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Tuesday, December 13, 2011

'Climate change killing trees'

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. The research, funded by NASA and the US 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 per cent.

"Rainfall in the Sahel has dropped 20 to 30 per cent 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, to be published on Friday, 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 US 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.

Through the Lenses !

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