The 1973 Endangered Species Act is at once the noblest and most contentious of the landmark environmental statutes enacted during the Nixon presidency. For 45 years it has been celebrated by conservationists for protecting, in Richard Nixon’s words, “an irreplaceable part of our natural heritage, threatened wildlife.” In equal measure, it has been reviled by developers, ranchers, loggers and oil and gas interests for elevating the needs of plants and animals and the habitats necessary for their survival over the demands of commerce. Approved by huge margins in both chambers (the House vote was an astounding 355 to 4), the act would stand zero chance of passage in today’s Congress and political climate.

The act’s three main purposes are simply stated: identifying species that need to be listed as endangered (headed toward extinction) or threatened (likely to become endangered); designating habitat necessary for the species’ survival; and nurturing the process until the species have not just survived but recovered in sustainable numbers.

The act has been around long enough to have accumulated plenty of enemies, and now, emboldened by a determined anti-regulatory president, its critics are again on the march. A suite of measures in the House and others in development in the Senate would, in aggregate, weaken the role that scientists play in deciding which species need help, while increasing the influence of state governments — many of which, particularly in the West, depend on revenues from royalties and jobs provided by extractive industries like mining, oil and gas, and care little for the species that occupy potentially productive lands.

Last week came the administration’s own unsettling proposals, announced by David Bernhardt, the deputy secretary of the Interior Department and one of several spear carriers for the oil and gas industry who have risen to commanding policymaking roles under Interior’s boss, Ryan Zinke. Mr. Bernhardt said the changes would streamline and clarify the regulatory process, and some of the 118 pages of daunting bureaucratic prose seem, innocently enough, to attempt to do just that. But several proposals bode ill for animals and plants and well for President Trump’s overarching ambition to reduce costs and other burdens for business, particularly the energy business. Here are three.