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The Evergreen Forests of the Pacific Northwest

By Frances Philipek, Shelley Smith, and Richard Brook

The wonder and the fragility of the world's tropical rain forests are widely known; nearly every American schoolchild can describe rain forest plants and animals and the threats to their habitat. What is not so well known is that the continental United States and Canada have a rain forest too. From Alaska to California, the Northwest Coast is banded by one of the world's largest contiguous temperate evergreen forests including the rain forest on the Olympic Peninsula. The region also hosts a redwood forest and other unique forest ecosystems.

This is a land of paradox. Under the quiet, cool forest shade and damp carpets of moss lies an area red-hot and roiling with geological activity. The tallest living organisms on the planet, the giant redwood trees, are found in this temperate forest. The ecosystem that supports them is fueled in many respects by miniature life forms—fungi, lichens, and insects. The area's majestic forests and grand rivers have been the scene of some of the most contentious environmental issues of our time, including logging of old-growth forest and restoration of wild salmon populations.

In this article we will explore America's Pacific Northwest Coastal forest ecosystems, including the geology, plants, and animals that characterize this land of hidden contrasts. We will also discuss the area's human history and current land management issues. Several activities included in the article illustrate important aspects of this ecosystem, and the accompanying foldout offers expanded activities and materials for classroom use.

Under the Green
The Northwest temperate evergreen forest extends from southern Alaska to northern California and is nestled between the Pacific Ocean and the rugged peaks of the Cascade Mountains. Hundreds of coastal islands and Washington's vast Olympic Peninsula are also part of this ecosystem.

Map showing temperate evergreen forest ecosystem of the Pacific Northwest

The eastern border of mountains was formed 12-26 million years ago when one plate of the Earth's crust slid under another. This massive movement heated the Earth's interior rock to the point that it melted and formed magma. Under immense pressure, this molten rock was forced to the Earth's surface through weak spots in the Earth's crust and erupted as volcanoes; today, this rock forms the snow-capped peaks of the Cascades. The Coast Mountain Range and the Olympic Mountains on the western edge of this region resulted from the same geologic pressures that formed the Cascades, but here the forces wedged and folded formations first laid down as ancient sea floor.

Fiery volcanic forces rapidly built the Cascades, and glaciers slowly continue to wear them down. Moist Pacific air assures that the mountains are well watered and that more than 700 glaciers in the Cascade Range actively shape the landscape. Ice sheets of the last glacial age some 13,000 years ago shaped the Olympic Peninsula and the coastal areas and also carved out Puget Sound. Glacial activity and the runoff of glacial meltwater influence the location and flow of the numerous streams and rivers that traverse the Pacific Northwest.

Even though the Cascades are sheathed in ice today, residents of Portland and Seattle sometimes witness ashy, steaming proof that these mountains are still volcanically active. This area is the youngest and most geologically active part of the continent, and the mountains are still rising and shifting. Mount St Helens, which erupted in May 1980, is a dramatic reminder of the underground powder keg. The spewing ash and gases leveled 60 km2 of countryside, burying it with rivers of hot mud. This area marks a 1,100 km segment of the eastern edge of the Pacific Rim's "Ring of Fire." The Ring touches East Asia as well as North and South America. The explosive magma underlying this ring is constantly being replenished as oceanic plates dive and melt beneath the coasts.

But in the peaceful forest one would not guess there is such chaos below. The temperate evergreen forest of the Northwest Coast is situated mostly in coastal areas and has mountains less than 3,000 m high. Precipitation is abundant, with 65400 cm of rain and snow a year.

Temperatures are cool, rarely below -5° BC or above 38° BC. The Columbia River, one of the nation's mightiest, drains large portions of Washington and Oregon before emptying into the Pacific Ocean, as do hundreds of other rivers and streams that flow across this region. These streams defined routes by which settlers and loggers accessed the forests. They are also the paths taken by migrating salmon to spawn in the waters of their birth.

