Great Bear Rainforest

Ecology of the Coastal Temperate Rainforests of British Columbia

Countless complex and unique ecological processes take place in ancient forests, most of which we do not fully understand (Crow 1990). There are several defining characteristics of ancient temperate rainforests on the west coast of North America. They contain many different kinds of trees of all ages but most of which are between 250 and 1000 years old (Bunnell and Chan-McLeod n.d.).

Both understory plants and small trees thrive beneath gaps in the forest canopy. Pounded by centuries of wind and rain, the canopies of ancient rainforests are rugged and uneven with many broken tree tops, and the upper branches of ancient trees are often covered with thick layers of moss and lichen. The diversity of lichen begins to increase when a forest is 150 years old and continues to increase until the forest is 350 years old. For this reason, lichen, perhaps more than any other group of organisms, are prime indicators of very old forests (Cannings and Cannings 1996).

Water

The North American temperate rainforest is located on the eastern edge of the Pacific Ocean, the largest body of water in the world. The forest and the sea are intimately connected in this unique ecosystem. Ocean winds and rain influence the character and species distribution of the trees, plants and animals that reside in the rainforest. Rivers and streams carry fresh water and nutrient-rich organic debris to the coast, replenishing the ocean waters and endowing them with essential nutrients. Trees and plants supply organic debris by shedding their leaves or needles, or by falling into the water after they die (Maser and Sedell 1994) (Cannings and Cannings 1996).

The nutrients and organic debris carried through the forest in rivers concentrate near the shore, creating estuaries which are one of the most biologically-rich environments on earth (Cannings and Cannings 1996). Shellfish such as mussels, clams and crabs break down the organic debris, thus adding even more nutrients to the estuary and marine environment (Kellogg 1992).

BC's estuaries are globally important habitats for fish, shorebirds and waterfowl. Some species of salmon spawn in estuaries while others stop to feed there during their migration to the ocean (Nehlsen and Lichatowich 1997). Migrating birds such as ducks, geese and swans travel from Siberia, Alaska and other parts of western Canada every fall to reap the bountiful harvest of seaweed and salt marsh plants (Cannings and Cannings 1996). Many coastal birds, such as the rare trumpeter swan, depend on the sheltered waters of rainforest estuaries for winter refuge (Bunnell and Chan-McLeod n.d.).

Plants and animals in other coastal areas also depend on the forest for their sustenance. Shallow tidal zones are home to over 600 different kinds of seaweed which are nourished by the water flowing from the forest. The seaweed in turn shelters over 70 species of sea star, a greater diversity than on any coast in the world. The coastal rainforest also nourishes underwater kelp forests dominated by giant kelp and bull kelp. These kelp beds provide food and shelter to hundreds of species, such as sea otters. Rivers and streams also transport nutrients to needy plants throughout the forest (Cannings and Cannings 1996). In addition, organic debris generated from the stream-side vegetation feeds everything that lives in the stream, from bacteria and fungi to insects and fish (Sedell 1990).

Despite the importance of streams and rivers, they are only one part of the system that controls the movement of water and nutrients in the forest. The forest canopy also plays an important role by catching snow and rain and then releasing it slowly to the ground, thus preventing floods and landslides (Franklin 1994). Thick beds of moss, which cover the ground like giant sponges, help canopies moderate water flows by absorbing and filtering excess moisture. When water does reach the forest floor, it is channelled down the sides of steep rainforest valleys, through a maze of dead, hollow underground tree roots, thus preventing winter storms from washing away forest soils (Beebe and Wolf 1991).

Soil

The soil in BC's temperate rainforest is maintained by a continual accumulation and decomposition of organic debris such as twigs, logs, flowers and animal feces and carcasses. Trees, plants and animals provide an endless supply of this debris and thus protect, nourish and replenish the shallow layers of organic soil. The debris is continually eaten by a host of bacteria, fungi and algae, causing it to decompose and release stored nutrients such as potassium, nitrogen and phosphorus that trees need to survive (Norse 1990).

