Overkill and Sustainable Use

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Science  21 Mar 2003:
Vol. 299, Issue 5614, pp. 1851-1853
DOI: 10.1126/science.1079823

For over two decades, the international conservation lobby has advocated economic development as the primary means of achieving sustainable living (1) [HN1]. This goal has proved elusive even when biological resources are controlled by local communities (2, 3) [HN2]. Nevertheless, many development agencies have accepted commercial incentives and regulations as the mainstay of their conservation effort (4), apparently without taking into account humankind's long history of exploiting wild living resources. Consideration of episodes of overkill and sustainable use in human history may inform the prevailing conservation paradigm.

“Overkill”—a conspicuous decline in a population of hunted animals without prospect of stabilization or recovery—is often coupled with trade in animal products and wastage of less valuable parts of the carcass. It has been cited in the late Pleistocene extinctions of large mammals [HN3] in Australia, New Guinea, and the Americas (5); the extinction of large flightless birds in New Zealand in the 14th century (6) [HN4]; the North American fur trade in the 17th and 18th centuries (7, 8) [HN5]; and the current harvest of wild meat from increasingly accessible tropical forests in west and central Africa (9) [HN6].

Rock painting of a Bushman hunter from the Western Cape of South Africa [HN14].

In contrast, sustainable harvesting ensures that wildlife populations remain numerically stable. It is usually assumed implicitly that hunters could kill at a higher rate if they so chose. Sustainable harvesting has been claimed in red deer stalking in the Scottish Highlands in the 19th and 20th centuries (10) [HN7]; the hunting of wildlife by Bushmen in the Kalahari in the mid-20th century (11); and the hunting of game animals on private farmland in southern Africa in the late 20th century (12).

Onset of Overkill

Four triggers are commonly associated with unsustainable hunting: occurrence of naïve prey, vulnerable animals, new technology, and trade.

Naïve prey is believed to have played a key role when paleolithic hunters crossed the Bering land bridge in about 12,000 B.C. and spread across North and South America, all the while hunting native large mammals so effectively as to bring about their extinction (5). The hunters invading the Americas may have been more effective than those in Africa and Asia because their prey lacked awareness of humans as predators (13).

Top predators and highly specialized species may be vulnerable to overexploitation because they reproduce slowly. Migratory animals may be at risk because of the perception that their populations are limitless. The northern Plains Indians believed that the bison herds disappeared each season to graze beneath the water on pastures where they bred in countless numbers (8). At the same time as the near extinction of bison, the passenger pigeon became extinct [HN8]. One of John Muir's characters remarks that “they were made to be killed, and sent for us to eat as the quails were sent to God's chosen people” (14). Prey animals are also vulnerable if another primary source of food is available to their predator, allowing the latter to persist at high density even when its prey has been reduced. Hence, Australian marsupials are vulnerable to foxes, which have rabbits as their primary prey (15).

New technology is often incriminated in wildlife overkills. The extinction of Pleistocene mammals in Africa has been linked to the development of hand axe cultures (16). Soon after Europeans arrived in the Americas, Native Americans began trading pelts for guns and steel traps that contributed to the decline in large mammals. In Africa, wire snares set in lines are one of the most effective overkill technologies. Declines in freshwater and marine fisheries have followed the introduction of ever more sophisticated and undiscriminating fishing craft and gear.

Efficient technology also tends to divorce hunters from their prey by reducing, or dispensing with, the respect often found in the human-wildlife relationship of indigenous peoples (17). Among modern recreational hunters, this respect is reflected in the notion of sportsmanship, which disapproves of methods that kill easily or indiscriminately.

Powerful market forces are frequently implicated in the overexploitation of animals and plants. For example, the ivory trade has long affected the fortunes of African elephants [HN9]. According to Pliny (23 to 79 A.D.), demand for ivory in the Roman Empire was so great that the elephants of North Africa succumbed. From the 16th to the early 20th century, the booming African ivory trade with Europe led to a continental decline in elephants. In the latter part of the 20th century, trade in ivory with Japan and Hong Kong precipitated yet another decline.

Overkill is thus clearly not a new phenomenon. Nor, however, is it the inevitable consequence of human utilitarianism in relation to hunting. The archaeological record indicates that certain pre-agricultural societies may have lived within the regeneration capacity of wildlife populations over long periods (18). Late Stone Age hunters seem to have adapted to their impoverished faunas after they had exterminated Pleistocene vertebrates. How they did so is seldom discussed.

