Like their tropical cousins, high levels of precipitation characterize temperate rainforests. These places have over 140 cm (55 inches) of rain per year, with many having far more. What makes them different is their location. Temperate rainforests are found not in the tropics, but in the earth's two temperate zones.
Characteristics of Temperate Rainforests
Some of the generally accepted characteristics scientists use to define temperate rainforests are:
- High levels of rainfall: One commonly accepted definition of a temperate rainforest lists 140 cm (55 inches) of rain per year as the minimum. It is common for the coastal temperate rainforests to receive over 200cm (80 inches) of rain each year. In some areas, such as Olympic National Park in Washington state, the rainforest receives over 425 cm (167 inches) of rain per year.
- Situated in a temperate zone: The temperate zones are the middle latitudes of the planet, between the tropics and the polar regions. The north temperate zone lies between the Tropic of Cancer and the Arctic zone, while the south temperate zone reaches from south of the Tropic of Capricorn to the Antarctic circle (from about 23 degrees latitude to 66 degrees latitude in both hemispheres).
- Proximity to the ocean: While there are a few inland pockets of forests that fit the basic definition of a temperate rainforest, the majority of these forests are located close to the coast where ocean rains provide the climate necessary to sustain the plants of the rainforest.
- An abundance of epiphytes: Epiphytes are plants that have no roots and don't touch the soil in any way. Instead, they actually grow on other plants and draw their water from the moist air of the rainforest and from rainfall.
- High levels of biomass: The coniferous temperate rainforests of the U.S. Pacific coast have the highest levels of biomass of any place on earth, outpacing even the dense rainforests and jungles of the tropics.
- Heavy summer fog: The fog creates the humid conditions required by epiphytes and other rainforest plants, such as ferns, during what would otherwise be a dry period. The rainy winter wet season provides moisture via precipitation.
Temperate rainforests are rare. Some of the largest temperate rainforests in the world are found along the U.S. and Canadian Pacific coast, on the coast of Chile in South America, in coastal Australia and New Zealand and on the coast of South Africa. Other smaller pockets of temperate rainforest can be found in Asia, North America and Western Europe.
These amazing areas are some of the most biologically diverse in the world, but they are in danger of being destroyed through logging and because of climate change. Like their cousins in the tropical regions, temperate rainforests are a fascinating and important part of the world's ecosystems.
Further Reading
Marietta College Department of Biology and Environmental Science's Biomes of the World web site.
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