Wednesday, September 12, 2007

Number of Threatened Species Increasing

The IUCN Red List of Threatened Species for 2007 was released this week. The Red List for 2007 includes 41,415 species, of which 16,306 are threatened with extinction, 785 are extinct, and 65 exist only in captivity. This year's list contains many more species than past lists because the status of several taxa, including corals and North American reptiles, were fully assessed for the first time. Only about 3% of the world's species have been assessed. (See the Guardian for video and images of some species on the list.)

BirdLife International, which maintains the bird portion of the Red List, reports that 1,221 birds are threatened, of which 189 are critically endangered. There are a total of 9,956 bird species on the list, which means that about 12% of the world's birds are threatened. This year's highlight is the decline of vultures in Asia and Africa. Several species moved to higher threat levels this year; most notable were the Red-headed Vulture, Egyptian Vulture, White-headed Vulture, White-backed Vulture, and Rüppell’s Griffon.

Mauritius ParakeetThe bird list contains the one Red List species to be downgraded this year. The Mauritius Parakeet (pictured right) was shifted from critically endangered to endangered thanks to successful conservation action.

Mauritius Parakeet Psittacula eques –a green parrot, males of which have a bright red bill - was once down to just 10 birds in the 1970s, but today saw the World Conservation Union (IUCN) announce its move from Critically Endangered to Endangered. ...

For Mauritius Parakeet, these threats included introduced nest predators (in particular Black Rat), decline of the native fruits on which the parakeets feed (itself outcompeted by invasive non-native plants, and eaten by feral pigs), and a loss of suitable nesting sites.

“These parrots only naturally nest in old canopy trees, which are disappearing across the island,” Vikash [Tatayah of the Mauritius Wildlife Foundation] explains. “Many years of hard work went into tackling the shortage of nest sites and finally we’ve come up with a design acceptable to Echo Parakeets and requiring less maintenance. The parakeets now nest in artificial cavities more than the traditional nest cavities.”

“The artificial cavities also control for invasive nest predators – another long-term threat to the birds,” Vikash continues. “The boxes are rat-proofed, overhanging trees are trimmed, we poison for rats on the ground, and staple plastic sheeting around trees to reduce predation of eggs and chicks by rats. These are simple but essential measures to help get the population back on its feet.”
If you want to check on the classification of your favorite species, you can use the IUCN search page. The Cerulean Warbler, for example, is listed as vulnerable, with the following threats:
Degradation of habitat through land use change is the major threat to this species. Conversion of mature deciduous forest to agricultural or urban areas, fragmentation and increasing isolation of remaining mature deciduous forest, the change to shorter rotation periods and even-aged management, and loss of key tree species to disease are all breeding season constraints. Wintering habitat is also threatened by conversion to other land uses such as pastureland and farms, and is converted into coca plantations which have a detrimental effect on suitable primary forest habitat. Attempts to eradicate coca plantations will also potentially damage forests. Mountaintop mining constitutes a known but as yet uncontrolled threat.
As Bug Girl comments, the current Red List seems weighted in favor of taxa from North America and Europe, and towards large organisms like birds and mammals. I suspect this is less because of outright bias than a result of where the resources (money and trained observers) are located, and which organisms are easiest to study. Future editions of the Red Lists will need to assess more of the species that so far have been omitted. Unfortunately this is likely to produce an even more depressing picture of the planet's loss of biodiversity.