Sustainable Harvesting

Three factors are associated with sustainable hunting: availability of alternative sources of food, ownership of wildlife resources, and existence of cultural and spiritual beliefs.

Alternative sources of food were available to Bushmen occupying traditional territories in the central Kalahari [HN10]. When game was in short supply, the Bushmen could survive on plants. But rather than using their plant-based subsistence to exterminate local prey species, they reduced their hunting and created a sustainable life-style (11). Their nomadic system of utilization is thought to have lasted for at least 2000 years, without evidence of environmental degradation or species loss. Only in recent decades have wildlife populations declined. This coincided with the Bushmen being dispossessed of their land and the right to manage their natural resources.

Control of wildlife resources has also been instrumental in creating one of the success stories in African conservation. Since a change in legislation provided commercial farmers in southern Africa with effective ownership of wildlife on their lands (12), a lucrative wildlife industry has arisen based on trophy hunting, wildlife harvesting, and tourism [HN11]. Wildlife populations have increased on many farms and ranches.

It has been suggested that a spiritual relationship with nature may preclude overexploitation (7). After the overkill episodes of the Pleistocene, Native Americans [HN12] coexisted with the remaining prey species [though some late Holocene cultures depressed populations of large fishes and mammals (19)]. The environment of the precontact peoples of eastern Canada seems to have been filled with spirits that imbued animals, plants, and everyday objects with power and influence, the people apparently maintaining amicable relations with these spirits.

It has, however, been pointed out that such a close spiritual relationship with game animals, despite dictating good conduct, does not necessarily prevent overexploitation (8). Native Americans believed that by honoring a slaughtered animal in a prescribed manner they could ensure its reappearance in future hunts. In this case, should beavers disappear from a region, the intensity of trapping would not be implicated. Rather, greater care would be taken to obey the proscribed taboos. The game animals may therefore have persisted through the Holocene owing to their lack of vulnerability—just as they had survived the Pleistocene extinction.

Given our limited knowledge of the precontact relationship between Native Americans and wildlife, it is difficult to assess the relative influence of these rival expositions. But in the case of the Bushman hunter-gatherers, there is evidence of a direct association between cultural beliefs and environmental policy. Among the G/wi, it was important that respect be shown to all creatures created by N!adima (the supreme being) because each has its own place in his world, being a part of his property. Killing more than one head of game at a time would anger N!adima. Anthropologists living with isolated bands have reported that the Bushmen understood the balance between the material needs of their groups and the productivity of their semi-arid environment (11, 20).

Social Disruption

If cultural or spiritual restraints underpin sustainable living, then episodes of overkill might be expected during periods of social disruption. When infectious diseases were brought to the New World by Europeans, the Native American peoples were devastated even before most had made direct contact. It has been suggested that the ensuing epidemics undermined the shamans' ability to influence the supernatural realm and invalidated the peoples' sacred relationship with wildlife. This apostasy may explain the enthusiastic participation of Native Americans in a trade that locally exterminated many valuable species (7). Others have argued that the material value placed on European goods by Native Americans alone brought about the overkill of fur-bearing animals (21). In either case, some Native American groups have reestablished sustainable forms of hunting several centuries after the disruption initiated by European contact (7).

At first thought the notion of sustainable harvesting may appear to be a precarious and unlikely human enterprise, particularly in regions with expanding human populations. As previously stated, there is some suggestion in the archaeological and anthropological records that a few subsistence economies have been stable over long periods (18). Perhaps times of overexploitation punctuate rather than dominate human history.

It is generally agreed that a stable society with a secure sense of ownership of prey animals is crucial for a sustainable use of wildlife. Here, the term “ownership” refers to the sense of exclusive access or use that in modern society can be traced back to the Norman game laws [HN13] in the 11th century (22). The term could also convey an intimate spiritual connection with animals and the environment. Ownership might furthermore be linked to an understanding of the habits and behavior of prey animals. Constantly knowing where one's prey is and what it is doing may elicit proprietary feelings, whereas if the behavior of prey animals is virtually unknown—for example, because they migrate quickly through the hunter's range—there is little incentive to care for them.

The latter type of ownership was probably absent among the bands of Paleolithic hunters moving swiftly into new hunting grounds each year, and among the Europeans of the 15th to 19th century in America, Africa, and elsewhere. All three senses of ownership would suffer in severely disrupted societies.


