Functional extinction is the

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 last individual of the species, although the capacity to breed and ...

of a

species In biology, a species is the basic unit of 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 individuals of the appropriate s ...

or other

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

such that: #It disappears from the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

, or historic reports of its existence cease; #The reduced population no longer plays a significant role in

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

function; or #The population is no longer viable. There are no individuals able to reproduce, or the small population of breeding individuals will not be able to sustain itself due to

inbreeding depression Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. In ...

and

genetic drift Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...

, which leads to a loss of fitness. In plant populations, self-incompatibility mechanisms may cause related plant specimens to be incompatible, which may lead to functional extinction if an entire population becomes self-incompatible. This does not occur in larger populations. In

polygynous Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women. Incidence Polygyny is more widespread in Africa than in any ...

populations, where only a few males leave offspring, there is a much smaller reproducing population than if all viable males were considered. Furthermore, the successful males act as a

genetic bottleneck A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as specicide, widespread violen ...

, leading to more rapid genetic drift or inbreeding problems in small populations.

Functionally extinct species in modern times

Baiji dolphin The baiji (; IPA: ; ''Lipotes vexillifer'', ''Lipotes'' meaning "left behind" and ''vexillifer'' "flag bearer") is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolph ...

Northern white rhinoceros The northern white rhinoceros or northern white rhino (''Ceratotherium simum cottoni'') is one of two subspecies of the white rhinoceros (the other being the southern white rhinoceros). Formerly found in several countries in East and Central Afr ...

Ivory-billed woodpecker The ivory-billed woodpecker (''Campephilus principalis'') is a possibly extinct woodpecker that is native to the bottomland hardwood forests and temperate coniferous forests of the Southern United States and Cuba. Habitat destruction and hunting ...

Christmas Island shrew The Christmas Island shrew (''Crocidura trichura''), also known as the Christmas Island musk-shrew is an extremely rare or possibly extinct shrew from Christmas Island. It was variously placed as subspecies of the Asian gray shrew (''Crocidura at ...

Yangtze giant softshell turtle The Yangtze giant softshell turtle (''Rafetus swinhoei''), also known as the Red River giant softshell turtle, the Shanghai softshell turtle, the speckled softshell turtle, and Swinhoe's softshell turtle, is an extremely rare species of turtle i ...

South China Tiger The South China tiger is a population of the '' Panthera tigris tigris'' subspecies that is native to southern China. The population mainly inhabited the Fujian, Guangdong, Hunan and Jiangxi provinces. It has been listed as Critically Endange ...

Bornean rhinoceros The Bornean rhinoceros (''Dicerorhinus sumatrensis harrissoni''), also known as the eastern Sumatran rhinoceros or eastern hairy rhinoceros, is one of three subspecies of Sumatran rhinoceros. The subspecies may be functionally extinct, with only o ...

North Atlantic right whale The North Atlantic right whale (''Eubalaena glacialis'') is a baleen whale, one of three right whale species belonging to the genus ''Eubalaena'', all of which were formerly classified as a single species. Because of their docile nature, their ...

Vaquita The vaquita ( ; ''Phocoena sinus'') is a species of porpoise endemic to the northern end of the Gulf of California in Baja California, Mexico. Averaging (females) or (males) in length, it is the smallest of all living cetaceans. The species i ...

Kouprey The kouprey (''Bos sauveli''), also known as forest ox is a forest-dwelling, wild bovine species native to Southeast Asia. A young male was sent to the Paris Zoological Park in 1937 and was described by the French zoologist Achille Urbain who ...

Northern Sumatran Rhinoceros The Northern Sumatran rhinoceros (''Dicerorhinus sumatrensis lasiotis''), also known as Chittagong rhinoceros or northern hairy rhinoceros was the most widespread subspecies of Sumatran rhinoceros, as well as the only known subspecies native to m ...

On May 10, 2019, the

Australian Koala Foundation The Australian Koala Foundation (AKF) is registered Australian charity created in 1986, dedicated to the effective management and conservation of the koala and its habitat. It is the principal non-profit, non-governmental organisation dedicate ...

issued a

press release A press release is an official statement delivered to members of the news media for the purpose of providing information, creating an official statement, or making an announcement directed for public release. Press releases are also considere ...

that opened with the sentence "The Australian Koala Foundation (AKF) believes Koalas may be functionally extinct in the entire landscape of Australia." The press release was reported on by multiple news agencies around the world, with most repeating the AKF's statement. Despite this,

koala The koala or, inaccurately, koala bear (''Phascolarctos cinereus''), is an arboreal herbivorous marsupial native to Australia. It is the only extant representative of the family Phascolarctidae and its closest living relatives are the womb ...

s are not currently considered functionally extinct; while their population has decreased, the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...

lists them only as " Vulnerable". The AKF's press release was released on the eve of the 2019 elections in Australia, where topics such as

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

were major issues. Distinct animal populations can also become functionally extinct. In 2011, a 3-year survey of the wildlife population in the Bénoué Ecosystem of North Cameroon (the Bénoué, Bouba-Ndjidda, and Faro national parks, and 28 hunting zones surrounding the parks), concluded that the North Cameroon population of

cheetah The cheetah (''Acinonyx jubatus'') is a large cat native to Africa and central Iran. It is the fastest land animal, estimated to be capable of running at with the fastest reliably recorded speeds being , and as such has evolved specialized ...

s (''Acinonyx jubatus'') and

African wild dog The African wild dog (''Lycaon pictus''), also called the painted dog or Cape hunting dog, is a wild canine which is a native species to sub-Saharan Africa. It is the largest wild canine in Africa, and the only extant member of the genus '' Ly ...

s (''Lycaon pictus'') were now functionally extinct. Non-Northern Cameroonian cheetahs are listed as "Vulnerable" by the

References

{{Extinction Extinction

Functionally extinct species in modern times

See also

References