The Aleutian Island chain extends from the Alaska Peninsula almost 1,500 kilometers (km) to the east between the Bering Sea and the Gulf of Alaska. It is composed of a series of sedimentary islands capped by steep volcanoes. Elevations range from sea level to over 1,900 meters (m), with the higher volcanoes glaciated. Vegetation at the higher and more exposed areas consists of dwarf shrub communities codominated by willow (Salix spp.) and crowberry (Empetrum nigrum). Lower, more protected areas support mesic graminoid herbaceous meadows dominated by bluejoint (Calamagrostis canadensis) with a variety of other herbs. Dry graminoid herbaceous communities occur in coastal areas, and bogs support low scrub communities, developing thick peat deposits.
The islands experience a maritime climate. Precipitation varies widely, from 530 millimeters (mm) up to 2,080 mm. Generally, larger islands receive more precipitation than smaller ones, and coastal areas more than inland areas. Temperatures range from average lows of -7O°C to -20°C in winter to average highs of 10°C to 13°C in summer. Most soils form in volcanic ash or cinders over basaltic rock, and dominant soil types are Typic Haplocryands and Typic Vitricryands. Higher elevations often are covered in bare rock and basaltic rubble. Only the easternmost part of the archipelago was glaciated during the Pleistocene, but many of the islands show a history of glacial presence.
The Aleutian Islands tundra ecoregion supports many seabird colonies of extraordinary size and global importance. The Pribilof Islands, for example, provide breeding habitat for approximately 3 million seabirds including virtually all of the world's 250,000 red-legged kittiwakes (Rissa brevirostris). Many of the islands also support endemic species, including the Pribilof Island shrew (Sorex hydrodromus) and the Aleutian shield fern (Polystichum aleuticum), the only federally-listed endangered plant in Alaska.
Several species introduced for ranching have become feral, including cattle, reindeer, and fox. These have caused habitat alteration through grazing and predation on seabird colonies. Rat introductions also are likely to be impacting the seabird colonies. Pollutants, associated primarily with military development, are locally acute. Radioactivity has persisted from the nuclear testing on Amchitka Island in 1971, according to studies conducted by Greenpeace in 1996.
Perhaps the conservation problem of most concern is the decline in almost all species of fish-eating seabirds in the Aleutians. Mortality and population decline is mostly likely a result of trophic changes in the Bering Sea ecosystem due to commercial harvests of fish and whales over the last four decades, according to a study by the National Research Council.
The Aleutian Islands are largely intact, with habitat alteration mostly resulting from widely scattered communities, military bases (some abandoned), cattle ranches (both ongoing and in disuse), fox farms (abandoned), and subsistence hunting.
Remaining Blocks of Intact Habitat
The largest islands (Attu, Umnak, Unalaska, Akun) all have blocks of habitat in excess of 1,000 km2. The chains of islands are also largely intact.
Degree of Fragmentation
The island chain is highly fragmented naturally, with few islands greater than 2,000-3,000 km2, but very little additional anthropogenic fragmentation has occurred.
Degree of Protection
Almost all of the islands are included in the Alaska Maritime National Wildlife Refuge (AMNWR), and many areas are also included in the Aleutian Islands Wilderness. Small areas already developed were excluded from AMNWR or wilderness designation. Designation of protected areas on land, however, does not address the threats from changes in the surrounding marine ecosystems on which the terrestrial systems depend or upon the residual effects of radioactivity and other pollutants.
Types and Severity of Threats
Major threats include:
- Continuation of habitat degradation and conversion, due to cattle ranching, feral cattle and introduced reindeer.
- Predation on seabirds by feral fox and rats.
- Continuation of decline in seabird populations due to commercial fisheries impacts on Bering Sea marine ecosystem.
Suite of Priority Activities to Enhance Biodiversity Conservation
- Highest priority should be a better understanding and management of the marine ecosystem on which the terrestrial systems depend.
- Continued pressure on military to clean up and restore bases, particularly as closures and abandonment happens.
- Eradication of feral cattle and fox from several islands.
- Alaska Marine Conservation Council
- Bering Sea Coalition
- The Nature Conservancy - Alaska
Additional information on this ecoregion
- For a shorter summary of this entry, see the WWF WideWorld profile of this ecoregion.
- To see species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
- World Wildlife Fund Homepage
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