Although timber companies, developers and other interests have complained bitterly about the Endangered Species Act ever since Richard Nixon signed it in 1973, the public has broadly supported the law's protections for threatened plants and animals, as well as for the habitat these species need to survive. Attempts to weaken the law have always failed. But the House of Representatives' recent approval of a bill written by Richard Pombo of California has given critics fresh hope that their campaign may yet succeed.

Mr. Pombo advertises his measure as a long-overdue balancing of the interests of private property owners and those of nature. It is in fact a dreadfully one-sided bill, cynical and fiscally irresponsible in the bargain.

Of the bill's multiple flaws perhaps the most glaring is its fundamental premise, namely that there is something wrong with the law because only a handful of the nearly 1,300 species listed as endangered or threatened have recovered to the point where they can be taken off the list. A species already on the brink of extinction can hardly be expected to rebuild healthy populations overnight, or even in several decades.

A better measure of the act's success is that only a handful of listed species have actually become extinct. An even better measure, one suggesting slow but steady progress, is the government's own finding that two-thirds of the species whose conditions are known are stable and improving.

But the House swallowed Mr. Pombo's dubious line of thinking, and that made it easy to sign on to a host of damaging provisions. One would give political appointees authority to make important scientific judgments now reserved for wildlife biologists. Another would weaken the current system of designating critical habitat by making it voluntary, not mandatory.

Among the worst provisions - one that Mr. Pombo personally regards as the most important - is a requirement that government reimburse property owners who lose money by forgoing commercial use of land required to protect the species. This would, in a stroke, destroy years of painstaking effort by past administrations to reconcile the claims of private landowners with the public's larger interest in protecting endangered animals.

The Clinton administration's answer was to negotiate "habitat conservation plans": individual deals under which landowners would agree to leave some property untouched in return for the right to develop the rest. Mr. Pombo's solution, by contrast, would ask nothing of the developer and everything of the taxpayer, who in effect would be required to pay people for obeying the law. The net result could be an open-ended entitlement program that could bankrupt federal conservation efforts already starved for money.

So far there is no companion bill in the Senate, although various right-wing enthusiasts - among them James Inhofe of Oklahoma and Michael Crapo of Idaho - are making noises about writing one. The Senate should resist. Even its most ardent proponents agree that the Endangered Species Act would benefit from careful revision - to simplify its cumbersome procedures, to make it less vulnerable to litigation and to provide positive incentives to landowners to preserve habitat. But the Pombo approach is wholly misguided.