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Conservation Biology


CONSERVATION BIOLOGY, an interdisciplinary, mission-oriented science with the goal of alleviating the extinction crisis and fostering biological diversity. Conservation biologists include researchers and managers from fields as varied as ecology, genetics, evolution, biogeography, wildlife biology, forestry, captive species breeding, and restoration ecology. Scientists hope that by studying why species become extinct, they can improve the management of natural areas and endangered species in ways that will prevent further extinctions.

The groundwork for the modern field of conservation biology was laid in the early 1900s with the development of the fields of fisheries, forestry, and wildlife management, along with the first modern formulation of a land ethic, generally credited to Aldo Leopold. Tremendous theoretical progress in community ecology and biogeography during the 1960s and 1970s established a scientific foundation for conservation. At the same time, growing evidence of the massive extinction of species was raising concern within the biological community. Experts estimated that as many as a quarter of all surviving species could be doomed to extinction by the year 2025 if current trends continued. As many as 20,000 species could be lost or doomed every year, most of them unknown to Western science, and virtually all of them victims of human activity.

According to Harvard professor E. O. Wilson, a leader in the field, the current rate of extinction (the number of species lost each year) is between 1,000 and 10,000 times greater than the estimated rate of extinction before the evolution of humans. A species may be vulnerable to extinction for many reasons. Small populations can be wiped out by random local events, social dysfunction, or genetic deterioration. Species that cannot disperse well or that reproduce slowly are in danger. Those exploited by humans are particularly vulnerable because harvesting may drive populations too low, either inadvertently or intentionally. Species dependent on a threatened habitat will suffer the fate of that habitat. Species with large home ranges, such as elk, caribou, bears, and wolves, are also vulnerable because it is difficult for conservationists to protect a land area large enough to support a viable population. (A viable population has a 95 percent probability or better of surviving for more than 100 years.)

From its inception, two core goals of conservation biology have been to preserve functioning samples of all global ecosystems in their natural range and to maintain viable populations of all native species within those ecosystems. Part of the challenge to conservation biologists has been to use scientific principles to select and manage wildlife reserves that meet these two goals. Historically, most parks and other protected areas were chosen for aesthetic or recreational value or because they appeared to have no desirable extractable resources. Conservation biologists now help to choose and redesign protected areas to foster biological diversity.

In practice, this has meant developing a few rules for designing refuges. First, large areas are preferable to small ones because larger areas are more likely to support species with extensive home ranges, and the larger area provides more of a buffer between the refuge and human activities on surrounding lands. Natural disturbances, such as fires and floods, are also less likely to cause extinctions when species can move away from the disturbance yet still remain on protected lands. This is particularly important because some ecosystems require periodic disturbances to maintain their integrity. Some tree species in Yellowstone National Park, for example, require fire to establish seedlings and regenerate the forest. Conversely, periodic fires help maintain midwestern prairie ecosystems where most tree species are not well-adapted to fire. Second, protected zones should have few roads, because they en-courage increased human activities, such as logging, trampling, hunting, and dumping, which may be detrimental to native flora and fauna, and because even the mere presence of roads themselves can affect the suitability of an ecosystem for certain species, especially certain birds. Third, protected zones should be close together and connected. Linkages increase the effective size of protected areas by permitting seasonal movements or migrations, dispersal to prevent inbreeding or to recolonize other sites, and long-distance range shifts in response to climate change.

Because of the sweeping ecological change that has already occurred, in addition to preventing further extinctions, many conservation biologists argue that attempts must be made to restore threatened and endangered ecosystems, populations, and species. Restoration ecology has been the subject of considerable controversy. Questions central to the debate include whether current levels of scientific knowledge and technology make restoration feasible, how scientists can measure the successes and failures of restoration projects, whether preservation is more cost-effective than restoration, and whether it is appropriate to remove preservationist constraints on one site, thus allowing rapid environmental change, on the promise that another site will be restored to a former habitat, a process often fraught with problems, delays, and unforeseen expenses.

