Washington ? America’s national parks are at risk of disappearing or being fundamentally changed as seas rise, glaciers melt, trees die and animal habitat changes as a result of climate change, according to a report Thursday from two environmental groups.

The assessment focuses on the 25 most threatened parks — from the Everglades in Florida to Denali in Alaska.

The report from the Rocky Mountain Climate Organization and the Natural Resources Defense Council says that the most important action needed to protect parks is to reduce the emission of heat-trapping gases, mostly from burning fossil fuels such as coal and gasoline. It also calls on the federal government to take other steps — such as expanding parks and creating wildlife migration corridors.

Theo Spencer of the NRDC said that although the report wasn’t timed for the recent PBS documentary series about the national parks by filmmaker Ken Burns, there’s a link: Treasured American lands again need protection. This time, however, he said, the parks have no champion like naturalist John Muir, who led the early drive for the parks, or President Theodore Roosevelt, who established so many of them.

“There was resistance by people who wanted to develop them, who saw economic gain in the parks. But the leadership at the time had the vision to think of the greater good, to think of the trust of the American public for the future,” Spencer said, speaking to reporters on a conference call.

“This is really a nonpartisan issue, and it desperately needs the leadership that was shown at the time these great parks were created.”

Stephen Saunders, the president of the Rocky Mountain Climate Organization and a principal author of the report, said that climate change was “the greatest threat our national parks have ever faced.”

The Everglades, Biscayne and Dry Tortugas national parks could be swamped by rising seas if climate trends continue, he said. All the glaciers in Glacier National Park could be gone in 12 to 13 years. Yosemite is changing as trees die at a faster rate and forests change with the warming winters.

The report recommended federal mandatory limits on global warming pollution and support for energy efficiency and clean energy, the main parts of a bill the Senate is expected to take up this fall. Other recommendations included expanding the parks, creating wildlife corridors, and using the National Park Service’s educational programs to explain how climate change is affecting the parks.