Endangered Species

Human causes of extinction and endangerme

Why are endangered species important?

Resources

An endangered species of plant, animal, or microorganism is at risk of imminent extinction or extirpation in all or most of its range. Extinct species no longer exist anywhere on Earth, and once gone they are gone forever. Extirpated species have disappeared locally or regionally, but still survive in other regions or in captivity. Threatened species are at risk of becoming endangered in the foreseeable future. In the United States, the Endangered Species Act (ESA) of 1973 protects threatened and endangered species that meet specified criteria. Many nations have their own version of the ESA and, like the United States, are members of the World Conservation Union (IUCN), and signatories of the Convention on International Trade In Endangered Species of Wild Fauna and Flora (CITES).

Species have become extinct throughout geological history. Biological evolution, driven by natural climate change, catastrophic geologic events, and competition from better-adapted species, has resulted in the extinction of billions of species since the advent of life on Earth about three billion years ago. In fact, according to the fossil record, only 2–4% of the species that have existed on Earth exist today. In modern times, however, species threatened by human activities are becoming extinct at a rate that far exceeds the pace of extinction throughout most of geologic history. (The mass species extinctions that occurred at the end of the Paleozoic and Mesozoic eras are noteworthy exceptions to this generalization. Geologic data show evidence that a cluster of very large meteorite impacts killed about 85% of Earth’s species, including the dinosaurs, about 65 million years ago at the end of the Mesozoic Cretaceous era.) Meteorite impacts notwithstanding, scientists approximate that present extinction rates are 1, 000 to 10, 000 times higher than the average natural extinction rate.

Human causes of extinction and endangerme

Human activities that influence the extinction and endangerment of wild species fall into a number of categories: (1) unsustainable hunting and harvesting that cause mortality at rates that exceed recruitment of new individuals, (2) land use practices like deforestation, urban and suburban development, agricultural cultivation, and water management projects that encroach upon and/or destroy natural habitat, (3) intentional or unintentional introduction of destructive diseases, parasites, and predators, (4) ecological damage caused by water, air, and soil pollution, and (5) anthropogenic (human-caused) global climate change. Alone, or in combination, these stressors result in small, fragmented populations of wild flora and fauna that become increasingly susceptible to inbreeding, and to the inherent risks of small abundance, also called demographic instability. Without intervention, stressed populations often decline further, and become endangered.

Why are endangered species important?

Sociopolitical actions undertaken to preserve endangered species and their natural habitats often conflict with human economic interests. In fact, efforts to protect an endangered species usually require an economic sacrifice from the very business or government that threatened the plant or animal in the first place. It is necessary, therefore, to define endangered species in terms of their aesthetic, practical, and economic value for humans. Preservation of endangered species is important and practical for a number of reasons: (1) organisms other than humans have intrinsic moral and ethical value, and a natural right to exist, (2) many plants and animals have an established economic value, as is the case of domesticated species, and

exploited wildlife like deer, salmon, and trees, (3) other species, including undiscovered medicinal plants and potential agricultural species, have as-yet unknown economic value, and (4) most species play a critical role in maintaining the health and integrity of their ecosystem, and are therefore indirectly important to human welfare. Such ecological roles include nutrient cycling, pest and weed control, species population regulation, cleansing chemical and organic pollution from water and air, erosion control, production of atmospheric oxygen, and removal of atmospheric carbon dioxide.

Rates of endangerment and extinction have increased rapidly in concert with human population growth. Though accelerating habit loss and extinction rates are hallmarks of the modern biodiversity crisis, the link between human enterprise and species extinction has existed for almost 100, 000 years, during which time Australia, the Americas, and the world’s islands lost 74–86% of their animals larger than 97 lb (44 kg). In North and South America, the disappearance of numerous large animals, including extraordinary species like mammoths, saber-toothed cats, giant ground sloths, and armored glyptodonts coincided with the arrival of significant population of humans between 11, 000 and 13, 000 years ago. More than 700 vertebrate animals, including about 160 species of birds and 100 mammals, have become extinct since 1600 AD.

There is no accurate estimate of the number of endangered species. A thorough census of Earth’s smallest and most numerous inhabitants—insects, marine microorganisms, and plants—has yet to be conducted. Furthermore, ecologists believe that a large percentage of Earth’s as-yet uncataloged biodiversity resides in equatorial rainforests. Because human development is rapidly converting their tropical forest habitat into agricultural land and settlements, many of the unnamed species of tropical animals and plants are likely endangered.

The 2006 IUCN Red List of Threatened Species lists 16, 118 species of plants and animals facing imminent extinction. The Red List includes approximately 1 in 5 mammal species, and 1 in 8 bird species. While only 3% of all plant species are included in the Red List; nearly one third of all gymnosperms are on the list. In the United States, where species must meet a stringent set of criteria to be listed as endangered under the ESA, in 2006 the list of endangered species included 932 animal species and 599 plant species. The humid Southeast and the Pacific Northwest have the largest numbers of endangered species in the United States. These regions tend to have unique ecological communities with many narrowly-distributed endemic species, as well as extensive human urbanization and resource development that threaten them.

There are numerous examples of endangered species. In this section, a few cases are chosen that illustrate the major causes of extinction, the socioeconomic conflicts related to protection of endangered species, and some possible successful strategies for wildlife protection and conflict resolution.

Species endangered by unsustainable hunting

Overhunting and overfishing have threatened animal species since aboriginal Europeans, Australians, and Americans developed effective hunting technology thousands of years ago. The dodo, passenger pigeon, great auk, and Steller’s sea cow were hunted to extinction. Unsustainable hunting and fishing continue to endanger numerous animals worldwide. In the United States, many of the animals considered national symbols—bald eagle, grizzly bear, timber wolf, American bison, bighorn sheep, and Gulf of Mexico sea turtles—have been threatened by over-hunting. (American bison, incidentally, are no longer considered threatened, but they exist mainly in managed herds, and have never repopulated their wide range across the American and Canadian west.)

The Eskimo curlew is a large sandpiper that was abundant in North America in the nineteenth century. The birds were relentlessly hunted by market gunners during their migration from the prairies and coasts of Canada and the United States to their wintering grounds on the pampas and coasts of South America. The Eskimo curlew became very rare by the end of the nineteenth century. The last observation of a curlew nest was in 1866, and the last “collection” of birds was in 1922. There have been a few reliable sightings of individuals in the Canadian Artic and small migrating flocks in Texas since then, but sightings are so rare that the species’ classification changes to extinct between each one.

The Guadalupe fur seal was abundant along the coast of western Mexico in the nineteenth century, numbering as many as 200, 000 individuals. This marine mammal was hunted for its valuable fur and almost became extinct in the 1920s. Fortunately, a colony of 14 seals, including pups, was discovered off Baja California on Guadalupe Island in 1950. Guadalupe Island was declared a pinnaped sanctuary

in 1975; the species now numbers more than 1, 000 animals, and has begun to spread throughout its former range. The Juan Fernandez fur seal of Chile had a similar history. More than three million individuals were killed for their pelts between 1797 and 1804, when the species was declared extinct. The Juan Fernandez seal was rediscovered in 1965; and its population presently numbers several thousand individuals.

Commercial whaling for meat and oil since the eighteenth century has threatened most of the world’s baleen whale species, and several toothed whales, with extinction. (Baleen whales feed by straining microorganisms from seawater.) Faced with severe depletion of whale stock, 14 whaling nations formed the International Whaling Commission (IWC) in 1946. While the IWC was somewhat successful in restoring whale populations, it lacks authority to enforce hunting bans, and non-member nations often threaten to disregard IWC directives. The Marine Mammal Protection Act of 1972 banned all whaling in United States waters, the CITES treaty protects all whale species, and many whales have been protected by the ESA. In spite of these measures, only a few whale species have recovered to their pre-whaling populations, and a number of species remain on the brink of extinction. Eight whales remain on the ESA list today: blue whale, bowhead whale, finback whale, gray whale, sei whale, humpback whale, right whale, and sperm whale. The California gray whale is a rare success story. This species was twice hunted near extinction, but it has recovered its pre-whaling population of about 21, 000 individuals. In 1994, the gray whale was delisted from the east Pacific Ocean, but remains an endangered species in the west Pacific Ocean.

Large predators and trophies

Many large predators are killed because they compete with human hunters for wild game like deer and elk, because they prey on domestic animals like sheep, or sometimes because they threaten humans. Consequently, almost all large predators whose former range has been developed by humans have become extirpated or endangered. The list of endangered large predators in the United States includes most of the species that formerly occupied the top of the food chain, and that regulated populations of smaller animals and fishes: grizzly bear, black bear, gray wolf, red wolf, San Joaquin kit fox, jaguar, lynx, cougar, mountain lion, Florida panther, bald eagle, northern falcon, American alligator, and American crocodile.

A number of generally harmless species are endangered because of their threatening appearance or reputation, including several types of bats, condors, non-poisonous snakes, amphibians, and lizards. Internationally, many endangered species face extinction because of their very scarcity. Though CITES agreements attempt to halt trade of rare animals and animal products, trophy hunters, collectors of rare pets, and traders of luxury animal products continue to threaten numerous species. International demand for products like elephant tusk ivory, rhino horn, aquarium fish, bear and cat skins, pet tropical birds, reptile leather, and tortoise shells have taken a toll on many of Earth’s most extraordinary animals.

Endangerment caused by introduced species

In many places, vulnerable native species have been decimated by non-native species imported by humans. Predators like domestic cats and dogs, herbivores like cattle and sheep, diseases, and broadly-feeding omnivores like pigs have killed, starved, and generally outcompeted native species after introduction. Some destructive species introductions, like the importation of mongooses to the Pacific islands to control snakes, are intentional, but most of the damage caused by exotic species and diseases is unintended.

For example, the native birds of the Hawaiian archipelago are dominated by a family of about 25 species known as honeycreepers. Thirteen species of honeycreepers have been rendered extinct by introduced predators and habitat loss since Polynesians discovered the islands, and especially since European colonization. The surviving 12 species of honey-creepers are all endangered; they continue to face serious threats from introduced diseases, like avian malaria, to which they have no immunity.

Deliberate introduction of the Nile perch caused terrible damage to the native fish population of Lake Victoria in eastern Africa. Fisheries managers stocked Lake Victoria, the world’s second-largest lake, with Nile Perch in 1954. In the 1980s the perch became a major fishery resource and experienced a spectacular population increase that was fueled by predation on the lake’s extremely diverse community of cichlid fishes. The collapse of the native fish community of Lake Victoria, which originally included more than 400 species, 90% of which only occurred in Lake Victoria, resulted in the extinction of about one-half of Earth’s cichlid species. Today, most of the remaining cichlids are endangered, and many of those species exist only in captivity.

Species living on islands are especially vulnerable to introduced predators. In one case, the accidental introduction of the predatory brown tree snake to the Pacific island of Guam in the late 1940s caused a severe decline of native birds. Prior to the introduction of the snake there were 11 native species of birds on Guam, most of which were abundant. By the mid-1980s seven of the native species were extinct or extirpated on Guam, and four more were critically endangered. The Guam rail, a flightless bird, is now extinct in the wild, although it survives in captivity and will hopefully be captive-bred and released to a nearby, snake-free island.

Endangerment caused by habitat destruction

Many species have become extinct or endangered as their natural habitat has been converted for human land-use purposes. The American ivory-billed woodpecker, for example, once lived in mature, bottomland hardwood forests and cypress swamps throughout the southeastern United States. These habitats were heavily logged and/or converted to agricultural land by the early 1900s. For more than 40 years there were no reliable sightings of the American ivory-billed woodpecker, and it was assumed to be extinct in North America. However, in 2002 and again in 2004, sightings of the ivory-billed woodpecker were confirmed in central Arkansas. Major efforts are underway to protect this rare animals habitat. A related subspecies, the Cuban ivory-billed woodpecker, is also critically endangered because of habitat loss, as is the closely related imperial woodpecker of Mexico.

The black-footed ferret was first discovered in the North American prairie in 1851. This small predator became endangered when the majority of its grassland habitat was converted to agricultural use. Farming in the American and Canadian plains also dramatically reduced the population of prairie dogs, the blackfooted ferret’s preferred food.

Furbish’s lousewort is an example of a botanical species endangered by habitat destruction. This herbaceous plant only occurs along a 143-mi (230-km) reach of the St. John River in Maine and New Brunswick. It was considered extinct until a botanist “re-discovered” it in Maine in 1976. At that time, a proposed hydro-electric reservoir threatened the entire habitat of Furbish’s lousewort. In the end, the controversial dam was not built, but the lousewort remains threatened by any loss of its habitat.

The northern spotted owl lives in the old-growth conifer forests of North America’s Pacific Northwest. These small owls require large areas of uncut forest to breed, and became endangered when their habitat was greatly reduced and fragmented by heavy logging. The Environmental Species Act prescribes, and legally requires, preservation of large areas of extremely valuable timberland to protect the northern spotted owl. Upon receiving its status as an endangered species, the otherwise unremarkable owl became a symbol of the conflict between environmental preservation and commercial enterprise. For environmentalists, endangered classification of northern spotted owl brought the possibility of protecting the forests from all exploitation; for timber industry workers, the decision represented the government’s choice to preserve a small bird instead of their livelihood. Small stores on the back roads of the Pacific Northwest expressed their resentment for the ESA by advertising such specialties as “spotted owl barbeque” and activities as “spotted owl hunts.”

Like the northern spotted owl, the endangered red-cockaded woodpecker of the southeastern United States requires old-growth pine forest to survive. The woodpecker excavates nest cavities in heart-rotted trees, and younger plantation trees do not meet its needs. Suitable forests have been greatly diminished by conversion to agriculture, logging, and residential development. Natural disturbance like hurricanes and wildfires threaten the remaining diminished and fragmented populations of red-cockaded woodpeckers. The ESA has attempted to protect the red-cockaded woodpecker by establishing ecological reserves and non-harvested buffers around known nesting colonies outside the reserves. Also like the spotted owl, the red-cockaded woodpecker is maligned by farmers, loggers, and developers for its role in their economic restriction.

Tropical deforestation presents represents the single greatest threat to endangered species today, though destruction of coastal and shallow marine habitats associated with anthropogenic global warming may present an even larger challenges in the future. While there was little net change (-2%) in the total forest cover of North America between the 1960s and the 1980s, the global area of forested land decreased by 17% during that period. Conversion of species-rich tropical forests in Central America, South America, Africa, and the Pacific islands to unforested agricultural land accounts for most of the decline. (Ironically, tropical soils have such poor structure and nutrient content that they generally cannot support profitable agriculture once the forest biomass has been removed.)

In the mid-1980s, tropical rainforests were being cleared at a rate of 15–20 million acres (6–8 million hectares) per year, or about 6–8% of the total equatorial forest area. The causes of tropical deforestation include conversion to subsistence and market agriculture, logging, and harvesting of fuelwood. All of these activities represent enormous threats to the multitude of endangered species native to tropical countries.

Recent efforts to slow the rate of deforestation have included international financial and scientific aid to help poorer tropical nations protect important ecosystems, and to adopt new, more sustainable, methods of profitable resource use.

Actions to protect endangered species

Numerous international agreements deal with issues related to the conservation and protection of endangered species. The scientific effort to more accurately catalog species and better define the scope of biodiversity has dramatically raised the number of recorded threatened and endangered species in recent years. In spite of these shocking statistics of endangerment, there is a good deal of evidence that national and international efforts to preserve endangered species have been very successful.

Some of the most important international conventions are ratified by most of the world’s nations, and have had significant power to enforce agreements in the decades since their introduction: (1) the 1971 Convention on Wetlands of International Importance that promotes wise use of wetlands and encourages designation of important wetlands as ecological reserves; (2) the 1972 Convention Concerning the Protection of the World Cultural and Natural Heritage that designates of high-profile World Heritage Sites for protection of their natural and cultural values; (3) the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES); (4) the 1979 Convention on the Conservation of Migratory Species of Wild Animals of 1979 that deals with species that regularly cross national boundaries or that occur in international waters; and (5) the 1992 Convention on Biological Diversity (CBD). The CBD was presented by the United Nations Environment Program (UNEP) at the United Nations Conference on Environment and Development at Rio de Janeiro, Brazil in 1992, and has been regularly updated since then; the most recent conference of the CBD occurred in 2006 in Curitiba, Brazil. The CBD is a central element of another international program called the Global Biodiversity Strategy, a joint effort by the IUCN, UNEP, and the World Resources Institute to study and conserve biodiversity.

Many countries, like the United States, have also undertaken their own actions to catalog and protect endangered species and other elements of biodiversity. Many of these national conservation efforts, like the ESA, have and international component that deals

KEY TERMS

Endangerment— Refers to a situation in which a species is vulnerable to extinction or extirpation.

Endemic— Refers to species with a relatively local distribution, sometimes occurring as small populations confined to a single place, such as a particular oceanic island. Endemic species are more vulnerable to extinction than are more widespread species.

Extinction— The condition in which all members of a group of organisms have ceased to exist.

Extirpation— The condition in which a species is eliminated from a specific geographic area of its habitat.

with species migration and trade across borders, and that mesh with the international conventions. Another important aspect of endangered species protection is collaboration with non-governmental organizations like the World Wildlife Fund, the Nature Conservancy and the Ocean Conservancy. The United States, for example, has a network of conservation data centers (CDCs) that gather and compile information on the occurrence and abundance of biological species and ecosystems that was designed and established by The Nature Conservancy. The Nature Conservancy has also facilitated development of CDCs in Canada and in Central and South America.

International, national and non-governmental agencies attempting to conserve biodiversity and protect endangered species choose whether to pursue single-species approaches that focus on particular species, or to develop more comprehensive strategies that focus on larger ecosystems. Because there are so many endangered species, many of which have not even been discovered, the single-species approach has obvious limitations. While the method works well for charismatic, large animals like giant pandas, grizzly bears, whales, and whooping cranes, this approach fails to protect most endangered species. More effective strategies focus on entire natural ecosystems that include numerous, hidden elements of threatened biodiversity. Furthermore, more conservation policies are attempting to consider the social, political, and economic ramifications of a species or environmental protection plan. As in the case of the northern spotted owl, policies that require large economic sacrifices and offer no immediate local benefits often alienate the very humans that could best help to preserve an endangered species or ecosystem. Modern environmental protection strategies attempt to present alternatives that permit sustainable human productivity.

See also Stress, ecological.

Resources

BOOKS

MacKay, Richard. The Penguin Atlas of Endangered Species: A Worldwide Guide to Plants and Animals. New York: The Penguin Group, 2002.

Wilson, E.O. The Diversity of Life. Cambridge: Harvard University Press, 1992.

OTHER

International Union for Conservation of Nature and Natural Resources. “IUCN Red List of Threatened Species.” October 2, 2006. <http://www.iucnredlist.org/> (accessed October 16, 2006).

United Nations Environment Programme. “Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).” 2005 <http://www.cites.org/index.html> (accessed October 16, 2006).

United States Fish and Wildlife Service. “The United States Endangered Species Program.” October12, 2006 web http://www.fws.gov/endangered/> (accessed October 16, 2006).

World Wildlife Fund. “Endangered Species.” 2006. <http://www.worldwildlife.org/endangered/> (accessed October 16, 2006).

Bill Freedman

Laurie Duncan

Endangered species

An endangered species of plant , animal , or microorganism is at risk of imminent extinction or extirpation in all or most of its range. Extinct species no longer occur anywhere on Earth , and once gone they are gone forever. Extirpated species have disappeared locally or regionally, but still survive in other regions or in captivity. Threatened species are at risk of becoming endangered in the foreseeable future. In the United States, the Endangered Species Act (ESA) of 1973 protects threatened and endangered species that meet specified criteria. Many nations have their own version of the ESA and, like the United States, are members of the World Conservation Union (IUCN), and signatories of the Convention on International Trade In Endangered Species of Wild Fauna and Flora (CITES).

Species have become extinct throughout geological history. Biological evolution , driven by natural climate change, catastrophic geologic events, and competition from better-adapted species, has involved extinction of billions of species since the advent of life on Earth about three billion years ago. In fact, according to the fossil record, only 2–4% of the species that have existed on Earth exist today. In modern times, however, species threatened by human activities are becoming extinct at a rate that far exceeds the pace of extinction throughout most of geologic history. (The mass species extinctions that occurred at the end of the Paleozoic and Mesozoic eras are noteworthy exceptions to this generalization. Geologic data show evidence that a cluster of very large meteorite impacts killed about 85% of the Earth's species, including the dinosaurs, about 65 million years ago at the end of the Mesozoic Cretaceous era.) Meteorite impacts notwithstanding, scientists approximate that present extinction rates are 1,000 to 10,000 times higher than the average natural extinction rate.