Conservationists wishing to reduce overkill are presented with two main options: make animals harder to market through restrictions in access, trade, and the use of modern technology, or provide resource users with a greater sense of ownership. The conservation community currently places much emphasis on granting exclusive rights to commercial harvesting, be it on private, state-owned, or common lands. The spiritual and knowledge-based dimensions of ownership are usually ignored. Possibly the spiritual relationship is seen as aboriginal and irrelevant to modern management, while the knowledge-based relationship is sidelined as academic and equally impertinent. When modern society does recognize these dimensions, it often employs them defensively: The inspiration from natural beauty is used to establish protected areas, and biological knowledge is used to set limits to the catch or bag. By contrast, the biological knowledge and spiritual understanding of the traditional hunter enhanced his sense of identity with the prey.

The role of indigenous peoples in sustaining wildlife resources is beginning to be recognized. In a few pioneering ventures, indigenous peoples have participated in the management of protected areas (23). There is room for much greater appreciation and wider incorporation of traditional beliefs, values, and knowledge in contemporary conservation and development. An ongoing exploration of these dimensions in the global context would also constructively broaden the current economic focus.

HyperNotes Related Resources on the World Wide Web

General Hypernotes

Dictionaries and Glossaries

The xrefer Web site provides scientific dictionaries and other reference works.

A glossary of biodiversity terms is provided by the World Resources Institute.

Web Collections, References, and Resource Lists

The Open Directory Project provides links to anthropology, sustainability, and sustainable development Internet resources.

Anthro.Net is a collection of links to anthropology resources on the Web.

EE-Link, a resource for environmental education Internet sources, has a page devoted to endangered species and offers a collection of Internet links on wildlife conservation.

The WWW Virtual Library of sustainable development is maintained by the Center for Economic and Social Studies on the Environment, Université Libre de Bruxelles, Belgium.

The Yearbook of International Co-operation on Environment and Development, a publication from the Fridtjof Nansen Institute in Norway, provides a collection of Internet sources within the field of environment and sustainable development.

A collection of Web resources on conservation and biodiversity is provided by K. Holsinger, Department of Ecology and Evolutionary Biology, University of Connecticut.

Research Resources for the Social Sciences provides a collection of sociology and anthropology Web links.

The Natural Resources Research Information Pages are maintained by Y.-F. Leung, Department of Parks, Recreation and Tourism Management, North Carolina State University.

The Anthropology and the Environment section of the American Anthropological Association provides a collection of Internet links and other resources.

Eco-Portal is an information gateway for resources relating to environmental sustainability.

Online Texts and Lecture Notes

The World Conservation Monitoring Centre of the United Nations Environment Programme (UNEP) provides information resources to support international conservation efforts.

The IUCN (International Union for Conservation of Nature and Natural Resources) has as its mission to influence, encourage, and assist societies throughout the world to conserve the integrity and diversity of nature and to ensure that any use of natural resources is equitable and ecologically sustainable; theme pages on sustainable use and ecosystem management are included. An educational Web site on the biodiversity of life is provided, as is a searchable version of the Red List of Threatened Species.

The World Resources Institute (WRI) offers resource pages on biodiversity and protected areas and governance and institutions, as well as EarthTrends: The Environmental Information Portal. The WRI provides the Sustainable Development Information Service.

The E-Study Center for the fifth edition of R. Ricklefs' The Economy of Nature provides chapter summaries, study aids, and Web resources.

Biodiversity and Conservation is a hypertext book by P. Bryant, School of Biological Sciences, University of California, Irvine.

J. D. Allen, School of Natural Resources and Environment, University of Michigan, offers lectures notes for a course on conserving biological diversity.

A. Galt, Anthropology Program, University of Wisconsin, Green Bay, offers lecture outlines and Web links for an anthropology course on the varieties of world cultures.

B. Orlove, Department of Environmental Science and Policy, University of California, Davis, provides lecture notes for a course on cultural ecology. He also makes available bibliographic and other resources for a course on conservation and sustainable development in third world nations, including a student paper on biodiversity and sustainable development.

E. Smith, Department of Anthropology, University of Washington, provides lecture notes for a course on ecological anthropology.

K. Holsinger, Department of Ecology and Evolutionary Biology, University of Connecticut, offers lecture notes for a course on conservation biology.

