Fencing has long been anathema to most conservationists, but Packer said it offers the best hope for saving iconic African wildlife, an undertaking that will require sweeping measures rather than piecemeal efforts. In an interview, he called for an international "Marshall Plan" to erect fences where possible to protect people, lions, elephants and other threatened wildlife species.

Most African governments don't have the resources to protect people and wildlife from each other, but without a massive increase in conservation funding nearly half of unfenced lion populations could decline to near extinction over the next 20-40 years. And in the long run, it would be more cost-effective to maintain lion populations in fenced reserves.

For the study, Packer and 57 colleagues compared population densities and management practices across 42 sites in 11 countries. Fenced reserves maintained lions at 80 percent of their potential population capacity on annual management budgets of about $500 per square kilometer, while unfenced populations required an average of $2,000 per square kilometer each year to remain at just 50 percent of their capacity.

"Even though lion habitat has been reduced by at least 75 percent over the last century, more still remains than can possibly be conserved," said Packer, a professor in the Department of Ecology, Evolution and Behavior. "Several of Africa's most famous wildlife areas involve large-scale migrations of wildebeest and zebra that could never be enclosed within a fenced reserve, so the lions' last stand should be thought out carefully in terms of those places that can safely be fenced and those that will be worth the enormous monetary investments because they can't be fenced."

As encroaching civilization has brought people and lions into much closer proximity the incidence of lion attacks on humans and livestock has increased substantially. Not surprisingly, villagers retaliate by killing lions to protect their families and their livestock.

"We must never lose sight of the fact that the costs of lion conservation ultimately derive from the need to protect people from these animals," said Packer. And lions are not alone in causing widespread human misery. "Elephants are in crisis, too, and although they are largely being decimated by ivory poachers, there's little support for elephant conservation in rural villages because of the enormous damage they cause to crops. A fence that is lion-proof is also elephant-proof, so a well-designed policy of fencing would protect more than just lions."

Because the findings from the Ecology Letters paper present such an enormous challenge for African governments and conservationists, the best hope may be to advocate for a "Marshall Plan" for African wildlife conservation, Packer said.

"If we're serious about this, it means establishing fences around very large areas, such as the Selous Game Reserve, which is home to the largest remaining lion population in the world. Fencing the Selous, which covers an area of about 17,000 square miles, would cost something like $30 million. None of the world's conservation agencies could afford that, but perhaps a global funding agency for developing countries would do it because fencing would protect humans as well as lions."

Packer's own research has focused on lions in Serengeti National Park for the past 35 years.

Note: If no author is given, the source is cited instead.

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