Endangered species come on lists. But lists obscure relationships. What can it mean that a few mussels, some snails we’ve never heard of, obscure crayfish in marginal headwaters and some island-confined songbirds are vanishing? Some 1,650 species of animals and plants in the United States are listed under federal law as endangered or threatened. But when they are reduced to a line item on a list, their multimillion-year existences and roles in the complex living communities that include human s become invisible. Each minor species , whispering its testimony quietly from its corner, cannot make the larger class-action case, which is that, everywhere, trouble finds them.

Now there’s more trouble. Until now, the principal existential threats to free-living species have included urbanization, expanding intensive agriculture, pesticides, plastics, river pollution, dams, invasive species and the three “overs”: overcutting, overhunting, overfishing. Now we can add to that list President Trump, his administration and complicit Republicans in Congress.

The Trump administration has announced new rules that will significantly weaken the way the nation’s Endangered Species Act is applied, potentially opening the way for mining, oil and gas drilling and development that will undermine or doom components of our nation’s living endowment. The rules affect future listings and threaten to throw into reverse the enormous success over nearly 50 years of saving animals and plants from extinction and elevating their prospects.

Unable to kill or neuter the act legislatively because of strong support for the law even in the Republican-held Congress of the first two years of his presidency, Mr. Trump now is eviscerating it by gutting regulations that make it effective. Perhaps most crucially, the rule diminishes “critical habitat” protections, like those for areas formerly occupied by now-endangered species, though such habitat is the only hope many depleted species have for eventual recovery. The rule is intended to impede the listing process and ignore declining habitat viability caused by climate change. And for the first time, a tally of financial considerations will accompany discussions on the fate of species.