Endangered Species in the Pacific Islands

The Final Recovery Plan for Four Species of Hawaiian Fern

This recovery plan covers four Hawaiian ferns that were added to the Federal list of endangered and threatened species on September 26, 1984. The four ferns and their habitats have been variously affected or are threatened by one or more of the following: habitat degradation and/or predation by feral or domestic animals; competition for space, light, water, and nutrients from alien plants; human impacts; and fire. In addition, these ferns are subject to an increased likelihood of extinction and/or reduced reproductive vigor from randomly occurring events due to the small number of existing individuals and their very narrow distributions.

Asplenium fragile var. insulare - Photo credit Tracey Wager, Colorado State University

The land that supports these four ferns is owned by the State of Hawai‘i, the Federal government, and private entities. Federally owned land consists of Hawai‘i Volcanoes National Park and Pohakuloa Training Area on the island of Hawai‘i, and Schofield Barracks Military Reservation on O‘ahu.

The recovery plan details the life history, habitat, reasons for decline, and conservation efforts for each plant.

Habitat & Distribution:
Three of the 4 endangered ferns have been reported from lowland forests. Ctenitis squamigera is typically found in lowland mesic forests, and Pteris lidgatei appears to be restricted to lowland wet forest. Diplazium molokaiensis has been reported from lowland to montane forests in mesic to wet settings. Asplenium fragile var. insulare has been reported from montane wet, mesic, and dry forest habitats as well as subalpine dry forest and shrubland habitat.

Asplenium fragile  var. insulare is a member of the spleenwort family and is currently known from 9 to 11 populations on Hawai‘i between 5,250 and 7,800 feet (1,600 and 2,380 meters) elevation. An additional population has been reported from East Maui, in Hanawi Natural Area Reserve, making a total of 10 to 12 known populations of this fern.

Ctenitis squamigera is a member of the wood fern family. The 10 populations of this fern that have been observed within the last 20 years are in the Waianae Mountains of O‘ahu, Lana‘‘i, East and West Maui, and Moloka‘i.

Recovery:
The 4 ferns in this recovery plan are currently found on lands owned or managed by the Federal government, where Federal law protects all plants from damage or removal: Hawai‘i Volcanoes National Park and U.S. Army installations.

The Service has a cooperative agreement with State and Federal agencies, and private organizations such as The Nature Conservancy, and private landowners in an effort to protect these 4 endangered plants.

Recovery actions recommended for these four ferns include the removal of feral animals, minimizing the impact of military training activities, monitoring known populations, controlling fires and alien weeds, building enclosures around some of the most intact portions of native forest in conjunction with hunting on Lana‘i, and the expansion of the Mount Ka‘ala Natural Area Reserve. Surveys to locate and map additional populations are also important to the recovery of these ferns.