Human causes of extinction and endangerment

Human activities that influence the extinction and endangerment of wild species fall into a number of categories: (1) unsustainable hunting and harvesting that cause mortality at rates that exceed recruitment of new individuals, (2) land use practices like deforestation , urban and suburban development, agricultural cultivation, and water management projects that encroach upon and/or destroy natural habitat, (3) intentional or unintentional introduction of destructive diseases, parasites , and predators, (4) ecological damage caused by water, air, and soil pollution , and (5) anthropogenic (human-caused) global climate change. Alone or in combination, these stressors result in small, fragmented populations of wild flora and fauna that become increasingly susceptible to inbreeding, and to the inherent risks of small abundance, also called demographic instability. Without intervention, stressed populations often decline further, and become endangered.

Why are endangered species important?

Sociopolitical actions undertaken to preserve endangered species and their natural habitats often conflict with human economic interests. In fact, efforts to protect an endangered species usually require an economic sacrifice from the very business or government that threatened the plant or animal in the first place. It is necessary, therefore, to define endangered species in terms of their aesthetic, practical, and economic value for humans. Preservation of endangered species is important and practical for a number of reasons: (1) organisms other than humans have intrinsic moral and ethical value, and a natural right to exist, (2) many plants and animals have an established economic value, as is the case of domesticated species, and exploited wildlife like deer , salmon , and trees, (3) other species, including undiscovered medicinal plants and potential agricultural species, have as-yet unknown economic value, and (4) most species play a critical role in maintaining the health and integrity of their ecosystem , and are therefore indirectly important to human welfare. Such ecological roles include nutrient cycling, pest and weed control, species population regulation, cleansing chemical and organic pollution from water and air, erosion control, production of atmospheric oxygen , and removal of atmospheric carbon dioxide .

Rates of endangerment and extinction have increased rapidly in concert with human population growth. Though accelerating habit loss and extinction rates are hallmarks of the modern biodiversity crisis, the link between human enterprise and species extinction has existed for almost 100,000 years, during which time Australia , the Americas, and the world's islands lost 74–86% of their animals larger than 97 lb (44 kg). In North and South America , the disappearance of numerous large animals, including extraordinary species like mammoths, sabre-toothed cats , giant ground sloths , and armoured glyptodonts coincided with the arrival of significant population of humans between 11,000 and 13,000 years ago. More than 700 vertebrate animals, including about 160 species of birds and 100 mammals , have become extinct since a.d. 1600.

There is no accurate estimate of the number of endangered species. A thorough census of the earth's smallest and most numerous inhabitants—insects, marine microorganisms , and plants—has yet to be conducted. Furthermore, ecologists believe that a large percentage of the earth's as-yet uncataloged biodiversity resides in equatorial rainforests. Because human development is rapidly converting their tropical forest habitat into agricultural land and settlements, these multitudinous, unnamed species of small invertebrates and tropical plants are categorically endangered. There are perhaps several million endangered species, most of which are invertebrates living in tropical forests .

The large number of recorded threatened and endangered species is particularly disturbing given the small percentage of organisms evaluated during compilation of lists. The 2000 IUCN Red List of Threatened Species lists 11,046 species of plants and animals facing imminent extinction around the world. The Red List includes approximately one in four mammal species, and one in eight bird species. Only 4% of the world's named plant species were evaluated for Red List. In the United States, where species must meet a stringent set of criteria to be listed as endangered or threatened under the ESA, the 2002 list of threatened or endangered species included 517 animal species and 745 plant species. Another 35 species had been proposed for listing, and 257 species had been suggested as candidate species.

The United States Fish and Wildlife service has been thorough in its assessment of the nation's ecological resources, but even the ESA list is incomplete. Endangered species listing favors larger, more charismatic plants and animals, especially vertebrate animals and vascular plants; endangered species of arthropods , mosses, lichens , and other less-well known groups remain undercounted. The humid Southeast and the arid Southwest have the largest numbers of endangered species in the United States. These regions tend to have unique ecological communities with many narrowly-distributed endemic species, as well as extensive human urbanization and resource development that threaten them.

There are numerous examples of endangered species. In this section, a few cases are chosen that illustrate the major causes of extinction, the socioeconomic conflicts related to protection of endangered species, and some possible successful strategies for wildlife protection and conflict resolution.

Species endangered by unsustainable hunting

Overhunting and overfishing have threatened animal species since aboriginal Europeans, Australians, and Americans developed effective hunting technology thousands of years ago. The dodo, passenger pigeon, great auk, and Steller's sea cow were hunted to extinction. Unstainable hunting and fishing continue to endanger numerous animals worldwide. In the United States, many of the animals considered national symbols—bald eagle, grizzly bear, timber wolf, American Bison , bighorn sheep , Gulf of Mexico sea turtles —have been threatened by overhunting. (American bison, incidentally, are no longer considered threatened, but they exist mainly in managed herds, and have never repopulated their wide range across the American and Canadian west.)

The eskimo curlew is a large sandpiper that was abundant in North America in the nineteenth century. The birds were relentlessly hunted by market gunners during their migration from the prairies and coasts of Canada and the United States to their wintering grounds on the pampas and coasts of South America. The eskimo curlew became very rare by the end of the nineteenth century. The last observation of a curlew nest was in 1866, and the last "collection" of birds was in 1922. There have been a few reliable sightings of individuals in the Canadian Artic and small migrating flocks in Texas since then, but sightings are so rare that the species' classification changes to extinct between each one.

The Guadalupe fur seal was abundant along the coast of western Mexico in the nineteenth century, numbering as many as 200,000 individuals. This marine mammal was hunted for its valuable fur and almost became extinct in the 1920s. Fortunately, a colony of 14 seals , including pups, was discovered off Baja California on Guadalupe Island in 1950. Guadalupe Island was declared a pinnaped sanctuary in 1975; the species now numbers more than 1,000 animals, and has begun to spread throughout its former range. The Juan Fernandez fur seal of Chile had a similar history. More than three million individuals were killed for their pelts between 1797 and 1804, when the species was declared extinct. The Juan Fernandez seal was rediscovered in 1965; and its population presently numbers several thousand individuals.

Commercial whaling for meat and oil since the eighteenth century has threatened most of the world's baleen whale species, and several toothed whales, with extinction. (Baleen whales feed by straining microorganisms from seawater.) Faced with severe depletion of whale stock, 14 whaling nations formed the International Whaling Commission (IWC) in 1946. While the IWC was somewhat successful in restoring whale populations, it lacks authority to enforce hunting bans, and non-member nations often threaten to disregard IWC directives. The Marine Mammal Protection Act of 1972 banned all whaling in United States waters, the CITES treaty protects all whale species, and many whales have been protected by the ESA. In spite of these measures, only a few whale species have recovered to their pre-whaling populations, and a number of species remain on the brink of extinction. Seven baleen whales, and four toothed whales, remain on the ESA list and the IUCN Red List today: northern and southern right whales, bowhead whale, blue whale, fin whale, sei whale, humpback whale, sperm whale, vaquita, baiji, and Indus susu. The California gray whale is a rare success story. This species was twice hunted near extinction, but it has recovered its pre-whaling population of about 21,000 individuals. The gray whale was removed from the endangered species list in 1993.

Large predators and trophies

Many large predators are killed because they compete with human hunters for wild game like deer and elk, because they prey on domestic animals like sheep, or sometimes because they threaten humans. Consequently, almost all large predators whose former range has been developed by humans have become extirpated or endangered. The list of endangered large predators in the United States includes most of the species that formerly occupied the top of the food chain, and that regulated populations of smaller animals and fishes: grizzly bear, black bear, gray wolf, red wolf, San Joaquin kit fox, jaguar, lynx, cougar, mountain lion, Florida panther, bald eagle, northern falcon, American alligator, and American crocodile.

A number of generally harmless species are, sadly, endangered because of their threatening appearance or reputation, including several types of bats , condors , non-poisonous snakes , amphibians , and lizards. Internationally, many endangered species face extinction because of their very scarcity. Though CITES agreements attempt to halt trade of rare animals and animal products, trophy hunters, collectors of rare pets, and traders of luxury animal products continue to threaten numerous species. International demand for products like elephant tusk ivory, rhino horn, aquarium fish, bear and cat skins, pet tropical birds, reptile leather, and tortoise shells have taken a toll on many of the earth's most extraordinary animals.

Endangerment caused by introduced species

In many places, vulnerable native species have been decimated by non-native species imported by humans. Predators like domestic cats and dogs, herbivores like cattle and sheep, diseases, and broadly-feeding omnivores like pigs have killed, starved, and generally outcompeted native species after introduction. Some destructive species introductions, like the importation of mongooses to the Pacific islands to control snakes, are intentional, but most of the damage caused by exotic species and diseases is unintended.

For example, the native birds of the Hawaiian archipelago are dominated by a family of about 25 species known as honeycreepers . Thirteen species of honeycreepers have been rendered extinct by introduced predators and habitat loss since Polynesians discovered the islands, and especially since European colonization. The surviving 12 species of honeycreepers are all endangered; they continue to face serious threats from introduced diseases, like avian malaria , to which they have no immunity.

Deliberate introduction of the Nile perch caused terrible damage to the native fish population of Lake Victoria in eastern Africa . Fisheries managers stocked Lake Victoria, the world's second-largest lake , with Nile Perch in 1954. In the 1980s the perch became a major fishery resource and experienced a spectacular population increase that was fueled by predation on the lake's extremely diverse community of cichlid fishes. The collapse of the native fish community of Lake Victoria, which originally included more than 400 species, 90% of which only occurred in Lake Victoria, resulted in the extinction of about one-half of the earth's cichlid species. Today, most of the remaining cichlids are endangered, and many of those species exist only in captivity.

Species living on islands are especially vulnerable to introduced predators. In one case, the accidental introduction of the predatory brown tree snake to the Pacific island of Guam in the late 1940s caused a severe decline of native birds. Prior to the introduction of the snake there were 11 native species of birds on Guam, most of which were abundant. By the mid-1980s seven of the native species were extinct or extirpated on Guam, and four more were critically endangered. The Guam rail, a flightless bird, is now extinct in the wild, although it survives in captivity and will hopefully be captive-bred and released to a nearby, snake-free island.

