*Temperate Rainforest: “any forest that receives more than 50-60 inches of rain per year and has a temperate climate.”

Native fir and cedar forest along the banks of Lookout Creek, H.J. Andrews State Forest, Oregon Cascades. (orgn0660) Photo by Brett Cole/Wild Northwest PhotographyAll Rights Reserved.

Temperate rainforests make up a small portion of the world’s forests, (2-3% of rainforests or 30-40 million hectares); yet harbor more biomass per acre than any other forest type including the tropical rainforest. The estimate biomass is between 500-2,000 metric tons per hectare! This surprises many people whom only picture the tropical rainforest as harboring such immense life. Not only is there an astounding amount of biomass, these temperate rainforests also harbor some of the only remaining old growth in the country or world for that matter. This is considerably important in the face of the devastating old growth logging that has been, and still is, a part of the history and fate of American forests.

Before they were logged, temperate rainforests covered a much larger area globally than can be found currently. In fact, temperate rainforests historically were to be found on every continent except for Africa and Antarctica for obvious climatic reasons. Currently these forests can be found mainly in Western North America, Canada, and South-East Alaska. There are also larger portions in the Southern hemisphere in a strip along Chile’s coastline. Other areas include a piece on the West coast of New Zealand’s South island and small pieces in Tasmania and Norway. The current state of these forests is a state of diminishing sustainability as they become smaller and smaller and thus are prone to becoming ‘edge’ forest with a less highly functioning ecosystem and a subsequent decreased level of biodiversity.

There are three requirements for a temperate rainforest; 1) a mild coastal climate, 2) heavy summer fog, and 3) very generous rainfall, (more than 50 inches per year). There are also six general characteristics of this forest type; 1) the presence of sitka spruce, 2) the presence of nurse logs, 3) the presence of colonnades, (trees standing in a row as a result of starting on nurse logs), 4) trees standing on stilts, (a result of seedlings sprouting on stumps that later decay away leaving a tree standing on the roots), 5) a profusion of lichens and mosses, and 6) bigleaf maples with clubmoss draperies.

Coast Redwoods in early morning fog. Damnation Creek, Del Norte Redwoods Park, California. (cali0116) Photo by Brett Cole

Heavy rainfall, along with the temperate climate, are however, both the main characteristics and requirements for this forest type. In some areas of temperate rainforest such as Olympic National Park in Washington state, USA, there can often be more than 150 inches of rain per year. This type of insanely heavy rainfall is what keeps the temperate rainforest so lush, verdant and green. These forests developed where moisture-rich air masses from the Pacific Ocean rise and become trapped by coastal mountain ranges, at this point moisture condenses and returns to earth as heavy, frequent rainfall. The mild climate of these forests where temperatures rarely go above 80c or below 30c coupled with the heavy rains allows for continuous year round growth. The mild summers bring with them the heavily moisture laden fog which prevents the occurrence of drought and sustains the moisture level of the forest in the drier season. These climatic factors are the allowing force of the temperate rainforests. Because of global warming however, there is a continuing threat to the stability of these weather systems and thus an increased risk to the wellbeing of the temperate rainforests.

Macro view of raindrops clinging to fir needles in the Umpqua National Forest, Oregon. (orgn0500) Photo by Brett Cole

As noted previously, these forests have the largest amount of biomass per hectare of anywhere in the world. Most of this biomass consists of leaf litter, wood, foliate, moss, living plants and soil. There is also a disproportionate amount of biomass present in the tropical rainforest with figures that trail not too far behind the temperate rainforest. There are several interesting differences between these two types of rainforests though.

Temperate rainforests provide habitat for more than 250 species of birds and mammals and also more than 30 species of trees. Although this is not remarkable by global standards, there are several rare and/or endangered species such as the infamous spotted owl that stirred up such a controversy in the Pacific Northwest and eventually throughout the country. These forests are also home to seven species of Pacific salmon. Some of the most dominant mammals would consists of several species of chipmunks and squirrels including the flying squirrel, voles, beavers, snowshoe hares, martens, weasels, black bears, bobcats, mule deer and elk. There are also a huge amount of bird species present in these forests and several different salamander and frog species including a tree frog. Finally there is the well known, (although not always well-loved), banana slug.

The dominant tree species in these forests consist of Sitka Spruce, Western Hemlock, Western Redcedar, Common Douglas Fir, Grand Fir, and Silver, Red, and White Fir. Then there is the Pacific Yew, Western Larch, Incense Cedar, Bigleaf Maple, Red Alder, Pacific Dogwood, Cascara Buckthorne, Pacific Madrone, Western White Pine and the Lodgepole Pine. Redwood trees are also existent in temperate rainforest but are almost in a class by themselves because of their immense size and stature.

