The Marin Headlands’ unique offering of breathtaking landscapes mixed with former military bases dating back to World War II has been a draw for millions of visitors through the decades. But the combination has not been without downsides. In the hills overlooking Rodeo Beach, the remnants of former U.S. Army buildings of Fort Cronkhite have slowly been eroding parts of the landscape, gouging deep trench-like gullies into the hillside that have drained natural wetlands. The National Park Service is now working to reverse the damage and restore more than an acre of wetlands that can be used as home to species such as the endangered red-legged frog, said park service ecologist Darren Fong.