Southwest Alaska Ecosystems

A researcher catalogues lichens.
Lichens are just part of the vast biodiversity in Kenai Fjords National Park.

NPS/M. Shepard

Ecoregion and Biological Diversity

Southwest Alaska parks are places where land and water meet. Lake Clark National Park and Preserve is often called “one park, four Alaskas,” referring to the diversity of landscapes relative to area. This diversity feature is shared by each of the Southwest Alaska Network parklands, which collectively span three Alaska climatic zones and 11 ecoregions.

Landscape diversity, the product of diverse bedrock types and climatic and disturbance regimes, provides the template for relatively high biological diversity. Coastal Aleutian, low-Arctic, interior-boreal, and Pacific coastal floras and faunas converge in southwest Alaska, with Southwest Alaska parklands supporting 60% of the state’s vascular plant flora. Vascular plant communities in the region continue to undergo changes in composition. Species distributions have shifted since the Last Glacial Maximum, and are continuing to shift. For example, Sitka spruce is migrating from the upper Alaska Peninsula west toward the Aleutians and southwest toward the Kodiak Island Archipelago, while alder has increased dramatically in the region over the last several centuries. Numerous species of animals, such as Dall’s sheep, black bear, and Trumpeter Swans, also reach the limits of their statewide range in Southwest Alaska parklands.

Climate change and its influence on the distribution of plants and animals have broad implications for long-term monitoring. The geographic ranges of most plant and animal species are limited by climatic factors, including temperature, precipitation, soil moisture, humidity, and wind. Peninsular landmasses are likely to respond to climate change more rapidly and severely than mainland interior areas because of a greater coast-to-interior ratio. Colonization by new species, changes in the distribution of existing species, or changes in the timing of critical life stages or patterns of migration all have implications for park management and resource protection.

A volcanic crater in Valley of Ten Thousand Smokes.
The Valley of Ten Thousand Smokes in Katmai National Park and Preserve has a multitude of volcanic features. Here a phreatic explosion crater in the foreground and Mt. Cerberus in the background.

NPS/M. Fitz

Dynamic Landform Processes and Patterns

The landscapes of the northern Alaska Peninsula and Kenai Peninsula have been shaped by volcanism, tectonic uplift and subsidence, and broad-scale glaciation. Approximately one-fifth of the landmass within Southwest Alaska parklands is covered by ice or permanent snowfields. Valley and tidewater glaciers radiate from massive snowfields along the coastal mountains. Ten of the 34 tidewater and hanging glaciers that emanate from the Harding Icefield are in Kenai Fjords National Park.

The region is a natural laboratory for geologic research and long-term ecological studies of the effects of infrequent, large-scale disturbances. For example, a unique opportunity exists to observe patterns and relative timing of ice retreat, primary and secondary plant succession, animal colonization, and evolutionary processes.

A steep, rocky coast with mountains in the background.
The rocky coast of Kenai Fjords National Park.

NPS/Jim Pfeiffenberger

Marine Coastline

Southwest Alaska parklands contain almost one-third of the marine coastline in the National Park System. This coastline spans 1,200 miles in the northern Gulf of Alaska, from the heavily glaciated Kenai Fjords National Park on the Kenai Peninsula to sparsely glaciated Aniakchak National Monument and Preserve on the Alaska Peninsula. Kenai Fjords National Park’s rocky headlands with extreme wave exposure are in contrast to the protected low-energy beaches and broad intertidal flats at Katmai and Lake Clark national parks and preserves. Southwest Alaska’s coastal waters are one of the most biologically productive nearshore ecosystems in the world. High tides, frequent storms, and upwelling produced by the Alaska Coastal Current bring essential nutrients to the surface euphotic zone, where they support growth and productivity along the continental shelf.

Sheltered salt marshes and tidal flats support highly productive sedge meadows and large populations of benthic organisms, and serve as important feeding and resting areas for brown bears, shorebirds, and fish. Cliffs, headlands, and islands support seabird rookeries and marine mammal haul outs. Eelgrass, surfgrass, and kelp beds provide herring spawning areas and a nursery substrate that supports the base of the nearshore food chain. Tidally influenced coastal freshwater streams support wild stocks of anadromous salmon.