Forest Tiers
The temperate evergreen forest consists of three components or "layers": the canopy, the understory, and the forest floor. The canopy, the highest layer, is where the crowns of the forest trees meet to form a dense ceiling. Most temperate evergreen forest animals live in the understory, well beneath the canopy, where small trees and shrubs are found. The forest floor functions as a vast recycling center where dead plant and animal materials are converted to nutrients that are channeled back to the trees. Invertebrates are the main inhabitants of the forest floor.

Until recently, the importance of the forest canopy was poorly understood because of the technical difficulty in conducting scientific investigations so high off the ground. Today, research pioneers are using specialized equipment to uncover unique features and relationships within the canopy. The canopy has been described as the temperate evergreen forest's "engine" because many of the important chemical reactions that build fuels for life and growth through photosynthesis take place here. Light, carbon dioxide, and nitrogen are captured in the canopy trees' leaves and needles. Roots draw water and other nutrients from the soil and carry these through the trees' trunks to feed into the photosynthetic process. All of this results in the manufacture of carbohydrates—the trees' food.

Common golden chanterelle fungus. Fungi depend on rotting wood and leaf litter on the forest floor for nutrients.
Common golden chanterelle fungus

Photo courtesy of BLM

The canopy also controls the humidity and temperature of the forest, "insulating" the forest understory and floor from summer's light and heat, thereby keeping these lower forest tiers dark and damp. By contrast, during winter storms the treetops absorb the impact of the rain, allowing the drops of water to gently drip down to the lower layers, thus minimizing compaction and erosion. In the dry season (July through September), the canopy captures water from fog, with each conifer needle acting as a condensation point. The trees in temperate evergreen forests are vertically oriented so that rainwater is channeled toward their root systems. The canopy also contributes needles, leaves, and twigs to the organic matter that blankets the forest floor.

The dominant canopy species in the temperate evergreen forest is the Douglas fir, which can live to be 1,000 years old. The world's largest coastal Douglas fir tree is found on land managed by the Bureau of Land Management in the Coos Bay District of Oregon. Known as the Doerner fir, it is 100 m tall, 3.5 m in diameter, and 11 m in circumference. Sitka spruce, western hemlock, western red cedar, bigleaf maple, red alder vine maple, and black cottonwood are also found in this rain forest

The large, horizontal limbs of taller trees afford nesting places for the marbled murrelet, an endangered seabird that nests in coastal evergreen forests and feeds in offshore waters. This may be the only species to have adapted a direct dependency on both the temperate evergreen forest and the coastal marine environment. The role of the marbled murrelet in the temperate evergreen forest ecosystem—other than that of prey for larger animals—is unclear, although it is thought that the murrelet may be an indicator species for ecosystem health.

Canopy trees play another important role in the temperate evergreen forest ecosystem: They provide microenvironments that sustain a multitude of small species, from spiders and insects to fungus and lichens. Broken-topped trees and snags—trees that remain standing after they die—provide additional microenvironments such as nesting places for raptors and woodpeckers. Snags may stand erect for up to 200 years. In the first few years after a tree dies, beetles chew tunnels through the outer layers of wood and deposit wood-decaying fungi and bacteria in their feces. Woodpeckers feed on the beetles while bats rear their young under the loose bark of the snag. Over time, the wood softens sufficiently for cavity-nesting birds to set up residence. As more decades pass, only the largest branches remain attached to the trunk. When these branches finally fall off, the resultant gaps in the canopy allow sunlight to reach the forest floor, fostering the growth of species that require large amounts of light.

The canopy contains more than trees, however. It also hosts other forms of vegetation that boast interesting and unusual adaptations. Among these are epiphytes (Greek for "upon plants"), which grow in the forest's upper reaches unconnected to the ground, using other plants for physical support. Epiphytes, which include some mosses, ferns, and lichens, are not parasitic (i.e., they do not directly harm the host plant). Rather, these "air plants" absorb what they need from the air and the falling rain. By growing on other plants, epiphytes can take advantage of locations where competition for light is minimal.