Pacific Salmon Five species of Pacific salmon (plus steelhead) live in the waters of the coastal temperate rainforest and adjacent landscapes. Nearly all of the streams, rivers and estuaries in the bioregion, extending from northern California to Alaska, are (or were) part of the salmon's extended home. Salmon begin their lives in rainforest streams, large rivers and in coastal estuaries and then migrate to the sea. They remain in the ocean for one to five years and then return to the streams of their birth to spawn (Nehlsen and Lichatowich 1997). Salmon are a key component of the rainforest ecology. Returning salmon substantially enrich carbon and nitrogen cycles in the vicinity of spawning areas and at least 22 forest and sea mammals and birds feed on salmon (including bears, eagles, orcas and sea lions). Salmon also play an important role in human societies. They have been a dominant part of the culture and diet of coastal indigenous people for thousands of years. Today, they are also of great economic and cultural importance to non-Native communities (Nehlsen and Lichatowich 1997). Healthy, multi-aged forests play a critical role in stream health and salmon survival. Streamside tree cover provides shade in summer, keeping salmon stream temperatures cool and ensuring salmon, which cannot tolerate high water temperatures, survive the drier, hot summer months. Clearcutting, particularly on steep slopes, can have a significant negative impact on fish and fish habitat. Landslides due to unstable slopes or poor road-building can cause debris to bury the gravel spawning beds in streams, smothering salmon eggs. Without the forest root systems to regulate water flow into salmon streams, torrents can wash away gravel spawning beds. A report from the Bolle Center for Forest Ecosystem Management details these problems: "Logging in numerous small streams in the Queen Charlotte Islands profoundly altered channel conditions and resulted in loss of cover habitat and dramatically less over-winter survival of coho salmon (Hicks et.al. 1991)." An intensive, long-term study of Carnation Creek on Vancouver Island revealed that subtle changes in erosion processes, streambed sediment, and water temperature can cause decline or collapse of salmon populations downstream of logged areas (Scrivener and Brownlee 1989). According to a study by the American Fisheries Society, in British Columbia 142 stocks of salmon are now extinct and another 624 are considered "at high risk of extinction" because runs have fallen to less than 200 fish. Photo: Ian McAllister

A constant supply of organic debris is essential in wet climates because nutrients are washed out of the soil very quickly by rains (Pojar, Klinka and Demarchi 1991). Trees in BC's rainforest get almost all of their nutrients from a shallow layer of organic soil near the surface of the forest floor (Cannings and Cannings 1996).

In a shovel full of rainforest soil there are kilometres of thin threads of mycelia, the root-like threads of fungi, which evergreen trees need to stay healthy. The most important of these fungi are mycorrhizal fungi. Mycorrhizal fungi form mutually beneficial relationships with tree roots, helping them extract nutrients from the soil and resist disease (Hammond 1991).

By attaching themselves to the tips of roots and reaching out into the soil to absorb nutrient-rich water from a much larger area than the tree could on its own, the fungi gather phosphorous and 'trade' it to the roots for carbon. Mycorrhizal fungi also strengthen the immune systems of trees and produce growth-regulating chemicals which help trees live longer, healthier lives. An ancient Douglas-fir may have up to 40 different kinds of these fungi attached to its root system at all times (Pielou 1996).

Mycorrhizal fungi are found primarily in mushrooms which grow both above and below the ground and are spread through the forest by the wind and in the feces of small animals. Underground mushrooms are called truffles and are abundant in and around big dead trees (Maser 1994). Their odour is irresistible to small animals such as flying squirrels, voles, chipmunks and deer mice. These animals dig up the truffles, eat them and then deposit spores full of mycorrhizal fungi throughout the forest in their droppings (Cannings and Cannings 1996) (Hammond 1991).

For this reason, many of the giant trees in ancient forests are dependent on animal droppings and mushrooms (Maser 1994). The fungi in turn depend on sugars produced by the trees for their survival. When trees are removed from the forest, the mycorrhizal fungi and other soil organisms begin to die. When soil organisms die, the soil's ability to store water and nutrients decreases and gradually the soil becomes inhospitable for all but a few opportunistic plants (Perry 1990, 1994).

Trees

The size and shape of a tree is determined by its genetic make up, but its growth is effected by environmental factors such as moisture, light and competition from other trees (Kavanagh 1993). Short, mild winters, combined with an abundance of moisture and ample sunlight, create perfect conditions for huge plant growth in coastal British Columbia (Alaback and Pojar 1997).

At every point from below ground to 200 feet in the air, trees stretch out their surfaces to receive what the sky and earth have to offer. A tree is like a vast collection system, gleaning light from the palest winter sun and moisture from the thinnest fog (Kelly and Braasch 1988). There are up to 60 million needles on a single ancient tree with a cumulative weight of 200 kilograms (440 pounds). If these needles were spread out on the ground, they would cover a surface area of 10 football fields (Waring 1979) (Maser 1989).

