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Endangered species

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For other uses, see endangered species (disambiguation).
The endangered Sea Otter

An endangered species is a population of organisms (frequently but not always a taxonomic species) which is either (a) so few in number or (b) threatened by changing environmental or predation parameters that it is at risk of becoming extinct. Many countries have laws offering special protection to these species or their habitats: for example, forbidding hunting, restricting land development or creating preserves. Only a few of the many endangered species actually make it to the lists and obtain legal protection. Many more species become extinct, or potentially will become extinct, without gaining public notice.

The greatest factor of concern is the rate at which species are becoming extinct within the last 150 years. While species have evolved and become extinct on a regular basis for the last several hundred million years, the number of species becoming extinct since the Industrial Revolution has no precedent in biological history. If this rate of extinction continues, or accelerates as now seems to be the case, the number of species becoming extinct in the next century could number in the tens of thousands. While most people readily relate to endangerment of large mammals or birdlife, some of the greatest ecological issues are the threats to stability of whole ecosystems if key species vanish at any level of the food chain.

Issues of extinction

Species extinction is the obvious ultimate concern, but there are four different reasons to have for concern with this outcome: (a) Loss of a species as a biological entity, (b) Destabilization of an ecosystem, (c) Endangerment of other species and (d) Loss of irreplaceable genetic material and associated biochemicals. The loss of a species in and of itself is an important factor, both as diminution of the enjoyment of nature and as a moral issue for those who believe humans are stewards of the natural environment. Destabilization is a well understood outcome, when an element of food or predation is removed from an ecosystem. Examples abound that other species are in turn affected, such that population increases or declines are forthcoming in these secondary species. Drastic change or an unstable spiral can ensue, until other species are lost and the ecosystem structure is changed markedly and irreversibly.

The fourth outcome is more subtle, but perhaps the most important point for mankind to grasp. Each species carries unique genetic material in its DNA and in its chemical factory responding to these genetic instructions. For example, in the valleys of central China, a fernlike weed called sweet wormwood grows, that is the only source of artemisinin, a drug that is nearly 100 percent effective against malaria (Jonietz, 2006). If this plant were lost to extinction, then the ability to control malaria, even today a potent killer, would diminish. There are countless other examples of chemicals unique to a certain species, whose only source is the species, whose genetic factory makes that given substance. How many further chemicals have not yet been discovered and could vanish from the planet when further species become extinct?

Conservation status

The conservation status of a species is an indicator of the likelihood of that endangered species continuing to survive. Many factors are taken into account when assessing the conservation status of a species; not simply the number remaining, but the overall increase or decrease in the population over time, breeding success rates, known threats, and so on.

The best-known worldwide conservation status listing is the IUCN Red List, but many more specialized lists exist.

The following conservation status categories are used in articles in this encyclopedia. They are loosely based on the IUCN categories.


The following lists are examples of endangered species. Note that because of varying standards for regarding a species as endangered, and the very large number of endangered species, these lists should not be regarded as comprehensive.

Endangered mammals

The endangered Island Fox
Humpback Whale
American bison skull heap. There were as few as 750 bison in 1890 from overhunting.

Endangered birds

Immature California Condor

Endangered reptiles

Endangered amphibians

File:Croceum.jpg
Santa Cruz Long-toed Salamander (photo courtesy of Don Roberson)

Endangered fish

Endangered crustaceans

Endangered arthropods

Endangered mollusks

Endangered plants

About 6% of the 300,000 identified species are endangered due to overcollection or destruction of habitat, among other causes. Pollinator decline is also a factor for some species.

Controversy

Some endangered species laws are controversial. Typical areas of controversy include: criteria for placing a species on the endangered species list, and criteria for removing a species from the list once its population has recovered; whether restrictions on land development constitute a "taking" of land by the government; the related question of whether private landowners should be compensated for the loss of use of their land; and obtaining reasonable exceptions to protection laws.

Being listed as an endangered species can backfire, since it could make a species more desirable for collectors and poachers [1]. However, this is usually a spurious argument by those favoring loose protection laws.

See also

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