This ecoregion surrounds the upper reaches of Cook Inlet in south central Alaska, and is in turn surrounded by the mountains of ecoregions 103 and 104. Its relatively mild climate, level to rolling topography, and coastal position have made it the focus of most of the human activity in Alaska. These factors have also contributed to the wide variety of vegetation communities found in the ecoregion. The most widespread are coniferous, broadleaf, and mixed forests, dominated in differing combinations by black spruce (Picea mariana), white spruce (P. glauca), Sitka spruce (P. sitchensis), quaking aspen (Populus tremuloides), balsam poplar (P. balsamifera), black cottonwood (P. trichocarpa) and paper birch (Betula papyrifera) (Gallant et al. 1995). Other important communities include low scrub, tall scrub, low scrub bog, mesic graminoid, graminoid herbaceous, and wet forb herbaceous communities. For more complete descriptions of these communities, see Gallant et al. (1995).
The Cook Inlet Taiga enjoys a generally mild climate in comparison with interior and arctic Alaska. Average annual precipitation ranges from 380 mm to 680 mm across the region. Average daily minimum temperature in winter is -15°C, while average daily maximum temperature in summer is 18°C. Soils are formed with wind-blown loess from the glacial floodplains and with volcanic ash from mountains to the west. The soils lie on top of glacial deposits. Unlike the majority of the other relatively low elevation ecoregions in Alaska, the Cook Inlet Taiga was extensively glaciated during the Pleistocene.
This ecoregion probably has experienced the most extensive human disturbance and alteration in Alaska. Nevertheless, it remains approximately 90 percent intact, and still supports all of the top level terrestrial predators within, or close to, their natural ranges of variation. (These predators include brown bear (Ursus arctos), wolf (Canis lupus), wolverine (Gulo gulo), and coyote(Canis latrans).) The ecoregion also produces all five species of Pacific salmon, which support a wide range of terrestrial species as well as large commercial, sport, and subsistence fisheries.
The Kenai River watershed is worthy of special note for its biological values. It supports all five species of Pacific salmon including a unique stock of the world's largest king salmon. The Kenai River also supports the second highest concentration of over-wintering American bald eagles in Alaska. Virtually the entire population of Wrangell Island snow geese uses the mouth of the Kenai River and Trading Bay (on the west side of Cook Inlet) as a migratory staging area each spring. Finally, populations of wolf, bear, lynx, and other animals on the Kenai Peninsula are separated from the rest of Alaska by water, glaciers, and development and subject to local extirpation as a result of development, exploitation, and habitat changes.
Wildfire occurrence is moderate to high (especially in dry years), and fires range in area from 1 ha to 22.7 km2, averaging 1.6 km2 (Gallant et al. 1995). Spruce bark beetle is also a common disturbance in the forests of this ecoregion. A current infestation has reached all parts of the ecoregion with up to 80 percent of the mature spruce in many stands killed. The spruce bark beetle is naturally occurring and may be the most important cause of stand renewal in the ecoregion.
Habitat Loss and Degradation
As stated above, although this ecoregion is the most impacted by human activity of any in Alaska, only approximately 10 percent of its area is altered or heavily altered. Most human disturbance is concentrated in the urban and residential development of the lower Kenai River, Anchorage Basin, and Palmer-Wasilla area. Some agriculture occurs in Palmer and Point McKenzie, across Knik Arm from Anchorage. Other forms of human land use include timber harvest and oil and gas exploitation on the Kenai Peninsula and across Cook Inlet from Anchorage.
Both areas have high potential for resource exploitation, however, with timber harvest occurring throughout most parts of the ecoregion (especially in response to an on-going spruce bark beetle epidemic), oil and gas development occurring in large parts of the Kenai Peninsula and on the west side of Cook Inlet, and potential coal mining on the west side of the Inlet in the future . Recreational and subsistence hunting and fishing are generally managed well, although potential for unsustainable hunting exists.
Remaining Blocks of Habitat
The ecoregion is naturally divided into two large blocks of relatively intact habitat by Cook Inlet. One block, covering the Susitna Valley and the west side of Cook Inlet, is larger than 10,000 km2. The second block, on the Kenai Peninsula, is subdivided into two smaller blocks of about 4,000 km2 each by the Kenai River and the human development along it.
Degree of Fragmentation
The ecoregion is fragmented into 3 major blocks, but this is due to major water bodies.
Degree of Protection
Important protected areas include:
•Kenai National Wildlife Refuge - southern Alaska
•Chugach State Park - southern Alaska
•Nancy Lake State Recreation Area - southern Alaska
•Redoubt Bay Critical Habitat Area - southern Alaska
•State Game Refuges: Susitna Flats, Trading Bay and Palmerr Flats - southern Alaska
Type and Severity of Threats
Major threats include:
•Continued development along the Kenai River and overuse of the Kenai River, restricting wildlife movement, removing habitat, and disturbing hydrologic functioning.
•Unsustainable timber harvest in the extensive forests throughout the ecoregion
•Expansion of oil, gas, and coal development on the Kenai Peninsula and west side of Cook Inlet with potential for localized but severe impacts on surrounding habitat.
•Over-exploitation of fish and game stocks.
•Killing of bears for defense of life and property that come into conflict with growing human residential areas.
Suite of Priority Activities to Enhance Biodiversity Conservation
•Kenai River watershed - balancing community needs and wildlife requirements.Susitna Valley forests - implement planning to prevent unsustainable timber harvest from occurring.Monitor coal and oil and gas development activities.
•Alaska Center for the Environment
•The Great Land Trust
•Kachemak Heritage Land Trust
•The Nature Conservancy-Alaska
Relationship to other classification schemes
This ecoregion is identical to Gallant (1995) ecoregion 115. Major delineation features are the low (less than 600 m), relatively gentle terrain, forest-dominated vegetation, and mild climate.
Prepared by: R. Hagenstein and T. Ricketts