BERKELEY, Calif., Dec. 12 (UPI) -- Human-caused climate change is killing trees in a region in Africa south of the Sahara Desert, a study by U.S. researchers says.
Scientists at the University of California, Berkeley, say their conclusion is based on climate change records, aerial photos dating back to 1954, recent satellite images and fieldwork involving counting and measuring more than 1,500 trees in the Sahel region.
"Rainfall in the Sahel has dropped 20-30 percent in the 20th century, the world's most severe long-term drought since measurements from rainfall gauges began in the mid-1800s," study lead author Patrick Gonzalez said. "Previous research already established climate change as the primary cause of the drought, which has overwhelmed the resilience of the trees."
One in six trees died between 1954 and 2002 from Senegal in West Africa to Chad in Central Africa, the researchers said.
"In the Sahel, drying out of the soil directly kills trees," Gonzalez said. "Tree dieback is occurring at the biome level. It's not just one species that is dying; whole groups of species are dying out.
"People in the Sahel depend upon trees for their survival," he said. "Trees provide people with food, firewood, building materials and medicine."
Gonzalez, who conducted the study while a visiting scholar at UC Berkeley's Center for Forestry, is the climate change scientist for the U.S. National Park Service.