Endangered Species

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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:

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

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

Environmental Science: In Context