While these issues remain unresolved, majority opinions within the world of conservation biology have emerged. First, preservation is generally more cost-effective than restoration. Second, because ecological change and damage are ongoing, restoration projects must be attempted despite failures. Third, it is unwise to allow the possibility of restoration to support the continued expansion of ecologically destructive practices. Fourth, measurement of restoration must include scrutiny of ecosystem function over the long term.

At the start of the twenty-first century, the Society for Conservation Biology (SCB), one of the most prominent organizations in the field of conservation biology, brought together a wide range of interested people, including resource managers, public and private conservation workers, and students and educators from around the world to study—and take action to solve—the problems associated with protecting biological diversity. Because the goals and purposes of conservation biology are political in addition to scientific, research in the field typically is linked to an explicit ecological agenda. Michael Soule, a cofounder of SCB, described conservation biology as a "crisis discipline," in which it is sometimes necessary to make tactical decisions without information. He proposes that in crisis disciplines "the risks of nonaction may be greater than the risks of inappropriate action."


Ehrlich, Paul R., and Anne H. Ehrlich. Extinction. New York: Random House, 1981.

Noss, Reed F. "The Wildlands Project Land Conservation Strategy." Wild Earth (1993): 10–25.

Soule, Michael E. Conservation Biology. Washington, D.C.: Island Press, 2001.

Susan J.Cooper/c. w.

See alsoConservation ; Endangered Species ; Marine Sanctuaries ; Species, Introduced ; Wildlife Preservation .

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Conservation Biology

Conservation Biology

Conservation biology is the study of the biological diversitybiodiversity for shortof Earth. Biodiversity is the variety of different living creatures, both plants and animals. Conservation biology is a relatively new field of study, having its start in the 1980s. It applies the principles of many sciences in order to preserve biodiversity throughout the world.

While at the end of the twentieth century the number of described species was about 1.7 million, estimates put the total number of species at 5 to 30 million. Many scientists believe that Earth is experiencing the greatest episode of mass extinction since the extinction of the dinosaurs 65 million years ago. Current rates of species extinctions throughout the world are believed to be 50 to 100 times greater than rates prior to human impact. In tropical forests, the extinction rates are believed to be 1,000 to 10,000 times higher than the expected rate. Given the current rates of extinction, by the year 2020, 30 to 70 percent of the world's species will be extinct. This crisis is thought to be due largely to human activities. Human population reached 6 billion in September 1999. Every day, this number increases by an estimated 250,000 (an extra 87 million people per year). This huge human population is straining Earth's natural resources in many ways.

The leading factor in the increasing rate of species extinctions has been the human destruction of natural areas where plants and animals live. Since 1950, one-third of the world's forests have been destroyed. Loss of tropical rain forest is estimated at an acre every second. It is estimated that humans consumed one-third of the world's natural resources during the period 1970 to 1995. It has also been estimated that the United States, with only about 5 percent of the world's population, consumes 25 percent of the world's resources and generates 25 to 30 percent of the world's waste.

Other human activities that are increasing species extinctions are the pollution of the environment and the overexploitation of animals, such as whales and tigers, that have commercial value.

There are many reasons to conserve and protect biodiversity. New species could provide new food sources for humans. Genes from wild plants are used to improve food crops. New plants and animals can be used as biological control agents to control pests. Nearly all the medicines used today were derived from plants or animals, and other species may provide important new medicines. Plants and animals carry out many functions in the environment that are critical to humans. For example, bees and bats pollinate flowering plants, and green plants provide oxygen.

There are other less practical reasons to preserve biodiversity. Plants and animals are beautiful and interesting. Humans gain much pleasure and peace of mind interacting with the natural world. In addition, there is the argument that all species have value regardless of their worth to humans.

Denise Prendergast


Meffe, Gary K., C. Ronald Carroll, et al. Principles of Conservation Biology, 2nd ed. Sunderland, MA: Sinauer Associates, Inc., 1997.

Internet Resources

Bryant, Peter J. Biodiversity and Conservation: A Hypertext Book. <>.

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