Read our COVID-19 research and news.

Lords of the Serengeti. Lions coexist with cheetahs, but not with wild dogs.

Lords of the Serengeti. Lions coexist with cheetahs, but not with wild dogs.

Alexandra Swanson

Want to Save Lions? Fence Them In

A new study of lions in African reserves suggests that most populations should be protected with fences, a strategy that can be expensive in the short-term and is at odds with some conservationists' vision of wildlife. The study also finds that half of unfenced populations of lions are likely to dwindle in the next few decades.

"This paper will cause a stir as it really is the first to scientifically illustrate the value of fencing for the conservation of a large predator," predicts Matt Hayward, a wildlife ecologist with the Australian Wildlife Conservancy in New South Wales, who was not involved in the study.

Lion conservation is difficult and expensive. Three-quarters of their African habitat has been taken over by humans, and over the previous century, their numbers have fallen by perhaps 50%, to an estimated 30,000 to 35,000. Some small populations are already suffering from inbreeding. Compounding the challenge is the fact lions aren't easy to live with. They attack villagers and kill their livestock. These problems can be minimized if lion habitat is isolated with an electrified chain link fence. But fences can cost up to $3000 per kilometer to install. If a smaller population is enclosed, managers have to maintain genetic diversity by introducing new animals every few years. Fences are also impractical if lions pursue migratory prey like wildebeest.

Ecologist Craig Packer of the University of Minnesota, Twin Cities, has seen a lot of the problems caused by lions in Tanzania when they attack cows. "It's a flash point for conflict," he says. People retaliate by killing the lion.

Intrigued by the success of fencing at minimizing conflict with lions in South Africa, Packer decided to take a broad look at the role of fencing in lion conservation. He asked 58 conservation managers in 11 African countries for information about their reserves. Some had records on lion numbers going back 46 years, and a dozen years was the average. Using an ecological model developed by co-authors from the University of Oxford in the United Kingdom, Packer and colleagues compared these figures to the number of lions those habitats ought to be able to support.

The analysis, published online on 5 March in Ecology Letters, showed that fenced reserves tend to have a higher density of lions and faster population growth than reserves that are open to neighboring land. Lions are doing relatively well in a few unfenced parks, such as Nairobi National Park in Kenya, but these places must spend much more money. Antipoaching patrols and other management costs in unfenced parks can run more than $2000 per square kilometer annually while fostering only half the number of possible lions. In contrast, a fenced reserve can attain 80% of its maximum population density at a quarter of the cost. The difference could be critical for the future of lions; the study found that almost half of unfenced lion populations may sink to less than 10% of their potential size over the next 2 to 4 decades.

"Too many conservationists are romantics at heart," Packer writes to ScienceNOW in an e-mail. "But the days of limitless vistas of unspoiled African savanna are gone forever. More parks must be fenced."

Co-author Luke Hunter of Panthera, a conservation organization based in New York City, has some reservations. Rather than fences, he would prefer to see the establishment of buffer zones to separate humans and lions, as well as more of the kinds of conflict mitigation initiatives that Panthera has helped establish to reduce the killing of lions. Packer says that this particular approach has done well in Kenya, but it is only feasible when lions are relatively scarce. And there's just not enough money to protect core reserves and buffer zones for all lions, he adds.

"This paper illustrates that successful conservation is not cheap, and given the increasing human pressures, it is not going to get any cheaper" says Graham Kerley, who directs the Centre for African Conservation Ecology at Nelson Mandela Metropolitan University in Port Elizabeth, South Africa. Packer says he hopes to convince development agencies, such as the World Bank, to consider lion fences as infrastructure that can generate revenue from reserves. "People have got to think big," he says.