Friday, August 31, 2012

[News 2006] Going or gone: defining 'Possibly Extinct - PE' species to give a truer picture of recent extinctions

Madagascar's Alaotra Grebe was last seen in 1985 and is now Extinct
photo: Paul Thompson

According to the IUCN Red List, 131 bird species have become Extinct since 1500, with an additional four species surviving only in captivity and classified as Extinct in the Wild. But a new paper by BirdLife’s Stuart Butchart and Alison Stattersfield and Conservation International’s Tom Brooks argues that the number of recent extinctions documented on the Red List is likely to be "a significant underestimate".

The paper, Going or gone: defining 'Possibly Extinct' species to give a truer picture of recent extinctions (published in The Bulletin of the British Ornithologists' Club), describes the method the authors have developed to identify 15 Critically Endangered species as Possibly Extinct (PE).

"A precautionary approach by IUCN to classifying extinctions is appropriate in order to encourage continuing conservation efforts until there is no reasonable doubt that the last individual of a species has died," says lead author Dr Stuart Butchart, BirdLife's Global Species Programme Coordinator. However, this approach means that analyses of recent extinctions are likely to come up with unduly optimistic figures.

"We defined ‘Possibly Extinct’ species as those that are, on the balance of evidence, likely to be extinct, but for which there is a small chance that they may be extant and thus should not be listed as Extinct until adequate surveys have failed to find the species and local or unconfirmed reports have been discounted," Butchart explains. "Adding this tag to the Red List allows more realistic assessment of extinction rates without giving up on species prematurely."

Some Possibly Extinct species have not been recorded for more than 50 years, with the record being held by Hooded Seedeater Sporophila melanops – not seen since it was discovered in central Brazil in 1823. Others have undergone well-documented declines, such as the Oloma'o Myadestes lanaiensis, a Hawaiian thrush that was last seen in 1980 following its disappearance resulting from habitat destruction and introduced avian malaria.

"Combining data on these 15 species with data for 135 Extinct and Extinct in the Wild species shows that over the last century bird species have become extinct at a rate of one every 1.8 years," says Butchart. "Habitat loss and degradation, invasive species, and exploitation have been the main causes of extinction."

Grimmer picture painted of recent extinctions
Going or gone: defining 'Possibly Extinct' species to give a truer picture of recent extinctions