General Reports and Articles

Humans and Other Catastrophes, presented by the American Museum of Natural History, offers symposium papers and other resources from a 1997 symposium on extinctions.

The IUCN makes available (in PDF format) their journal World Conservation.

The 3 May 2002 issue of Science had a report by G. Ceballos and P. Ehrlich titled “Mammal population losses and the extinction crisis.” The 19 March 1999 issue had a Policy Forum by A. Inamdar, H. de Jode, K. Lindsay, and S. Cobb titled “Capitalizing on nature: Protected area management.”

Population Action International makes available (in PDF format) a 2000 report titled Nature's Place: Human Population and the Future of Biological Diversity and a March 2003 occasional paper by K. Mogelgaard titled “Helping people, saving biodiversity” about integrated conservation and development projects.

Nature and Human Society: The Quest for a Sustainable World, edited by P. Raven and T. Williams, is a 2000 book made available on the Web by the National Academies Press, which also makes available the 1988 bookBiodiversity, edited by E. O. Wilson, and the 1996 bookBiodiversity II, edited by M. Reaka-Kudla, D. Wilson, and E. O. Wilson.

Numbered Hypernotes

1. Sustainable development. An Encyclopedia of Sustainable Development is provided by the Atmosphere, Climate & Environment Information Programme, Manchester Metropolitan University, UK. Sustainable development Web pages are provided by the United Nations, the Food and Agriculture Organization, the European Commission, and the World Bank. The National Strategies for Sustainable Development Web site provides (in PDF format) Sustainable Development Strategies: A Resource Book and other documents on sustainable development, as well as a collection of Internet links. The International Development Research Centre provides information about its sustainable use of biodiversity program and other environment and natural resource management programs.

2. Community control of natural resources. The IUCN's Commission on Environmental, Economic and Social Policy provides information about the working groups on sustainable livelihoods and collaborative management of natural resources. WRI makes available in PDF format a 2002 report by J. Ribot titled “Democratic decentralization of natural resources: Institutionalizing popular participation” and a 2002 report by M. Dupar and N. Badenoch titled “Environment, livelihoods and local institutions: Decentralization in mainland southeast Asia.” The Biodiversity Support Program makes available a case study by R. Hitchcock titled “Decentralization, development, and natural resource management in the northwestern Kalahari Desert, Botswana.” The International Foundation for the Conservation of Wildlife offers a presentation on sustainable wildlife utilization in sub-Saharan Africa. The Community Based Natural Resource Management (CBNRM) in Southern Africa Web site provides background information about the program and Internet links to related resources. The CBMRM Support Programme in Botswana provides information on conservation issues and indigenous peoples; a collection of links to related or similar programs are provided. CAMPFIRE (Communal Areas Management Programme for Indigenous Resources) in Zimbabwe seeks to involve rural communities in conservation and development by returning to them the stewardship of their natural resources.

3. The overkill hypothesis and Pleistocene extinctions. A section on the Pleistocene overkill hypothesis is included in a student presentation on Pleistocene extinctions by A. Lee, prepared for a biogeography course taught by R. Byrne, Department of Geography, University of California, Berkeley. The BBC's Extinction Files include a section on the overkill hypothesis for the Pleistocene extinction. Humans and Other Catastrophes includes an introduction to the overkill hypothesis as a cause of Pleistocene extinctions in North America. The Emuseum of Minnesota State University, Mankato, offers a presentation on ancient hunters of North American megafauna. The chapter on Pleistocene extinctions from The Ecological Indian by S. Krech is available on the New York Times Web site (free with registration). The Illinois State Museum offers a presentation on late Pleistocene extinctions. J. Aber, Earth Science Department, Emporia State University, KS, provides lecture notes on megafauna extinctions in North America for a course on Ice Age environments.

4. Extinction of large flightless birds in New Zealand. The 24 March 2000 issue of Science had an Enhanced Perspective by J. Diamond titled “Blitzkrieg against the moas” about a report in that issue by R. N. Holdaway and C. Jacomb titled “Rapid extinction of the moas (Aves: Dinornithiformes): Model, test, and implications.” The University of Wisconsin's Why Files offer a presentation on the moa extinction in New Zealand.

5. The North American fur trade. P. Bryant's Biodiversity and Conservation includes a section on the American fur trade in the chapter on extinction and depletion from over-exploitation. The online Canadian Encyclopedia provides information about the fur trade. R. Schaetzl, Department of Geography, Michigan State University, provides lecture notes on the fur trade for a course on Michigan geography. In Pursuit of Adventure: The Fur Trade in Canada and the North West Company is a research resource made available by the McGill University Digital Collections Program; a section on the effects of the fur trade on native peoples is included.

