Dan Kitwood / Getty Images stock

Lion populations have been shrinking across Africa as they rub up against growing human populations. Herding cultures, such as the Maasai or the Zulu, may convert wild habitat to grazing land, thereby reducing the population of natural prey for the majestic cats.

By Tia Ghose
LiveScience

Nearly half of all of Africa's lion populations could face extinction in the next 40 years if conservation measures aren't changed, according to a new study.

The study, published Wednesday in the journal Ecology Letters, found that lion populations that were fenced into conservation areas rebounded in recent years, whereas lions in open preserves were challenged by prey loss and predation by human neighbors.

"Lions in fenced reserves tend to do much better, they're achieving much better populations," said Luke Hunter, a conservation biologist with Panthera, an organization that works to protect endangered big cats. "It's also cheaper to achieve those outcomes."

Big cats
Lion populations have been shrinking — across Africa as they rub up against growing human populations. Herding cultures, such as the Maasai or the Zulu, may convert wild habitat to grazing land, thereby reducing the population of natural prey for the majestic cats. So instead of going after a zebra, lions will hunt people's livestock (and occasionally kill people).

"More and more people live in fairly rural areas where there is wildlife, but those people rely on livestock, so they're really coming into conflict often with lions," Hunter told LiveScience. "They just see them as a really dangerous enemy." [In Photos: A Day in the Life of a Lion]

To understand what strategies might best protect lions, Hunter and a few dozen colleagues analyzed lion population data from 42 sites across Africa. Some parks reported 46 years of data, whereas others had only three years of data.

They then compared the population trajectories with fencing, the money allocated to conservation and nearby human population density.

Fenced reserves cost a fourth of the cost to maintain and achieve the same results as unfenced reserves. Fenced reserves also had the highest lion numbers.

Unfenced lions, by contrast, faced attacks by neighboring people, poaching and declining prey populations.  Nearly half of the populations will dwindle to near extinction levels in the next 20 to 40 years if no conservation measures are taken, the study showed.

Don't fence us in
But while the fencing is incredibly effective for preserving lions, not every conservationist loves them, Hunter said.

"I would hate to see more of Africa fenced," Hunter said. "It just takes away from a sense of wilderness."

Fencing can disrupt the great migrations of herbivores and the movements of free-roaming animals such as the African wild dog or the cheetah, he said. But it may be the most effective way to save lions, he said.

"Whether it's a fence or some other form of barrier it's really clear that lions need physical separation from people if we're going to save them."

Follow Tia Ghose on Twitter @tiaghose. Follow LiveScience on Twitter @livescience, Facebook or Google+. Original article on LiveScience.com. 

• Cat Album: The Life of a Cheetah
• Image Gallery: One-of-a-Kind Places on Earth
• Photos: The Wild Cats of Kruger National Park

Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Nickson Parmisa / Wildlife Direct

This lioness was killed on June 20, 2012, along with her sister and four cubs in Sholinge, Kenya, just outside Nairobi National Park. The lionesses had gone into a cattle area to teach the cubs to hunt.

Africa's lions are running out of habitat and some populations, especially those in West Africa, are running toward extinction, according to a study published Tuesday.

Using new satellite data, a research team at Duke University found that about 75 percent of Africa's savannahs were fragmented by farmers and other development in the last 50 years.

"Only 25 percent remains of an ecosystem that once was a third larger than the continental United States," co-author Stuart Pimm, a Duke conservation ecology professor, said in a statement issued with the study.

"The situation in West Africa is particularly dire," the experts wrote, noting that human populations have doubled there over the last three decades. Fewer than 500 lions remain in West Africa, the study estimated.

The team and a panel of lion experts used the savannah data to refine estimates of lion populations, which had ranged between 20,000 and 40,000 across Africa. Their estimate: 32,000 lions remain, down from an estimated 100,000 in 1960.

"Given that many now live in small, isolated populations, this trend will continue," the experts wrote in the study published in the peer-reviewed journal Biodiversity and Conservation. 

"Lions are not going to go extinct, but they are indeed going extinct locally," Pimm told NBC News. "Those in West Africa are in particularly bad shape. It would be tragic if one could see lions only in a couple of places in Africa."

The study estimates that more than 6,000 lions are in populations that have "a very high risk of local extinction."

Only nine African countries have at least 1,000 lions, and five have likely lost all their lions since a 2002 study, the experts said. The biggest stronghold is in Tanzania, which has more than 40 percent of all African lions as well as a strong conservation program.

National Geographic, which funded the study, hopes to use the results to plan where to focus on saving lions.

"The research will help us better identify areas in which we can make a difference," said study co-author Luke Dollar, a former graduate student of Pimm's and now the grants director at National Geographic's Big Cats Initiative.

Related: South Sudan's elephants could be gone in 5 years, group warns

The study estimated that some 24,000 lions are in "strongholds" -- particularly within national parks, where ecotourism can protect the animals while creating local jobs.

But even that designation isn't a guarantee, noted Pimm. "Some large parks in West Africa have lost all their lions and essentially all of their wildlife," he said. "There has to be a political commitment to protect wildlife and, of course, a recognition that viewing wildlife can bring in substantial revenues."

Stuart Pimm

This high fence was built to protect cattle from lions.

A secondary problem is that "lions go beyond the national parks, straying onto land where people live," Pimm said. "The difficulty is to prevent the conflicts that occur when lions take livestock, typically at night."

The Duke team also works with National Geographic and others to mitigate those conflicts -- one approach is to build higher livestock fences. The goal, Pimm said, is to "protect livestock from lions and so stop the need for people to retaliate."

The study follows a move last week by the U.S. Fish and Wildlife Service to study whether to list African lions under the Endangered Species Act. The biggest impact of a listing would be to bar U.S. hunters from bringing back any lion trophies from Africa, where some countries with healthy populations allow legal hunts.

The Associated Press contributed to this report.

More world stories from NBC News:

• Cops hurt as British unionist protesters try to storm Belfast City Hall in flag spat
• Supporters of Islamist president push Egypt to tipping point
• North Korea pays tribute to Kim Jong Il's 'threadbare' parka
• ANALYSIS: Egyptians warn Morsi is no friend of US
• Bread and expired milk: School lunch scandal sparks outrage in China
• PhotoBlog: Building South Sudan from scratch
• ANALYSIS: UN Palestinian vote a personal victory for Abbas
• Fast cars go cheap as bubble bursts in 'China's Dubai'
• Experts: Antarctica, Greenland ice melting into sea

Follow World News from NBCNews.com on Twitter and Facebook