The head of the city department that drafts many of San Francisco’s greenest rules and regulations uses one word to explain her greatest fear for the environment during Trump’s presidency: “preemption.”

If some of the deepest concerns of climate-focused bureaucrats from San Francisco to Massachusetts and New York come true, the Trump administration will preemptively prevent them from acting to slow global warming.

With Trump and Republicans in Congress widely expected to unite to undermine federal environmental protections, progressive states and cities are making plans to fight global warming within their borders without being helped or required to do so by the U.S. government.