The Endangered Species Act, which marked its 40th anniversary Saturday, is as controversial as it is essential. It also is ironic: The ESA was signed into law by President Richard Nixon, a cynic who understood the political currency of environmentalism. The backdrop of endangered bald eagles, America’s natural symbol, along with Earth Day in 1970 and the fire that engulfed Ohio’s Cuyahoga River in 1969 set the stage for muscular conservation. How muscular? No one had a clue.

When Nixon signed the National Environmental Policy Act in 1970, it was ho-hum, page 2 news. NEPA’s environmental impact statements reshaped the responsibility of government, documenting how we affect the natural world and reining in (some) of the damage. It created a Council on Environmental Quality headquartered in the White House and incorporated language promising “productive and enjoyable harmony between man and his environment.”

The ESA was similarly elastic and ambitious. All federal departments would need to work in common cause to conserve the habitats of threatened and endangered species. It was a watershed law that has made a tangible difference not only for threatened critters but for entire ecosystems.

As The Herald’s Bill Sheets reports, 99 percent of the listed species have avoided extinction. And many of the success stories had a positive effect on mammals of the bipedal variety (read: you and me.)

“It has pulled people together to talk about what to do,” said Daryl Williams, environmental liaison for the Tulalip Tribes.

It’s also been a point of division, even used as a brickbat. After U.S District Judge William Dwyer knocked down a toothless forest management plan to protect the northern spotted owl in 1991, feathers flew. The spotted owl was scapegoated for the rapid decline in the Northwest timber industry (the subsequent 1994 plan that put approximately 70 percent of old-growth forests on federal lands off limits was OK’d.) Politicians demagogued, pointing to the ESA rather than overharvesting and automation as cause for the timber slump.

Threatened Puget Sound chinook salmon, Puget Sound steelhead and bull trout have been a unifier, as Williams noted. How often do sports fishers, tribes, farmers, the feds and conservationists come together to problem solve? The ESA isn’t perfect, with Williams observing that habitat restoration often involves bureaucratic roadblocks. But the perfect can’t be the enemy of the good. Without an ESA, we would have a less ecologically rich planet. And just like NEPA, the Endangered Species Act has served as a template, which dozens of countries have duplicated.

“I think it’s been very positive overall,” said the EPA’s first administrator, Republican William Ruckelshaus. Indeed it has.