Needles are so well adapted to combing moisture from fog and mist that approximately one quarter of the annual moisture in the rainforest comes from water dripping off the needles of trees (Kelly and Braasch 1988). For this reason, forested land is believed to collect and return to the air at least 10 times as much moisture as bare, deforested land, and twice as much moisture as land covered by plants other than trees (Young 1985).

One ancient tree also supports thousands of smaller specialized plants, insects and animals. The huge upper branches of old trees are covered with debris, moss, lichen and organic soil which is often several inches thick and supports entire communities of small mammals and birds. Some animals, such as the tree vole, spend their entire lives in the top of an old tree. Tree voles survive by eating needles, licking them for water and using them to build their nests (Kelly and Braasch 1988).

The Life of Dead Trees

When trees die it is usually a result of an accumulation of injuries caused by lightening, wind and fire, or disease and insect infestation. Once dead, trees either get blown to the ground or remain standing. Either way, big, old, dead trees are a very important part of the rainforest (Maser 1989, 1994).

Trees that remain standing after they die are called snags. Snags may stand erect for up to 200 years. In the first six years of a snag's existence, beetles chew tunnels throughout the outer layers of wood and introduce wood-decaying fungi and bacteria with their feces. Woodpeckers feed on the beetles and the tree's branches begin to fall off. Bats use the spaces under the loose bark of the snag for roosting and rearing their young (Maser 1989).

During the ensuing decades, the snag's wood softens enough for cavity-nesting birds to excavate new residences. Only ancient trees grow big enough to accommodate these birds. These cavities, when vacated by their initial residents, provide other birds and small mammals with warm winter and cool summer homes, giving them the temperature stability they need to survive (Maser 1989).

As more decades pass, the snag shrinks in height and width, and after a half century, only the largest branches remain attached to the trunk. When the branches fall off, sunlight is able to reach the forest floor, allowing species of plants and trees that need light to grow. As decades turn into centuries, trees and shrubs begin to grow on the snag, using its soft nutrient-rich wood as soil (Maser 1989).

When an ancient tree dies and falls to the ground, it starts ecological processes which may continue for more than four centuries. As with snags, beetles enter the downed logs first and introduce fungi and bacteria which further the processes of decay. The beetles are quickly followed by mites, termites and carpenter ants which hollow out galleries that salamanders, spiders and newts use to hunt for food. These teeming populations of insects become food for birds and mammals (Kelly and Braasch 1988). Eventually, winter wrens, marten and bears may nest or den in the upturned roots or hollows of fallen trees (Bunnell and Chan-McLeod n.d).

Tree seedlings germinate on dead trees because the dead trees' spongy, nutrient-rich wood provides an ideal nursery. As decades pass, a small number of trees grow to maturity with their exposed roots hugging the nurse log. Eventually the nurse log completely disappears, leaving the trees it nurturedstanding on stilts. As the tree decomposes it releases its stored nutrients back into the forest floor, which is why the area between the soil and the bottom of a log is the most nutrient-rich place in the forest (Maser 1989, 1994).

Under the Trees

Plants in BC's rainforest often form a nearly impenetrable thicket under the towering ancient trees. This jungle of shrubs and tree seedlings is collectively referred to as understory. A rich and complex understory is an important part of a healthy natural forest.

Understory plants have diverse habitat needs, some requiring constant sun, others needing constant shade, some liking swampy areas, while others prefer dry places (Alaback and Pojar 1997) Dense salmonberry thickets thrive in areas with rich soils and lots of light. The leathery, evergreen leaves and small bell-shaped flowers of salal bushes are familiar to anyone who has visited the rainforest in BC. Salal grows in dry areas and thrives on poor soil. Red huckleberry grows best on fallen logs and is seeded through bird droppings. Huge skunk cabbages grow in very wet, nutrient rich sites and fill the air with their pungent, skunky odour in early spring (Cannings and Cannings, 1996). The only BC plant with bigger leaves than skunk cabbage is devil's club, whose infamous prickly leaves can be up to 46 cm (18 inches) across (Young, 1985).

However, nothing characterizes BC's rainforest more than the abundant waist-high thickets of ferns. The most common types are deer, sword, bracken and small licorice ferns which grow in living tree trunks. Understory plants provide food for insects, animals and in some cases humans.

Disturbance and Succession

Forests are continually modifying themselves. The basic pattern by which forests alter and recreate themselves are called disturbance and succession.

