Thursday, October 28, 2010

20% of Vertebrates Endangered with Extinction

According to a recent report by the International Union for the Conservation of Nature (IUCN), one-fifth of vertebrate species worldwide are threatened with extinction. The situation continues to worsen, as over 50 animals move closer to extinction each year, as measured by the IUCN's Red List. The hardest-hit areas are in the tropics, especially Southeast Asia. (Dark areas on the map at left show the highest numbers of endangered animals.) A high concentration of unique species combines with rapid environmental change to create a difficult biodiversity situation in Southeast Asia, eastern Africa, and the Andes in South America.
Even Southeast Asia's most iconic species—rhinos, orangutans, tigers, and elephants—face extirpation and in some cases total extinction. The Javan rhinoceros is down to some 40-60 individuals, none of which are in captivity.

But as far as type of species goes, nothing is worse than being a frog: according to the study 41% of the world's amphibians are threatened with extinction. In contrast, 33% of cartilaginous fishes, 25% of mammals, 22% of reptiles, 15% of bony fishes, and 13% of birds are threatened.

Highly-sensitive to environmental changes amphibians face a barrage of threats, including habitat loss, pollution, climate change, agricultural chemicals, and overconsumption for food and the pet trade. However, the largest threat to amphibians is known as the 'amphibian plague': chytridiomycosis, a fungal disease, has decimated amphibian populations even in pristine environments. Recent studies have shown that frog species never known to science have already been lost. At least 120 amphibians have vanished entirely in the past three decades, making this group a poster child for the extinction crisis.

But of all the world's species—vertebrates, plants, fungi, insects, etc.—vertebrates make up just 3% of the total. The study also reported on a number of non-vertebrate species types—not included in the overall analysis—finding, for example, that 14% of seagrasses, 32% of freshwater crayfish, and 33% of coral reef species are threatened with extinction. An earlier study, looking at a representative sample of plants, found that 22% of the world's plant species are threatened with extinction.

One of the most threatened groups of species on Earth is the cycads, an ancient group of plants: 63% percent of cycads face extinction.
The one bit of good news that the report offered was that conservation has worked to reduce the threat of extinction. According to the report, the biodiversity crisis would be 18% worse without conservation action over the past several decades, and 7% of the species that changed categories moved from a worse category to a safer one. Unfortunately, relatively few threatened species benefit from concrete actions or even a conservation plan, as most of the attention goes to a handful of iconic species. In some cases, scientists do not even know how secure or threatened a species is. The report's findings underscore the need for continued protection of threatened species and preservation of habitats where unique species occur.