The North Pacific coastal forests occupy a narrow (about 160 kilometers (km) wide) coastal band extending from the southern portion of the Alexander Archipelago to the Prince William Sound region and eastern Kodiak Island. This ecoregion contains more than one-fourth of the world's coastal temperate rainforest and is one of the largest and most pristine temperate rain forest and shoreline ecosystems in the world. Most of the ecoregion lies within the Tongass National Forest (6.8 x 104 square kilometers (km2)), the Chugach National Forest (3.5 x 104 km2), and Glacier Bay National Park (1.3 x 104 km2).
This ecoregion consists of thousands of small and several large mountainous islands (elevation to 1,500 meters (m)), long coastal valleys, and outburst flood fans. Some of the largest islands in North America are found here, including the eastern portion of Kodiak Island and Prince of Wales Island. Several long-narrow bays have been carved into mountainous terrain by glaciers, creating an extremely irregular coastline. The northern portion of the ecoregion consists of a mosaic of foothills, coastal lowlands of alluvial fans, uplifted estuaries, morainal deposits, dunes, river deltas, and terraces. Notably, limestone karst topography characterized by numerous sinkholes, caves, underground streams, and fractured bedrock is prominent in the southern portion of the region (Prince of Wales Island and Ketchikan area). This karst landscape is a three-dimensional system that includes productive forests and peatlands on top of karst, the surface and subsurface interactions, and groundwaters originating from these systems.
Glacial influences have shaped landform features throughout the region and are particularly evident from the numerous fjords in the southern portion of the region and the drumlin fields (small hills) of Prince of Wales Island. However, some areas have escaped glaciation and may provide refugia for remnants of ancient flora present before the period of last glacial advance. In addition, the presence of numerous islands of various sizes and distances from the mainland has influenced the distribution of local flora and fauna. For instance, brown bears (Ursus arctos horribilis) are present only on Admiralty, Baranof, and Chichagof Islands (the so called ABC islands). In addition, the Alexander Archipelago and Queen Charlotte Islands to the south contain endemic subspecies of invertebrates, birds, and mammals.
Climate in this region is generally characterized by a unique combination of moderate temperatures and high rainfall resulting from the warm Alaska Current. Annual precipitation averages 2,450 millimeters (mm), but is quite variable (range 762 mm - 5,588 mm) both within the region and on individual islands. These localized differences in climate are known to be important factors influencing site productivity and distribution of plant associations. High annual precipitation has resulted in the relative absence of fire throughout the region. Wind is the primary disturbance; however, landslides, avalanches, floods, and glacial disturbances also occur. The absence of fire in this region has resulted in few forests of intermediate ages (50-150 years).
Plant species diversity varies extensively across the ecoregion, reflecting complex interactions of climate, geomorphology, history, and species interactions. The predominant forest type in the region is coastal Sitka spruce (Picea sitchensis) and hemlock (Tsuga spp.). However, poorly-drained sites contain muskegs and low lying areas along river channels contain alder (Alnus spp.), cottonwood (Populus trichocarpa), and Alaska paper birch (Betula papyrifera). Twenty-one ecological provinces have been recognized in southeast Alaska and seven vegetation series and 41 associations have been identified in this area, including shore pine (Pinus contorta), mixed conifer, western hemlock (T. heterophylla), western red cedar (Thuja plicata), western hemlock, western hemlock-yellow cedar (Chamaecyparis nootatensis), mountain hemlock (T. mertensiana), and Sitka spruce. In general, species richness (conifers, plant associations, birds, mammals) declines with increasing latitude. For instance, the southern portion of the region contains 60 percent of the species on only 20 percent of the land base.
The extensive coastline juxtaposed with numerous mountainous islands, streams, estuaries, and dense forests makes this ecoregion one of the most productive (marine and terrestrial biomass) in North America. Because this ecoregion also contains one-fourth of the world's temperate rainforest it was considered globally outstanding. Many of the few remaining intact (unlogged) watersheds in North America (primarily in the northern portion of the ecoregion) and relatively abundant old-growth forest further contribute to the global significance of this ecoregion. Also of global importance is the capacity of these forests to store carbon and the subsequent role they play in regional and global climates. Old-growth forests in particular are critically important fish and wildlife habitat and are characterized by unique structural attributes (e.g., multi-layered canopies, diverse forb and shrub layers, coarse-woody debris, large diameter trees). These attributes are usually present when a forest reaches 150 years (although this varies with plant association). In addition, old-growth forests in this region are classified by the USDA Forest Service by timber volume classes ranging from low-volume muskeg (volume class 4) to high-volume and commercially productive forests (volume class 7) that are generally found along valley bottoms and low-elevation areas. High volume old-growth forests are of greatest importance to wildlife because they contain relatively high levels of species richness, provide important winter refugia for birds and mammals, and support superabundant anadromous fish runs.
