Study: Traditional ranching helps, not hurts, African ecosystems

Traditional ranching practices can enhance African savanna, going against a common view that human land use destroys natural ecosystems, U.S. ecologists say.

The finding that traditional techniques in the African savanna enhance the local abundance of wild, native animals offers a new perspective on the roles humans play in natural systems, they said.

For thousands of years, pastoralists in East African savannas have penned their cattle overnight in brush-walled corrals called bomas that remain in use for about a year, resulting in tons of manure fertilizing small areas.

After abandonment, a lush carpet of grass springs up and these fertile "glades," sometimes as large as a football field, can remain visibly distinct from the surrounding savanna for over a century, the scientists said.

"The effect of these glades is clear," said Colin Donihue, a Yale University doctoral student who led the research working with ecologists at the Mpala Research Center in Kenya. "Our findings are particularly exciting given how long glades persist in the savanna.

"This means that even decades after the pastoralists move on, they leave fertile footprints across the landscape that significantly alter the dynamics of the entire ecosystem," Donihue said in a Yale release Wednesday.

The glades are preferred grazing sites for many large African mammals, the researchers said, and the effects of glades cascade to a far broader swath of the savanna's plant and animal inhabitants.

"With human populations booming, we must look beyond the 'leave no trace' conservation ethic," Donihue said. "We must strive to find ways that our impacts on ecosystems can work in concert with natural processes. Our study suggests that traditional practices, honed over millennia, offer insightful lessons on how to do it."