Endangerment caused by habitat destruction

Many species have become extinct or endangered as their natural habitat has been converted for human land-use purposes. The American ivory-billed woodpecker, for example, once lived in mature, bottomland hardwood forests and cypress swamps throughout the southeastern United States. These habitats were heavily logged and/or converted to agricultural land by the early 1900s. There have been no reliable sightings of the American ivory-billed woodpecker since the early 1960s, and it is probably extinct in North America. A related subspecies, the Cuban ivory-billed woodpecker, is also critically endangered because of habitat loss, as is the closely related imperial woodpecker of Mexico.

The black-footed ferret was first discovered in the North American prairie in 1851. This small predator became endangered when the majority of its grassland habitat was converted to agricultural use. Farming in the American and Canadian plains also dramatically reduced the population of prairie dogs, the black-footed ferret's preferred food.

Furbish's lousewort is an example of a botanical species endangered by habitat destruction. This herbaceous plant only occurs along a 143-mi (230-km) reach of the St. John River in Maine and New Brunswick. It was considered extinct until a botanist "re-discovered" it in Maine in 1976. At that time, a proposed hydroelectric reservoir threatened the entire habitat of Furbish's lousewort. In the end, the controversial dam was not built, but the lousewort remains threatened by any loss of its habitat.

The northern spotted owl lives in the old-growth conifer forests of North America's Pacific Northwest. These small owls require large areas of uncut forest to breed, and became endangered when their habitat was greatly reduced and fragmented by heavy logging. The Environmental Species Act prescribes, and legally requires, preservation of large areas of extremely valuable timber land to protect the northern spotted owl. Upon receiving its status as an endangered species, the otherwise unremarkable owl became a symbol of the conflict between environmental preservation and commercial enterprise. For environmentalists, endangered classification of northern spotted owl brought the possibility of protecting the forests from all exploitation; for timber industry workers, the decision represented the government's choice to preserve a small bird instead of their livelihood. Small stores on the back roads of the Pacific Northwest expressed their resentment for the ESA by advertising such specialties as "spotted owl barbeque" and activities as "spotted owl hunts."

Like the northern spotted owl, the endangered redcockaded woodpecker of the southeastern United States requires old-growth pine forest to survive. The woodpecker excavates nest cavities in heart-rotted trees, and younger plantation trees do not meet its needs. Suitable forests have been greatly diminished by conversion to agriculture, logging, and residential development. Natural disturbance like hurricanes and wildfires threaten the remaining diminished and fragmented populations of red-cockaded woodpeckers . The ESA has attempted to protect the red-cockaded woodpecker by establishing ecological reserves and non-harvested buffers around known nesting colonies outside the reserves. Also like the spotted owl, the red-cockaded woodpecker is maligned by farmers, loggers, and developers for its role in their economic restriction.

Tropical deforestation presents represents the single greatest threat to endangered species today, though destruction of coastal and shallow marine habitats associated with anthropogenic global warming may present an even larger challenges in the future. While there was little net change (-2%) in the total forest cover of North America between the 1960s and the 1980s, the global area of forested land decreased by 17% during that period. Conversion of species-rich tropical forests in Central America, South America, Africa, and the Pacific islands to unforested agricultural land accounts for most of the decline. (Ironically, tropical soils have such poor structure and nutrient content that they generally cannot support profitable agriculture once the forest biomass has been removed.)

In the mid-1980s, tropical rainforests were being cleared at a rate of 15–20 million acres (6–8 million hectares) per year, or about 6–8% of the total equatorial forest area. The causes of tropical deforestation include conversion to subsistence and market agriculture, logging, and harvesting of fuelwood. All of these activities represent enormous threats to the multitude of endangered species native to tropical countries. Recent efforts to slow the rate of deforestation have included international financial and scientific aid to help poorer tropical nations protect important ecosystems, and to adopt new, more sustainable, methods of profitable resource use.

Actions to protect endangered species

Numerous international agreements deal with issues related to the conservation and protection of endangered species. The scientific effort to more accurately catalog species and better define the scope of biodiversity has dramatically raised the number of recorded threatened and endangered species in recent years. In spite of these shocking statistics of endangerment, there is a good deal of evidence that national and international efforts to preserve endangered species have been very successful. Some of the most important international conventions are ratified by most of the world's nations, and have had significant power to enforce agreements in the decades since their introduction: (1) the 1971 Convention on Wetlands of International Importance that promotes wise use of wetlands and encourages designation of important wetlands as ecological reserves; (2) the 1972 Convention Concerning the Protection of the World Cultural and Natural Heritage that designates of high-profile World Heritage Sites for protection of their natural and cultural values; (3) the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES); (4) the 1979 Convention on the Conservation of Migratory Species of Wild Animals of 1979 that deals with species that regularly cross national boundaries or that occur in international waters; and (5) the 1992 Convention on Biological Diversity (CBD). The CBD was presented by the United Nations Environment Program (UNEP) at the United Nations Conference on Environment and Development at Rio de Janeiro, Brazil in 1992, and has been regularly updated since then; the most recent amendments to the CBD occurred at the 2002 United Nations Earth Summit in Johannesburg, South Africa. The CBD is a central element of another international program called the Global Biodiversity Strategy, a joint effort by the IUCN, UNEP, and the World Resources Institute to study and conserve biodiversity.

Many countries, like the United States, have also undertaken their own actions to catalog and protect endangered species and other elements of biodiversity. Many of these national conservation efforts, like the ESA, have and international component that deals with species migration and trade across borders, and that mesh with the international conventions. Another important aspect of endangered species protection is collaboration with non-governmental organizations like the World Wildlife Fund, the Nature Conservancy and the Ocean Conservancy. The United States, for example, has a network of conservation data centers (CDCs) that gather and compile information on the occurrence and abundance of biological species and ecosystems that was designed and established by The Nature Conservancy. The Nature Conservancy has also facilitated development of CDCs in Canada and in Central and South America.

International, national and non-governmental agencies attempting to conserve biodiversity and protect endangered species choose whether to pursue single-species approaches that focus on particular species, or to develop more comprehensive strategies that focus on larger ecosystems. Because there are so many endangered species, many of which have not even been discovered, the single-species approach has obvious limitations. While the method works well for charismatic, large animals like giant pandas , grizzly bears , whales, and whooping cranes , this approach fails to protect most endangered species. More effective strategies focus on entire natural ecosystems that include numerous, hidden elements of threatened biodiversity. Furthermore, more conservation policies are attempting to consider the social, political, and economic ramifications of a species or environmental protection plan. As in the case of the northern spotted owl, policies that require large economic sacrifices and offer no immediate local benefits often alienate the very humans that could best help to preserve an endangered species or ecosystem. Modern environmental protection strategies attempt to present alternatives that permit sustainable human productivity.

See also Stress, ecological.

Resources

books

Beacham, W. and K.H. Beetz. Beacham's Guide to International Endangered Species. Osprey, FL: Beacham Publications, 1998.

Burton, J.A., ed. The Atlas of Endangered Species. New York: Macmillan Library Reference, 1998.

Wilson, E.O. The Diversity of Life. Cambridge: Harvard University Press, 1992.

other

International Union for Conservation of Nature and Natural Resources. "IUCN Home Page." October 17, 2002 [cited November 21, 2002]. <http://www.iucn.org/>.

United Nations Environment Programme. "Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)." November 15, 2002 [cited November 19, 2002]. <http://www.cites.org/index.html>.

United States Fish and Wildlife Service. "The United States Endangered Species Program." [cited November 19, 2002]. <http://endangered.fws.gov/>.

World Wildlife Fund. "Endangered Species." October 17, 2002 [cited November 19, 2002]. <http://www.wwfus.org/species/species.cfm>.

Bill Freedman
Laurie Duncan

KEY TERMS

Endangerment

—Refers to a situation in which a species is vulnerable to extinction or extirpation.

Endemic

—Refers to species with a relatively local distribution, sometimes occurring as small populations confined to a single place, such as a particular oceanic island. Endemic species are more vulnerable to extinction than are more widespread species.

Extinction

—The condition in which all members of a group of organisms have ceased to exist.

Extirpation

—The condition in which a species is eliminated from a specific geographic area of its habitat.

Endangered Species

Introduction

An endangered species is any species of animal or plant whose numbers have declined drastically due to natural or human causes, threatening it with extinction. The designation of endangered to a species means that there is still time to save it; once it is extinct, it is gone forever. Also of concern are threatened species—species whose numbers are low or declining, which are likely to become endangered if not protected. Extirpated species are species that have disappeared locally or regionally, but survive in other regions or in captivity. Because human activities have greatly increased the rate of endangerment of the world’s species, international efforts are in place to try to preserve as many species as possible.

Historical Background and Scientific Foundations

Throughout Earth’s history, billions of species have become extinct due to natural processes and occurrences. In fact, according to the fossil record, only 2 to 4% of the species that have existed on Earth exist today. One single catastrophic event that occurred some 65 million years ago—the collision of an asteroid with Earth—brought about the extinction of an estimated 85% of Earth’s species, including the dinosaurs. But catastrophes are not the only causes of natural extinction. Disease, natural climate change, and competition between species have resulted in a steady rate of extinction of species throughout geologic history.

In modern times, human activities have greatly increased the rate at which species are becoming extinct or threatened. At present, scientists estimate that extinctions caused by humans are taking place at 100 to 1,000 times nature’s normal rate. It is impossible to measure the total number of species going extinct because only a small percentage of the world’s species have been named and described: about 1.9 million species out of an estimated 10 million to 100 million. Particularly in the tropical rain forests, where many species have not yet been discovered by scientists, species become extinct before humans even know they exist. Conservation organizations around the world have taken on the task of trying to catalog as many of the world’s species as possible.

Human activities that influence the extinction and endangerment of wild species fall into several categories:

1. unsustainable hunting and harvesting that kill members of the species faster than the species can repopulate;
2. land use practices like deforestation, urban and suburban development, agricultural cultivation, and water management projects that encroach upon and/or destroy natural habitat;
3. intentional or unintentional introduction of destructive diseases, parasites, and predators;
4. ecological damage caused by water, air, and soil pollution;
5. anthropogenic (human-caused) global climate change.

