population pressures > features > habitable earth is shrinking
Habitable earth is shrinkingPosted: 28 Nov 2006
by Lester R. Brown
Our early twenty-first century civilization is being squeezed between advancing deserts and rising seas. Measured by the land area that can support human habitation, the earth is shrinking.
Mounting population densities, once generated solely by the addition of over 70 million people per year, are now also fueled by the relentless advance of deserts and the rise in sea level.
The newly established trends of expanding deserts and rising seas are both of human origin. The former is primarily the result of overstocking grasslands and overploughing land. Rising seas result from temperature increases set in motion by carbon released from the burning of fossil fuels.
The heavy losses of territory to advancing deserts in China and Nigeria, the most populous countries in Asia and Africa respectively, illustrate the trends for scores of other countries. China is not only losing productive land to deserts, but it is doing so at an accelerating rate. From 1950 to 1975 China lost an average of 600 square miles of land (1,560 square kilometres) to desert each year. By 2000, nearly 1,400 square miles were going to desert annually.
A US Embassy report entitled Desert Mergers and Acquisitions describes satellite images that show two deserts in north-central China expanding and merging to form a single, larger desert overlapping Inner Mongolia and Gansu provinces.
To the west in Xinjiang Province, two even larger deserts - the Taklimakan and Kumtag - are also heading for a merger. Further east, the Gobi Desert has marched to within 150 miles (241 kilometres) of Beijing, alarming China's leaders. Chinese scientists report that over the last half-century, some 24,000 villages in northern and western China were abandoned or partly depopulated as they were overrun by drifting sand.
All the countries in central Asia - Afghanistan, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan - are losing land to desertification. Kazakhstan, site of the vast Soviet Virgin Lands Project, has abandoned nearly half of its cropland since 1980.
In Afghanistan, a country with a Canadian-sized population of 31 million, the Registan Desert is migrating westward, encroaching on agricultural areas. A UN Environment Programme (UNEP) team reports that "up to 100 villages have been submerged by windblown dust and sand." In the country's northwest, sand dunes are moving onto agricultural land, their path cleared by the loss of stabilizing vegetation from firewood gathering and overgrazing. The UNEP team observed sand dunes nearly 50 feet (15 meters) high blocking roads, forcing residents to establish new routes.
Iran, which has 70 million people and 80 million goats and sheep, the latter the source of wool for its fabled rug-making industry, is also losing its battle with the desert. Mohammad Jarian, who heads Iran's Anti-Desertification Organization, reported in 2002 that sand storms had buried 124 villages in the southeastern province of Sistan-Baluchistan, forcing their abandonment. Drifting sands had covered grazing areas, starving livestock and depriving villagers of their livelihood.
Africa, too, is plagued with expanding deserts. In the north, the Sahara Desert is pushing the populations of Morocco, Tunisia, and Algeria northward toward the Mediterranean. In a desperate effort to halt the advancing Sahara, Algeria is geographically restructuring its agriculture, replacing grain in the south with orchards and vineyards.
On the southern edge of the Sahara, in the vast east-to-west swath of semi-arid Africa between the Sahara Desert and the forested regions to the south lies the Sahel - a semiarid region where herding and farming overlap. In countries from Senegal and Mauritania in the west to Sudan, Ethiopia, and Somalia in the east, the demands of growing human and livestock numbers are converting land into desert.
Nigeria, slightly larger than Texas, is losing 1,355 square miles of rangeland and cropland to desertification each year. While Nigeria's human population was growing from 33 million in 1950 to 134 million in 2006, a fourfold expansion, its livestock population grew from 6 million to 66 million, an 11-fold increase. With the food needs of its people forcing the ploughing of marginal land and the forage needs of livestock exceeding the carrying capacity of its grasslands, the country is slowly turning to desert. Nigeria's fast-growing population is being squeezed into an ever-smaller area.
In Latin America, deserts are expanding in both Brazil and Mexico. In Mexico, with a large share of arid and semiarid land, the degradation of cropland now forces some 700,000 Mexicans off the land each year in search of jobs in nearby cities or in the United States. In scores of countries, the growth in human and livestock numbers that drives desertification is continuing unabated.
While deserts are now displacing millions of people, rising seas promise to displace far greater numbers in the future given the concentration of the world's population in low-lying coastal cities and rice-growing river deltas. During the twentieth century, sea level rose by 6 inches (15 centimeters). In its 2001 report, the Intergovernmental Panel on Climate Change projected that during this century seas would rise by 4 to 35 inches. Since 2001, record-high temperatures have accelerated ice melting making it likely that the future rise in sea level will be even greater.
The earth's rising temperature is raising sea level both through thermal expansion of the oceans and the melting of glaciers and ice sheets. Scientists are particularly concerned by the melting of the Greenland ice sheet, which has accelerated sharply in recent years. If this ice sheet, a mile thick in some places, were to melt entirely it would raise sea level by 23 feet, or 7 metres.
Even a one-metre rise would inundate vast areas of low-lying coastal land, including many of the rice-growing river deltas and floodplains of India, Thailand, Viet Nam, Indonesia, and China. A World Bank map shows a one-meter rise in sea level inundating half of Bangladesh's riceland. Some 30 million Bangladeshis would be forced to migrate, either internally or to other countries.
Hundreds of cities, including some of the world's largest, would be at least partly inundated by a one-meter rise in sea level, including London, Alexandria, and Bangkok. More than a third of Shanghai, a city of 15 million people, would be under water. A one-metre rise combined with a 50-year storm surge would leave large portions of Lower Manhattan flooded with seawater.
If the Greenland ice sheet should melt, the resulting 23-foot rise in sea level would force the abandonment of thousands of coastal cities and communities. Hundreds of millions of coastal residents would be forced to migrate inland or to other countries, spawning conflicts over land and living space. Together, rising seas and desertification will present the world with an unprecedented flow of environmental refugees - and the potential for civil strife.
During this century we must deal with the effects of the trends - rapid population growth, advancing deserts, and rising seas- that we set in motion during the last century. Growth in the human population of over 70 million per year is accompanied by a simultaneous growth of livestock populations of more than 35 million per year. The rising atmospheric concentrations of carbon dioxide that are destabilizing the earth's climate are driven by the burning of fossil fuels. Our choice is a simple one: reverse these trends or risk being overwhelmed by them.
Lester R. Brown is President of the Earth Policy Institute and author of Plan B 2.0: Rescuing a Planet Under Stress and a Civilization in Trouble.
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