This story first appeared on National Geographic Voices. On Tuesday, President Donald Trump took his most concrete step thus far to unravel his predecessor's legacy on climate change, with a wide-ranging executive order that dismantles several Obama-era policies to restrict greenhouse gas pollution. The order outraged environmentalists—Sen. Ed Markey (D-Mass.) called it "a declaration of war on American leadership on climate change"—but it wasn't very surprising: It simply followed through on a threat contained in the budget Trump proposed two weeks ago. "We're not spending money on that anymore," Mick Mulvaney, director of the White House's Office of Management and Budget said then, in response to a question about climate change during a press conference.