1976

Temperate Rainforests

Tropical rainforests (which generally occur within about 25 degrees of the equator) contain the highest densities of living organisms and the greatest range of species diversity of any biome on the Earth. Not far behind, however, are different kinds of 102between the Tropic of Cancer and the Arctic Circle (23.5°N to 66.5°N) and in the southern hemisphere between the Tropic of Capricorn and the Antarctic Circle (23.5°S to 66.5°S).

Temperate rainforests are densely wooded areas that receive heavy annual rainfall (greater than 55 inches [140 centimeters]) and are populated with both conifer and broadleaf trees and a wide variety of mosses and ferns. The trees form a canopy (top-level habitat which collects most of the rain and sunlight) that can rise 300 feet (100 meters) or more above the forest floor and that can shade as much as 95 percent of the floor during the summer. Little sunlight and cool temperatures keep the forest floor damp year-round, and promote the growth of mosses, ferns, lichens, slugs, and a variety of shade-tolerant shrubs.

Temperate rainforests occur in only a few places around the world, and are generally associated with regions that receive significant moisture from the ocean; among the largest regions are along the coast of the North American Pacific Northwest, along the southwestern coast of South America, and in southern China and northern North Korea. Much of the temperate rainforest in the Pacific Northwest, including the Hoh rainforest (the largest temperate rainforest in the US) became protected land when it was incorporated into a national monument in 1909 and then the Olympic National Park in 1938. Recognizing its importance as one of a rare and dwindling number of special ecosystems in the world, UNESCO designated the Olympic National Park as a Biosphere Preservation District in 1976.

The lush Hoh rainforest of Washington state’s Olympic Peninsula, which receives over 127 inches (323 centimeters) of rain each year, is a classic example of “old growth” temperate rainforest. The Hoh’s canopy consists of enormous (23-foot/7-meter diameter) spruce and hemlock trees as well as Douglas fir, cedar, maple, and cottonwoods, many of which are between 150 and 300 years old.

SEE ALSO Flowers (c. 130 Million BCE), Oldest Living Trees (c. 3000 BCE), Deforestation (c. 1855–1870), National Parks (1872), Tropical Rain/Cloud Forests (1973), Boreal Forests (1992), Temperate Deciduous Forests (2011)

A 2007 photo of lush temperate vegetation along the Hall of Mosses Trail, in the Hoh Rainforest, Olympic National Park, in the US state of Washington.