Functional extinction is the
extinction
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
of a
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
or other
taxon
In biology, a taxon (back-formation from ''taxonomy''; : 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 name and ...
such that:
#It disappears from the
fossil record, or historic reports of its existence cease;
#The reduced population no longer plays a significant role in
ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
function;
#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 and
genetic drift, 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 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, leading to more rapid genetic drift or inbreeding problems in small populations.
Functionally extinct species in modern times
*
Baiji
*
Northern white rhinoceros
*
Ivory-billed woodpecker
*
Imperial woodpecker
*
Christmas Island shrew
*
Yangtze giant softshell turtle
*
South China tiger
*
Barbary lion
*
Bornean rhinoceros
*
Vaquita
*
Fernandina Island tortoise
*''
Hyophorbe amaricaulis''
*
North Atlantic right whale
On May 10, 2019, the
Australian Koala Foundation issued a
press release 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 (''Phascolarctos cinereus''), sometimes inaccurately called the koala bear, is an arboreal herbivorous marsupial native to Australia. It is the only Extant taxon, extant representative of the Family (biology), family ''Phascolar ...
s are not currently considered functionally extinct; while their population has decreased, the
IUCN Red List 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
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
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 Felidae, cat and the Fastest animals, fastest land animal. It has a tawny to creamy white or pale buff fur that is marked with evenly spaced, solid black spots. The head is small and rounded, wit ...
s (''Acinonyx jubatus'') and
African wild dogs (''Lycaon pictus'') were now functionally extinct. Non-Northern Cameroonian cheetahs are listed as "Vulnerable" by the
IUCN Red List.
See also
*
Conservation genetics
*
Mutational meltdown
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Small population size
*
Extinction vortex
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Extinction debt
References
{{Extinction
Extinction