Ecology of Lake Clark

Image of a forested landscape and islands with a large lake in the background.
The roadless wilderness of Lake Clark National Park and Preserve provides habitat for a variety of species from migratory birds to brown bears and caribou

NPS Photo/K. Miller

Lake Clark National Park and Preserve is a beautiful landscape of boreal forest, tundra, freshwater lakes and rivers, snow and glacier covered mountains, and coastal beaches and salt marshes along the ocean. Each of these ecosystems have plants and animals that live specifically within them. An ecosystem is a community of organisms, such as plants and animals, that live and interact with each other in their environment. Some plants and animals, like bears and blueberries, can live in several ecosystems. Others like sedges (a grass-like plant that grows in wet ground or near water) live rooted in salt marshes and need a specific environment in which to live.
Image of open tundra, varied and colorful with mountain range and clear skies in the background.
Alpine tundra is found at high elevations in Lake Clark National Park and Preserve. This view across open tundra looks up into the Neacola mountain range in Lake Clark National Park and Preserve.

NPS Photo/E. Wilcox

Tundra: A Land of Extremes

Alpine tundra is found in the mountains of Lake Clark National Park at high elevations. Tundra is a low growing mat of lichens, mosses, and small plants, such as cranberries or blueberries. Tundra grows in places with cold temperatures and long winters. Caribou, ground squirrels and ptarmigan (a type of bird found in mountains and in northern regions) are some of the wildlife that call tundra home. Snow covers this landscape most of the year. Plants have less time to grow during this short and harsh growing season. Plants grow closer to the ground in dense, low-lying mats to conserve valuable heat and moisture in a place with dry, howling winds. Plants grow tiny leaves and flowers here. Due to these harsh conditions, tundra plant life becomes a world in miniature!
Image of a wildland fire and flames rising in a black spruce forest.
Fire is a natural disturbance that helps shape the landscape of the boreal forest. Pictured here, flames rise from black spruce in a wildfire.

NPS Photo/Y. Matsui

Boreal Forest

Boreal forests have short cool summers and long cold winters. Common trees found in the boreal forest of Lake Clark are black spruce, white spruce, cottonwood, birch, aspen, willow, and alder. The ground within the boreal forest is a thick mat of mosses, lichens, sedges, grasses, and berries. Wildfire is common in the boreal forest. Wildfire can be dangerous to people but is natural in the boreal forest. Fire helps create patches of open areas in the forest for new plants to grow. Black spruce seeds even need fire to sprout. The forest is a patchwork of trees, shrubs, meadows, marshes, lakes, and braided rivers. Animals and plants in the boreal forest, such as lynx, red fox, and moose must survive long winters and short dry summers.
Image of large glacier in Tuxedni region of Lake Clark with tall mountains in the background.
Glaciers are not permanent on the landscape, they are always moving. As glaciers move, they scrape and scratch the bedrock beneath them. Glaciers shape the landscape of Lake Clark National Park and Preserve.

NPS Photo/K. Lewandowski

Freshwater Ecosystems


A glacier is a massive river of ice that flows slowly downhill. Glaciers form high in the mountains from snowpack that doesn't melt in the summer. Layers of snow build up over time and become heavy, eventually compressing into solid ice. This can take hundreds of years. Like bulldozers moving downhill, glaciers carve the park’s rugged terrain beneath them into wide U-shaped valleys. Glacier meltwater in the summer sends clean, cold water to lower elevations. This freshwater flows to the headwaters of the rivers and lakes where sockeye salmon hatch. Today, as the climate is warming, the glaciers in the park are melting and becoming smaller.
Image of freshwater flowing into a clear blue lake.
Water flowing from the mountains support the world's most productive sockeye salmon fishery.

NPS Photo/T. Vaughn

Lakes and Rivers

Mazes of creeks, rivers and lakes cover the Lake Clark landscape. Look at a map of the park. How many lakes can you count? Lake Clark is the largest lake in the park. It is 41 miles long, ranging from 1 to 4 miles wide, and reaches a depth of 870 feet. Lakes carved by glaciers, such as Lake Clark, are long, narrow, deep and surrounded by mountains. Water flowing from the mountains into the lakes and rivers supports the world’s most productive sockeye salmon fishery. Each year salmon return to the waterways where they were born. The freshwater that provides the habitat to support salmon, supports people too. The Dena’ina people have lived in Lake Clark for thousands of years. The clean, cold freshwater and the salmon that return are part of the the reason people have lived here so long.
Image of brown bears roaming and foraging in green meadow.
Brown bears feast on vegetation in the Chinitna Bay Meadow on the coast of Lake Clark National Park and Preserve.

NPS Photo/J. Pfeiffenberger

Coastal Salt Marshes:
Vibrant and Lively

Salt marshes are located along the park’s coastline. The land meets the sea here as tides carry nutrients and saltwater to the land. Salt-tolerant plants, such as hardy sedges and grasses, grow in this mix of fresh and salt water. Fish, migratory birds, and mammals call this rare habitat home. We can think of a salt marsh as a biological supermarket. It absorbs nutrients from the ocean water and provides food for other animals. Dead plants break down in the water feeding insects and small fish. These smaller fish are then food for larger fish, birds, and mammals.
Image of a sow and her cub standing in vegetation in a meadow.
The coast of Lake Clark National Park and Preserve provides brown bears with plants high in protein early in the season, while they wait for salmon to arrive. Here, a brown bear and her cub stand in the meadow at Silver Salmon Creek, located along the coast.

NPS Photo/K. Jalone

Brown Bear Necessities

Salt marshes are essential for brown bears along the park’s coastline. Bears are hungry when they leave their dens in the spring. After a long winter, the coast is the supermarket bears use to fill up. Lake Clark’s coastal sedges are high in protein and an important food for bears early in the season. These salt-tolerant plants are necessary for bears to survive and feed young cubs while they are waiting for salmon to arrive.

Secrets in the Soil!

Salt marshes improve water quality. They clean the water and hold onto nutrients that feed plants and animals. They also take carbon dioxide from the air for storage in plants and soil. Salt marshes limit coastal erosion by slowing waves and trapping sediment. This protects shorelines from erosion caused by wind, water, and ice.

Lake Clark National Park & Preserve

Last updated: September 15, 2021