Forests everywhere have a history of disturbance of one kind or another. Some disturbances are quite mild, such as a single tree or clump of trees falling over after they have been hit by lightening. Other disturbances can be catastrophic, such as when a fire destroys large areas of forest. Natural disturbances are a normal and necessary part of the ecology of all forests (Perry 1990, 1994).

Different forest types are adapted to specific kinds of disturbances (Perry 1990, 1994). Small disturbances are common and beneficial in BC's rainforest. For example, in coastal British Columbia trees are easily blown over, as they get their nutrients near the surface of the soil and therefore have shallow roots (Bunnell and Chan-McLeod n.d.). These small disturbances allow light to penetrate the forest canopy and nourish plants on the forest floor, and create nurse logs which enable many different kinds of trees to grow (Franklin 1994).

Huge winds, like hurricanes, are uncommon in coastal British Columbia and the constant moisture helps prevent fire. Therefore, unlike most forest types, large disturbances are uncommon (Kellogg, 1992). On the very rare occasion when large scale disturbances do occur, they neither kill all of the trees nor remove the wood. Even large, very hot fires leave pockets of unharmed trees (Bunnell and Chan-McLeod n.d.).

Industrial foresters often claim that clearcutting mimics natural disturbances in BC's rainforest. However, a natural opening in these rainforests is generally less than two tree lengths in diameter, unlike clearcuts (Meidinger and Pojar, eds. 1991).

Succession is the long-term survival pattern of forests. It is the process whereby the forest vegetation adjusts to ensure that the landscape remains alive after a disturbance. For example, after a landslide, a diverse mixture of shrubs, herbs and pioneer species of trees will begin to grow. Pioneer species of trees are those which can only grow in exposed conditions and therefore are the first to reforest a disturbed landscape. Red alder is the most common pioneer tree species in British Columbia. Pioneer species are important because they replace nitrogen in the soil and provide new forest cover (Young, 1985).

In the rainforest, once red alder is in place, western hemlock will slowly start to grow. After pioneer species have reestablished a forest, their dead leaves and trunks start to decompose and rebuild the soil so that the trees that are to dominate the landscape over the long-term are able to grow again (Young, 1985).

Industrial foresters, anxious to have commercially valuable trees grow sooner, often try to kill pioneer species of trees with fires or herbicides.

Creatures of the Rainforest

The most varied forest habitat in Canada is in coastal BC. The massive size of the trees, the hospitable climate, and disparate landforms, including islands, plains, estuaries, streams, lakes, lush forest and mountain peaks, provide suitable homes to one of the most diverse populations of animals in the northern hemisphere (Bunnell and Chan-McLeod n.d.).

Many rainforest creatures depend on the specific ecological characteristics of the ancient rainforest to survive. One such creature is the pileated woodpecker which is the largest species of woodpecker in the rainforest, growing up to 46 centimetres (18 inches) long. These woodpeckers build their nests by hollowing cavities in ancient trees. After they leave, their abandoned homes are used by many other creatures, including tree swallows, chickadees, bushy tailed woodrats, martens, bats and owls (Maser 1989).

