雅思阅读精选：旷野的屈服 非洲狮数量锐减

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

　　A male lion feeds in South Africas Kruger National Park. The Kruger Park area is one of only ten strongholds left for lions in Africa. National Geographic photo by James P. Blair.

　　The most comprehensive assessment of lion numbers to date determined that Africas 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 weeks journalBiodiversity and Conservation.

　　Some 24,000 of the continents 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.

　　Population size classes of all lion areas. Figure used in the research study ,courtesy of Stuart Pimm and other authors/Biodiversity and Conservation journal.

　　These research results confirm the drastic loss of African savannah and the severe decline in the number of remaining lions, said Big Cats Initiative 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.

　　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 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 worlds 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.

　　Your study found that the population of wild lions in Africa plunged by two-thirds in 50 years. Whats the methodology to determine the populations then and now?

　　Scientists estimated that 50 years ago, approximately 100,000 lions made their home in Africas 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 continent-wide 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.

　　Lion cubs surround a patient lioness, nipping and playing, Londolozi private game reserve, South Africa. National Geographic photo by Chris Johns.

　　Counting carnivores is a tricky business. Individual identification is a tremendous challenge and requires high-resolution 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.

　　What are the main causes of lion decline?

　　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 worlds 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.

　　How many of the remaining 32,000 wild lions in Africa are in stable populations in viable habitat? Where are the strongholds?

　　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.

　　Whats 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 . 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 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.

　　Why is it important that we try to sustain the survival of wild lions in Africa?

　　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.

　　How is the National Geographic Big Cats Initiative helping the situation for lions?

　　The Big Cats Initiative has quickly become a major player in lion conservation. We have sent nearly U.S.$800,000 into the field of which nearly all is in Africa and over half is dedicated directly for lion conservation. However, we are not doing this alone. Other international organizations like Panthera also contribute. We have developed collaborations with these types of groups to identify and execute important work, and many BCI grantees have contributing funds from other organizations. However, because we focus on actual conservation efforts and not research, we fund many projects that do not have a chance elsewhere. We identify innovative projects that halt lion decline, bring them to global attention, and help them to increase in size. This stepwise process of giving start-up money and then escalating funds to increase scale is unique and the only way to meaningfully contribute to halting lion decline across large swaths of Africa.

　　We have two excellent examples of this process. The Anne Kent Taylor Fund operates in the Masai Mara region of Kenya. This program collaborates with locals to strengthen livestock corrals, or bomas. The boma fortification is so successful that demand is outstripping supply of chain link fencing and many locals are copycatting and experimenting with their own designs. This is the hallmark of a successful program. Another fantastic operation is the African People Wildlife Fund that works on the border of Tarangire National Park, in northern Tanzania. Their flagship activity is building stronger bomas, but they employ a large variety of tools and methods to interrupt the circle of retaliatory killing of cats. They work at all levels of the community from the schoolchildren to the leaders. Their long-term commitment is helping build a community that sees tangible benefits from preserving big cats, and a culture where retaliatory killing or poaching is unacceptable.

　　A lion pushes on through a gritty wind in the Nossob Riverbed, Kalahari Gemsbok National Park, South Africa. National Geographic photo by Chris Johns.

　　Research Paper: The size of savannah Africa: a lions view

　　Published online journal Biodiversity and Conservation: 2 December 2012

　　Abstract: We define African savannahs as being those areas that receive between 300 and 1,500 mm of rain annually. This broad definition encompasses a variety of habitats. Thus defined, savannahs comprise 13.5 million km2and encompass most of the present range of the African lion . Dense human populations and extensive conversion of land to human use preclude use by lions. Using high-resolution satellite imagery and human population density data we define lion areas, places that likely have resident lion populations. In 1960, 11.9 million km2 of these savannahs had fewer than 25 people per km2. The comparable area shrank to 9.7 million km2 by 2000. Areas of savannah Africa with few people have shrunk considerably in the last 50 years and human population projections suggest they will likely shrink significantly in the next 40. The current extent of free-ranging lion populations is 3.4 million km2 or about 25 % of savannah area. Habitats across this area are fragmented; all available data indicate that between 32,000 and 35,000 free-ranging lions live in 67 lion areas. Although these numbers are similar to previous estimates, they are geographically more comprehensive. There is abundant evidence of widespread declines and local extinctions. Under the criteria we outline, ten lion areas qualify as lion strongholds: four in East Africa and six in Southern Africa. Approximately 24,000 lions are in strongholds, with an additional 4,000 in potential ones. However, over 6,000 lions are in populations of doubtful long-term viability. Lion populations in West and Central Africa are acutely threatened with many recent, local extinctions even in nominally protected areas.

　　Authors: Jason Riggio , Andrew Jacobson , Luke Dollar , Hans Bauer , Matthew Becker , Amy Dickman , Paul Funston , Rosemary Groom , Philipp Henschel , Hans de Iongh , Laly Lichtenfeld and Stuart Pimm .

　　 Nicholas School of the Environment, Duke University, Durham, NC 27708, USA

　　 Department of Biology, Pfeiffer University, Misenheimer, NC 28109, USA

　　 Wildlife Conservation Research Unit, University of Oxford, Recanati-Kaplan Centre, Tubney, OX13 5QL, UK

　　 Zambian Carnivore Programme, PO Box 80, Mfuwe, Zambia

　　 Department of Ecology, Montana State University, Bozeman, MT 59717, USA

　　 Department of Nature Conservation, Tshwane University of Technology, Pretoria, South Africa

　　 Department of Zoology, University of Johannesburg, PO Box 524, Auckland Park, 2006, South Africa

　　 African Wildlife Conservation Fund, 10564 NW 57th St., Doral, FL 33178, USA

　　 Panthera, 8 West 40th Street, 18th Floor, New York, NY 10018, USA

　　 Institute of Environmental Sciences, PO Box 9518, 2300 RA Leiden, The Netherlands

　　 Department Biology, Evolutionary Ecology Group, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium

　　 African People Wildlife Fund, PO Box 624, Bernardsville, NJ 07924, USA

　　 Department of Forestry and Environmental Studies, Yale University, New Haven, CT 06511, USA

　　 National Geographic Society, Big Cats Initiative, Washington, DC, USA