Some epiphytes, such as nitrogen fixing-lichens, bring new nutrients into the ecosystem by capturing them from the air and converting them to forms that can be used by other plants. When epiphytes die, some of their parts fall to the forest floor, providing nutrients to be recycled; parts that are retained within the canopy in little pockets along branches or in the nooks of tree trunks act as soils that can support other plants. The evergreen huckleberry, for example, can sometimes be found exploiting such a pocket of soil 30 m or more above the forest floor. Other plants, such as bigleaf maples, can develop roots to tap these high-elevation pockets of soil and nutrients, offering opportunities for additional epiphytic growth.

Artist's depictions of Pacific Yew, Douglas Fir, Western Hemlock, and Western Red Cedar
Pacific yew (5-15 m is common height)
Douglas fir (80 m is common height)
Western hemlock (30-50 m is common height)
Western red cedar (30-55 m is common height)
More Than Just Pretty Foliage
The evergreen forests of the Pacific Northwest were highly valued by the native peoples of this region. Western hemlock was used for making teas, salves, and medicines. Western red cedar was called the "tree of life," and was used for making baskets, rope, clothes, fish traps, canoes, shelters, spear poles, arrow shafts, coffins, dishes, and a red dye. Today, Douglas fir is the most important tree species in the United States. Wood from this species is used for construction and for making plywood composite boards and paper. The bark and needles of the Pacific yew contain taxol, a cancer-fighting substance.

Some of the plants and fungi found in the temperate evergreen forest canopy are parasitic. Though they take nutrients directly from trees and other plants, they ultimately contribute to the rich mix of organic substances in the canopy and, eventually, on the forest floor.

The animals that occupy the forest canopy play an important role in the temperate evergreen forest ecosystem, eating and breaking down materials into nutrients that can be recycled. The pileated woodpecker, for example, breaks up decaying wood in its search for carpenter ants. Other animals generate compounds that foster decay or protect a plant or tree from diseases or predators.

The temperate evergreen forest canopy has important functions that affect more than the forest itself. The trees absorb carbon dioxide and release oxygen, an exchange that helps offset the excess carbon dioxide released into the atmosphere when humans burn fossil fuels. By minimizing the impact of falling rain, the canopy lessens erosion on the forest floor and reduces the amount of sediment that runs off into streams. This helps keep the streams healthy and their waters clean. The rivers and streams that run through the temperate evergreen forest carry fresh water and nutrient-rich debris to the coast, depositing essential nutrients and replenishing ocean waters. This debris is deposited near the shore creating estuaries, some of the most biologically rich environments on Earth. Some Pacific salmon spawn in such estuaries, while others stop to feed in them before continuing to the ocean.

The jumbled shrubs, tree seedlings, and ferns that collect under the towering canopy trees are collectively referred to as the understory. Most plants in the understory never grow to adult size because the dense canopy blocks out all but about 2 percent of the sunlight. Temperate evergreen forest understory vegetation provides excellent habitat and forage for insects and other forest animals which in turn contribute to the health of this layer by keeping rampant vegetation in check In some places, the understory also provides food and other products used by humans, such as huckleberries, mushrooms, bear grass, and Spanish moss. A rich, complex understory is an important part of a healthy natural forest.

Olympic (Cascade) salamander. Salamanders hunt for food on the forest floor.
Olympic (Cascade) salamander

Photo courtesy of John and Karen Hollingsworth, U.S. Fish and Wildlife Service

warty jumping slug
The warty jumping slug (Hemphilia gladulosa) is found west of the Cascade Mountains from southern British Columbia to the northern coastal mountain ranges of Oregon. Usually much smaller than the width of a dime, it may be found under mats of damp moss or in piles of rotting wood around stumps.

