Alaska, a region often associated with glaciers and tundra, is home to a rainforest. This ecosystem is a temperate rainforest, thriving along the state’s southeastern coast. Its presence, unexpected given Alaska’s northern latitude, represents a globally significant natural area. Specific climatic conditions allow lush, dense vegetation to flourish in this cooler environment.
Defining a Temperate Rainforest
Temperate rainforests are distinguished from tropical ones by their geographical location and temperature range. Unlike tropical rainforests near the equator, temperate rainforests occur in middle latitudes, typically between 40° and 60° in both Northern and Southern hemispheres. They experience moderate temperatures throughout the year, usually ranging from 4 to 12 degrees Celsius (39 to 54 degrees Fahrenheit), and exhibit distinct seasons. These forests require substantial annual precipitation, generally receiving between 140 to 500 centimeters (55 to 200 inches) of rain or moisture from coastal fog. This consistent moisture and mild temperatures foster the growth of towering coniferous trees, a characteristic that sets them apart from the broadleaf trees prevalent in tropical rainforests.
Alaska’s Coastal Rainforest Ecosystem
Alaska’s temperate rainforest is located in Southeast Alaska, within the Tongass National Forest. This forest spans approximately 16.7 million acres, making it the largest national forest in the United States and the largest intact temperate rainforest globally. The climate is influenced by the Pacific Ocean, which brings consistent moisture and moderates temperatures, preventing extreme cold. Annual precipitation in the Tongass often exceeds 100 inches, creating a consistently wet environment. Dominant tree species include Sitka spruce, western hemlock, and cedars like western red and Alaska yellow, which grow to immense sizes due to the mild, moist conditions.
The Rainforest’s Ecological Importance
Alaska’s temperate rainforest is a biodiverse ecosystem, supporting a wide array of wildlife including brown bears, bald eagles, and all five species of Pacific salmon. Abundant salmon runs provide a food source for many species and contribute to the forest’s nutrient cycling. This rainforest also serves as a carbon sink, storing carbon in its old-growth trees and soils, which helps mitigate climate change. The Tongass National Forest alone holds approximately 20% of all U.S. national forest carbon, making it a globally important climate solution. Beyond its environmental contributions, the forest holds cultural significance for Indigenous communities like the Tlingit, Haida, and Tsimshian, who have lived on these lands for thousands of years.