Pacific Coastal Mountain icefields and tundra
The Pacific Coastal Mountain Icefields and Tundra ecoregion consists of a steep, very rugged range of mountains that stretches from the Kenai Penninsula along the Gulf of Alaska Coast and the Canadian/Alaskan border to the southern end of the Alaska panhandle. In Canada, this ecoregion encompasses the extreme southwestern corner of the Yukon Territory and parts of the coastal mountains in British Columbia south to Portland Inlet.
Elevations range from sea level to over 4,500 meters (m), and slopes generally are steeper than seven degrees, ranging to over 20 degrees. The landscape of this ecoregion is dominated by mountains of great height. Most peaks reach between 2,100 m and 3,050 m, but some are over 5000 m (Mount Logan is 5,959 m, and King Peak is 5,175 m). In this high, extreme northern part of the ecoregion, the Seward, Hubbard, and Malaspina glaciers are the dominant physiographic influences, and the area is, in fact, part of largest nonpolar icefield in the world. In the south, along the Boundary Ranges, glaciation is also a factor, especially from the Grand Pacific and Llewellyn glaciers. The mountains are composed of crystalline gneisses and granite rocks, and are cut into several segments by large, steep-sided transverse valleys. Isolated patches of permafrost are found throughout the ecoregion at elevations above 2,500 m.
This ecoregion generally experiences a transitional climate between maritime and continental effects, and climate patterns vary considerably with elevation, latitude, and topography. There are no long-term weather stations in the region, but estimates based on data from low-elevation stations in ecoregion 23 suggest annual precipitation ranging from about 2,000 millimeters (mm) to over 7,000 mm. Soil development is not widespread, and consists of poor, gravely soils which form in till and colluvium. The ecoregion was extensively glaciated in the Pleistocene, and most of it still is. In Canada, this ecoregion is characterized by a combination of glacierized, alpine, subalpine, and maritime North Pacific Cordilleran ecoclimate. Because of the great height of the mountains in the region, the mean annual temperature is cold: -0.5°C (an average summer temperature of 10°C, and -11.5°C in the winter). Also, because of the extreme elevation, and the proximity to the Pacific coast, the region receives an extraordinary amount of precipitation, from a low of 1,000 mm in the eastern part of the Boundary Ranges, to 2,400 mm in the icefields of the Fairweather Ranges, to as much as 3,500 mm around Mount Logan, Canada’s highest peak. In the high alpine, the great majority of this precipitation falls as snow, and the proportion of rain increases in correspondence to lower elevation, which, in rare cases, reaches as low as sea level in southeastern Alaska.
Much of the ecoregion lies beneath glaciers and icefields and most of the rest is devoid of vegetation. Where the ground is vegetated, communities are dominated by dwarf and low shrub communities, including mountain heath (Phyllodoce aleutica) and ericaceous shrubs (e.g. Cladothamnus pyrolaeflorus). Mountainous terrain and coastal influence result in three vegetation zones following elevational gradients: alpine tundra vegetation of variable ground cover; subalpine forests of alpine fir (Abies lasiocarpa), mountain hemlock (Tsuga mertensiana), and some Sitka spruce (Picea sitchensis) at middle elevations; and closed forests of western hemlock and some Sitka spruce at warmer, more humid, lower elevations. In the north, around Mount Logan, there is no terrestrial vegetation or soil development, due to the extreme elevation. A narrow zone of temperate coniferous rain forest extends between this ecoregion and the coast for much of its length. These stands are dominated by hemlock (Tsuga herophylla or T. mertensiana) and subalpine fir (Abies lasiocarpa), or by Sitka spruce. The forests on the Kenai Penninsula represent a transitional forest type between coastal temperate rain forests characteristic of coastal areas and boreal forest and taiga communities characteristic of interior Alaska.
