, the Nairobi proceedings made some encouraging progress. Scientists presented many carefully prepared technical analyses of desertification and ways to combat it. The U.S. pitched in with an offer to train a cadre of 1,000 Peace Corps volunteers for antidesertification work. Before the delegates disband this week, they are expected to adopt a 15-point plan that calls for a worldwide effort against the deserts' encroachment with everything from the planting of new vegetation to the settlement of nomads to control grazing.
Some scientists feared that the document placed too much faith in technological—rather than "human"—solutions, but the plea nonetheless represents a milestone. For the first time, the international community is committing itself to the fight against the growth of deserts. While the document leaves action up to individual countries, the incentive to collaborate—perhaps even with old enemies—is great. To many countries, doing battle against the deserts is the only alternative to poverty, starvation and chaos.
time.com
Today, the same ecofreaks are making a fuss over the "expanding tropics"?!? DID I MISS SOMETHING????
Expanding tropics 'a threat to millions'
By Steve Connor, Science Editor
Published: 03 December 2007
The tropical belt that girdles the Earth is expanding north and south, which could have dire consequences for large regions of the world where the climate is likely to become more arid or more stormy, scientists have warned in a seminal study published today.
Climate change is having a dramatic impact on the tropics by pushing their boundaries towards the poles at an unprecedented rate not foreseen by computer models, which had predicted this sort of poleward movement only by the end of the century.
The report comes as representatives from 191 countries around the world assemble on the island of Bali in Indonesia, to negotiate a new international treaty to cut down on greenhouse gas emissions. Scientists have found that, during the past 25 years the equatorial region classified as climatologically tropical has expanded polewards by about 172 miles which has meant that a further 8.5 million sq miles of the Earth are now experiencing a tropical climate, compared to 1980.
The scientists warned there are grave implications for the many millions of people living in dry, subtropical regions bordering the tropics, which are at risk of becoming even more arid because of changes to rainfall patterns and wind directions.
"Several lines of evidence show that, during the past few decades, the tropical belt has expanded. This expansion has potentially important implications for subtropical societies and may lead to profound changes to the global climate system," the scientists say in their study published online in the journal Nature Geoscience.
"Most importantly, poleward movement of large-scale atmospheric circulation systems, such as jet streams and storm tracks, could result in shifts in precipitation patterns affecting natural ecosystems, agriculture and water resources," they say.
They are particularly concerned about the poleward movement of subtropical dry belts that could affect water supplies and agriculture over vast areas of the Mediterranean, the south-western United States, northern Mexico, southern Australia, southern Africa and parts of South America.
"A poleward expansion of the tropics is likely to bring even drier conditions to these heavily populated regions but may bring increased moisture to other areas," the scientists warn.
"An increase in the width of the tropics could bring an increase in the area affected by tropical storms, or could change climatologically tropical cyclone development regions and tracks," they say.
They also point out that the expansion of the tropical band could exacerbate global warming by increasing the rate at which water vapour – an important greenhouse gas – is being pumped naturally into the upper atmosphere. They warn that could lead to irreversible climate change.
The study was carried out by Dian Seidel of the US National Oceanic and Atmospheric Administration in Washington, her colleagues from the National Centre for Atmospheric Research in Boulder, Colorado, and the universities of Washington in Seattle and Utah in Salt Lake City.
They found that, during the past quarter-century, the area defined as tropical, based on a list of five recognised climatological criteria, has moved further north and south by about 2.5 degrees of latitude, or about 172 miles in total in both directions. That is greater than the predicted shift of 2 degrees by 2100 predicted under the "extreme scenario" envisaged by the Intergovernmental Panel on Climate Change.
"We looked at how certain aspects of the structure and circulation of the atmosphere have been altered over the past few decades and how models predict they may change as the climate changes in the future," Dr Seidel said. "We are seeing indications that a warming climate is associated with expansion of the tropical region towards the poles, and the rate of expansion that has occurred in recent decades is greater than projected by climate models to occur in the 21st century," she said.
Climatologists have long suspected that a warmer world will lead to an expansion of the tropics, which are defined by patterns of wind circulation, ozone concentrations and the height of the troposphere, but few had predicted that the dramatic shift observed by Dr Seidel and her colleagues would have occurred already.
Computer models of the global climate, for instance, had suggested a polewards shift of the tropics by as much as 2 degrees of latitude by the end of the 21st century. "Remarkably, the tropics appear to have already expanded – during only the last few decades of the 20th century – by at least the same margins as models predict for this century," Dr Seidel said.
"The edges of the tropical belt are the outer boundaries of the subtropical dry zones and their poleward shift could lead to fundamental shifts in ecosystems and in human settlements.
"Shifts in precipitation patterns would have obvious implications for agriculture and water resources and could present serious hardships in marginal areas," she said.
Australia is one of the countries likely to be worst affected by the shifting tropics because westerly winds bringing much-needed rain to the continent's arid south coast are likely to be pushed further south, dumping their water over open ocean rather than on land, scientists said.
"An expansion of tropical pathogens and their insect vectors is almost certainly sure to follow the expansion of tropical zones," said Professor Barry Brook of the University of Adelaide.
"The global implication is the unexpectedly rapid expansion of the tropical belt constitutes yet another signal that climate change is occurring sooner than expected," Professor Brook said.
"The case for rapid action on greenhouse gas emissions becomes that much more compelling," he said.
A defining feature of our climate system
The tropics are one of the defining features of the Earth's climate system. Their existence is due to the fact that the region receives the greatest amount of the Sun's energy per unit of surface area. Map makers define the boundaries as the Tropic of Cancer, about 23.5 degrees north of the equator, and the Tropic of Capricorn in the south. These are the points where the Sun is directly overhead during the summer and winter solstices. However, climatologists define the tropical boundaries in a more complicated manner, based on five different sets of criteria, which are mostly connected to the way the air and oceans circulate around the hot equatorial region. Directly over the equator, the hot air rises, bringing with it moisture that accounts for tropical storms. Further away from the equator, the air descends, which tends to make these subtropical regions drier. Scientists have found that the boundaries of the tropics are shifting polewards.
environment.independent.co.uk |
