Sir

Until recently, marine systems have experienced remarkably few extinctions1. But this state of affairs is changing, as reported in your News story “Researchers take US government to court over threat to turtles”2 and by Spotila et al. in their Brief Communication3 on the potential extinction of the Costa Rican nesting population of leatherback sea turtles (Dermochelys coriacea). Many other long-lived marine organisms are also threatened, often because of unintended capture in fishing gear4,5,6. A global solution is urgently needed to protect these species. It is possible: numbers of Kemp's Ridley (Lepidochelys kempi), formerly the most endangered sea turtle, have increased tenfold since 1986 thanks to an international effort.

Leatherbacks nest primarily in four Pacific rookeries, and have declined dramatically over the past 20 years to about 250 in Mexico, 117 in Costa Rica, 2 in Malaysia and fewer than 550 in Indonesia. The Pacific Ocean may now contain as few as 2,300 adult females, making Pacific leatherbacks the world's most endangered sea turtle.

Last autumn, a US judge closed one million square miles of the North Pacific to the Hawaii-based longline fishery, and the US National Marine Fisheries Service recently proposed another closure that would reduce leatherback takes by 45 per cent. But given the critical status of leatherbacks, this response is inadequate. Environmentalists believe that the United States must take decisive action, but closures in US fisheries alone will not resolve the problem — leatherbacks in both the North and South Pacific are killed by fishing vessels from several countries.

The leatherbacks' nesting habitat must be protected throughout the Pacific. Direct harvest of eggs or turtles must be banned everywhere. Wherever fishing occurs, the bycatch of leatherbacks must be reduced to as close as possible to zero. Once countries such as the United States have minimized their own bycatch, they should encourage other nations to adopt protection measures. The US government and environmental organizations need to support research and management programmes in less developed countries, with environmental organizations educating the public and encouraging consumers to avoid products resulting from longline fishing.

Current treaties and organizations need to address the issue of leatherback bycatch directly. The Convention on Conservation and Management of Highly Migratory Fish Stocks is at the final negotiation stages, and contains provisions to reduce bycatch; sea turtles should be explicitly included. The international agencies responsible for administering other conventions, including the Biodiversity Convention and the UN Convention on the Law of the Sea, should evaluate bycatch of protected species and report possible solutions. CITES (the Convention on International Trade in Endangered Species) has enforcement powers, but does not protect endangered species caught as bycatch.

The international community should prohibit trade in items caught in ways that harm endangered species — whether through an amendment to CITES or in a separate agreement. Whatever actions we decide to take, we must act quickly, or the 100-million-year reign of leatherback sea turtles will end in just a few decades.