Sword Fern Decline at Seward Park

Sword Fern Decline at Seward Park. The photo on the left shows the sword fern population in 2011,  the photo the right shows the same area in 2017.

Background

Seward Park is celebrated by Seattleites for its lush forest dominated by native plant species like sword fern. Unfortunately, large numbers of sword ferns have died and are in declining health. The decline was first noticed in the autumn of 2013 in Seward Park at what we now refer to as Ground Zero. By July of 2014, the stand of dense sword ferns on about a quarter acre of gently sloping land on the south side of the Hatchery Trail was more than 90% dead, leaving bare ground.

In subsequent years, the decline has spread, doubling in size each year, as can be seen on the map below. Sword fern are now dead across a 15-acre area, about 10% of the old-growth forest in the park, and in isolated patches on Bailey peninsula, home to Seward Park. Unfortunately, other sites with declining fern populations have been identified in Western Washington and British Columbia.

The Sword Fern, Polystichum munitum, is the dominant understory plant of the Pacific Northwest’s forests. Sword ferns colonize recently disturbed forested sites, for example after fire, floods, or logging. They are forage for a variety of herbivores, from ungulates to rodents and insects.  Past research has found that individual sword ferns can persist for centuries in static forested environments where they are native.

June 2011. Photo by Jordan Jackson
May 2017. Photo by Paul Shannon

Working Group Efforts

Concerned Forest Stewards, park users, academic partners, and Seattle Parks and Recreation staff, have come together to form the Sword-Fern Decline Working Group. Although numerous possible causes of the decline have been suggested to date, none have been validated through extensive monitoring and research efforts. The Sword Fern Decline Working Group will continue monitoring and researching the cause of decline, along with implementing active restoration of sword ferns. In 2018, the working group will develop a research plan, helping to define a systematic regional strategy to understand the causes of the decline. Please contact, Seattle Parks and Recreation Plant Ecologist Lisa Ciecko for more information or to be added to the email list – Lisa.Ciecko@Seattle.gov.

Learn more about the sword fern decline: