The Coastal Western Hemlock (CWH) ecosystem dominates most of the coast of British Columbia. It lies in a broad band west of the Coast Mountains along the entire coast of BC (also extending from Alaska down through to Oregon), and also covers most of the Queen Charlotte Islands and Vancouver Island.

western hemlock 1 385
Coastal Western Hemlock ecosystem, shown in light green
(© Source: BC Government)

This ecosystem is the wettest overall in BC. The prevailing westerly winds bring storms off the Pacific, which push up against the Coast Mountains and release most of their moisture. The ocean moderates winter temperatures, while the mountains act as a barrier that prevents cooler continental air masses in the interior from moving west. All this results in a large amount of rain, and mild winters, creating the perfect conditions for the highly productive CWH ecosystem — also sometimes called a temperate rainforest.

What lives in Coastal Western Hemlock ecosystems?

Plant growth in CWH ecosystems is very lush, due to the mild winters, high rainfall and a long growing season. Coniferous trees in CWH ecosystems can reach massive proportions. Common varieties include western hemlock, western red cedar, Amabilis fir, and in some places Sitka spruce and yellow cedar. Other common plants include:
  • A well-developed shrub layer composed of Huckleberry, Alaska blueberry, salal, and dull Oregon grape
  • A fairly sparse herb layer composed of deer fern; and a diverse moss layer
The CWH ecosystem harbours an enormous variety of wildlife, including most of the important coastal species. Examples include:
  • Large mammals such as black tailed deer, black bear, coyote, grey wolf and grizzly bear (on the mainland)
  • Most species of resident and migratory seabirds, shorebirds and waterfowl, and forest-dwelling birds such as Great Horned Owl, Barred Owl, Blue Grouse, Ruffed Grouse, Band-tailed Pigeon, Pileated Woodpecker, Northern Flicker, Hairy Woodpecker, Common Raven, Grey Jay, Steller's Jay, Varied Thrush, Chestnut-backed Chickadee, Red-breasted Nuthatch, Winter Wren and Vaux's Swift
  • Small mammals such as raccoons, river otters, mink, pine marten, squirrels, mice, voles and bats
  • Amphibians such as northwestern salamander, western red-backed salamander, Ensatina salamander, clouded salamander, and western toad
  • Countless species of insects and other invertebrates
CWH ecosystems do not only include forests; bogs are also a common component. Bogs are characterized by saturated acidic soil conditions, peat (Sphagnum moss), cool temperatures, and a slow rate of decomposition that results in a deep layer of organic matter. Shrubs such as Bog Blueberry, Labrador Tea, Bog Cranberry, Crowberry, and stunted trees often grow in bogs.

Why are Coastal Western Hemlock ecosystems important?

Since they cover such a large portion of coastal British Columbia, CWH ecosystems are important for harbouring the many species of plants, animals and microbes that live within them. Biodiversity, within the genes of a species, among different species and among ecosystems, is very important for increasing the resilience of living systems to disturbances such as disease, fire and climate change.

Some of the components of CWH ecosystems include forests, watersheds, wetlands, streamsmarine shorelines and riparian areas. These ecosystems provide us with many ecosystem services that are necessary for sustaining and benefiting people. Some examples of these services include purification of the air and water, provision of materials and food, pollination of wild and cultivated crops, nutrient cycling, water supply and regulation of water flows, recreation and cultural uses.

What threatens Coastal Western Hemlock ecosystems?

western hemlock 2  166x268 tall CWH ecosystems are threatened principally by the tremendous rate of change that is occurring throughout most areas in BC as the human population grows and expands.

Logging, while an important part of the economy and culture in BC, can take its toll on coastal forests. The large amount of rainfall on the coast makes CWH ecosystems particularly susceptible to erosion and loss of nutrients from exposed soil. Awareness is increasing about the need to practice more sustainable logging.

Development of urban, industrial, agricultural and residential areas, usually involving clearing the land of forest, is occurring at ever greater rates. This results in the loss and fragmentation of CWH ecosystems. Although some impact may be an inevitable consequence of development, principles of "Smart Growth" are now coming more to the forefront, as a way to concentrate development in areas that have already been altered, and to plan communities for a minimal impact on the surrounding natural areas. 

Invasive species are an ever-present threat to CWH ecosystems. Plants and animals that have been accidentally or intentionally imported from distant areas can upset the natural balance in ecosystems, by competing for food, growing sites and habitat.

Where can I see Coastal Western Hemlock ecosystems near Victoria?

Victoria itself is situated in the Coastal Douglas Fir ecosystem, which covers a narrow zone along southeastern Vancouver Island. However, past Sooke, to the west of Victoria, the Coastal Western Hemlock ecosystem predominates.

The Juan de Fuca Trail is a provincial park that spans a narrow fringe along southwestern Vancouver Island, between China Beach, near the community of Jordan River, and Botanical Beach at Port Renfrew. Some old-growth forest remnants exist in the park, among second growth. The trail itself is a 47 km long wilderness trail, with a number of day access locations.

Most other parks and wilderness areas on Vancouver Island contain CWH ecosystems. Some popular examples are Pacific Rim National Park (including the popular West Coast Trail and Long Beach) and Carmanah Walbran Provincial Park.

How can I help protect Coastal Western Hemlock ecosystems?

For information on protecting CWH ecosystems, please visit our How Can I Help section.

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