More than a third of species assessed in a major international biodiversity study are threatened with extinction, scientists have warned.

科学家警告，一项主要的国际生物多样性研究评估得出结论，超过三分之一的物种处于灭绝的危险之中。

Out of the 47,677 species in the IUCN Red List of Threatened Species, 17,291 were deemed to（被认为） be at serious risk.

These included 21% of mammals（哺乳动物）, 30% of amphibians（两栖类）, 70% of plants and 35% of invertebrates（无脊椎动物）.

Conservationists warned that not enough was being done to tackle the main threats, such as habitat（栖息地） loss.

"The scientific evidence of a serious extinction crisis is mounting," warned Jane Smart, director of the International Union for the Conservation of Nature's (IUCN) Biodiversity Conservation Group.

"The latest analysis... shows that the 2010 target to reduce biodiversity loss will not be met," she added.

"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 are rapidly running out of time."

The Red List, regarded as the most authoritative assessment（估价，评估） of the state of the planet's species, draws on the work of thousands of scientists around the globe.

The latest update lists amphibians as the most seriously affected group of organisms（生物体） on the planet, with 1,895 of the 6,285 known species listed as threatened.

Of these, it lists 39 species as either "extinct" or "extinct in the wild". A further 484 are deemed "critically endangered", 754 "endangered" and 657 "vulnerable".

The Kihansi Spray Toad (Nectophyrnoides asperginis) is one species that has seen its status change from critically endangered to extinct in the wild.

It was only found in the Kihamsi Falls area of Tanzania, but its population had crashed in recent years from a high of an estimated 17,000 individuals.

Conservationists suggest that the rapid decline was primarily the result of of a dam being constructed upstream from the toads'（癞蛤蟆，蟾蜍） habitat, which resulted in a 90% reduction in the flow of water.

"In our lifetime, we have gone from having to worry about a relatively small number of highly threatened species to the collapse of entire ecosystems（生态系统）," observed Professor Jonathan Baillie, director of conservation programmes at the Zoological Society of London (ZSL).

"At what point will society truly respond to this growing crisis?"

The updated data from the 2009 Red List is being made publicly available on the IUCN website on Tuesday.