Vertical view of very tall Douglas-fir trees in the Umpqua National Forest, Oregon. Nearly 275 feet tall and 500 years old, trees like this are still being cut by the Forest Service. (orgn0503) Photo by Brett Cole

For this reason there is a whole specified redwood zone subtype of temperate rainforest. There are also three other subtypes of temperate rainforest making four total subtypes. The distribution and categorization of these subtypes is based upon temperature and precipitation distribution. Along with these four zones come distinct pattens of dominant tree species. In the subpolar zone the dominant species are Sitka Spruce, and Western and Mountain Hemlock. In the perhumid zone Sitka Spruce is again a dominant species along with Western Redcedar and Western Hemlock. In the seasonal zone, Douglas Fir is added to the aforementioned species in the perhumid zone to complete the characteristics of this seasonal zone. Finally there is the previously mentioned redwood zone which obviously bows to the dominance of the Redwood tree species.

Redwood trees are definitely some of the more amazing trees of the temperate rainforest type. They are the tallest trees on earth. For comparison one can imagine the statue of liberty in New York City, USA, which dwarfs a human and is 300 some feet tall. Well, Redwood trees can be taller than the statue of liberty! Not only are the Redwoods some of the tallest trees, they are also some of the oldest and can live more than 2,000 years although most live between 500-700 years depending on conditions.

Redwoods like most conifers have both a male and female cone and pollination occurs by wind. The seedlings can actually grow in a darkened forest as they are tolerant of shade. Redwoods are one of the only tees that have burls. Burls are wrinkled balls of tissue found in places along the tree’s trunk. Burls can dramatically range in size from a small ball to the size of a table. They consist of dormant tissue that is capable of sprouting new tree growth. In this way Redwoods have a competitive advantage, if one falls over but has an intact root system then the burl can sprout and become another whole tree.

As we already know the temperate rainforests are intimately connected to the hydrologic cycle and the effects of coastal fog and rain. However, there are also hugely important terrestrial and marine ecosystem connections. First of all, most of these forests actually stand in watersheds that empty directly into the ocean. There are also delicate networks of streams, wetlands and estuaries running through them. These waterbodies create habitats for both freshwater and anadromous fish, (such as salmon, whom live out their lives between both fresh and salt water). These waterbodies are also important for other wildlife that depend on aquatic habitats and plants that have specifically adapted to living in, on or near them. Many natural corridors are created by the riparian habitats created by these water networks. The plant and animal communities in, around and below these riparian zones make up biodiversity that can only be found in these forests. Not only this, but a considerable amount of the biological production of the world’s oceans can be found on the edges of the temperate rainforests. Many animals carry marine nutrients back into coastal watersheds which makes them and the forest more productive. Preserving undeveloped watersheds has become and important issue in rainforest conservation as they are so closely linked to the overall health of these forests and provide and often clean watersource for humans also.

There are many natural resources to be found in the temperate rainforest of the world. These all have definite economic value, especially the natural resource of wood. Loggers highly value the wood to be found in these forests and can harvest very valuable timber from them. There are also many plant, animal and fungal resources to be found. Besides this there are numerous as of yet undiscovered resources that may prove to be invaluable to us humans. For example, some species of plants may yield cures for diseases. There is so much that is still not yet researched about these forests and if we were to care for them irresponsibly we may be losing out literally on the chance of a lifetime. What an unforgivable shame that would be.

There are also numerous cultural resources to be found in the temperate rainforests of the world. Their use as recreational resources is well known and people come from around the globe to see such forests as the Redwoods. These forests are a wonderful place to learn, explore, relax and reflect.

Currently the major threats to these forests is from humans, mainly attributable to logging and development. Around 44% of these forests have already been developed and only 16% of what is left is protected. These forests are not prone to many natural disturbances. Fire is rare due to the high moisture content in the tree’s bark, the soil and the air. Redwood forests are the most fire prone and the trees usually still survive an incident. Other disturbances would consist of wind throw and landslides of which neither are severely or permanently damaging. The largest threat to these rainforests is unequivocally human driven.

Big Leaf Maple Photo by Brett Cole

The temperate rainforests are certainly a jewel to be treasured. Aesthetically, biologically, recreationally they are a wonder of nature. People often feel some of the greatest, deepest peace in their lives while in these forests. They deserve our most attentive and nourishing care. If protected and cherished they may just save us someday, they are part of the planet’s lungs after all. Truly the trees of majesty and mystery reside in these spiritually infused, diverse and wise forests. Lets work towards saving them together…..

Works Consulted: www.ecotrust.org/publications/rain-forests-atlas.html Alden, Peter and Dennis Paulson. National Audubon Society Field Guide to the Pacific Northwest. New York: Chanticleer Press, 1998. Kricher, John and Gordon Morrison. California and Pacific Northwest Forests. New York: Houghton Mifflin Co., 1993. Miller, Tyler. Sustaining the Earth. Belmont, C.A.: Wadsworth/Thomson Learning, 2002. Pojar, Jim and Andy MacKinnon. Plants of the Pacific Northwest Coast; Washington, Oregon, British Columbia and Alaska. Vancouver, B.C.: Lone Pine Publishing, 1994. Pynn, Larry. Last Stands; A Journey through North America’s Vanishing Ancient Rainforests. Corvallis, O.R.: Oregon State University Press, 2000. Wright-Frierson. A North American Rain Forest Scrapbook. USA: Walker Publishing Co., 1999.