Climate change killing trees in Sahel - study

Source: Thomson Reuters Foundation - Tue, 13 Dec 2011 13:24 GMT
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LONDON (AlertNet) - Long-term drought linked to climate change is causing trees to die in Africa's Sahel region, south of the Sahara desert, according to a scientific study to be published on Friday.

The research, funded by NASA and the U.S. Geological Survey, focused on six countries from Senegal in West Africa to Chad in Central Africa. It found that one in six trees died between 1954 and 2002, and one in five tree species disappeared locally. Indigenous fruit and timber trees that need more moisture were hardest hit by hotter, drier conditions.

In the sites studied, the average temperature warmed by 0.8 degrees Celsius and rainfall declined by up to 48 percent.

"Rainfall in the Sahel has dropped 20 to 30 percent in the 20th century, the world’s most severe long-term drought since measurements from rainfall gauges began in the mid-1800s,” lead author Patrick Gonzalez, who conducted the research while a visiting scholar at the University of California, Berkeley, said in a statement.

"Previous research already established climate change as the primary cause of the drought, which has overwhelmed the resilience of the trees."

The results of the research indicate that climate change is shifting vegetation zones south toward moister areas, the statement added. Human population is another, less important, factor reducing tree cover, the research found.

The study, published in the Journal of Arid Environments, was based on climate change records, aerial photos dating back to 1954, recent satellite images and field work that included counting and measuring over 1,500 trees.

Gonzalez, now a climate change scientist for the U.S. National Park Service, said drying out of the soil directly kills trees in the Sahel. "Tree dieback is occurring at the biome level," he said. "It’s not just one species that is dying; whole groups of species are dying out."

The trend will affect people in Sahel countries who "depend upon trees for their survival”.

“Trees provide people with food, firewood, building materials and medicine," Gonzalez said. "We in the U.S. and other industrialised nations have it in our power, with current technologies and practices, to avert more drastic impacts around the world by reducing our greenhouse gas emissions.”

Governments agreed on Sunday at U.N. climate talks in Durban to forge a new deal forcing all the world's biggest polluters for the first time to limit greenhouse gas emissions from 2020. But critics have said the plan is too timid to slow global warming.

Climate data from U.N. agencies indicates that the accumulation of heat-trapping gases will rise to such levels over the next eight years - before the newly agreed regime of cuts in emissions is supposed to be in place - that the planet is set for permanent environmental change.

Helen Gichohi, president of the African Wildlife Foundation, said at the U.N. summit last week that sub-Saharan Africa lost nine percent of its forests between 1995 and 2005, at an average loss of 40,000 square kilometres of forest per year - four times the world average for deforestation.