Photo courtesy of Stephen Dowlan

The floor of a temperate evergreen forest contains a large number of nutrients that are constantly being recycled into organic compounds that are once again used by trees. Tree limbs, leaves, needles, and duff—a substance that develops from fallen bark at the base of trees such as the Douglas fir—support plant growth, provide habitat for insects and amphibians, and gradually decompose into a rich soil layer. Fallen snags and branches provide food, first for beetles and then for mites, termites, and carpenter ants. By eating dead leaves, needles, fungi, algae, animal droppings, carcasses, and other detritus and organisms, the forest's snails and slugs (including the native banana slug) play an important housekeeping role on the forest floor and help spread seeds and fertilizer throughout the ecosystem. Salamanders, spiders, and newts hunt insects on the forest floor and serve as prey for birds and other larger animals. Eventually, winter wrens, martens, and bears take up residence in the upturned roots and hollows of fallen trees.

Hundreds of varieties of mosses are found on the coastal rain forest floor. Plants such as bigleaf maples insert roots into the spongy moss to tap stored water and nutrients. During dry periods, mosses cease photosynthesis and lie dormant, becoming active again only when the rains begin anew.

Fungi, which have no chlorophyll and therefore cannot manufacture food via photosynthesis, depend on rotting wood and leaf litter on the forest floor for nutrients. Scientists have identified about 40 different kinds of mycorrhizal fungi attached to the root systems of Douglas firs. These specialized fungi form mutually beneficial relationships with the trees' roots, helping the roots resist disease and procure nutrients: The fungi extract phosphorus from the soil and "trade" it to the tree for carbon in the form of sugars. In one shovelful of forest soil are several kilometers of tiny Mycelia, the fungi's threadlike roots.

Mycorrhizal fungi produce mushrooms on the forest floor, including underground varieties known as truffles. These are eaten by small animals, which deposit feces containing fungal spores throughout the forest. These spores are then "absorbed" by the trees, which produce the sugars that the fungi need to survive. When trees are removed from the forest, mycorrhizal fungi and other soil organisms begin to die, impairing the soil's ability to store water and nutrients.

On the temperate evergreen forest floor, dense groundcovers, such as Oregon oxalis, can prevent tree seedlings from taking root, and fallen, decaying trees often act as "nurse logs" for new seedlings. Initially, the roots of these young trees hug the nurse log, so when the log decomposes and disappears, the roots of the now-established trees resemble stilts. A column of such trees standing in a row indicates grown-up seedlings that got their start on the same nurse log.

People of the Northwest Coast
People have lived in the Pacific Northwest for more than 10,000 years. Archaeological evidence shows that in the earliest sites, people focused their activities on estuarine habitats. By 5,500 years ago, substantial shell middens appear along the coast. Also, it is not uncommon for excavated sites to produce bones and shells representing hundreds of animal species. Among vertebrates, fish remains predominate followed by aquatic and marine birds, marine mammals, and in very small numbers, terrestrial mammals.

When first encountered by the Europeans, American Indian populations along the Northwest Coast were dense and diverse. In Oregon alone, languages from five major language families--Athapaskan, Chinookan, Alsean, Siuslaw, and Coos--were spoken. Such diversity, along with archaeological evidence, suggests a long and complex history for the peopling of the coast and for the development of coastal cultures.

Clatsop Indian women
Clatsop Indian women (1894)

Oregon Historical Society

European interest in this region was spurred by the search for the Northwest Passage, a waterway that could link the east and west coasts of North America. Fur traders were the first Euro-American visitors, followed by wave after wave of emigrants via the Oregon Trail after 1841. At that time the rain forest was viewed as remote and undesirable, and travel routes to the coast were difficult. Because farmland was limited, homesteaders practiced subsistence living—hunting, trapping, gathering, fishing, raising livestock, and gardening. This subsistence economy remains a prevalent lifestyle for area residents today.

With the start of the gold rushes in California, Alaska, and Oregon in the late 1840s and 1850s, the need for lumber to build camps, towns, and mines fostered a budding timber industry. Logging and milling of lumber also intensified in response to the needs of settlers. Initially, milled lumber had to be brought from the East Coast by ship. By the 1850s, local mills began to supply lumber for settlers' homes.

