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Two letter-writing campaigns by ecologists intended to influence congressional action on the Endangered Species Act have touched off a heated debate about the advice scientists should give lawmakers.

Several authors of a letter sent in January to Senate sponsors of a bill to reauthorize the act (see Nature 391, 829; 1998) have criticized a second letter signed by the presidents of the Society for Integrative and Comparative Biology (SICB) and eight other scientific organizations, which ran as a full-page advertisement in The New York Times last month.

The SICB letter was organized by its conservation chairman, Fraser Shilling of the University of California at Davis, and takes a harder line on species protection than most of the scientists who advocate reform of the act. It calls for a complete ban on killing any endangered animal or plant, including the ‘incidental takes’ permitted for landowners who file habitat conservation plans.

Even though many conservationists worry that such plans are too inflexible, and sometimes based on inadequate science, they have become the primary means of setting aside privately owned land for conservation.

Frances James, a biologist at Florida State University who is leading a review of habitat conservation plans by the American Institute of Biological Sciences, was so upset with the Times advertisement that she persuaded half a dozen colleagues to sign a letter chastising the signatories of the Shilling letter. The latter include the presidents of the Ecological Society of America, the Botanical Society of America and the Entomological Society of America.

James wrote that their action was “causing consternation among many biologists who have been working with endangered-species issues”. She described early drafts of Shilling's recommendations — which had been circulating among scientists for a year — as “counterproductive and naïve”.

Challenging ten specific points, she wrote that the blanket opposition to ‘incidental takes’ was “not scientifically valid”, as it would prohibit valid conservation measures, such as the prescribed burning of habitat and control of invasive species. “We were sorry to see your letter in The New York Times, because it means that scientists will probably have to disagree in public about endangered species protection,” she wrote.

Joining James were Gary Meffe of the University of Florida, Stuart Pimm of the University of Tennessee, and Peter Brussard and Dennis Murphy of the University of Nevada at Reno, all of whom signed the more moderate January letter to Senate leaders.

Murphy agrees that “we don't want a split in the scientific community”. But he is not shy about criticizing the SICB letter which he says “reads like the Sierra Club [conservation lobby group] wrote it instead of a group of scientific societies”. He says the James letter is “an attempt by those who are doing their homework on this issue to police themselves and their colleagues”.

Shilling says the criticism has less to do with science than politics. He calls the dispute a “territorial battle” between scientists too quick to yield to property rights advocates in the reauthorization battle and those — like himself — who would first “figure out what the standards [for species recovery] are, and then go in with our armour girded”. Murphy counters by saying it is “not logical to ask a Republican Congress to make the act more stringent by orders of magnitude”.

Although no signatories of Shilling's letter have retracted their endorsement, the Ecological Society of America considered withdrawing just before publication, because of the ‘incidental take’ clause and other objections. Another society president who signed admits: “We may have been caught by not being experts in this area, and by just feeling in general that we wanted to support a good cause.”

To some, the incident illustrates how organized advocacy still does not come naturally to many scientists. “Scientific societies weren't put together as lobbying organizations,” says Murphy.