The Beringia Lowland Tundra ecoregion is formed by three major disjunct areas along the Bering Sea coast of Alaska from the base of the Alaska Peninsula to Kotzebue Sound, as well as one smaller area on the east side of St. Lawrence Island and St. Matthew Island. The ecoregion is characterized by low, flat or gently rolling terrain, wet soils, and resulting predominance of wet and mesic graminoid herbaceous vegetation. In better drained areas, especially in the somewhat more rolling portions of the section surrounding Bristol Bay, dwarf shrub communities occur interspersed with the wet herbaceous tundra, dominated by sedges, including Eriophorum angustoifolium and Carex spp. Dwarf shrub vegetation is usually dominated by ericaceous species, including crowberry (Empetrum nigrum). In some limited areas of favorable soil drainage and microclimate, stands of black and white spruce (Picea mariana, P. glauca) occur, with understories of alder (Alnus spp.), willow (Salix spp.) and dwarf birch (Betula spp.). Lakes and ponds cover 15-25 percent of the surface area, and wetlands cover between 55 percent (southern portions) to 78 percent (northern portions) of the region.
The region experiences a climate that is transitional between maritime and continental influences. Average annual precipitation varies widely, ranging from 250 mm in Kotzbue Sound to 860 mm near Bristol Bay. Mean daily minimum temperatures in winter range from -25°C in the northern parts to -10°C along the Alaska Penninsula. Summer high temperatures can reach 18°C. In the Koetzebue Sound and the Yukon-Kuskokwim Delta areas, soils are shallow to permafrost and consist mostly of Histic Pergelic Cryoquepts and Pergelic Cryofibrists. In the more southerly and better drained Bristol Bay area, the permafrost table is deep to discontinuous and somewhat more developed soil profiles can occur (Gallant et al. 1995). All but the Yukon-Kuskokwim delta was covered in Pleistocene glaciation (Pielou 1994, Gallant et al. 1995).
The abundance of surface water makes this ecoregion excellent habitat for waterfowl, and the tidal flats of the coast provide an abundance of habitat for shorebirds. Many species of birds depend on the habitats of this ecoregion for the majority, if not all, of their nesting habitat. These include the Arctic loon (Gavia artica), Canada geese (Branta canadensis), bristle-thighed curlew (Numenius tahitiensis), dovekies (Alle alle), McKay's buntings (Plectrophenax hyperboreus), and white wagtails (Motacilla alba). The highest densities of nesting tundra swans, the majority of the world's emperor swans, and 50 percent of the world's black brant (Branta bernicla) are supported by the Yukon-Kuskokwim delta alone (McNab and Avers 1994). This delta is the most expansive area of highly productive waterfowl nesting habitat in Alaska, and among the most significant on earth. Izembek Lagoon, on the Alaska Peninsula, is the most important migratory staging area for black brant in Alaska. St. Lawrence and St. Matthew Islands also support large seabird colonies. St. Lawrence Island colonies support approximately 2,000,000 seabirds, including the largest murre (Uria spp.) colonies in the eastern Bering Sea (Alaska Fish and Wildlife Research Center, 1988).
Mammals include river otters (Lontra canadensis), short-tailed and least weasels (Mustela erminea and M. nivalis), brown bear (Ursus arctos horribilis), moose (Alces alces), and caribou (Rangifer spp.). Populations of all top-level predators are intact, and brown bears reach extraordinary natural densities in the Katmai and Lake Iliamna areas. All five species of North American Pacific salmon are native here, and Bristol Bay supports the largest run of sockeye salmon (Oncorhynchus nerka) in the world (McNab and Avers 1994.
Habitat Loss and Degradation
The Beringia Lowland Tundra is almost entirely intact. Human disturbance consists of small permanent and seasonal settlements, mostly along rivers and coasts. These communities depend on subsistence fishing and on hunting of marine mammals (seals, whales), caribou, moose, and birds. For the most part, the terrestrial impacts of these settlements are local and slight.
Remaining Blocks of Intact Habitat
The largest blocks of intact habitat include the Ahklun Mountains and the Bendeleben Mountains, which contain diverse habitat types.
Degree of Fragmentation
This ecoregion is naturally fragmented into three large mainland areas and numerous islands. The southernmost block of habitat around the Ahklun Mountains is relatively unfragmented. The norrthernmost block is still mostly intact but is becoming trisected by roads and is increasingly impacted by mining. This area has the potential to be much more fragmented in the future.
Degree of Protection
This ecoregion is represented by several protected areas. Those in the Seward Peninsula/Kotzebue area include:
•Bering Land Bridge National Park - western Alaska
•Selawik National Wildlife Refuge - western Alaska
The Yukon-Kuskokwim Delta is contained completely within the Yukon Delta National Wildlife Refuge. Protected areas of the ecoregion surrounding Bristol Bay and on the Alaska Peninsula include:
•Togiak National Wildlife Refuge - western Alaska
•Egegik, Pilot Point, Cinder River, Pt. Moller State Critical Habitat Areas - western Alaska
•Izembek National Wildlife Refuge - western Alaska
•Alaska Peninsula National Wildlife Refuge - western Alaska
•Becharof National Wildlife Refuge - western Alaska
•Katmai National Park and Preserve - western Alaska
Finally, a number of islands scattered throughout the ecoregion, especially St. Matthew Island, are included as units of the Alaska Maritime National Wildlife Refuge.
Types and Severity of Threats
Currently, waterfowl harvests are managed by USFWS, through co-management agreements with Native communities, and through international treaty. Although there is some potential for unsustainable waterfowl harvests from local communities, the harvests are at present well managed and represent less of a threat than habitat destruction in wintering areas for nesting waterfowl.
Commercial fishing is a significant presence, and can affect not only the marine ecosystem but the many terrestrial species that rely on the abundant fish runs each year. Salmon fisheries in the area are generally well-managed to ensure sufficient spawning stock returns to the rivers. As with any commercial fishery, there is a concern with overharvesting, particularly of? weak stocks in years of generally abundant returns.
Suite of Priority Activities to Enhance Biodiversity Conservation
The biggest gap in the protected areas of this ecoregion are in the Nushagak River Valley and along the west side of the Alaska Peninsula.
•Alaska Marine Conservation Council
•National Audubon Society - Alaska-Hawaii Regional Office
•The Nature Conservancy - Alaska
Relationship to other classification schemes
This ecoregion combines Gallant et al. (1995) ecoregions 109 and 112. Major delineation features are the low topography, poor to moderate drainage, dominant wet tundra and dwarf shrub communities, and coastal position. Combination decisions are based on Gallant et al (1995) and Küchler (1985).
Prepared by: R. Hagenstein, T. Ricketts