Just a few months after the United Nations warned of the planet’s looming biodiversity crisis, the U.S. Department of the Interior and U.S. Department of Commerce have finalized the most dramatic rollback of the Endangered Species Act in the law’s 45-year history. Both wildly popular and effective, the bedrock conservation law has so far saved 99 percent of its listed plants and animals from extinction, bringing back iconic species like the gray wolf and bald eagle from the brink. But the law won’t work if the Trump administration waters it down. Now, for the first time, agencies can insert economic costs into the discussions over a species' listing. One of the law’s core principles has always been to base those decisions strictly on scientific data. The rollback also weakens protections for species designated as threatened—a status less dire than endangered but nonetheless requiring urgent action. There’s a lot at stake: The Endangered Species Act not only protects individual imperiled species but also the interconnected ecosystem of plants, animals, waterways, and lands that make up its habitat.