African Savannahs

Africa’s Savannah Ecosystems — and Their Lions — Declining At Alarming Rate

Lion Population Estimates as Low as 32,000, Habitat Reduced by 75% (full article...‌)

Durham, North Carolina (Dec. 4, 2012)—Researchers coordinated by a team at the Nicholas School of the Environment have determined that Africa’s once-thriving savannahs are in trouble, due to massive land-use conversion and burgeoning human population growth. The decline has had a significant impact on the lions that make their home in these savannahs; their numbers have dropped to as low as 32,000, down from nearly 100,000 just 50 years ago, according to a paper published online in this week’s journal “Biodiversity and Conservation.” The research is the most comprehensive assessment of lion numbers to date.

African savannahs are defined as those areas that receive between 300 and 1500 mm (approximately 11 to 59 inches) of rain annually. “These savannahs conjure up visions of vast open plains,” said Stuart Pimm, co-author of the paper who holds the Doris Duke Chair of Conservation at Duke University. “The reality is that from an original area a third larger than the continental United States, only 25% remains.” In comparison, 30% of the world’s original rain forests remain.

Lions in West Africa are at highest level of risk, the researchers found. “The lions in West Africa have suffered the greatest declines,” said Andrew Jacobson, another co-author from Duke. “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.”

The paper’s senior author, Jason Riggio of Duke University’s Nicholas School of the Environment assembled a team of fellow graduate students to examine very high-resolution satellite imagery of Africa from Google Earth to produce a map of where lions might still exist. “Based on our fieldwork, we knew that most of the information out there from low-resolution satellite-based studies was wrong,” said Riggio. “Existing global maps are quite coarse and show large areas of African woodlands as being intact. Only by utilizing very high-resolution imagery, were we able to identify many of these areas as being riddled with small fields and extensive, if small, human settlements that make it impossible for lions to survive.”

The next phase of research was a systematic evaluation of all existing data on lion populations in Africa. To complete the task, Pimm assembled an international team of co-authors who were familiar with existing reports on lion populations and who had contributed to the process of making those reports. Data also were pulled from various “user communities,” including assessments that were funded by hunting organizations. Data from “user community,” proved to be broadly similar with those of other researchers. Prior to this research, various estimates of lion populations in Africa ranged from 20,000 to 40,000.

Once the data were compiled and analysed, the team created a detailed map that outlined areas of low human impact, more favourable to lion populations. The analysis identified only 67 isolated areas across the continent where lions might survive. They identified 10 strongholds where lions have an excellent chance of survival, many of them within national parks. None of the strongholds is located in West Africa, where countries have doubled their human population in the last 20 to 30 years. According to the research, fewer than 500 lions remain in this area, scattered across eight isolated sites.

“This research is a major step in helping prioritize funding strategies for saving big cats,” said Luke Dollar. Dollar is a co-author of the paper and the grants program director of National Geographic’s Big Cats Initiative (BCI) that provided partial funding for this work. “Of the estimated 32,000-35,000 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.”