Thirty years ago the bald eagle, that flinty-eyed patriotic icon, could mainly be found on our money but not in the nation's forests. Peregrine falcons were having trouble cracking out of pesticide-weakened shells and the howl of the wolf was a faded echo.

Today the bald eagle population has soared from less than 500 nesting pairs in 1973 to more than 6,000 pairs and sightings are common in the Allegheny National Forest and along the Allegheny, Clarion, Youghiogheny, Susquehanna and Delaware rivers.

Peregrine falcons are so numerous that two nesting pairs make Pittsburgh skyscrapers their home. And wolves are once again prowling and howling around Yellowstone National Park and in other Western states.

The catalyst for the survival of those species and hundreds more was the nation's most revolutionary and maligned environmental law -- the Endangered Species Act -- which takes note of species that have been lost but focuses on how many it is still possible to save.

Yesterday was the 30th anniversary of that legislation, which was passed on overwhelming bipartisan votes of 355-4 in the House and 92-0 in the Senate and signed into law by then-President Richard Nixon.

The law marked the first time the nation pledged it would not permit any of the living species of plants and animals that shared its territory to become extinct if it could prevent it. It also was just about the last time there was any agreement about whether that could or should be done.

Today, 1,263 U.S. plant and animal species and 558 foreign plant and animal species are listed as threatened or endangered under the act. Another 31 species have been formally proposed for listing and 259 are under consideration, but the process has been stalled because of court challenges and lack of funding.

Only 37 species have been removed from the threatened or endangered lists since the law was enacted, and only seven of those -- including the American alligator, the Peregrine falcon and the Aleutian Canada goose -- were removed because they recovered. Seven were removed because they became extinct and the rest were determined to be improperly listed.

Despite that mixed scorecard, environmentalists say the act has been invaluable, not only as the bulwark of protections for the nation's most vulnerable biological heritage but also as the educational tool that has altered the American mindset about the importance of a diverse biota and the critical habitats needed to support the most fragile of species.

Opponents, including developers, some current members of Congress and the Bush administration, say the law is "broken," and cite the low recovery numbers, big conflicts with private landowners and numerous lawsuits filed by environmentalists and developers.

The biggest battles now are over the act's requirement that endangered species listings be accompanied by designations of "critical habitat'' areas. Such a designation requires scientific review and a formal declaration by the U.S. Department of Interior that precludes habitat changes that would adversely affect the endangered species.

Craig Manson, assistant secretary of the interior for fish and wildlife and parks, has said a flood of court orders requiring the government to designate critical habitat for endangered species already on the list is eating up the program's $9 million annual budget. He said the requirement has become an obstacle to private landowner cooperation and has delayed the listing of other species that are in need of the act's protections.

Only about 400 species have had critical habitat designations, Manson said, and to do the work for designating habitat for the other 800 species on the list would cost more than $150 million. Pending court orders require the Interior Department to perform assessments and designate critical habitat for 32 species on the endangered list.

The Bush administration, like the Clinton administration before it, has put a low priority on such designations, and Manson testified at a House Committee on Small Business hearing in July that they provide little conservation benefit to at-risk species.

But two U.S. Fish and Wildlife Service reports submitted to Congress in June compared species with critical habitat designations to those without them and found species with the habitat designations were more than twice as likely to be improving as those without it. The findings, which were not announced or distributed by the Department of Interior, mirrored those in a 1999 Fish and Wildlife Service report.

"The Bush administration has made a habit of suppressing, delaying, doctoring, and ignoring scientific research," said Kieran Suckling, executive director of the Center for Biological Diversity, a Tucson-based non-profit environmental group that analyzed the reports and specializes in endangered species work.

"It has never presented any data to support the dubious assertion that critical habitat does not help endangered species, just worn out legal theories. The Fish and Wildlife Service's own data show that critical habitat works."

The studies show that critical habitat designations have protected oceans from over-fishing in Alaska, deserts from mining and off-road vehicles in California, and rivers from livestock grazing in Arizona and New Mexico.

Despite those findings, the Bush administration has lobbied Congress to override the Endangered Species Act to make critical habitat protection discretionary everywhere, and specifically exempt military bases.

Suckling said the administration has not budgeted enough funds to carry out court orders to protect critical habitats, and has refused a Congressional invitation to submit a supplemental budget request for enough money to implement the critical habitat law.

"The Bush administration is purposefully starving the Fish and Wildlife Service's budget," said Suckling. "It is using the budget as a weapon to slow the protection of critical habitats and cause a legal train wreck.

"No other aspect of the Endangered Species Act defines the ground rules as clearly as critical habitat," he said. "It identifies the most important habitats and requires that they be protected. It is the best way to move from species-by-species conservation to real ecosystem protection."

Charles Bier, director of the Western Pennsylvania Conservancy's natural heritage program, said critical habitat designation can reduce the government's ability to protect an at-risk species in other, non-designated areas. That's the reason that the Fish and Wildlife Service hasn't pursued a designated habitat for three endangered freshwater mussels in Pennsylvania.

Still, he said, species can't survive if their habitat is lost.

"The government needs to take a wider view of species recovery and environmental factors that might stress those species and systems,'' Bier said. "It needs a long-term vision and a palate of approaches that includes conservation, landowner incentives, partnerships and regulations to maintain ecosystems and watersheds.''

Bier said the conservancy, in partnership with the Pennsylvania Fish and Boat Commission and the Fish and Wildlife Service, this year initiated a two-year study of the eastern Massasauga rattlesnake, a candidate for the federal Endangered Species List, to understand the massive decline of the snake's habitat and recommend conservation measures for private landowners.

The snake, found in Allegheny, Lawrence, Crawford, Butler, Mercer and Venango counties as recently as 30 years ago, is now only known to exist in the last three of those.

"We want to do outreach and education with the landowners to develop a perspective for valuing the species. If we can do that we can generate a private-public protection plan to manage and monitor the species,'' Bier said.

"The Massasauga is a pit viper. It's not cuddly. But it's part of a complex and ancient ecological system, and the more we educate people about them, the more people will value these species as parts of the natural heritage and recognize we have a responsibility to other species.''