The annual report card on the state of the planet's species contains some sobering statistics. According to this year's Red List of Threatened Species, compiled by the World Conservation Union (IUCN), a total of 15,589 species are currently at risk for extinction, with more than 3,330 new threatened plants and animals added to the roll since last year. As it stands now, one in three amphibians, one in four mammals and one in eight birds stand to disappear permanently.

This year's Red List and the accompanying Global Species Assessment (GSA) include many animals and plants that have not appeared before, because of increased monitoring data. For example, the Global Amphibian Assessment, which was completed in September, provided information on species not evaluated in previous surveys. Still, the picture is incomplete. Although 15,589 species are known to be threatened with extinction, this greatly underestimates the true number, as only a fraction of the known species have been assessed, explains Red List program officer Craig Hilton-Taylor. There is still much to be discovered about key species-rich habitats, such as tropical forests, marine and freshwater systems; or particular groups, such as invertebrates, plants and fungi, which make up the majority of biodiversity.

The major pressures on species on the Red List are habitat loss and degradation, which endanger more than 85 percent of all threatened birds, mammals and amphibians. Other major forces behind species loss include exploitation through overhunting or fishing, invasive alien species and climate change. In addition, this year's report notes that continental species extinctions are nearly as common as those occurring on islands, which are typically considered more ecologically fragile and were a focus of last year's assessment. The announcement of the Red List and GSA marks the start of the third IUCN World Conservation Congress in Thailand, which will host more than 4,000 researchers, conservationists and politicians.