Officials tracking the forest dwelling sword ferns in the 300-acre (121-hectare) Seward Park in Seattle say the ferns have been dying at an accelerating rate in the last few years.
Forest Steward Paul Shannon says studies found 3 percent of the park’s sword ferns dead in 2015 but that jumped to 33 percent in 2016.
Tim Billo teaches environmental sciences at the University of Washington.
He tells KING-TV that young ferns aren’t replacing dead ferns and the problem is spreading in the park.
Officials say similar die-offs of sword ferns that can be 6 feet (1.8 meters) long have been noted on nearby Mercer Island and the Kitsap Peninsula.