Intensive logging started in the 1860s, beginning the waxing and waning cycles of timber harvest that characterize this economy. Railroad expansion and homesteading in the late 1880s, rebuilding San Francisco after the devastating 1906 fire, and World War I all created an enormous demand for timber products. The Depression of the 1930s saw a decline in timber harvests and caused a surge of displaced people into the forest uplands to follow a subsistence lifestyle. World War II also caused an increase in the nation's need for timber products, and technological advances made for a more profitable industry. In 1939, the bulldozer was invented to pick up logs and quickly build dirt roads. Mills began to use trucks to haul logs out of the woods, replacing the earlier transportation methods of railroads and water flotation. Likewise, gasoline-powered chain saws came into regular use during World War II; by the end of the war, technology allowed logging to proceed at a much faster rate.

A strong, growing economic market for logs continued after World War II into the 1950s. As timber on easier-to-log terrain was depleted, new methods were developed. Today, helicopters and hot-air balloons are used to remove logs from hard-to-reach locations. Oregon still produces more timber than any other state in the continental United States, followed closely by Washington State.

Management Challenges
The thriving logging industry in the Pacific Northwest has not been without serious environmental consequences. Clear-cutting forests and using trucks on streamside roads cause rapid erosion. Sediment-clogged waters make streams inhospitable to native fish populations and reduce water quality for human communities. Many streams have been so degraded that once-dense salmon runs are all but gone. High timber harvests and the cutting of old-growth forests have threatened wildlife populations that depend upon functioning forest ecosystems. Especially threatened are the Northern spotted owl and the marbled murrelet. Even when logged areas are replanted, plant diversity is initially low—the complex ecological interworkings of a mature forest take hundreds of years to regenerate.

Shell midden excavation
Yaquina Head, Oregon, shell midden excavation.

Fran Philipek

Federal and state agencies and communities are working cooperatively to repair damage to the Pacific Northwest ecosystems. One complication of this effort is the patchwork of land ownership in some places.

Public land managed by the BLM is intermixed with land-managed by the U.S. Forest Service and the state, and with land owned by large timber companies and individuals. This ownership pattern presents special challenges for land managers because every action taken on one parcel of land has the potential to immediately and directly affect the neighboring landowner. However, this ownership pattern does offer land managers opportunities for partnerships, shared resources, and cooperative work.

Decommisioned Road

Road decommissioning (removing the hard surface to allow revegetation).
Crooked Creek, Oregon.

Steve Cyrus

An example of one such partnership was an effort to improve fisheries in the checkerboard landscape of the Coast Range on Schoolhouse Creek in the Alsea River watershed. The BLM hired a contractor to install instream features to enhance spawning habitat for salmon. The adjacent private landowner, a timber company, planned and performed similar work on its part of the creek in conjunction with BLM. The timber company supplied logs for the BLM; in return BLM provided an equipment operator to place logs instream on the private portion. The result was 8 km of improved fish habitat.

Old-growth forest habitat and watershed issues have made management of federal forests in the Northwest contentious. By the early 1990s, with only 10 percent of the original old-growth forest remaining, controversy over the management of federal forests ran high. The result was a gridlock of lawsuits, court rulings, and polarized public debate. On one side were the timber commodity interests and communities with economic dependence on harvesting lumber. On the other side were those primarily concerned with maintaining old-growth forests and the species dependent upon them, especially the endangered Northern spotted owl.

Artist's depiction of sockeye salmon
Male sockeye salmon.

Shelly Fischman

Seeking a solution to the controversy, President Clinton held a Forest Conference in Portland in 1993, where citizens and scientists voiced their concerns. As a result of the conference, a team was assembled to prepare and assess alternative strategies that would apply an ecosystem approach to forest management, recognizing that viable communities with sustainable economies are a component of a healthy ecosystem. The result of the team's work is the Northwest Forest Plan, which applies to lands administered by the BLM and U.S. Forest Service.