Sunrise over Kontrashinbuna Lake.
Sunrise over sublime Kontrashibuna Lake, Lake Clark National Park and Preserve.

NPS/T. Vaughn

Freshwater Systems, Anadromous Fish, and Ecological Interrelationships

Freshwater resources in Southwest Alaska parklands are abundant, featuring thousands of kilometers of streams and rivers and two of the largest lakes in the National Park System: Naknek Lake (58,824 hectares) and Lake Clark (31,117 hectares). In fact, the Naknek Lake and Lake Clark watersheds are so extensive that they cover 49% and 32% of the land area within their respective parks. In establishing these parks, Congress recognized the cultural, ecological, recreational, and economic importance of aquatic resources with reference to protecting and maintaining lakes and rivers in their natural state in the enabling legislation.

Freshwater resources in Southwest Alaska parklands are generally considered pristine in that (a) water quality is, by national standards, unimpaired (i.e., no 303(d) surface waters exist within the park); (b) natural processes related to water quantity are unimpeded, including disturbances such as floods and seasonal changes in discharge; and (c) the diversity and productivity of freshwater fauna vary naturally, both spatially and temporally.

The vast and relatively pristine freshwater resources within Southwest Alaska parklands provide the backdrop for a “living natural museum,” punctuated by Pacific salmon and the people these fish have sustained for hundreds of years throughout the Bristol Bay region. The return of spawning Pacific salmon (Oncorhynchus spp.) from the ocean to lakes and rivers is a classic example of a critical biological phenomenon that links freshwater systems in these parks within a broader regional context. After spawning, Pacific salmon die, providing a source of marine-derived nitrogen, carbon, and phosphorus that alters nutrient dynamics throughout watersheds where spawning occurs. Flora and fauna across all trophic levels in aquatic and terrestrial systems benefit from this annual influx of nutrients. Thus, salmon serve as biological conveyor carrying critical nutrients across ecosystem boundaries (e.g., marine, estuarine, and freshwater). Maintaining the ecological integrity of freshwater resources is vital to ensuring the long-term preservation of Pacific salmon in the region.

A wild and vast valley.
The Neacola Valley, between Upper Twin Lake and Kijik in Lake Clark National Park and Preserve. Alaska's parklands include vast wilderness that allow for naturally functioning ecosystems.

NPS/B. King

Wilderness-dependent Large Mammals and Species Interactions

Despite hunting and other human activities, all parks in Southwest Alaska possess intact, naturally functioning terrestrial ecosystems with their historic complement of species, including large apex carnivores and predator-predator, predator-prey interactions. Intact, functioning ecosystems with historic levels of biodiversity are becoming extremely rare globally and supply a resource of great value locally and internationally.

Some key wilderness-dependent mammals in Southwest Alaska are wolverines, brown bears, wolves, and lynx. These species require wilderness to avoid conflicts with humans and to avoid human-caused mortality. They also depend on populations of free-roaming, naturally cycling prey. Wilderness-dependent interactions include wolf-ungulate, brown bear-ungulate, carnivore-carnivore, predator-scavenger, and cyclic lynx-snowshoe hare interactions.

Because such species are sensitive to human disturbance and need large tracts of wild land or wilderness to survive, their status signals impending environmental change across broad geographic areas. For example, wolverines are a classic wilderness-dependent species because they require large home ranges with a full array of seasonal habitats, intact populations of prey, larger apex predators that provide scavenging opportunities, and refugia from human influences. Studies have shown that the persistence of wolverines in southwestern Alberta is due entirely to the presence of large refugia in the form of national parks. As wild ecosystems are progressively compromised by a variety of human activities, such as mining, logging, recreation, and settlement, what is left becomes increasingly valuable as laboratories of natural ecological processes.

Last updated: February 27, 2018