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Local extinction, also known as extirpation, is the condition of a
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...
(or other
taxon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
) that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global
extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the endling, last individual of the species, although the Functional extin ...
s. Local extinctions mark a change in the
ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Topics of interest include the biodiversity, di ...
of an area. In recent times, local extinction has sometimes been followed by a replacement of the species taken from other locations; wolf reintroduction is an example of this.


Conservation

The area of study chosen may reflect a natural subpopulation, political boundaries, or both. The Cetacean Specialist Group of the IUCN has assessed the threat of a local extinction of the Black Sea stock of harbour porpoise (''Phocoena phocoena'') that touches six countries. COSEWIC, by contrast, investigates wildlife only in Canada, so assesses only the risk of a Canadian local extinction even for species that cross into the United States or other countries. Other subpopulations may be naturally divided by political or country boundaries. Many crocodilian species have experienced localized extinction, particularly the
saltwater crocodile
saltwater crocodile
(''Crocodylus porosus''), which has been extirpated from Vietnam, Thailand, Java, and many other areas. Often a subpopulation of a species will also be a
subspecies In Taxonomy (biology), biological classification, the term subspecies refers to one of two or more populations of a species living in different subdivisions of the species' range and varying from one another by Morphology (biology), morphologi ...
. For example, the recent disappearance of the black rhinoceros (''Diceros bicornis'') from
Cameroon Cameroon (, french: Cameroun), officially the Republic of Cameroon (french: République du Cameroun, links=no), is a country in West Africa, west-central Africa. It is bordered by Nigeria to the west and north; Chad to the northeast; the Cen ...
spells not only the local extinction of rhinoceroses in Cameroon, but also the global extinction of the western black rhinoceros (''Diceros bicornis longipes''). In at least one case, scientists have found a local extinction useful for research: In the case of the Bay checkerspot butterfly, scientists, including Paul R. Ehrlich, chose not to intervene in a local extinction, using it to study the danger to the world population.Holsinger, Kent.
Local extinction
". ''Population Viability Analysis: Bay Checkerspot Butterfly''. URL accessed August 11, 2006.
However, similar studies are not carried out where a global population is at risk. Wolves have been a species that have been reintroduced into their historical range. This has happened with red wolves ('' Canis lupus rufus'') in the United States in the late 1980's and also grey wolves in Yellowstone National Park in the mid 1990's. There have been talks of reintroducing wolves in Scotland, Japan, and Mexico. Reintroduction of wolves is a controversial subject and there are pro's and con's on each side.


IUCN subpopulation and stock assessments

While the World Conservation Union (IUCN) mostly only categorizes whole species or subspecies, assessing the global risk of extinction, in some cases it also assesses the risks to stocks and populations, especially to preserve genetic diversity. In all, 119 stocks or subpopulations across 69 species have been assessed by the IUCN in 2006. Examples of stocks and populations assessed by the IUCN for the threat of local extinction: * Marsh deer (three subpopulations assessed) * Blue whale, North Pacific stock and North Atlantic stock * Bowhead whale, ''Balaena mysticetus'' (five subpopulations assessed), from critically endangered to LR/cd * Lake sturgeon, ''Acipenser fulvescens'', Mississippi & Missouri Basins subpopulation assessed as vulnerable species, vulnerable * Wild common carp, ''Cyprinus carpio'' (River Danube subpopulation) * Black-flanked rock-wallaby ''Petrogale lateralis'' (MacDonnell Ranges subpopulation and Western Kimberly subpopulation) The IUCN also lists countries where assessed species, subspecies or subpopulations are found, and from which countries they have been extirpated or reintroduced. The IUCN has only three entries for subpopulations that have become extinct the Aral Sea stock of Ship sturgeon (''Acipenser nudiventris''); the Adriatic Sea stock of beluga sturgeon (''Huso huso''); and the Mexican wolf, Mexican subpopulation of wolf (''Canis lupus''), which is extinct in the wild. No plant or fungi subpopulations have been assessed by the IUCN.


Local extinction events

Major environmental events, such as volcanic eruptions, may lead to large numbers of local extinctions, such as with the 1980 Mount St. Helens eruption, which led to a fern spike extinction. Heat waves can lead to local extinction. In New Zealand, during the summer of 2017–2018, sea surface temperatures around parts of South Island exceeded , which was well above normal. Air temperatures were also high, exceeding . These high temperatures, coupled with small wave height, led to the local extinction of Durvillaea, Bull Kelp (''Durvillaea'' spp.) from Pile Bay. Lagoa Santa, Brazil has lost almost 70% of the local fish species over the last 150 years. These include ''Acestrorhynchus lacustris'', ''Astyanax (fish), Astyanax fasciatus'', and ''Characidium zebra''. This could be caused by the introduction of non-native species, like ''Redbreast tilapia, Talapia rendalli,'' into the lagoon, changes in water level and organic pollution. Glacial period, Glaciation can lead to local extinction. This was the case during the Quaternary glaciation, Pleistocene glaciation event in North America. During this period, most of the native North American species of earthworm were killed in places covered by glaciation. This left them open for colonization by European earthworms brought over in soil from Europe.


See also

*List of extinct animals *Threatened species *Extinct in the wild


References

{{DEFAULTSORT:Local Extinction Extinction