Large carnivores

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LION NUMBERS PLUNGE AS AFRICAN WILDERNESS SUCCUMBS TO HUMAN PRESSURE

Posted by David Braun of National Geographic on December 6, 2012

The king of the African savannah is in serious trouble because people are taking over the continent’s last patches of wilderness on unprecedented scale, according to a detailed study released this week. 

The most comprehensive assessment of lion (Panthera leo) numbers to date determined that Africa’s once-thriving savannahs are undergoing 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 hundreds of thousands estimated just 50 years ago.

The study, funded in part by the National Geographic Big Cats Initiative, was published online in this week’s journal Biodiversity and Conservation. Some 24,000 of the continent’s remaining lions are primarily in 10 strongholds: 4 in East Africa and 6 in southern Africa, the researchers determined. Over 6,000 of the remaining lions are in populations of doubtful long-term viability. Lion populations in West and central Africa are the most acutely threatened, with many recent local extinctions, even in nominally protected areas.

“These research results confirm the drastic loss of African savannah and the severe decline in the number of remaining lions,” said Big Cats Initiative (BCI) Grants Committee Chair Thomas E. Lovejoy, University Professor for Environmental Science & Public Policy at George Mason University and Biodiversity Chair of The Heinz Center. “Immediate and major action is required to save lion populations in Africa.”

African savannahs are defined by the researchers 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 Chair of conservation at Duke University. “The reality is that from an original area a third larger than the continental United States, only 25 percent remains.” In comparison, 30 percent of the world’s original rain forests remain.

Lions in West Africa are at highest level of risk, Pimm and the other researchers found. “The lions in West Africa are essentially gone,” said Pimm. “Only a radical effort can save them at this stage.”

Stuart Pimm is also a member of the Big Cats Initiative Grants Committee and a regular blogger for National Geographic News Watch. We interview him here about the research released this week.

Scientists estimated that 50 years ago, approximately 100,000 lions made their home in Africa’s iconic savannahs. This estimate was made using rough calculations of the size of remaining habitat and lion density. Our research suggests that lion populations have experienced a dramatic decline, and numbers have dropped to as low as 32,000 individuals. We compiled all of the most current available estimates of lion numbers and distribution – continentwide reports, country-specific lion conservation strategies and action plans, and newly published lion population surveys. To fill in any gaps, we drew from the knowledge of the co-authors and colleagues working across Africa to conserve lions.
Counting carnivores is a tricky business. Individual identification is a tremendous challenge and requires highresolution cameras or good, unobstructed views in person. They are often shy and cover large distances. Lions are difficult to count even though they are social and sleep most of the day. Only a very few lion populations are known at the individual level, such as Liuwa Plains National Park, Zambia. Individual recognition of every lion in an area requires intense study, significant resources, and low numbers of individuals. Therefore, researchers use a variety of other imperfect techniques to estimate lion population size in all other lion areas. Some more common estimation techniques include spoor tracking or call-up surveys.

There is a variety of factors leading to lion decline across their range. One of the most important things we identified was habitat loss. People usually think of savannah Africa as being comprised of wilderness, vast open grasslands stretching to the horizon in all directions. However, our analysis showed that from an original area a third larger than the United States, only 25% remains. In comparison, 30% of the world’s original tropical rainforest remain. Most of this reduction has come in the last 50 years due to massive land-use conversion and burgeoning human population growth. Besides habitat loss, another major driver of decline is human-caused mortality. This includes poaching, retaliatory killing, and trophy hunting.

Our analysis identified only 67 largely isolated areas across the entire African continent where lions might survive. Of these 67 areas, only 10 qualified as strongholds where lions have an excellent chance of survival. These strongholds are located across East and Southern Africa, but importantly no areas in West or Central Africa qualify. Unfortunately this means that for the remaining 32,000 wild lions in Africa, only approximately 24,000 are in populations that can be considered at all secure. More than 5,000 lions are located in small, isolated populations, putting their immediate survival in doubt.

What’s the prognosis for wild lions? Extinction?
The drastic reduction in lion numbers and habitat highlighted by our research is certainly alarming from a conservation standpoint. Yet, African lions are not in immediate danger of extinction. Substantial lion populations exist in large, well-protected areas such as the Serengeti or Kruger ecosystem. Many of the remaining lion populations in East or Southern Africa are in well-protected areas such as national parks and game reserves (although some of these allow hunting). Nevertheless, this should not be used as a blanket statement; there are populations and even countries in these regions that have few or no lions remaining. Overall, lions in West and Central Africa are in the gravest danger of extinction. More than half of the populations vital to lion conservation in these regions (as noted by the IUCN) have been extirpated in the past five years, with several countries losing their lions entirely. According to our research, fewer than 500 lions remain in West Africa, scattered across eight isolated sites. This is of serious concern as these populations contain the most genetically unique lions in all of Africa and are most closely related to the Asiatic lion.

Large carnivores play valuable ecological roles in “top-down” structuring of the ecosystem. For instance, removal of lions may allow populations of mid-sized carnivores to explode which would have cascading impacts on other flora and fauna. From an ecological perspective, large carnivores are crucial for balanced, resilient systems. However, the lion is so much more than just the largest carnivore in Africa. It is a powerful cultural and political symbol. Attempting to list all the uses of lions in African proverbs, symbols, names etc. would be a nearly impossible task. Finally, lions are vital to the tourism trade, which in turn is economically critical for many African nations. 

How does your study help conservation of the big cats? 
You cannot protect what you do not know you have. This is a simple but true adage. Our compilation needed to occur in order to prioritize areas for conservation action. With a good map, numbers, and some understanding of connectivity between the lion areas, we now know which populations are threatened with extinction or conversely, which are well connected and well protected.

http://newswatch.nationalgeographic.com/lion-numbers-plunge-as-african-wilderness-succumbs-to-humanpressure/