BioEd Online

Nearly half of the turtle species on the planet are in trouble, according to the latest Red List report from the World Conservation Union.

The group, which used data from around 8,000 scientists to compile its report, has added over 3,000 animals to its annual list of species threatened with extinction, pushing the number above 15,000 for the first time.

The report is based on an assessment of approximately 3% of the world's 1.9 million described species. Although the number of endangered species has risen across all groups, the researchers say that freshwater species are particularly badly hit.

For example, the number of amphibian species listed as threatened has jumped from 146 in 2000 to 1,856 this year (see " Amphibians face a bleak future").

The most-studied freshwater animals are turtles, according to Craig Hilton-Taylor, who helped to coordinate the Red List. The figures show that they are in trouble, too. Researchers found that more than 40% of turtle species are threatened, mainly as a result of humans harvesting their eggs and destroying their natural habitat.

Of these, the report categorizes one tenth as "critically endangered", meaning that they will go extinct within the next century unless something is done to protect them. One example is the painted terrapin (Callagur borneoensis), which inhabits southern Thailand and Borneo.

The report speculates that the threat is likely to spread. As populations of turtles disappear from Southeast Asia, for example, people may begin harvesting the animals' eggs more heavily in the Indian subcontinent.

A fresh look

These new theories and statistics come from the first detailed review of freshwater systems in four years, according to Hilton-Taylor. The increased number of threatened species that the team found this time around is cause for concern, he says.

"We don't have a full picture yet, but it appears that freshwater species are more threatened than terrestrial species," says Hilton-Taylor. The researchers believe this is partly because water systems are more sensitive to pollution than land environments.

The team only studied a limited number of animals, but they think that the specific findings apply to aquatic ecosystems in general. "We suspect that what we've seen is affecting all systems," Hilton-Taylor says.