The Aleutian shield fern is a small (6 inches tall) fern that grows in rock caves and moist crevices at the base of steep rock outcrops on east to northeast-facing slopes. It is often found with dwarf willow-moss and dwarf willow-sedge-moss.
The Aleutian shield fern was originally discovered on Atka Island, Alaska; however, it has not been relocated on that island since its original discovery in 1932. It has since been found on Adak Island, but searches on 11 other Aleutian Islands have not found the plant.
This species is rare and has very specific habitat requirements. Unstable habitat, collection, and trampling by nonnative caribou are identified as threats. Increases in both the human and caribou populations may increase the risk of habitat destabilization and destruction.
The known plants currently occur on the Alaska Maritime Wildlife Refuge and therefore, receive protection through Refuge regulations. A study is underway to assess the threat of trampling by caribou. An effort to propagate and maintain a greenhouse population has had limited success but has increased our understanding of the plant’s reproductive biology.