Overhunting and overfishing have threatened animal species since aboriginal Europeans, Australians, and Americans developed effective hunting technology thousands of years ago. Unsustainable hunting and fishing continue to endanger numerous animals worldwide. In the United States, many of the animals considered national symbols—bald eagle, grizzly bear, timber wolf, American bison, bighorn sheep, and Gulf of Mexico sea turtle—have been threatened by overhunting. Commercial whaling for meat and oil since the eighteenth century has threatened most of the world’s baleen whale species, and several toothed whales, with extinc-

WORDS TO KNOW

BIODIVERSITY: Literally, “life diversity”: the wide range of plants and animals that exist within any given geographical region.

EXTINCTION: The total disappearance of a species or the disappearance of a species from a given area.

HABITAT: The natural location of an organism or a population.

THREATENED: When a species is pressured, but technically not yet endangered.

tion. Despite measures to protect them, eight whales remain endangered today: blue whale, bowhead whale, finback whale, gray whale, sei whale, humpback whale, right whale, and sperm whale.

Large predators have long been killed because they compete with human hunters for wild game like deer and elk, because they prey on domestic animals like sheep, or sometimes because they threaten humans. Consequently, almost all large predators whose former range has been developed by humans have become extirpated or endangered. The list of endangered large predators in the United States includes: grizzly bear, black bear, gray wolf, red wolf, San Joaquin kit fox, jaguar, lynx, cougar, mountain lion, Florida panther, northern falcon, American alligator, and American crocodile. A number of generally harmless species are endangered because of their threatening appearance or reputation, including several types of bats, condors, non-poisonous snakes, amphibians, and lizards. And despite international regulations to halt the trade of rare animals, trophy hunters, collectors of rare pets, and traders of luxury animal products continue to trade in products like elephant tusk ivory, rhino horns, aquarium fish, bear and cat skins, tropical birds, reptile leathers, and tortoise shells, threatening the survival of many of Earth’s most extraordinary animal species.

In many places, vulnerable native species have been decimated by non-native species imported by humans. Predators like domestic cats and dogs, herbivores like cattle and sheep, and broadly feeding omnivores like pigs have killed, starved, and generally out-competed native species after introduction to a new region. Some destructive species introductions, like the importation of mongooses to the Pacific islands to control snakes, are intentional, but most of the damage caused by exotic species and diseases is unintended. For example, the native birds of the Hawaiian archipelago are dominated by a family of about 25 species known as honeycreepers. Thirteen species of honeycreepers have been rendered extinct by introduced predators and habitat loss since Polynesians discovered the islands, and especially since European colonization.

Many species have become extinct or endangered as their natural habitat has been converted for human land-use purposes. The American ivory-billed woodpecker, for example, once lived in mature, bottomland hardwood forests and cypress swamps throughout the southeastern United States. These habitats were heavily logged and/or converted to agricultural land by the early 1900s. For more than 40 years there were no reliable sightings of the American ivory-billed woodpecker, and it was assumed to be extinct in North America. However, in 2002 and again in 2004, sightings of the species were confirmed in central Arkansas.

The black-footed ferret became endangered when the majority of its grassland habitat in the North American prairie was converted to agricultural use. The northern spotted owl lives in the old-growth conifer forests of North America’s Pacific Northwest. These small owls require large areas of uncut forest to breed, and became endangered when their habitat was greatly reduced and fragmented by heavy logging. Like the northern spotted owl, the endangered red-cockaded woodpecker of the southeastern United States requires old-growth pine forest to survive. The woodpecker excavates nest cavities in heart-rotted trees, and younger plantation trees do not meet its needs. Suitable forests have been greatly diminished by conversion to agriculture, logging, and residential development. Natural disturbance like hurricanes and wildfires threaten the remaining diminished and fragmented populations of red-cockaded woodpeckers.

Conversion of species-rich tropical forests in Central America, South America, Africa, and the Pacific islands to unforested agricultural land accounts for a huge portion of endangered and threatened species. In the mid-1980s, tropical rain forests were being cleared at a rate of 15 to 20 million acres (6 to 8 million hectares) per year, or about 6 to 8% of the total equatorial forest area. The causes of tropical deforestation include conversion to subsistence and market agriculture, logging, and harvesting of fuel wood. All of these activities represent enormous threats to the multitude of endangered species native to tropical countries.

Most species that are endangered are those found only in small, limited, or unusual habitats. If that limited habitat disappears or transforms due to a catastrophic change, habitat destruction, or climate change, the species can suddenly become endangered or extinct. In contrast, species that have populations spread out over several large regions are more likely to survive a regional catastrophe because individuals living elsewhere will escape the damage.

Tropical rain forest deforestation represents the single greatest threat to endangered species today, although destruction of coastal and shallow marine habitats asso-

ciated with anthropogenic (human-caused) global warming may present even larger challenges in the future. Global warming is also thought to be accelerating the degradation of arid and semi-arid regions around the world as well as melting glaciers in some of the coldest regions of the world. The changes in these habitats have dire consequences for species that live within them.

Impacts and Issues

For a variety of reasons, it is critical that humans act to preserve endangered species and their natural habitats. All species have value in their own right, and many species also have a known value to humans and to all life on Earth. Some species, such as undiscovered medicinal plants and species with potential for agricultural uses, have values unknown at the present time to humans. Most species play a critical role in maintaining the health and integrity of their ecosystem and are therefore indirectly important to human welfare. Such ecological roles include nutrient cycling (a process in which nutrients, such as carbon, nitrogen, and phosphorus, circulate between the nonliving and living forms of an ecosystem), controlling pests and weeds, regulating the populations of other species, cleansing chemical and organic pollution from water and air, controlling erosion, producing atmospheric oxygen, and removing atmospheric carbon dioxide.

The International Union for Conservation of Nature and Natural Resources (IUCN; the World Conservation Union), the world’s oldest international conservation organization, works with nations and organizations worldwide to protect the world’s natural resources. The IUCN Red List of Threatened Animals and the IUCN Red List of Threatened Plants present scientifically based information on the status of threatened species around the world. The red lists rank the species by levels of threat. The 2006 IUCN Red List of Threatened Species listed 16,118 species of plants and animals facing imminent extinction.

In spite of dismal statistics of endangerment, there is evidence that national and international efforts to preserve endangered species have been successful. Important international conventions, ratified by most of the world’s nations, have made significant progress in regulating some of the human activities responsible for threatening species. These conventions include: (1) the 1971 Convention on Wetlands of International Importance; (2) the 1972 Convention Concerning the Protection of the World Cultural and Natural Heritage, which designates high-profile World Heritage Sites for protection of their natural and cultural values; (3) the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which aims to ensure that international trade in specimens of wild animals and plants does not threaten their survival; and (4) the 1992 Convention on Biological Diversity (CBD), which was presented by the United Nations Environment Programme (UNEP) at the United Nations Conference on Environment and Development in 1992. The CBD is a central element of another international program called the Global Biodiversity Strategy, a joint effort by the IUCN, UNEP, and the World Resources Institute to study and conserve biodiversity. The World Wildlife Fund, Conservation International, and other similar nongovernmental organizations promote field research, sponsor species recovery efforts, and increase the public visibility of endangered species issues and their impact.

In the United States, species must meet a stringent set of criteria to be listed as endangered or threatened under the Endangered Species Act (ESA). In 2007, the U.S. Fish and Wildlife Service (FWS) listed 1,174 animal species and 1,921 plant species as threatened or endangered around the world. A listing under the ESA provides a species with a number of conservation benefits including protection from harm due to federal activities,

restrictions on hunting and trade, development and implementation of recovery plans by the FWS (for species under U.S. jurisdiction), and protection of critical habitat.

Studies of threatened and endangered species are not consistent around the globe. What has become evident, however, is that species are declining fastest in tropical and subtropical regions and in the poorer regions of the world where conservation responses are often limited. Brazil, Indonesia, and the Philippines are among those regions.

Although limited when compared to the enormity of the problem, there have been some success stories. The California condor has been successfully returned to the wild as a result of a concerted captive breeding and release program, and the black-footed ferret is making a comeback in the western prairies of the United States due to a similar program. A wide range of recovery initiatives extending over several decades resulted in the removal of the bald eagle from the U.S. endangered species list in 2007. In Canada, a red squirrel population seems to be adapting successfully to changing climate conditions. Scientists studying these squirrels have found that they now produce offspring on average 18 days earlier in the year than their great-grandmothers did, probably due to warmer spring temperatures. These squirrels provide some of the first hard evidence that some mammals can adapt to a warmer world within a few generations.

Primary Source Connection

The following news article recognizes that the Endangered Species Act of 1973 might legally provoke the U.S. federal government to enforce laws to further cut greenhouse-gas emissions from the environment in the name of protecting the critical habitat of certain species. Elkhorn and staghorn coral are the first species to be named as “threatened by global warming.” Many environmentalists are excited about the prospect of legislation aimed at protecting endangered species that would be triggered by concern for greenhouse emissions.

NEW TOOL TO FIGHT GLOBAL WARMING: ENDANGERED SPECIES ACT?

Environmentalists may have gained a powerful new legal weapon to fight global warming: the Endangered Species Act.

That’s the fallout some expect from a settlement last week between environmentalists and the National Marine Fisheries Service. The government agency agreed to protect the “critical habitat” of elkhorn and staghorn coral, the first species to be recognized as threatened by global warming.

By protecting habitat, not just species, the federal government could be in a position to fight any threats to that habitat, including possibly, global warming, some environmentalists say. While no one expects the US to stop, say, a coal-fired power plant in the Midwest to save Florida coral, the settlement does expand the leverage of the 1973 law that protects species from extinction.

“We think this victory on coral critical habitat actually moves the entire Endangered Species Act [ESA] onto a firm legal foundation for challenging global-warming pollution,” says Kieran Suckling, policy director of the Center for Biological Diversity, an environmental group based in Tucson, Ariz., that filed both coral suits.

Indeed, the coral-protection victory may be just the beginning of a push to use the ESA to fight global warming, he and other environmentalists suggest.

The pair of coral species are struggling to survive because Florida’s and the Caribbean’s waters have become warmer and more acidic. Many scientists attribute the change to global warming.

Protected coral gets habitat safeguards

The elkhorn and staghorn coral won protected status under the ESA in May 2006. But it took a second legal battle to win a preservation of the corals’ “critical habitat,” part of last week’s settlement between environmentalists and the US fisheries service.

The act’s leverage will grow, environmentalists say, as climate change becomes recognized as a factor in species’ decline. The number of species-recovery plans that cite global warming as a damaging factor has gone from zero as recently as 1990 to 141 today—with most of the growth since 2000.

