Hundreds of threatened species not on official U.S. list, research shows

National "red lists" are used by many countries to evaluate and protect locally threatened species. The ESA is one of the best known national lists and arguably the world's most effective biodiversity protection law.

A study -- now published in the latest issue of Conservation Letters -- has compared the ESA list of endangered species with the world's leading threatened species list, the International Union for the Conservation of Nature (IUCN) Red List.

The study has found that of the American species included on the IUCN Red List, 40% of birds, 50% of mammals, and 80-95% of other species such as amphibians, gastropods, crustaceans, and insects, were not recognised by the ESA as threatened.

This amounts to approximately 531 American species on the IUCN Red List that have not made the ESA protection list. These include bird species such as the critically endangered Kittlitz's murrelet (Brachyramphus brevirostris), the endangered ashy storm-petrel (Oceanodroma homochroa), and the vulnerable cerulean warbler (Dendroica cerulea).

"The ESA has protected species since its establishment in 1973, and it may have prevented 227 extinctions. However, the implementation of the ESA by successive US governments has been problematic, including poor coverage of imperilled species, inadequate funding, and political intervention," says study leader Bert Harris, a native of Alabama who is undertaking his PhD with the University of Adelaide's Environment Institute and School of Earth & Environmental Sciences.

"Vague definitions of 'endangered' and 'threatened' and the existence of a 'warranted but precluded' category on the ESA list are also contributing to the gap in species classification," he says.

Mr Harris says a detailed evaluation of the ESA's coverage of the IUCN Red List was "well overdue."

"The ESA is a powerful environmental law but its impact is limited. With many species being overlooked, this does not bode well for the ESA's ability to mitigate species decline before they become critically imperilled.

"The IUCN Red List is imperfect, but it is the leading global threatened species list. It involves collaboration of many scientists, and regular refinement of its categories and criteria," Mr Harris says.

The study was conducted in collaboration with the University of California, Santa Cruz, the National University of Singapore and the University of Göttingen, Germany.