The changes have drawn widespread condemnation from the scientific community, including complaints the administration is weakening protections for vulnerable species just as scientific consensus is converging on the idea that Earth is now in the midst of its sixth mass extinction event, a man-made disaster with radically destabilizing consequences.

In North America alone, at least 277 plant and animal species have gone extinct since Europeans first arrived on the continent, according to the International Union for Conservation of Nature, regarded by scientists as the gold standard for data on threatened and endangered species.

The list of the fallen includes some relatively familiar creatures, such as the passenger pigeon and the Steller’s sea cow. But it’s composed primarily of mollusks, insects and other more obscure organisms. Most importantly, it’s egregiously incomplete: Biologists estimate that only about 10 percent of the world’s plant and animal species has been identified and categorized, meaning that many are being killed off before humans are even aware of their existence.

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“We’re obliterating landscapes before we’ve even had a chance to catalogue the species that lived there,” said Tierra Curry, a senior scientist at the Center for Biological Diversity. The true number of species that we’ve wiped out, she says, is “completely unknown.”

We do know, however, that the current rate of species extinction is orders of magnitude above what the geological record indicates is normal. “The rate of species extinction is already at least tens to hundreds of times higher than it has averaged over the past 10 million years, and it is set to rise sharply still further unless drivers are reduced,” according to a U.N. report released in May.

In the past 500 years, humans have wiped out nearly 2½ percent of amphibian species, 2 percent of mammals and birds, and about 1 percent of reptiles and fish. At a geological scale that’s a stunning rate of extinction in a vanishingly brief period of time. Before mass extinction “events” in the Earth’s history unspooled over hundreds of thousands of years. Geologically speaking, the human era resembles one of these catastrophic events more than anything else.

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The U.N. report warns that human activity is pushing more than a million of earth’s species toward extinction. Beyond that, “as many as half a million terrestrial species of animal and plant may already be doomed to extinction because of habitat loss and deterioration that have already taken place,” according to the report.

Biologists say this would be nothing short of a calamity — not just for biodiversity, but for humankind. “Our destiny is intertwined” with the plants and animals we share the planet with,” Curry says. “We can’t survive on this planet without the services that wildlife and plants provide for us — pollination, water and soil cleaning, pest control, oxygen.”

Even the loss of less charismatic species, such as the mussels and snails that make up the bulk of known North American extinctions, will cause significant spillover effects. Each freshwater mussel, for instance, filters eight to 10 gallons of water a day, according to Curry, easing the burden of water purification for cities and towns. “While we are sleeping, they are working for us,” she says.

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The U.N. report warns that as dire as the situation is, it would be even worse were it not for ongoing conservation efforts like the Endangered Species Act, the 1973 wildlife conservation law that protects threatened species and the habitats in which they are found.

“This new rule will result in less protection for America’s threatened wildlife and a higher likelihood of losing species forever as Earth’s sixth mass extinction occurs,” wrote Jacob Carter, a research scientist with the Union of Concerned Scientists. Rebecca Riley of the Natural Resources Defense Council wrote that the change demonstrates “willful ignorance from the Trump Administration about the looming impacts climate change will have on the American landscape.”

For Curry, the issue is deeply personal. She became active in conservation biology, she says, after growing up in Appalachia and watching a coal company raze forests in which she had played as a child. “The mining ruined our well water, it cracked the foundation of our house,” she said. “The mountains were blown up for coal and the forests were taken down to dirt.”

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One of the Trump administration’s changes to the Endangered Species Act would put economic costs at the forefront of public discussion over whether to protect a species. That’s one reason industry groups, like home builders and energy producers, have embraced the move.

But biologists like Curry say the dollars and cents are beside the point when you’re talking about life on the only planet known to support it. “We have a moral obligation to preserve life on earth,” she says. She cites Pope Francis’ encyclical on the environment, which says that “each creature reflects something of God,” something that “human beings have no right to ignore.”

Meanwhile, the sixth mass extinction rolls on. While the Trump administration was rewriting the Endangered Species Act earlier this year, the Fish and Wildlife Service was preparing a separate action to remove 23 plant and animal species, including the ivory-billed woodpecker, from the endangered list.