While that’s still just 9 percent of the 1,494 species listed at one time or another, the increase suggests that a large group of species still awaiting listing will have global warming cited as a major cause in their decline. The polar bear, 12 species of penguins, and the Kittlitz’s Murrelet, an Alaskan bird that nests on the edges of glaciers, are all candidates, Mr. Suckling says.

Specific effects of warming speculative

Right now, any bid to fight the construction of a power plant by arguing that emissions might harm a species would probably be thrown out of court, because such climate-change effects remain speculative, Mr. Suckling concedes.

But in the next few years, if evidence of the threat of global warming on endangered species grows, so could the legal argument that the ESA be considered when a power plant or other carbon-intensive project is proposed, he adds.

Others are far less sure about that. Even some environmentalists are skeptical.

It is, for instance, unlikely that any judge will halt a power plant project just because its emissions contribute to a huge pool of global emissions that collectively harm coral, says Michael Bean, senior attorney at Environmental Defense, a Washington-based environmental group.

“The list of endangered species will in the future include many species threatened by global warming,” he says. “But I’m skeptical that the [ESA] itself will be the source of any new restrictions on greenhouse-gas emissions. I think those will come from new legislation.”

While winning a place on the endangered species list is always a big step—it’s only the first. Habitat loss is the primary cause of species loss.

But only about 38 percent of the 1,367 species on the federal endangered species list actually have the much tougher protection that mandates critical habitat protection. Under the law, no area designated as critical habitat can be destroyed or adversely modified.

Those legal protections have played a major role in limiting development in key areas of the country. Critical-habitat designations covering 80 million acres along the West Coast have sharply reduced fishing in the breeding grounds of the Steller Sea Lion, a move many credit for the recent rebound in the population.

First listed as “threatened” in May 2006, the two coral species have declined 80 to 98 percent across their range. This spring a study found that 10 percent of the Caribbean’s 62 reef building corals were threatened, including elkhorn and staghorn corals that used to be prominent.

Scientists studying the decline of coral that used to be the dominant reef-builders off the Florida coast are cheering the new settlement. They say they hope the critical-habitat designation will restrict access to the last remaining coral stands—and help win the legal fight on global warming.

“It’s pretty exciting to find that a lowly marine invertebrate might actually someday be the legal catalyst for rulings against greenhouse-gas emissions,” says Andrew Baker, a University of Miami marine biologist specializing on climate change impact on coral. “IIt’s like getting Al Capone for tax evasion.”

Mark Clayton

CLAYTON, MARK. “NEW TOOL TO FIGHT GLOBAL WARMING: ENDANGERED SPECIES ACT?” CHRISTIAN SCIENCE MONITOR (SEPTEMBER 7, 2007).

See Also Biodiversity; CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora); Extinction and Extirpation;Habitat Alteration; Habitat Loss; Wildlife Population Management; Wildlife Protection Policies and Legislation; Wildlife Refuge

BIBLIOGRAPHY

Web Sites

Black, Richard. “Gorillas Head Race to Extinction.” BBC News, September 12, 2007. http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/6990095.stm (accessed May 22, 2008).

Carlton, Jim. “Is Global Warming Killing the Polar Bears?” Wall Street Journal Online, December 14, 2005. http://online.wsj.com/public/article_print/SB113452435089621905-vnekw47PQGtDyf3iv5XEN71_o5I_20061214.htm (accessed May 22, 2008).

IUCN-The World Conservation Union.http://www.iucn.org (accessed May 10, 2008).

United Nations Environmental Programme. Convention on Biological Diversity. “Climate Change and Biodiversity.” http://www.cbd.int/climate/default.shtml (accessed May 10, 2008).

U.S. Fish and Wildlife Service. “The Endangered Species Act and What We Do.” http://www.fws.gov/endangered/whatwedo.html (accessed May 10, 2008).

U.S. Geological Survey. “New Polar Bear Findings.” http://www.usgs.gov/newsroom/special/polar_bears/default.asp (accessed May 10, 2008).

World Wildlife Fund. “Endangered Species.” http://www.worldwildlife.org/endangered/ (accessed May 10, 2008).

René Nougayrède
Miriam C. Nagel

Endangered Species

Introduction

A species whose numbers have declined so drastically that it is in danger of extinction throughout all or a significant part of its habitat is considered endangered. Extinct species no longer occur anywhere on Earth, and once they have disappeared, they are gone forever. Extirpated species have disappeared locally or regionally, but still survive in other regions or in captivity. Threatened species are at risk of becoming endangered in the foreseeable future. Drastic reductions in the population of a species or its complete disappearance diminish the bio-diversity of the ecosystems it inhabits and the planet as a whole.

Historical Background and Scientific Foundations

There are many reasons that a species may become threatened or endangered. Species have become extinct throughout the history of life on Earth due to selective pressures, natural climate changes, and catastrophic geologic events. However, the pace of extinction has accelerated dramatically in modern times due to human activities, and scientists estimate that present extinction rates are 1,000 to 10,000 times higher than the average natural extinction rate. Among the human activities that contribute to species endangerment are: land use practices, such as urban development, agricultural conversion, and deforestation; unsustainable levels of hunting or harvesting; habitat damage due to water, air, or soil pollution; intentional or accidental introduction of predators or diseases; and global climate change caused by humans.

An accurate assessment of the number of endangered species worldwide does not yet exist. This is due, in part, to the fact that the smallest, yet most multi-tudinous, species of plants, insects, and microorganisms have not been tallied. In addition, scientists believe that large numbers of as yet unknown (to science) and

unnamed species can be found in tropical rainforests. Since these forests are disappearing rapidly due to timber extraction and human population encroachments, all the species that inhabit these forests are likely to be endangered.

Since the number of species evaluated in the compilation of lists of endangered species is limited, the large numbers of plants and animals recorded on these lists is particularly alarming. IUCN-The World Conservation Union through its Species Survival Commission (SSC) has been assessing the status of species, subspecies, varieties, and selected subpopulations on a global scale for more than 40 years to highlight those at risk and promote their conservation. The IUCN Red Lists are intended to provide a comprehensive, apolitical, global approach for evaluating the conservation status of plant and animal species. The 2007 Red List of Threatened Species, released in September 2007, assessed 41,415 species. Of these species, 16,306 are threatened with extinction to a greater or lesser degree, an increase of nearly 200 species over the previous year. In addition, 65 species are found only in captivity or cultivation. According to the 2007 IUCN Red List, 25% of mammals, 12.5% of birds, 33% of amphibians, and 70% of the world's assessed plants are in jeopardy.

In the United States, species must meet a stringent set of criteria to be listed as endangered or threatened under the Endangered Species Act (ESA). In 2007, the U.S. Fish and Wildlife Service (FWS) listed 1,174 animal species and 1,921 plant species as threatened or endangered around the world. A listing under the ESA provides a species with a number of conservation benefits including protection from harm due to federal activities, restrictions on hunting and trade, development and implementation of recovery plans by the FWS (for species under U.S. jurisdiction), and protection of critical habitat.

Studies of species are often grouped by habitat. Freshwater ecosystems are among the most threatened. Marine species have historically been poorly covered in studies of endangered species due to the difficulties of studying these species in the world's vast oceans. Arid and semi-arid regions urgently need further study particularly since severe degradation of arid and semi-arid lands around the world is being accelerated by global warming. Global warming has also recently focused attention on polar regions, since one of the effects of global climate change appears to be accelerated melting of glaciers and Arctic ice. The plight of polar bears has attracted significant media attention.

Polar bears and other cold-loving species have very specialized adaptations for the harsh environments at the poles, and they have low tolerance for environmental change. Reductions in sea ice due to global warming influence not only the availability of polar bear hunting and denning habitat, but may impact the overall distribution and abundance of polar bears. Scientists have found evidence of polar bear drownings because some bears must swim longer distances (up to 60 mi/96 km) over open ocean in their search for food. In 2007, scientists studying the effects of climate and ice changes to help determine whether polar bears should be protected under the ESA estimated that two-thirds of the world's polar bears will disappear by 2050. These scientists concluded that polar bears are unlikely to be driven to extinction, but their habitat will contract significantly to the Arctic archipelago of Canada and areas off the northern coast of Greenland where sea ice persists even in warm summers.

Arid regions are getting hotter and drier, threatening the survival of plant and animal species already at their heat-tolerance limits. In marginal drylands, biodiversity is threatened by over cultivation. In the United States, for example, more than 50 species are now endangered in the Arizona desert, including some cactus varieties.

Marine and coastal waterways and freshwater systems also are vulnerable to climate changes. Freshwater fish have been seriously impacted with an estimated 20% of these fish species now extinct. Spawning and feeding habitats have changed. A number of salmon varieties are on the endangered species list due to habitat disruption, water pollution, and overfishing.

WORDS TO KNOW

BIODIVERSITY: Literally, “life diversity”: the number of different kinds of living things. The wide range of organisms—plants and animals—that exist within any given geographical region.

EXTINCTION: The total disappearance of a species or the disappearance of a species from a given area.

EXTIRPATED: The condition in which a species is eliminated from a specific geographic area of its habitat

HABITAT: The area or region where a particular type of plant or animal lives and grows.

THREATENED: When a species is capable of becoming endangered in the near future.

Plants have received less attention than animals, but they have not escaped the effects of climate changes. One quarter of all the wild potato species are predicted to be extinct within 50 years. Changes in rainfall patterns and increasing temperatures cause soil erosion and an increased leaching of soil nutrients. Wildfires are increasing in drier regions. In general, there are three main categories of potential effects of climate change on plant species. For plants existing in areas of climatic extremes, global warming may have drastic impacts, for example, forcing plants that require cold temperatures out of habitats like mountain peaks. If this is their only habitat, extinction will occur. Shifts in global biome distribution are another likely impact of global warming. Coniferous forests will shift farther north and grasslands and deserts will expand. Global warming also may alter how plants function in their existing environment by lengthening the growing season in some areas, especially in northern latitudes.

Impacts and Issues

Climate changes are affecting the environments inhabited by endangered species in many ways, including altering the timing of ecological events, such as the flowering of plants and the breeding of animals. Such changes are impacting the relationships of interdependent species whose interactions may be disrupted by differing rates of change. The habitats of species are shifting with the changing temperatures, but some habitats are disappearing rather than shifting. The species that inhabit these habitats may become extirpated from that region or may be driven to extinction.