The ecosystems of this ecoregion remain generally intact, with their full range of top predators existing in their natural ranges of variation. Wildlife includes moose (Alces alces) mountain goat (Oreamnos americanus), grizzly and black bear (Ursus arctos and U. americanus), wolf (Canis lupus), wolverine (Gulo gulo), ptarmigan (Lagopus spp.), and spruce grouse (Dendragapus canadensis). There are also black-tailed deer (Odocoilus hemionus) in the lower river valleys. The portion on the Kenai Penninsula holds particular biological interest as a mixing area of populations from the forests of both sides, specifically between the Snow River drainage on the west side to King's Bay in Prince William Sound. Additionally, major rivers that bisect this ecoregion, including the Copper, Alsek, Taku, and Stikine Rivers, provide migratory corridors for waterfowl, passerines, and terrestrial mammals that connect the coastal forests with interior areas. In addition, salmon stocks (Oncorhynchus spp.) in this ecoregion are of continental significance.
This ecoregion remains almost entirely intact, with very little habitat loss, degradation, or fragmentation. Habitat loss is restricted to mine sites and the few roads and communities. Other human impacts are mostly limited to recreation and subsistence hunting and fishing. The habitat is essentially intact. Data on wildfire occurrence are few, but occurrence is thought to be very low. In the Chugach Range, in the northern part of the ecoregion, fires are very infrequent and range in size from 0.01 to 0.4 square kilometers. Large-scale forest disturbance from spruce bark beetle infestations may be a more dominant influence than fires in this area. The overall amount of intact habitat is estimated at 95 percent of the total area of the ecoregion.
Degree of Protection
Important Protected Areas include:
- Kenai Fjords National Park - southern Alaska
- Chugach National Forest (however, no areas within the Chugach have been designated as wilderness as yet) - southern Alaska
- Wrangell-St. Elias National Park and Preserve - southeastern Alaska
- Glacier Bay National Park - southeastern Alaska
- Tongass National Forest - southeastern Alaska
- Kluane National Park - southwestern Yukon (partially in ecoregion) - 22,015 km2
- Tatshenshini-Alsek Provincial Park - northwestern British Columbia (partially in ecoregion) - 9,580 km2
- Stikine Provincial Park - northwestern British Columbia - 2,170 km2
Including the following wilderness areas:
- Russell Fiord Wilderness - southern Alaska
- Tracy Arm-Fords Terror Wilderness - southern Alaska
- Stikine-LeConte Wilderness -southern Alaska
- Misty Fjords Wilderness - southern Alaska
- Endicott River Wilderness - southern Alaska
- Tatshenshini Wild and Scenic River - southern Alaska
- Taku (proposed)
Types and Severity of Threats
Most major threats relate to mining potential and the proposed roads and development associated with mineral exploitation. For example, two proposed roads would cut through the British Columbia coast range: one at Taku Inlet and one at the Stikine River. The ecoregion contains a variety of extractable minerals, such as gold, silver, copper, and [zinc], as well as coal, petroleum, and uranium.
Much or the area has experienced small-scale gold mining through the present century and some of this activity continues on a modest scale. There have also been a number of significant mineral deposits located throughout the ecoregion, though few have been fully developed.
The Kenai Penninsula has the highest chance of experiencing significant timber harvest or wildlife exploitation in the future. Planned timber harvests in response to mortality from a spruce bark beetle infestation could cause damage to streams important for salmon spawning and to declining brown bear populations on the Kenai Penninsula.
Suite of Priority Activities to Enhance Biodiversity Conservation
- Monitor mining proposals over time. This ecoregion has experienced a history of small-scale mining and several large-scale mining proposals.
- Address the unsustainable timber harvest practices on the Kenai Penninsula. The best approach could be to build public pressure to use sustainable harvest practices.
- Establish a protected area in the Taku watershed - British Columbia
- Establish an ecologically representative protected area in the lower Stikine watershed - British Columbia
- Alaska Center for the Environment
- Alaska Rainforest Campaign
- Canadian Arctic Resources Committee
- Canadian Parks and Wilderness Society, British Columbia Chapter
- Canadian Parks and Wilderness Society, Yukon Chapter
- Friends of the Stikine National Parks and Conservation Association
- Interrain Pacific
- Prince William Sound Science Center
- Southeast Alaska Conservation Council (SEACC)
- Taku Wilderness Association
- World Wildlife Fund Canada
- Yukon Conservation Society
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