The black rhinoceros (Diceros bicornis) is listed by the IUCN as critically endangered. Encyclopædia Britannica, Inc.
Although there were about 65,000 black rhinoceroses in the world in 1970, at the start of the 21st century there were fewer than 3,000 left. Even rarer was the mandrinette, a shrub from Mauritius with bright red flowers. Fewer than 50 of the plants were known in the wild. The black rhinoceros and the mandrinette are endangered species: they face a high risk of extinction throughout all or a significant portion of their range. An extinct species is one that has completely died out; living individuals of its kind no longer exist. By 2006 the International Union for Conservation of Nature and Natural Resources (IUCN) estimated that more than 16,000 species of animals and plants around the world were threatened with extinction. The protection of endangered species is a key component of the environmental movement.
Plants and animals have become extinct and new species have evolved since life on Earth began. Preliterate human cultures may have caused the extinction of some species, but the primary causes for species to become extinct were natural ones. Major environmental changes resulted in the eventual disappearance of species unable to adapt to new conditions. Well-known natural extinctions include that of the dinosaurs and many other species represented in the fossil record.
The black rhinoceros (Diceros bicornis) is listed by the IUCN as critically endangered. Encyclopædia Britannica, Inc.
Natural forces are still at work, but human activities cause most of the rapid and widespread environmental changes that affect plants and animals today. Many species have been unable to make the biological adjustments necessary for survival. Thus more species than ever before are threatened with extinction.
Destruction of forests, draining of wetlands, and pollution are environmental changes that may eliminate species in an area. Some herbicides and pesticides can severely affect certain species. Many species have small geographic ranges, so habitat alteration may eliminate them entirely. The logging of tropical forests, with their tremendous diversity of species having specialized requirements, has caused a steady increase in the extinction rate. Excessive hunting and trapping for commercial purposes also cause major problems. Elephants have been reduced to critically low numbers because of uncontrolled killing for their tusks, which are used to make ivory piano keys, jewelry, and other art objects. Plants also can be reduced to near extinction levels by extensive collecting. Many cactus species of the arid southwestern United States are now legally protected by state laws to prevent their removal.
The Tasmanian wolf is presumed extinct. The last known living specimen died in a private zoo in Hobart, Australia, in 1936. Encyclopædia Britannica, Inc.
The Sneed pincushion cactus is an endangered plant species. Encyclopædia Britannica, Inc.
The planned or accidental introduction of exotic species to a region can also lead to extinction. An introduced species often has no natural enemies to control its spread, and native species may have no natural protection against it. The introduction of the fungus that causes Dutch elm disease to North America, mongooses to Jamaica, and pigs to Hawaii resulted in the loss of native species that had inadequate defenses.
Only since the 19th century has there been international concern about the plight of species in their natural environments. In earlier times, when human population sizes were small and modern technology was developing, the effects of human activities on natural populations seldom seemed significant. Protection of animal species on an international scale was initiated as early as 1916 with the Migratory Bird Treaty between the United States, Great Britain, Canada, and later Mexico.
A far-reaching wildlife conservation measure came from a United States–hosted conference in 1973 that resulted in an international treaty known as CITES—the Convention on International Trade in Endangered Species of Wild Fauna and Flora. This program involves more than 170 countries working together to protect endangered species through worldwide control of exports and imports. The United States Fish and Wildlife Service (FWS) of the Department of the Interior is authorized to assist in the development and management of endangered species programs in foreign countries.
The IUCN, founded in 1948, is the world’s largest conservation organization. It is headquartered in Gland, Switzerland. The goal of the IUCN is to promote the protection of endangered and threatened “living resources.” It publishes information on endangered species worldwide in the IUCN Red List of Threatened Species.
One of the earliest official recognitions of an endangered species problem in the United States was the Buffalo Protection Act of 1894. The enormous herds of buffalo that roamed through North America had been reduced to just a few individuals by the late 1800s. The law to protect the few remaining in Yellowstone National Park was the first federal legislation that focused on conserving a once-vast wildlife resource. Other national laws and regulations followed. In 1900 the Lacey Act made it illegal to import certain birds and mammals that other countries had identified as requiring protection. The National Wildlife Refuge System was started in 1903 to protect habitats that harbored fast-disappearing wildlife species. In 1940 Congress enacted the Bald Eagle Act to protect the national bird.
The Endangered Species Preservation Act of 1966 and the Endangered Species Conservation Act of 1969 demonstrated concern for disappearing species on a worldwide scale, but the laws did not directly protect the species themselves. The 1973 Endangered Species Act was the most effective and far-reaching law ever passed in the United States to protect plants and animals in natural ecosystems. The act obligates the government to protect all animal and plant life threatened with extinction, defining as threatened any species “which is likely to become endangered in the foreseeable future throughout all or a significant portion of its range.” It also provides for the drawing up of lists of such species and promotes the protection of critical habitats (areas designated as critical to the survival of a species).
The Endangered Species Act is administered by the FWS and the National Marine Fisheries Service (NMFS) of the Department of Commerce. Species are officially added to the endangered list through an established administrative process. A proposed listing of a species is published in the Federal Register. Scientists, conservationists, and government officials are asked to provide information about the biological status of the species. The FWS or NMFS accumulates the data and makes a decision about the species within the guidelines specified in the Endangered Species Act. A species may be listed as endangered or threatened, it may be removed from consideration, or more information may be required. Once a species has been listed, the FWS or NMFS develop programs to protect the remaining members of the species and return the species to a point at which it can function in a natural manner. Programs for raising some species in captivity have been carried out in attempts to restore population levels.
Further aid for vanishing species comes from private organizations involved in educating the public about environmental issues. Many organizations promote species preservation through magazines, lecture series, Web sites, and television programs. In addition, many groups lobby legislators to support protection laws. Some also take more direct action. The Nature Conservancy, for example, buys and preserves tracts of habitat vital to endangered species. The World Wildlife Fund monitors the illegal trade in endangered animals and helps establish reserves for threatened wildlife, among many other projects. The primary tactic of Greenpeace has been “direct, nonviolent actions,” such as steering small inflatable craft between the harpoon guns of whalers and their endangered prey.
Blue whale. Encyclopædia Britannica, Inc.
The 1973 Endangered Species Act addressed the issue of why an endangered species of plant or animal should be offered formal protection. As stated in the act, such species “are of esthetic, ecological, educational, historical, recreational, and scientific value to the Nation and its people.” Numerous species are medically or agriculturally significant because of their unique properties or traits. It cannot be predicted when a species might be discovered to be of direct value to humans. Once a species becomes extinct, any benefits it might have provided are lost forever.
As scientists unravel the intricate network of plant-animal relationships in the natural world, more and more species are discovered to have a vital, and often unsuspected, dependence on other species. Obviously, if the extinction of one species is permitted through rapid, human-caused activities that do not permit natural adaptations and evolution to occur, certain other species may also be affected. This can result in a “domino effect” of potential extinctions.
The whooping crane was on the verge of extinction in 1941–42, when only 15 or 16 of the birds remained. Conservation programs increased the population, but the bird is still endangered. Encyclopædia Britannica, Inc.
Through breeding programs and reintroduction of animals into their natural habitats, several species have been brought back from the brink of extinction, including the black-footed ferret and the California condor, though both are still endangered. Several more species are undergoing such programs, and they will eventually be reintroduced into the wild.