December 4, 2012
Africa’s Disappearing Savannahs Threaten Lion Populations
Brett Smith for redOrbit.com - Your Universe Online
While lions have always been known as the kings of the jungle, the big cats actually roam mostly on Africa´s savannahs. And a new report from Duke University researchers suggests that those friendly environs have been disappearing at an alarming rate.According to the report, which was published recently in the journal Biodiversity and Conservation, 75 percent of the continent´s savannahs have been compromised by human activity in the past 50 years.
The disappearance of this habitat has had a devastating effect on the lion population, driving their numbers down from around 100,000 to as few as 32,000 in the last half century.
“The word savannah conjures up visions of vast open plains teeming with wildlife,” said co-author Stuart Pimm, a professor at Duke´s Nicholas School of the Environment. “But the reality is that massive land-use change and deforestation, driven by rapid human population growth, has fragmented or degraded much of the original savannah. Only 25 percent remains of an ecosystem that once was a third larger than the continental United States.”
The researchers used satellite imagery taken from Google Earth, human population density data from Columbia University´s Center for International Earth Science Information Network (CIESIN) and several different estimates and surveys of local lion populations to determine which areas were still favorable for the big cats´ survival.
They were only able to establish 67 isolated areas of suitable grassland across Africa with low human impacts and densities. Only 10 of these spots were determined to be “strongholds” where lions should have an excellent chance of survival and many of the strongholds are already located within protected national parks.
“Existing maps made from low-resolution satellite imagery show large areas of intact savannah woodlands. Based on our fieldwork in Africa, we knew they were wrong,” said lead author Jason Riggio, currently a PhD student in ecology at the University of California at Davis.
“Using very high-resolution imagery we could tell that many of these areas are riddled with small fields and extensive, if small, human settlements that make it impossible for lions to survive.”
The researchers noted that West Africa is without any potential lion strongholds and fewer than 500 animals are broadly scattered across the region´s eight isolated sites.
“Giving these lions something of a fighting chance will require substantial increases in effort. The next 10 years are decisive for this region, not just for lions but for biodiversity, since lions are indicators of ecosystem health,” said Andrew Jacobson, a member of Pimm´s lab.
“This research, which is the most comprehensive assessment of lion numbers to date, is a major step in helping prioritize funding strategies for saving big cats,” said co-author Luke Dollar, currently the grants program director at National Geographic´s Big Cats Initiative. “Of the estimated 32,000 to 35,000 lions, more than 5,000 of them are located in small, isolated populations, putting their survival in doubt. The research will help us better identify areas in which we can make a difference.”
In their study, the authors concluded that more mapping and studying could be done to better enable the conservation of the African lion.