As part of the Northwest Forest Plan, about 80 percent of the Northwest federal forests are now reserved from logging and are managed to protect habitat and forest species, while other areas are allocated for timber harvest. A buffer of land is reserved from use along all streams, ponds, and lakes to retard sediment flow into the water and to keep the streams shaded and water temperatures cool. The time frame for improvements on the landscape will be measured in hundreds of years. The goal of protecting and enhancing the old-growth ecosystem involves several related efforts—surveys, inventories of species, streamside improvements, and road closings.

Thousands of kilometers of roads weave through the forest, most of them originally built to access harvestable timber and without consideration for engineering methods that would have minimized erosion. The roads themselves continue to be a cause of excess stream sediment from erosion- and road-related landslides. Likewise, ready access allows more people into remote areas and increases the risk of unwanted fire. For all of these reasons, many roads are being decommissioned. All the roadbed material is removed, and the cut-and-fill areas are reshaped to replicate the original contours of the land. The area is then planted with seeds and seedlings.

Loggers cutting a tree in early 1900's
Timber felling (1905-1910), Oregon.

Oregon Historical Society

Log raft and loggers in early 1900's
Yeon and Pelton logging
company log raft (c. 1905),
Rainier, Oregon

Oregon Historical Society

Stream restoration methods include placing structures such as large rocks and logs in the stream, and replacing culverts so that they do not impede fish from moving through the stream. Instream structures slow down the water and create quiet pools. Fish eat insects that hatch in these pools and young fish are reared in them. Slow flowing water also allows the streambed to develop the gravel base necessary for the protection of fish eggs. Water quality and aquatic habitat both improve through these restoration actions.

The Northwest Forest Plan seeks to maintain both a healthy ecosystem and viable communities. However, placing large areas of forest in reserve status means that less timber is available for harvest, leaving many local timber-dependent communities with significant unemployment problems. To help remedy this situation, the Ecosystem Workforce Program (EWP) was created to link federal and state agencies in a program that maintains a highly skilled, specialized workforce within the local communities. The goal includes creating long-term, high-skill and high-wage jobs in the newly established ecosystem management industry.

The EWP has taken different routes to success. Agreements were signed between a variety of government and private entities to bring together complementary programs for training, worker identification and recruitment, ecosystem management contracting, and job needs in watershed restoration. As the trained workforce grew, partner agencies sought innovative ways to bundle contract work across agencies to create long-term jobs. As a result, work is retained within local areas, employment durations have increased, and pay and benefits meet family needs.

In addition to changing the nature of people's work, the Northwest Forest Plan has also changed how people recreate. For example, some campgrounds, many of which were built in the 1930s within stands of large old trees, may need to be closed because they are in areas designated as riparian reserves (streamside areas). Continued use of these campgrounds could frustrate efforts by land managers to restore the areas, which are critical to water quality and ecosystem health. In other campgrounds, routine maintenance has become more complicated. For example, as trees mature they are susceptible to disease and insects and they may lose branches or topple over in windstorms, presenting a public safety issue. Before implementation of the Northwest Forest Plan, it was a simple process to remove the trees or branches with minimal impact on public use of the campground. Now, a variety of studies must be completed before such maintenance can take place. Until the studies are completed and the proposed actions approved, affected portions of the campgrounds may be closed to the public for months instead of days.

Ski area expansion is another issue that stirs debate. Established ski resorts in the Cascades wish to expand their runs to accommodate snowboard enthusiasts. Yet expansion is unlikely where this would mean sacrificing parts of the forest reserves or impacting aquatic resources. Resorts must modify even their established operations to meet standards for forest and aquatic health.

While the questions of whether and how much to log the federal forests have been answered by the Northwest Forest Plan, other uses of the forest pose the same challenge—how to incorporate the needs of both human communities and ecosystem health. Science can inform decision makers about certain consequences of their choices, but it will take the cooperation of all who have a stake in and care about this unique ecosystem to ensure that it thrives. The majesty of the Northwest Forests and the remarkable web of life that supports them are a legacy that future generations should have the opportunity to experience.

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Last updated: 11-13-2009