HENRY LANSFORD

Among the many natural ecosystems of our planet that are threatened with disruption or destruction by human activities, the rain forest has become one of the most venerated icons of the environmental movement. Partly because their preservation has been taken up as a cause celebre by such high-profile advocates as actor Robert Redford and rock superstar Sting, tropical rain forests have been the focus of a great deal of attention from the news media and the public. Vast areas in South America, Southeast Asia and Africa--treasuries of biodiversity that play a key role in the chemical balance of the global atmosphere--are rapidly being deforested by logging, farming and ranching. Less than half of our planet's tropical rain forests still stand, and the destruction continues at the frightening pace of some 50,000 square miles each year.

Not all rain forests are tropical, however. Although the rain forests of the temperate zones are not as extensive or as well publicized as those that lie between the Tropics of Capricorn and Cancer, they are just as fragile, complex and fascinating. In North America, temperate rain forests stand on Washington's Olympic Peninsula, along the west coast of Canada's Vancouver Island and in southeastern Alaska. In the southern hemisphere, they are found in Chile and Tasmania.

Temperate rain forests are similar to tropical ones in some ways. They both have big trees with crowns that grow together to form closed canopies; a lush understory of smaller trees, shrubs and vines; and lots of epiphytes--plants that draw their nutrients from the air and rain--growing on tree trunks and branches. There also are many differences. Tropical rain forests have more varieties of plant and animal life. Many temperate-zone species became extinct during the frigid periods that we call ice ages, but tropical species have been evolving without interruption for a hundred million years. A National Academy of Sciences report estimates that a typical four square miles of tropical rain forest contains 100 species of reptiles, 125 species of mammals and 400 species of birds. Temperate rain forests have fewer species, but they appear to support a greater biomass--total amount of living matter--per square mile, as their trees tend to be taller and more massive. Much more animal life--monkeys, birds, frogs and lizard--lives in the canopies of tropical rain forests. Many of these tree-dwelling creatures make raucous noises, and some others, such as leeches, snakes and spiders, have habits that are generally regarded by North Americans and Europeans as obnoxious at best and dangerous at worst. Most of the animals in temperate rain forests live on the ground and tend to be quiet and inoffensive. On the whole, the temperate rain forest is a kinder, gentler place than the tropical version.

What is a rain forest? In the simplest sense, whether tropical or temperate, it is simply a forest that gets a lot of rain--by scientific definition, upwards of 100 inches of precipitation a year. In wet tropical regions of South America, Africa and Australia, as well as many tropical islands, that amount of rainfall is not exceptional. But in temperate forests, it usually occurs only in coastal regions between 45 and 55 degrees latitude where west-facing mountain ranges rise abruptly from the ocean's edge. Such regions also are characterized by cool summers and moderate winters with temperatures that seldom drop below freezing, providing a very benign physical environment for the survival and growth of trees and many other plant and animal species. The conditions are especially favorable in the west-facing valleys of the Hoh, Queets and Quinault Rivers along the Olympic coast, where the trees grow considerably bigger than they do in the Canadian and Alaskan rain forests farther to the north.

The Olympic Peninsula is dominated by the soaring peaks of the Olympic Range, which rise nearly 8,000 feet above sea level. These mountains dramatically illustrate the role that topography plays in the weather patterns that nurture temperate rain forests. The official U.S. annual precipitation record--184.56 inches in 1931--is held by the weather station at Wynoochee Oxbow on the western side of the Olympic Range. But the town of Sequim, Washington, less than 50 miles away at the northeastern foot of the mountains, averages only 16 inches of precipitation annually. The meteorological explanation is simple. As the prevailing westerly winds bring moist air over the peninsula from the open Pacific, they are forced upward by the western slope of the mountains. The moist air cools and expands as it rises, and its moisture changes state from water vapor into liquid droplets or ice crystals. As a result, the 7,965-foot summit of Mount Olympus gets an estimated 200 inches of rain and snow annually, and the west-facing river valleys along the Olympic coast are bathed in gentle rain throughout the long, mild winter wet season and have many damp, foggy days even during the relatively dry summer. On the other side of the mountains, the now-dry, downward-flowing air grows warmer and denser, which allows it to retain even more water vapor. Thus Sequim, located in this so-called "rain shadow" of the Olympics, gets about the same amount of rain as Denver, which stands on the semiarid high plains at the eastern foot of the Colorado Rockies.

