Red alert: scientists identify 17,000 endangered species

Six years ago, tiny mustard-coloured toads could be found in their thousands living under the spray from an African waterfall. No one even knew they existed until 1996. Yet today the Kihansi spray toad will be declared extinct in the wild, a symbol of the plight facing 17,000 species that are slipping towards obscurity.

In the case of this charming creature, which unusually for a toad does not start life as a tadpole but as a tiny purple-hued toadlet, a dam and a fungus have combined to bring about its extermination.

Almost one-third of amphibians are at risk, making them the most endangered group on the planet, according to the latest Red List of Threatened Species, published today by the International Union for Conservation of Nature. The registers assesses the status of 47,677 species. Of the 6,285 assessed amphibian types, 1,895 are in peril.

The Kihansi spray toad, three-quarters of an inch long when fully grown, lived in a wild gorge beneath the Kihansi waterfall in Tanzania. As recently as June 2003 there were reckoned to be almost 21,000 of them; it was only officially discovered in the mid-1990s, when an environmental study was carried out to test the impact of a power dam that the Tanzanian government proposed to build above the waterfall.

Work on the dam began in 2000, and an artificial spray system was used to protect the toads. But in 2003, it broke down. At about the same time, the dam was briefly opened to flush out sediments, including pesticides which sluiced across the toads' habitat. By the following January, the sound of the male toad calling for his mate had all but disappeared.

With their numbers down and their resistance weakened, the toads were finished off by the fungal disease chytridiomycosis. The only known survivors are in zoos.

In 2006, the chytrid fungus also made an ominous appearance in that part of the jungle of central Panama that is home to Rabb's Fringe-Limbed Tree Frog, a much large creature than the Kihansi Spray Toad, which used its huge feet to glide from tree tops to the ground. The male of this frog, uniquely, allows tadpoles to feed by scraping nutrients off his back. But the male's call has been heard only once since the fungus was first spotted, and all attempts to breed this frog in captivity have so far failed.

"The continued and unprecedented loss of species must not be accepted as just a sad reality we can do nothing about," said Mark Wright, conservation science advisor at WWF-UK. "Biodiversity loss is an alarming indicator of the general health of our planet and of the well-being of our own species. We must act to halt this decline."

Of the world's 5,490 mammals, 79 are extinct in the wild, 188 critically endangered, 449 endangered, and 505 vulnerable.

The Eastern Voalavo, a rodent found only in the tropical forest of Madagascar, features on the red list as an "endangered" species for the first time because slash-and-burn is destroying its habitat.

The new list features 293 reptiles which were not there last year, bringing the total threatened to 1,677, including 469 that face extinction and 22 are that are believed extinct. On the Philippine islands alone, 165 endemic species of reptile have been included for the first time, such as the herbivorous Panay Monitor Lizard, and the spectacular Sail-fin Water Lizard, which can be a metre long and is so named because it has a "sail" at the end of its tail which it uses for propulsion through the water. The young walk on water, using their large, flattened toes. Both species are under threat from the destruction of their habitat and because they are hunted for food.

The new red list also includes 12,151 plants, among them the extraordinary Queen of the Andes, found high up in Peru and Bolivia, which seeds only once in 80 years before dying and grows up to 9ft tall. It is suffering from climate change and is being trampled or eaten by free-roaming cattle.

There are also 7,615 invertebrates, such as the Giant Jewel, a huge, red dragonfly found in south-east Nigeria and south-west Cameroon, vulnerable because of the destruction of the forest; and 3,120 freshwater fishes, of which 1,147 are close to extinction. The Brown Mudfish, found only in New Zealand, which can survive out of water during a drought by burying itself in the mud, has been moved into the "vulnerable" category because drainage, irrigation or land development has destroyed up to 90 per cent of its wetlands habitat.

"The scientific evidence of a serious extinction crisis is mounting," said Jane Smart, Director of IUCN's Biodiversity Conservation Group. "January sees the launch of the International Year of Biodiversity. The latest analysis of the IUCN Red List shows the 2010 target to reduce biodiversity loss will not be met. It's time for governments to start getting serious about saving species and make sure it's high on their agendas for next year, as we're rapidly running out of time."