Yet even though the IUCN frequently points out that the Red List should not be used alone to set conservation priorities, it often is, and this means money can be wasted on species that could be better spent elsewhere (see "Deciding what to save").
"The Red List is a framework to make the best guess you can. The process is supposed to capture that uncertainty, but the uncertainty is not transmitted when the results are published, or used to inform policy," says Newton, who argues that the Red List should not be used to judge the success of the 2010 goal of the Convention on Biological Diversity next year.
"The Red List is an unbelievably powerful, innovative conservation tool that has captured the world's imagination," says Webb. "But it needs to continue to improve, to become more accurate."