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The Top of the IUCN Red List

The 61 Most-Threatened Species:

Identifying a definitive list of the most threatened species is a difficult and sensitive exercise. Although lists are popular and useful, a comprehensive list of the Most Threatened Species depends on what you think makes a species most at risk of extinction and could conceivable contain all 4,286 Critically Endangered species on the IUCN Red List.

Partula nodosa
Partula nodosa is one of ten species of Polynesian Tree Snails that are Extinct in the Wild. Starting in 1977 their populations were decimated in an ironic effort to control the spread of the Giant African Land Snail (Achatina fulica) by the purposeful introduction of a species of carnivorous snail (Euglandina rosea) to Tahiti. Photo courtesy of Ryan Hawk and the Woodland Park Zoo Partulid Snail Conservation Program.

Rarity is often used as a criterion in most threatened lists, but rarity alone neglects the fact that some species naturally occur at low densities. Rarity combined with a small ranges or endemism increases the chances that a flood, fire, or other natural disaster will wipe out an entire species. Each of these criteria when paired with threats like habitat loss or degradation can place species even higher on the list, but at the top are the species that no longer exist in the wild.

There are some famous examples of species that met extinction in captivity: including Benjamin the Tasmanian Tiger (Thylacine), Martha the Passenger Pigeon, and Lonesome George the Pinta Island Tortoise. Each of these species was already extinct in the wild and died as the last of its kind in captivity. Thankfully, people had taken enough notice of these species that their extinctions were documented. Unfortunately, many species still quietly meet extinction.

The IUCN Red List of Threatened Species contains 61 species that are Extinct in the Wild. Most of these species require concerted effort by people to maintain a small subset of individuals in captivity to prevent the extinction of their species.

Cyprinodon alvarezi_EW_copyright Barbara Nicca
Perrito De Potosi (Cyprinodon alvarezi) is a species that jumped from Vulnerable in 1994 to Extinct in the wild in 1996. It now survives only in captivity. Photo courtesy of Barbara Nicca

Animals Extinct in the Wild

There are currently thirty-two species of animal listed as Extinct in the Wild on the IUCN Red List. These include two arthropods (a cricket and an isopod), fourteen species of snail, two species of toad, four species of bird, seven species of fish, two species of mammal, and one species of reptile.

Acanthobrama telavivensis  · Ameca splendens  · Anaxyrus baxteri  · Aylacostoma chloroticum ·Aylacostoma guaraniticum · Aylacostoma stigmaticum · Corvus hawaiiensis · Cyprinodon alvarezi · Cyprinodon longidorsalis · Elaphurus davidianus · Gallirallus owstoni · Leptogryllus deceptor · Megupsilon aporus · Mitu mitu · Nectophrynoides asperginis · Nilssonia nigricans · Partula dentifera: · Partula faba · Partula hebe · Partula mirabilis · Partula mooreana · Partula nodosa · Partula rosea · Partula suturalis · Partula tohiveana · Partula tristis · Partula varia · Skiffia francesae · Stenodus leucichthys · Thermosphaeroma thermophilum · Zenaida graysoni

Cyprinodon longidorsalis_EW_copyright Heiko Kaerst
The La Palma Pupfish (Cyprinodon longdorsalis). Photo courtesy of Heiko Kaerst.

Plants Extinct in the Wild

Twenty-nine species of plants round out the list and include four species of cycad, two species of grass, two species of palm, a birch, a gumwood, a series of five Hawaiian plants from three different genera, two Indonesian species in the cashew family, the world’s smallest water lily, a legume native to Easter Island, and ten other species that span flowering plant taxonomy.

Betula szaferi · Bromus bromoideus · Bromus interruptus · Clermontia peleana · Commidendrum rotundifolium · Corypha taliera · Cryosophila williamsii · Cyanea pinnatifida · Cyanea superba · Cyanea truncata · Cyrtandra waiolani · Encephalartos brevifoliolatus · Encephalartos nubimontanus · Encephalartos relictus · Erythroxylum echinodendron · Euphorbia mayurnathanii · Firmiana major · Franklinia alatamaha · Kokia cookei · Lysimachia minoricensis · Mangifera casturi · Mangifera rubropetala · Nymphaea thermarum · Rhododendron kanehirai · Senecio leucopeplus · Sophora toromiro · Terminalia acuminata · Trochetiopsis erythroxylon

Kokia cookei_EW_copyright Forest Starr and Kim Starr
Molokai Koki`o (Kodia cookei) was first discovered in the 1860s and only three trees were described before the species was feared extinct in 1918. In 1970 one living individual was discovered and this species now only survives in captivity. Photo courtesy of Forest Starr and Kim Starr.

Often the survival of these species does not garner the attention you might think (how many of these species do you know?) and many only have scientific names . However, there are a few, dedicated people and institutions who work to preserve these species. Where possible, IUCN Red List assessments include recommendations for conservation actions, and for the 61 species that are privileged enough to survive only in captivity, captive breeding is one of the last remaining options. Ideally, and if possible, the aim is to release captive-bred individuals back into the wild should appropriate habitat be restored and managed effectively.

Today we can put these species at the top of the IUCN Red List of Threatened Species, but with the continued support of people in conserving natural habitat and biodiversity these species might eventually make the transition from Extinct in the Wild back to their places in healthy and productive ecosystems.

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