6. The “bushmeat” crisis. BBC News provides a 3 August 2000 article by A. Kirby titled “Bush meat 'destroying African species'” and a 4 June 2002 article by Kirby titled “The cost of bushmeat,” as well as a 10 April 2002 article titled “UK project tackles bushmeat diet.” A section on the bushmeat crisis is included in Saving the Last Edens, a Why Files presentation. The June 2001 issue of Scientific American had an article by J. Hearn titled “Unfair game: The bushmeat trade is wiping out large African mammals.” The Jane Goodall Institute provides a bushmeat factsheet. TRAFFIC, the wildlife trade monitoring network, issued a 2000 report titled “Food for Thought: The utilization of wild meat in eastern and southern Africa.”

7. Red deer stalking in the Scottish highlands. The UK Deer Initiative Web site provides information on red deer and conservation and red deer stalking. A report on red deer in Scotland is provided in PDF format by WWF-UK.

8. Passenger pigeons. P. Bryant's Biodiversity and Conservation includes a section on the passenger pigeon extinction. The Canadian Museum of Nature includes an entry on the passenger pigeon in its presentation on endangered and extinct animals. The Birds of Stanford Web site offers an essay on passenger pigeons. G. Landry's passenger pigeon history Web page makes available Audubon's writings on passenger pigeons.

9. African elephants and the ivory trade. WWF provides a resource page on the African elephant. The IUCN's African Elephant Specialist Group provides background information and reports and other resources on African elephants. The African Wildlife Foundation offers a presentation on elephant conservation. The Elephants of Africa is a production of PBS's Nature. The Elephant Information Repository includes sections of links on conservation and ivory. American University's Trade and Environment Database makes available case studies on the legal elephant ivory trade and the elephant ivory trade ban. CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) provides information on monitoring projects to track illegal activities involving elephants; the text of the current CITES resolution on trade in elephant specimens is made available.

10. The Bushmen of the Kalahari. The online Columbia Encyclopedia has entries for the San (Bushmen) and the Kalahari. An entry for Kalahari Desert is included in xrefer's Macmillan Encyclopedia; an entry about the Khoisan (the Bushman and Hottentot peoples of southern Africa) is also available. The Iziko Museums of Cape Town offer a presentation on hunter-gatherers in southern Africa. The Working Group for Indigenous Minorities of Southern Africa provide an introduction to the San. The Kalahari Peoples Fund provides information about the San. N. Brett makes available a presentation on San culture. The December 1997 issue of Out There Magazine had an article by E. Koch and P. Weinberg about the San people tilted “Portrait of a culture in crisis.”

11. Private wildlife conservation in southern Africa. The Center for Private Conservation makes available (in PDF format) a paper by K. Muir-Leresche and R. Nelson titled “Private property rights to wildlife: The southern African experiment.” The IUCN's Biodiversity Economics Library makes available (in PDF format) a meeting paper by W. Krug titled “Private supply of protected land in southern Africa: A review of markets, approaches, barriers and issues.”

12. Native Americans. The Native Americans and the Environment Web site, a part of the National Library for the Environment, provides online documents and links to Internet sites; a collection of links to publications on cultural and historic issues is included. The National Humanities Center offers essays on Native Americans and the land. The Religious Movement Home Page at the University of Virginia makes available a presentation on Native American spirituality with links to Web resources on Native Americans. The Canadian Museum of Civilization makes available a history of the native people of Canada.

13. An entry on game laws is provided by the online Columbia Encyclopedia. The online 1911 Encyclopedia includes an article on game laws in Britain and their history. The New Forest Web site offers a presentation on the forest's history up to 1189 with an account of the game (forest) laws.

14. An entry for Bushman painting is included in xrefer's Thames & Hudson Dictionary of Art and Artists. The Iziko Museums of Cape Town offer presentations on southern African rock art and an article by W. J. van Rijssen titled “Rock paintings and engravings: Artistic keys to the past.” The Rock Art Research Institute, Department of Archaeology, University of the Witwatersrand, provides information about its mission and research.

15. M. Murray is at the Institute of Cell, Animal and Population Biology, University of Edinburgh.

References and Notes


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