One defining characteristic of North American rain forests is the predominance of Sitka spruce (in the southern hemisphere, the dominant species are a variety of beeches--broadleaf evergreens of the genus Nothofagus). Western hemlock and bigleaf maple also are common in the Olympic rain forest, and Douglas-fir grows in clearings opened up by fire or windstorms. Stands of western red cedar, which likes a lot of moisture, dominate marshy areas, and red alders thrive along the river banks. Sitka spruce and western hemlock trees often grow in regular rows known as colonnades. Because the plant growth in the rain forest is so lush and the forest floor is covered with a dense mat of living and dead vegetation that can be two or three feet deep, the competition for growing space is intense--seeds have a hard time finding a place to germinate and take root. Colonnades result when seedlings sprout in the relatively open areas atop fallen tree trunks known as nurse logs. As the trees grow, their roots reach down around the sides of the nurse log, which eventually rots away, leaving a straight row of trees standing on arched roots like stilts. Isolated specimens on stilts result when seedlings sprout atop stumps.

Spruces, hemlocks and other trees grow to prodigious sizes in the old-growth temperate rain forest of the Olympic Peninsula, reaching 300 feet in height and more than 20 feet in circumference. The largest known specimens of Douglas-fir and western red cedar are found there. To see the record Douglas-fir, you have to hike about three miles up a trail beside the Queets River, but the biggest cedar, a contorted old giant about 170 feet tall, stands in the middle of a logged-over area less than two miles by gravel road from the main traffic artery of the peninsula, U.S. Highway 101.

The dense canopy of leaves above the rain forest filters the light, suffusing the air with a hazy green glow. A lush and jungly profusion of vines, mosses, lichens, and ferns drapes every trunk and branch. Although epiphytes such as club mosses and liverworts survive without any contact with the ground, they are not parasites--they draw nourishment from the air and rainwater, not from their host trees. Ferns flourish everywhere, and the forest floor is carpeted with low plants such as oxalis, which looks like an overgrown shamrock. Thousands of kinds of mushrooms grow in the Olympic rain forests; some are still unnamed and unclassified.

The intricate ecological fabric of the Olympic rain forests also includes a great diversity of animal life, ranging in size from Roosevelt elk, cougars and black bears down to river otters, jumping mice, shrews and bright yellow banana slugs. The elk play a key role in the dominance of Sitka spruce over western hemlock. The hemlock produces more seeds than the spruce and thrives in heavy shade, so it logically should dominate the forest. But elk browse on young hemlocks and ignore the spruces, reducing the rate of hemlock population growth.

Although the rain forest of the Hoh, Queets and Quinault valleys is well protected by its inclusion within the boundaries of Olympic National Park, it is only a remnant of a much larger forest that was cut down for timber. Scientists who have studied the existing Olympic rain forest say that its relatively small size limits its genetic diversity. Logging and other human encroachment also threaten temperate rain forests in Canada, Alaska and the southern hemisphere.

The Olympic rain forest is a pleasant and peaceful place to spend some time walking, observing and meditating. It presents a sweeping and provocative panorama of birth, growth, death and decay. The infant seedlings fighting for growing space atop the rotting cadavers of fallen giants, the standing trees of many ages from youth to senescence, the profusion of large and small organisms competing for support and nourishment from a benign natural environment--all this rich diversity of life forms and survival strategies can tell us a lot that we need to know about this planet where we live.

Author's note: I am grateful to Prof. Robert L. Edmonds of the College of Forest Resources, University of Washington, for providing some fundamental but valuable information about the definition and structure of temperate rain forests. However, I take total responsibility for the way I have used that information in this article.