Temps de lecture :4 minutes
Empty reservoirs, dried-up rivers and eroded soils that have haunted southern Europe in recent years could signal a permanent shift in climate
WHEN IT rained in Spain earlier this year, the nation celebrated. The torrential storms broke a five-year drought, refilling many reservoirs and aquifers and bringing hope to some of Europe’s most parched regions.
But the jubilation was short-lived. Far from allaying fears about long-term water shortages across the Mediterranean, it is now clear that the downpours simply reinforced the trend of a generation, in which long periods of drought are broken by intense storms. Soils made dry and arid by months without water were simply washed away by the first rains.
There is now growing concern that, because of global warming, such conditions will become the norm in southern Europe. As the signatories to the Climate Change Convention meet in Geneva next week to discuss how to prevent disruptive climate change in the 21st century, climatologists are claiming that the first stages of “desertification” can already be seen in Spain, Portugal, Greece and Italy. In fact, they argue that the process has been under way for three decades.
The most detailed warning to date comes in a report completed earlier this year by a research programme called Medalus. funded by the European Commission and coordinated by John Thornes, a geographer at Kings College, London. Medalus has spent five years bringing together climate modelling, remote sensing and detailed studies of land and water at field sites to build up a picture of ecological change in the region. Drawing on the expertise of more than 40 European scientists, the report concludes that climate change is happening now, in Europe, with potentially devastating consequences for millions of people.
The implications have already been recognised in the UN Convention to Combat Desertification, agreed in 1994. Though primarily designed to address the problems of Africa, the convention contains a special section on Mediterranean Europe. And in May this year, the UN Food and Agriculture Organization (FAO) warned that “the sustainability of Mediterranean agriculture appears questionable unless urgent and drastic measures are taken“.
In southeast Spain, for instance, average rainfall is only around 20 centimetres a year, with only 5 centimetres in a very dry year such as 1995. Of that, most evaporates; perhaps a tenth reaches rivers.
Water supply is becoming a major constraint in the development of Mediterranean cities, industry, farming and the region’s biggest earner, tourism. Thornes identifies it as the most pressing issue for the region, especially in Spain, which has the largest per capita water demand in Europe and one of the lowest rainfalls.
Some hard-pressed Spanish regions do not want to wait for central government. Catalonia recently proposed importing French water from the Rhône. But, says Thornes: “Water supply problems cannot be solved by continuing to build new and larger reservoirs. There are not the sites; there isn’t the capital; and there are grave environmental impacts.”
With two-thirds of Spain’s water supply used to irrigate crops, he calls for a major rethink of land use policy. “We have to match agricultural practice to soil and climate conditions,” he told the Brussels meeting. “We have to persuade politicians to consider long-term remedial action.” The FAO is calling for the promotion of water-saving farming techniques—such as drip irrigation—and better use of existing water resources. It also says that “environmentally benign technologies should be further developed and shared among countries”. These include an end to overgrazing and overintensive cultivation.
Spain’s increasingly desperate search for water is having a big environmental impact. Almost two-thirds of the country’s inland wetlands have disappeared since 1965. Parts of the Doñana National Park, the largest natural wetland in southwest Europe, have dried up during the 1990s due to drought and the extraction of groundwater. A study for the UN’s Intergovernmental Panel on Climate Change, published in June, concludes that global warming will eliminate up to 85 per cent of remaining wetlands in Spain and Greece.
Vegetation loss often triggers erosion, as soil is left bare. Rainwater runs off the land quickly, rather than infiltrating soils, causing the paradox of more flooding and drier soils. In Greece and Spain, more than 40 per cent of the soil is already suffering from erosion; in Turkey the figure is 70 per cent. In parts of Spain and Italy, annual soil loss exceeds 250 tonnes per hectare.
These countries suffer from a deadly combination of drought and damaging farming methods. The FAO warned in May that in the more arid parts of Spain and Greece “overexploitation of the land is leading to desertification“, and that “advancing erosion seems irreversible“.
Few of these processes are new to the Mediterranean. There is little entirely natural vegetation left anywhere in the region, and Thornes says land degradation has been forcing people from their homes and farms for 4000 years and may have played a part in the decline of past civilisations.
For example, the famous cedars of Lebanon disappeared 2000 years ago. Many areas have been deforested for cultivation—and abandoned again when yields fell—several times over. A typical cycle can be seen in the Agri basin in southern Italy over the past century, where deforestation has caused soil erosion, floods and the formation of a depopulated “badland“.
Humans have sometimes improved the environment. The construction over many centuries of terraces for olive and fruit trees from Spain to Palestine has often cut soil erosion to below “natural” levels.
However, unmaintained terraces quickly crumble away, causing landslips, and the regrowth of scrub and woodland on abandoned fields can trigger fires during dry weather. Fires have destroyed a fifth of Spain’s woodlands since 1975. In two weeks during July 1994, a total of 140 000 hectares in eastern Spain went up in flames.
There is much scientific debate around the world about desertification and the processes that cause it. Some scientists argue that human abuse of the land only rarely leads to its permanent loss. What few doubt is that permanent climate change will create deserts. And permanent climate change is what the highly vulnerable lands of southern Europe face today. Global warming is not just on Europe’s doorstep. It has stepped inside.
Deserts on our doorstep
6 juillet 1996
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