Many species that are threatened in the lower 48 states are present in far greater numbers in this ecoregion. Some of the highest nesting concentrations of bald eagles (Haliaeetus leucocephalus) and marbled murrelets (Brachyramphus marmoratus) in North America occur in southeast Alaska, Prince William Sound, and the Kodiak Archipelago. Likewise, some of the highest concentrations of brown bear in North America occur in southeast Alaska and Kodiak Island. Similarly, the region is known for some of the most productive salmon (five species) runs in North America. However, when compared to other temperate coniferous forests within its Major Habitat Type (MHT), this ecoregion contains relatively low species richness because its northern distribution lies outside the geographic range of most taxa. In particular, few herpetofauna (4 amphibian and 1 reptile) and conifer species (8) exist in these northern latitudes. Bird species represent the majority (59 percent) of taxa evaluated; however, many forest dwelling families are poorly represented, particularly the woodpeckers and woodwarblers. Although not included in this assessment, the region contains high levels of bryophytes and epiphytes; these taxa are the subject of ongoing investigation.
On a coarse scale, old-growth losses (all volume classes combined) have not been as extensive as other temperate coniferous forests within this MHT. For instance, logging has eliminated 7 percent of productive old-growth since the early 1950's. However, an additional 23 percent of old growth is scheduled for harvest over the next 15 years. Such losses are taking place in some of the most productive (high volume) forested ecosystems remaining in the ecoregion. For instance, roughly 10 percent of the high-volume old-growth remains on the Tongass National Forest and much of this is scheduled for harvesting. In addition, logging and extensive road building in some ecological provinces (e.g., Prince of Wales Island northern and southern provinces) will eliminate up to 70 percent of the total old growth over the next 150 years. Projected logging levels in old-growth systems are expected to result in significant population declines in several species, including northern goshawk (Accipiter gentilis laingi), Alexander Archipelago wolf (Canis lupus ligoni), marten (Martes americana), northern flying squirrel (Glaucomys sabrinus), brown bear, and some neotropical and resident birds. In addition, well-drained karst terrain has been particularly impacted by logging, as well as species rich estuarine and riparian fringes (protected on national forests by narrow (150-300 m) buffers). Village corporation lands (managed by Native Alaskan corporations) have been particularly impacted by extensive logging.
Remaining Blocks of Intact Habitat
Within the ecoregion, several blocks of relatively intact habitat remain. The Southeast Alaska Conservation Council has mapped 17 intact but threatened forests in southeast Alaska, four areas in the Gulf of Alaska, nine areas in the Prince William Sound region, and five areas in the Kenai Peninsula and Kodiak Archipelago. Similarly, EcoTrust mapped several intact watersheds (greater than 1,000 km2) in the region of which many are threatened by logging. Workshop participants during this assessment identified the following intact blocks:
- Admiralty Island - southeastern Alaska
- West side of Chichagof Island - southeastern Alaska
- South Baranof Island - southeastern Alaska
- South Kupreanof Island - southeastern Alaska
- Cleveland Peninsula (logging is occurring) - southeastern Alaska
- Misty Fjords National Monument - southeastern Alaska
- Southern half of Kuiu Island - southeastern Alaska
- Coastal areas of Glacier Bay National Park - southeastern Alaska
- Most of Prince William Sound (logging is occurring or planned on Native Corporation lands) - southeastern Alaska
- Kachemak Bay State Park - southeastern Alaska
- Yakutat Forelands - southeastern Alaska
- Honker Divide and the Thorne River on Prince of Whales Island (logging is planned) - southeastern Alaska
Degree of Fragmentation
Because most of the ecoregion is distributed across several archipelagos, the system is naturally fragmented. In addition, drainage and soil development within the ecoregion is highly variable, resulting in a mosaic of various forest volume classes (muskeg to volume class 7), estuarine areas, beach fringe, and riparian areas. However, several large relatively intact blocks of forest exist in many of the ecological provinces providing good connections among related patch types.