Climate change impacts biodiversity by changing the distribution of species and threatening their survival as warm seasons grow longer. Global warming is reducing sea ice in polar regions and this melting is, in turn, accelerating global warming. Snow and ice reflect sunlight, but exposed darker land and ocean surfaces increase absorption of solar radiation. The melting ice caps in Greenland and Antarctica raise the sea level and add freshwater to the ocean. The added freshwater alters salinity and may cause shifts in ocean circulation.

Studies of threatened and endangered species are not consistent around the globe. The status of vertebrates is best documented with about 40% assessed. Species-rich environments, such as tropical forests and the oceans, are not well studied. What has become evident, however, is that species are declining fastest in tropical and subtropical regions and in the poorer regions of the world where conservation responses are often limited. Brazil, Indonesia, and the Philippines are among those regions.

A number of conservation organizations and governmental initiatives have been created to address the threats to Earth's biodiversity, including the World Summit on Sustainable Development, the international Convention on Biodiversity, and the United Nations Framework Convention on Climate Change and its Kyoto Protocol. More than 170 countries have signed the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES), which aims to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Many individual countries have passed legislation to protect endangered species within their borders and to provide funding for recovery efforts. The World Wildlife Fund, Conservation International, and other similar nongovernmental organizations promote field research, sponsor species recovery efforts, and increase the public visibility of endangered species issues and their impact.

IN CONTEXT: POLAR BEARS AND THE ENDANGERED SPECIES ACT

Initial studies suggest that global climate change may already have taken a toll on Arctic polar bear populations. Polar bears require summer sea ice for hunting. Typically, polar bears swim between large and stable patches of sea ice, but the animals cannot swim long distances. Already researchers are noting thinner polar bears, decreasing birth rates, and declining cub survival rates in Arctic bear populations. The National Center for Atmospheric Research (NCAR) stated that, under a worst-case scenario, summer sea ice could disappear by 2040.

The U.S. Minerals Management Service released a report that documented the drowning deaths of at least 4 polar bears off of the Alaskan coast in September 2004. The report asserted that warmer than average temperatures prompted record melting of sea ice, stranding hunting polar bears. The report prompted several environmental organizations—including the Center for Biological Diversity, the Natural Resources Defense Council (NRDC), and Greenpeace—to sue the U.S. government for failing to take action on an earlier petition to have polar bears evaluated for inclusion as a threatened species under the Endangered Species Act. Environmental groups and researchers asserted that the U.S. government failed to address the question of adding polar bears to the threatened species list because of a policy of downplaying the possible effects of global climate change. Under the act, the secretary of the interior should have responded within 90 days and opened the issue for public comment. Government officials claimed that they were actively studying polar bear populations for over two years.

Under a court settlement, the U.S. Department of the Interior announced that it was formally proposing to designate polar bears as a threatened species. Identifying polar bears as threatened could give environmental groups more power to challenge current standards governing carbon dioxide emissions and other leading contributors to climate change.

Although extremely limited when compared to the enormity of the problem, there have been some success stories. The California condor has been successfully returned to the wild as a result of a concerted captive breeding and release program, and the black-footed ferret is making a comeback in the western prairies of the United States due to a similar program. A wide range of recovery initiatives extending over several decades resulted in the removal of the bald eagle from the U.S. endangered species list in 2007. In Canada, a red squirrel population seems to be adapting successfully to changing climate conditions. Scientists studying these squirrels have found that they now produce offspring on average 18 days earlier in the year than their great-grandmothers did, probably due to warmer spring temperatures. These squirrels provide some of the first hard evidence that mammals can adapt to a warmer world in a few generations.

Primary Source Connection

This article discusses how climate change may affect the production of baseball bats. For decades, ash from the Northeastern and Midwestern United States has been the wood of choice for baseball bats. Warmer temperatures could cause ash wood to become softer, and some fear the species could be wiped out.

BALMY WEATHER MAY BENCH A BASEBALL STAPLE

RUSSELL, Pa. —Careers at stake with each swing, baseball players leave little to sport when it comes to their bats. They weigh them. They count their grains. They talk to them.

But in towns like this one, in the heart of the mountain forests that supply the nation's finest baseball bats, the future of the ash tree is in doubt because of a killer beetle and a warming climate, and with it, the complicated relationship of the baseball player to his bat.

“No more ash?” said Juan Uribe, a Chicago White Sox shortstop, whose batting coach says he speaks to his ash bats every day. Uribe is so finicky about his bats, team-mates say, that he stores them separately in the team's dugout and complains bitterly if anyone else touches them.

At a baseball bat factory tucked into the lush tree country here in northwestern Pennsylvania, the operators have drawn up a three-to-five-year emergency plan if the white ash tree, which has been used for decades to make the bat of choice, is compromised.

In Michigan, the authorities have begun collecting the seeds of ash trees for storage in case the species is wiped out, a possibility some experts now consider inevitable.

As early as this summer, federal officials hope to set loose Asian wasps never seen in this country with the purpose of attacking the emerald ash borer, an Asian beetle accused of killing 25 million ash trees in Michigan, Illinois, Indiana, Ohio and Maryland since it was spotted in the United States five years ago.

In late June, officials found signs of the ash borer's arrival in Pennsylvania, setting off a new alarm for the makers of baseball bats, most of which come from this rocky, cool range on the New York border.

Along with the ash borer beetle, a warming of the local climate could also affect the ash used for bats, some scientists say. As temperatures rise, the ash wood that now makes an ideally dense but flexible bat might turn softer because of a longer growing season. Eventually, some scientists predict, the ash tree could vanish from the region.

A warmer climate could also aid the emerald ash borer's invasion, some scientists contend, although others disagree, by creating stressed trees and the possibility of a quicker reproduction cycle in the beetle.

“We're watching all this very closely,” said Brian Boltz, the general manager of the Larimer & Norton company, whose Russell mill each day saws, grades and dries scores of billets destined to become Louisville Slugger bats. “Maybe it means more maple bats. Or it may be a matter of using a different species for our bats altogether.”

Such uncertainty does not sit well with professional players, some of whom shun (or break) bats that have failed them and worship those that have sent balls out of the park. (Some widely suspect that the well-known players get the best-quality wood, and the rookies, something softer.) Baseball, after all, is a game of routine, of instinct, of superstition.

The magic in a perfect bat is not easy to define. “You can't describe it—it's a feel,” said Scott Podsednik, an outfielder for the White Sox. “When you pick it up and take a couple of swings with it, you just know.”

After batting practice one morning, Podsednik's team-mate Uribe sheepishly confirmed his lectures to his bats (his beloved “Hoosier HB 23” models). “I tell them: ‘do your job and if you don't do your job, I'm going to have to go back to the Dominican Republic,’” Uribe said in Spanish. “Sometimes they listen; sometimes they don't.”

For much of a century, ash was the wood that ruled the realm of baseball bats, but it has faced threats before: First, competition from aluminum and composite bats (which whisked away much of the youth and amateur market but are barred from professional baseball) and then, in the past decade, from the sugar maple.

When it became known that Barry Bonds of the San Francisco Giants, who is closing in on baseball's career home-run record, was using maple bats, change swept through baseball's clubhouses.

Some bat makers say professional players are now about evenly divided between ash and maple, which is more expensive and which some players (catchers, especially) say tends to explode more violently when a bat breaks.

“Maple is all the rage with the young players coming up now,” said Tom Hellman, the clubhouse manager for the Chicago Cubs, whose responsibilities include ordering bats and keeping track of them. “But the older players still want their ash.”

Science has never definitively established whether ash makes the optimal bat. Terry Bahill, an engineer at the University of Arizona and a co-author of “Keep Your Eye on the Ball: Curveball, Knuckleballs and Fallacies of Baseball,” said researchers could measure how much energy was dissipated when a bat struck a baseball and how much force was required to bend a bat.

“But in the end,” Mr. Bahill said, “we can't tell you which bat is going to be more effective because a human being is going to be swinging this bat. So the players making decisions about bats are making them on feelings, not scientific data.”

Some scientists, however, do see a threat to the quality of the northern white ash posed by rising temperatures over a period of decades. Ash that grows in the warmer Southeastern States is held to be softer, in part because of the longer growing season, said Ron Vander Groef, who runs a factory in Dolgeville, N.Y., which make Rawlings bats.

There are also some concerns that the numbers of white ash trees in the North could significantly decline. Louis R. Iverson, a research landscape ecologist with the United States Forest Service, has helped map how habitat changes could affect 134 tree species by the end of the century. In a worst-case scenario, the white ash (and the sugar maple) diminish in numbers and shift farther north.

Still, the emerald ash borer, or Agrilus planipennis Fairmaire, is the most immediate threat. Discovered in the United States near Detroit in 2002, the beetles, which are shiny green, will destroy a tree in two to three years. The larvae tunnel inside the trees, cutting off water and food.

The ash borer is native to Asia, where the trees are naturally resistant to it.

“It just doesn't look good,” Dan Herms, an associate professor of entomology at Ohio State University, said of the prospect of stopping the beetle in this country. “The current technology won't be able to stop it.”

Dr. Herms strongly disputes any link between the ash borer and climate change, saying that the beetle has survived in a wide range of temperatures in Asia.

For now, the baseball bat makers are bracing for the worst. At the mill in Russell, even as machines cranked and hummed with ash billets last month, state investigators were barring the movement of wood from four Western Pennsylvania counties after adult beetles were discovered.

Some suppliers say they are harvesting trees years earlier than planned because of the ash borer's arrival.

In the end, baseball players may be faced with switching to, and holding conversations with, bats made of maple or some new wood yet untested by the hardball.

Monica Davey

davey, monica. “balmy weather may bench a baseball staple.” the new york times. july11, 2007.

See Also Desert and Desertification; Extinction; Forests and Deforestation; United Nations Environment Programme (UNEP.)

BIBLIOGRAPHY

Web Sites

Biever, Celeste. “Red Squirrels Evolving with Global Warming.” New Scientist, February 12, 2003. < http://environment.newscientist.com/channel/earth/climate-change/dn3382> (accessed September 21, 2007).

Black, Richard. “Gorillas Head Race to Extinction.” BBC News, September 12, 2007. < http://news. bbc.co.uk/go/pr/fr/-/2/hi/science/nature/6990095.stm> (accessed September 14, 2007).

Carlton, Jim. “Is Global Warming Killing the Polar Bears?” The Wall Street Journal Online, December 14, 2005. < http://online.wsj.com/public/article_print/SB113452435089621905-vnekw47PQGtDyf3iv5XEN71_o5I_20061214.html> (accessed September 14, 2007).