Grizzly Bear Historically, grizzly bears roamed more places in the world than any other kind of bear, finding wild homes in Europe, Asia, North Africa and North America. Today, there are very few wild areas left on earth big enough to sustain a population of grizzly bears. European grizzlies are barely surviving in small, isolated pockets in Scandinavia, have been completely extirpated from all but a few places in western Asia and are extinct in Africa, and only have healthy populations in Russia. The grizzly population in North America has decreased by half in the last century and 99 per cent of their habitat has been destroyed in the United States south of the Canadian border (MacHutchon, Himmer, Bryden 1993). The rainforest on the central and north coasts of British Columbia is one of the very few remaining wild places in the world big enough to support a healthy population of grizzly bears. Half of Canada's grizzlies make their homes on BC's coast and have evolved there for a millennia in the ancient rainforest. Grizzly bears are prominent in the stories, songs and dances of coastal First Nations, who regard these bears as healers (Ministry of Environment, Lands and Parks 1995). The traditional wisdom of the Nuxalk First Nation tells that bears know which roots and herbs to seek when they are injured or sick. Grizzly bears thrive in the most productive parts of the ancient rainforest. Scientific studies demonstrate that they spend most of their time on low elevation mountain slopes, the bottoms of river valleys, floodplains, wetlands and in estuaries, gorging themselves on berries, devil's club, clams, salmon and colonies of insects in rotting wood. Grizzlies prefer to hibernate under the canopy of the ancient rainforest and most often build their winter dens in the bases of huge hollow ancient trees (MacHutchon, Himmer, Bryden 1993). Grizzlies need very large expanses of secure habitat to survive because they are solitary creatures with high resource demands. They are also especially vulnerable to extinction because, even under ideal circumstances, grizzlies reproduce very slowly. On average, a female grizzly only conceives every three years, producing approximately eight cubs in her lifetime. Female bears will only conceive if they can find sufficient food to build up their fat reserves enough to support both the mother and the fetus during hibernation (Ministry of Environment, Lands and Parks 1995). Logging is increasingly fragmenting BC's rainforest, rendering many of the places grizzlies hunt barren. Although bears may initially feed on the berries that grow in clearcuts, they cannot hunt for food in the tree farms that inevitably replace them because few understory plants grow in tree plantations. This threatens the survival of grizzly bears because when the quality and quantity of habitat decreases it takes female bears longer to build the fat reserves they need to conceive, so they reproduce more slowly. In addition, logging roads disrupt the bears natural travel routes and provide easy access for hunters and poachers (Ministry of Environment, Lands and Parks 1995). Clearcut logging has already drastically reduced, and in some cases locally extirpated, grizzly bear populations in coastal British Columbia (Archibald, Ellis and Hamilton 1987). Grizzly bears were listed as vulnerable to extinction by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1992. BC's coastal grizzlies will likely face extinction in the next four decades if logging operations continue to move north up the coast. Photo: Ian McAllister

Coastal BC and southeast Alaska are also home to the largest population of bald eagles in the world. These massive birds rely on many types of huge ancient trees to build their nests. Marbled murrelets are another species of bird that can only live in ancient rainforests. Murrelets are characterized by their short wings which they use to propel themselves under-water in pursuit of fish (Maser 1989). Pairs of murrelets spend most of their lives in the sea but the females fly inland up to 64 kilometres (40 miles) to nest. They lay a single egg in a shallow depression in the moss on branches of trees that must be at least 60 metres (200 feet) tall. These birds are now classified as threatened with extinction because clearcut logging is reducing their old-growth nesting habitat (Henderson, Bindernagel and Blood 1996).

Northern flying squirrels are another creature which can only live in ancient forests. These squirrels make their homes in any cavity large enough to accommodate them, usually preferring those abandoned by woodpeckers. Northern flying squirrels are most abundant in areas that have large numbers of slowly decomposing old trees, as they feed mainly on truffles. They also depend on gaps in the forest canopy, as they hunt for food by jumping out of trees and gliding through the forest from one tree to another (Maser 1989) (Cannings and Cannings 1996).

One ancient tree in BC's rainforest may be so large and structurally complex that it can provide breeding habitat for several different bird or mammal species. In a single ancient Sitka spruce, brown creepers might live under the bark three metres (10 feet) off the ground, a pileated woodpecker may have its nest in a cavity 15 metres (49.5 feet) from the forest floor and a marbled murrelet may lay her egg on a tree limb 40 metres (132 feet) off the ground. If these creatures are unlucky a predator such as a red squirrel or a marten may also have a home in the tree (Bunnell and Chan-McLeod, n.d.).

The Pacific giant salamander, the largest salamander in Canada, is one of many amphibians that can only live in the ancient rainforest. They share streams with tailed frogs and are also eaten by them. Tailed frogs are the most primitive frogs in North America and have evolved to breed in cold, swift rainforest streams. Their tadpoles have sucker devices that enable them to adhere to rocks (Maser 1989). Tailed frogs are classified as vulnerable to extinction by the government of BC, primarily due to the destruction of stream habitat caused by clearcut logging.

Some mammals that live in alpine areas in warmer months migrate to rainforest valleys during the winter (Bunnell and Chan-McLeod n.d.). Black-tailed deer and Roosevelt elk survive winter months by finding shelter in ancient forests and eating lichen and needles which grow on old trees. Clearcutting is causing serious declines in the populations of these animals on northern Vancouver Island (Young 1985).

Mountain goats spend most of their lives in alpine areas but ancient forests provide them with necessary protection from cold temperatures and heavy winter snowfall. Like the deer, they also depend on needles and lichen for food during harsh winter months. Wolves spend their winters in the forest, hunting the deer and goats (Henderson, Bindernagel and Blood 1996).