Habitat fragmentation due to anthropogenic factors also varies across the region. Several ecological provinces have been substantially affected by logging, particularly those on Prince of Whales Island where 70 percent of two ecological provinces are scheduled for logging over the next 150 years. Logging has produced the most extensive road system for any of the ecological provinces on the Tongass National Forest.
Degree of Protection
While landmark conservation acts were passed in the 1980s (e.g., Alaska National Interest Lands Conservation Act) protecting several important areas in this ecoregion, most of the biologically rich and productive lands remain vulnerable to logging, particularly high-volume old-growth. The Tongass Land Management Plan provides maps of these areas as well as several large roadless and wilderness complexes under land protection categories. Additional protected areas include: Glacier Bay National Park, Admiralty Island Wilderness, Kachemak Bay State Park, Misty Fjords Wilderness, West Chichagof Island, South Baranof Island, Kuiu Island, Southern Prince of Wales Island, Southern Etolin, and the Stikine Delta. Additional areas may be protected in the near future through land acquisitions made possible by the Exxon Valdez oil spill settlement funds; many lands available for acquisition are threatened rainforest areas.
The greatest obstacle to conserving future lands in this ecoregion is political will. The Alaska delegation has blocked numerous attempts at protection of additional rainforest lands on the Tongass and has proposed land exchanges that would remove or substantially weaken protection of rainforest areas. At a minimum, conservation in this region needs to focus on blocking such Congressional measures while building support for additional protection of high-volume old-growth.
Types and Severity of Threats
While there are still many pristine areas remaining in this ecoregion, old growth is on a trajectory similar to the extensive degradation that has characterized the Pacific Northwest during the past 50 years. Population viability concerns already exist for several species associated with old-growth and trends in these species over the next century are alarming (several species have low persistence probabilities). Other threats include expansion of roads and highways to accommodate the explosive growth in tourism, increases in cruise ships visiting popular tourism destinations such as Glacier Bay National Park, pollution from pulp mills and mining tailings, and potential long-term reductions in subsistence species (e.g. deer) due to logging in winter habitat areas.
Suite of Priority Activities to Enhance Biodiversity Conservation
The recommendations of the interagency viability population task force are an excellent starting point for identifying lands in need of additional protection on the Tongass National Forest in order to achieve more stable population trajectories for old-growth associated species. Other conservation measures identified by the Southeast Alaska Conservation Council and Ecotrust should be adopted. In addition, conservation groups will need to balance protection of old-growth areas with ecologically appropriate logging (e.g., under the auspices of the Forest Stewardship Council principles and standards) while communities transition to more diversified economies. Recommendations for small-scale logging (outside high volume old-growth) are available from the Tongass Conservation Society, Alaback, and DellaSala. The following suite of priority activities were identified by workshop participants:
- Protect all remaining high-volume old growth on Prince of Wales Island, Kuiu Island, southeast Chichagof Island, southeast Revillagigedo Island.
- Protect Wild and Scenic Rivers (e.g., Thorne River on Prince of Wales Island).
- Maintain connections across ecological provinces (e.g., south and north Prince of Wales Island, Stikine Delta, Copper River Delta).
- Institute habitat conservation areas as proposed by Suring et al.
- Secure protection of roadless areas (Land Use Designation II)
- Continue to use Exxon Valdez oil spill settlement to purchase habitat in the oil spill region.
- Formerly designate additional wilderness areas (e.g., several on the Chugach National Forest)
- Alaska Rainforest Campaign
- The Nature Conservancy
- The Nature Conservancy of Alaska
- Sierra Club - Alaska Field Office
- Southeast Alaska Conservation Council (SEACC)
- Tongass Conservation Society
- The Wilderness Society - Alaska Region
Relationship to Other Classification Schemes
The classification system used to delineate this ecoregion is similar to Omernik's ecoregion #120 and Bailey's ecosections 245A-C. The ecoregion described here is also concordant with Ecotrust's classification for temperate rainforest in the subpolar and per-humid zones. We did not, however, include the seasonal and coastal redwood zones and instead split them into separate ecoregions out of concerns for species assemblages, climate, disturbance regimes, and physiography.
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.