“Climate Change and Biodiversity.” United Nations Environmental Programme. Convention on Biological Diversity. < http://www.cbd.int/climate/default.shtml> (accessed August 27, 2007).

“Endangered Species.” World Wildlife Fund. < http://www.worldwildlife.org/endangered/> (accessed August 27, 2007).

“The Endangered Species Act and What We Do.” U.S. Fish and Wildlife Service. < http://www.fws.gov/endangered/whatwedo.html> (accessed August 27, 2007).

IUCN-The World Conservation Union. < http://www.iucn.org> (accessed August 27, 2007). “New Polar Bear Findings.” U.S. Geological Survey. < http://www.usgs.gov/newsroom/special/polar_bears/default.asp> (accessed September 21, 2007).

Miriam C. Nagel

Endangered Species

An endangered species is a species that is in immediate danger of becoming extinct. The designation of endangered to a species means that there is still time to save it but once it is extinct it is gone forever. Also of concern are threatened species, species whose numbers are low or declining but not in immediate danger of extinction. A threatened species is likely to become endangered if it is not protected.

Most species that are endangered are found in only limited geographic areas. Because these plants or animals are not widespread to begin with, they are more likely to be affected by major or catastrophic changes in their environment. Widespread common species, while sometimes significantly hurt by a regional catastrophe, are more likely to survive because many individuals will escape the damage elsewhere. In contrast, species found only in small and unusual habitats can suddenly become endangered or extinct if their limited habitat disappears.

Processes That Threaten Endangered Species

Extinction can be part of the natural order. Only about one in a thousand of all of the species that have ever lived on Earth is still living today. The vast majority became extinct because of naturally changing physical and biological conditions. Changing climate such as that experienced during the Ice Age (which eliminated many plant species from very large areas of North America and Europe) and other natural events such as volcanic activity have caused localized plant extinctions. The slow movement of the continents (most notably Antarctica and Australia) into unsuitable climate zones caused many organisms to become extinct. Far more widespread and devastating natural extinctions have been caused by the rare impacts of asteroids and comets on the Earth. Some impacts have caused the extinction of even common species on a global scale.

The danger to plants and animals today is most often a direct result of human activities and human population increase. These activities have taken the form of habitat alteration, economic exploitation, the intentional elimination of pests, the introduction of exotic (nonnative) organisms, the increase of invasive native grazers, and the effects of environmental pollution.

Habitat alteration is the main factor endangering species throughout the world, from the American Midwest where the prairies have been converted to cropland to the equator where the tropical rain forests are being cut and burned. Wetlands filling and draining, agricultural expansion, and residential housing development are all significant factors in habitat destruction.

Trade in live plants and animals and the products made from them is the second greatest factor endangering species. The cutting of forests for wood and fuel, the digging of rare plants for sale, and the harvesting of medicinal plants for commerce is as common as the illegal hunting and poaching of animals for sport, food, products, or pets. Plant examples include such species as ginseng, which has been harvested in several states to the point of near extinction.

The intentional elimination of species is a third human factor endangering species. Many plants and animals have become endangered or extinct simply because people decided they were pests. Killing for the sake of elim-inating an unwanted animal or plant has been common, as seen in the burning or clearing of forests for agriculture or other development, or in the killing of lions, wolves, sharks, or many snakes considered to be pests.

Invasions by exotic species (animal or plant species that have been introduced to an area where they did not naturally occur) threaten many endangered plants. When plants or animals are introduced into an area where they have no natural enemies, they may start to compete with the native plants and animals for food, water, shelter, and space and often replace them. Some plant examples include teasel and aggressive European pasture grasses that have invaded the few remaining tallgrass prairies or aquatic plants that have clogged streams and canals. The introduction of goats to tropical islands, for example, has caused the endangerment and extinction of many plant species that were not adapted to such grazing. A similar impact to plants can occur from locally overabundant or expanding native species such as beavers, rabbits, and deer that have altered many habitats because of the elimination of their former natural predators. For example, in many areas of the midwestern and eastern United States, heavy browsing by white-tailed deer is preventing the regeneration of the endangered components of native plant communities. Conservation biologists must be as effective in controlling invasive and destructive species as they are at saving endangered native species.

Environmental poisons and pollution are endangering numerous plants and animals worldwide as well. Examples of plants and animals today that are being poisoned by environmental toxins and solid wastes such as deadly chemicals, oils, and acids are numerous. Scientists learned long ago that groups of organisms in a limited environment can be killed by their own wastes.

Many Plants Are Endangered

One in ten, or a total of about three thousand plants native to the United States is endangered. Many of these endangered plants include some of the most showy, such as the large-flowered orchids. Increasingly, many plants around the world no longer reseed and therefore remain as lone survivors of their species. For example, the Presidio manzanita is so rare that only one plant survives in the wild, at San Francisco's Golden Gate Park. While cuttings have been propagated , they cannot self-fertilize. Another example of a lone survivor can be found on the Indian Ocean's Mascarene Islands where a palm tree, the Hyophorbe amaricaulis, survives as a single individual. One severe storm could cause its extinction. More than two hundred other plant species have also stopped reproducing. Worldwide, an impressive one in eight plants is endangered, according to the 1997 IUCN Red List of Threatened Plants.

Plant Extinctions Are Increasing

Although conservation efforts have begun in recent years, people are still exterminating entire species at an ever-increasing rate. Since the Pilgrims landed at Plymouth Rock, more than five hundred species, subspecies, and varieties of our nation's plants and animals have become lost forever. By contrast, during the three thousand years of the Pleistocene Ice Age, all of North America lost only about ninety species. The situation is even worse in many other parts of the world. Some scientists believe that if present trends continue, two-thirds of the world's three hundred thousand plant species will disappear by the end of the twenty-first century.

Extinction is a difficult concept to fully grasp. We are very aware that dinosaurs no longer exist and that other animals (such as the mammoth, dodo, Carolina parakeet, passenger pigeon, and the Atlantic grey whale) are gone forever due to human activity. The Sexton Mountain mariposa lily, a flower of southwestern Oregon, was unintentionally exterminated by a road crew when Interstate 5 was built in the 1960s. The maidenhair (ginkgo) tree was planted by the Chinese in gardens many centuries ago before it became extinct in the wild. A few plants that have become extinct in the wild in recent times have been saved in some form in cultivation . The Franklin tree (Franklinia, named after Ben Franklin) was last seen in the wild in 1803 in Georgia. However, a few individuals were planted in gardens at that time and have been propagated, saving the species from total extinction. In the mid-1990s the Graves's beach plum, a seashore tree found only in Connecticut, became extinct in the wild when the only known individual died. A few cuttings have been saved in botanical gardens. Although cloning results in plants that are genetically identical, those that have become extinct in the wild but that have been saved in cultivation cannot effectively reproduce.

Mechanisms of Environmental Protection for Endangered Species

Enacted in 1973, the Endangered Species Act (ESA) is the principal tool in the United States for slowing or stopping what has become the greatest rate of extinction worldwide since the disappearance of the dinosaurs sixty-five million years ago. In adopting the Endangered Species Act, Congress found that "various species have been rendered extinct as a consequence of economic growth and development untempered by adequate concern and conservation." In addition, Congress recognized that threatened and endangered species "are of aesthetic, ecological, educational, historical, recreational, and scientific value to the Nation and its people." Congress enacted the ESA in order "to provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved" and to provide a program for the conservation of the species themselves. Under the ESA, species are listed as endangered or threatened. The Interior Secretary is generally required to designate critical habitats (areas essential to the survival and recovery of a species) for threatened and endangered species. In addition, recovery plans (blueprints for bringing species back to a point where they are no longer threatened or endangered) must be developed and implemented. About one-third of listed species are now stable or improving as a result of the ESA Protections for Listed Species. Effective protection is limited by the degree of funding and enforcement of the law.

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), convened in Washington, D.C., in 1973, has been signed by more than 120 countries. CITES was established for the purposes of controlling and monitoring international trade in plants and animals considered to be threatened or likely to be threatened through commercial exploitation. It states that flora and fauna comprise an "irreplaceable part of natural systems which must be protected for generations to come" and "international cooperation is essential for the protection of certain species … [endangered by] over-exploitation through international trade." This treaty was one of the first to take account of the need for conservation of both plants and animals and provided the legal framework within which those in trade can be protected from extinction.

Conservation practices provide the only solution for protecting endangered species. Propagation centers, such as botanical gardens, are actively attempting to save some endangered plant species. Protected collections of seeds and plants can help stop species loss, but protection in the wild is much more desirable because propagating endangered species can be considered to be meaningless if they do not have a home. Managing ecosystems or saving species collectively is the best known solution. Around the world more than thirty-five hundred protected areas (with a total of about 2 million square miles [5 million square kilometers], or 3 percent of Earth's land area) exist in the form of parks, wildlife refuges, and other reserves. Three percent of the planet's area, however, can only protect a relatively small number of species.

see also Biodiversity; Botanical Gardens; Ginkgo; Invasive Species; Rain Forests; Seed Preservation.

Steven R. Hill

Bibliography

Alvarez, L. W., W. Alvarez, F. Asaro, and H. V. Michel. "Extraterrestrial Cause for the Cretaceous-Tertiary Extinction." Science 208 (1980): 1095-1108.

Frankel, O. H., A. Brown, and J. J. Burdon. The Conservation of Plant Biodiversity. Cambridge, England: Cambridge University Press, 1995.

Garrott, R. A., and C. A. Vanderbilt White. "Overabundance: An Issue for Conservation Biologists?" Conservation Biology 7 (1993): 946-49.

Head, S., and R. Heinzman. Lessons of the Rainforest. New York: Random House, 1990.

Hecht, J. Vanishing Life: The Mystery of Mass Extinctions. New York: Charles Scribner's Sons, 1993.

Hunter, M. L., Jr. Fundamentals of Conservation Biology. Cambridge, MA: Blackwell Science, Inc., 1996.

Masters, L. L. "Assessing Threats and Setting Priorities for Conservation." Conservation Biology 5 (1991): 559-63.

Morse, L. E. "Rare Plant Protection, Conservancy Style." Nature Conservancy Magazine 37 (1987): 10-15.

Walter, K. S., and H. Gillett, eds. 1997 IUCN Red List of Threatened Plants. Cambridge: International Union for Conservation of Nature and Natural Resources— World Conservation Union, 1998.