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For other uses, see endangered species (disambiguation).
The critically endangered Amur Tiger, a rare subspecies of tiger. Tigers, as a whole, are an endangered species.
Conservation status
Extinct
Threatened
Lower Risk
Other categories
Related topics
IUCN Red List category abbreviations (version 3.1, 2001)
Comparison of Red List classes above
and NatureServe status below
NatureServe category abbreviations

An endangered species is a population of an organism (usually a taxonomic species), which because it is either (a) few in number or (b) threatened by changing environmental or predation parameters, 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 decade could number in the millions[1]. 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

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Main article: Extinction

Species extinction is the ultimate concern, but there are four different reasons to have for concern with this outcome:

  1. Loss of a species as a biological entity;
  2. destabilization of an ecosystem;
  3. endangerment of other species;
  4. 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 (as well as some who believe that animal species have rights in and of themselves). 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. Marked 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 cannot be determined, but it is a highly debated and influential point.

Though extinction can be a natural effect of the process of natural selection, the current extinction crisis is not related to that process. At the present, the Earth has fallen from a peak of biodiversity[1] and Earth is undergoing the Holocene mass extinction period.[2] These periods have occurred before without human intervention; however the current extinction period is unique. Previous periods were triggered by physical causes, such as meteorite collision and volcanic eruption, all leading to climate change. The current extinction period is being caused by humans and began approximately 100,000 years ago with the diaspora of humans to different parts the world. By entering new ecosystems which had never before experienced the human presence, humans disrupted the ecological balance by hunting and also possibly bringing disease. From this time up to approximately 10,000 years ago is known as "phase one" of the sixth extinction period.

Phase two of the period began approximately 10,000 years ago with the birth of agriculture. With the birth of agriculture, humans did not have to rely on interaction with other species for survival and so could begin to domesticate them, and they also did not have to adhere to the limitations of the ecosystem's carrying capacity. Thus, humans became the first species able to live outside local ecosystems. As Niles Eldridge says "Indeed, to develop agriculture is essentially to declare war on ecosystems - converting land to produce one or two food crops, with all other native plant species all now classified as unwanted "weeds" -- and all but a few domesticated species of animals now considered as pests."[3] With the ability to live outside of a local ecosystem, humans have been free to breech the "carrying-capacity" of areas and overpopulate, putting ever more stress on the environment with destructive activities necessary for more population growth. Today, those activities include tropical deforestation, coral loss, other habitat destruction, overexploitation of species, introduction of alien species into ecosystems and pollution (such as soil contamination and greenhouse gases).

Conservation status

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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. In many areas this is referred to as a red-listed species. Internationally, 189 countries have signed an accord agreeing to create Biodiversity Action Plans to protect endangered and other threatened species. In the USA this plan is usually called a species Recovery Plan.

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. It is important to stress that the following lists are a miniscule fraction of the total endangered species. It is also worth noting that the number of species becoming extinct each year is many times as large as the number of species classified as endangered; this fact arises from the extensive and slow review process for listing new species as endangered. It also arises from the voluminous number of yearly extinctions, often for species about which little documentation exists. 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

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The endangered Island Fox

The following list is a very small fraction of known endangered mammals:

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

Endangered birds

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Immature California Condor

Endangered reptiles

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Loggerhead Sea Turtle

Endangered amphibians

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Endangered fish

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An Asian arowana

Endangered arthropods

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Endangered mollusks

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Endangered plants

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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. The following is a very small fraction of the endangered plants:

Controversy

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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 [4]. However, this is usually a spurious argument by those favoring loose protection laws.

Another argument against listing species is the use of the "shoot, shovel, and shut up"[5] method of clearing endangered species from an area of land. Due to the fact that landowners currently may perceive a diminution in value for their land after finding an endangered animal on it, some owners have opted to silently kill and bury the animals, thus removing the problem from their land, but at the same time further reducing the population of an endangered species. It has also been noted that the effectiveness of the Endangered Species Act (ESA), which coined the term "endangered species", has been questioned. Only 15 species have been de-listed to date, and many of those species recovered from the stoppage of practices not related to the ESA, such as the use of DDT.

See also

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References

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  1. ^ S.L. Pimm, G.J. Russell, J.L. Gittleman and T.M. Brooks, The Future of Biodiversity, Science 269: 347-350 (1995)
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