The Coastal Douglas-fir (CDF) is the smallest of the 14 BC ecosystems listed in the Biogeoclimatic Ecosystem Classification system. It is restricted to low elevations along southeastern Vancouver Island, from Bowser to Victoria, the Gulf Islands south of Cortes Island, and a narrow strip along the Sunshine Coast near Halfmoon Bay.
CDF zone, shown in light green (Source: BC Government)
The CDF zone is in the rainshadow of Vancouver Island and Washington’s Olympic Mountains. Rainstorms that approach from the west hit these mountains first and discharge much of their moisture. Consequently, the summers are warm and dry, and the winters are mild and wet, although drier than most other BC coastal zones. This Mediterranean-type climate creates a unique set of conditions, allowing for a diverse group of plants and animals.
Within the CDF zone, Garry oak ecosystems occur in sites characterized by particularly shallow, dry and/or rocky soils. Some Garry oak meadows
were also maintained with controlled fire by First Nations.
Coastal Douglas-fir ecosystems are among the most imperiled coastal ecosystems. Since they occur along the coast, in regions favoured by people, they were some of the first forest types targeted for logging, and cleared for urban and agricultural development. Today, very few older forest ecosystems remain in the CDF zone, and those that do are highly fragmented. In other words, they exist as isolated "islands" among a landscape altered by human development.
What lives in Coastal Douglas-fir ecosystems?
One of the most inconspicuous but important types of organisms in Coastal Douglas-fir forests is mycorrhizal fungi. These fungi form vast networks of filaments that grow underground, on and among plant roots, in a mutually beneficial relationship. The fungi are nourished by carbohydrates exuded from the plant roots, and they in turn help the roots absorb water and nutrients. The fruiting bodies of these fungi form some of the mushrooms we are accustomed to seeing in the forest, such as chanterelles. Plant growth is greatly enhanced by mycorrhizal fungi, and some plants cannot grow without them.
About 100 species of plants are found in CDF ecosystems, including:
- Trees such as Douglas-fir, Western Red cedar, Grand Fir, Western Flowering Dogwood and (less commonly) Garry Oak and Arbutus
- Shrubs such as Salal, Dull Oregon Grape and Ocean Spray
- Herbaceous plants such as Twinflower, Bracken Fern, Starflower and Vanilla Leaf
- Mosses such as Oregon Beaked moss and Electrified Cat's Tail.
These plants, fungi and the associated soil microorganisms form the structure of the forest, and provide habitat and food for animals, including:
- Large mammals such as black tailed deer, black bear and cougar, although they are often excluded from urbanized areas
- Birds, including the Pileated Woodpecker, Yellow-bellied Sapsucker, Hairy Woodpecker, Downy Woodpecker, Steller's Jay, Raven, Chestnut-backed Chickadee, Brown Creeper, Winter Wren, and Varied Thrush, all of which eat conifer seeds or wood-boring insects. Owls, swallows and chickadees also nest in cavities made by woodpeckers, while Bald Eagles rely on Douglas-fir trees to support their enormous nests
- Red squirrels, which nest in cavities created by woodpeckers, and harvest Douglas-fir cones
- Many species of bats, which roost in the spaces behind Douglas-fir bark
- Hundreds to thousands of species of insects, that live among the forest canopy and/or near ground level
- Amphibians, including the western toad, Pacific tree frog, western red-backed salamander, Ensatina salamander and northwestern salamander
- Ten provincially rare and endangered animals species, including the Marbled Murrelet and the sharptail snake
Why are Coastal Douglas-fir ecosystems important?
Coastal Douglas-fir ecosystems help to maintain biodiversity, help to prevent flooding by soaking up rainwater, filter contaminants in runoff, purify the air, provide forestry jobs and revenue, and provide natural areas for research, recreation and aesthetic enjoyment.
Coastal Douglas-fir ecosystems host a wide assortment of plants and animals, some of which are threatened with extinction. Therefore, they contribute to genetic, species and ecosystem biodiversity, a principle very important to the survival of species and the proper functioning of ecosystems. For CDF ecosystems to survive, connections and corridors between isolated protected areas need to be established. Connections permit sufficient exchange of genes between individuals, and reduce the stresses placed on the edges of habitat "islands." This can be accomplished with corridors such as the CRD’s Sea to Sea Green Blue Belt, which links parks and other protected areas between Sooke and Saanich Inlet.
Since CDF ecosystems are adapted to warm, dry conditions, they may have a special role to play if this part of the world warms due to climate change, as predicted. If this occurs, some areas of wetter forests may die out and allow CDF ecosystems to expand. Although these changes may occur too quickly for forests to migrate naturally, people may be able to facilitate the process by establishing CDF ecosystems in restored areas. The current fragmented state of CDF ecosystems, as well as the abundance of invasive species
, creates uncertainties about how well they may be able to adapt or expand.
Particularly near urban areas, forests are valuable for providing spongy soil and organic matter that allows rainwater to soak into the ground, where it replenishes groundwater and is naturally decontaminated as it filters through rock, soil and plant roots. In contrast, rainwater that falls on impervious surfaces, such as pavement, flows across the surface, picks up contaminants, and eventually damages streams and other water bodies with sudden floods and pollution. CDF ecosystems are therefore ideal candidates for preservation and restoration projects in the Capital Region, since they naturally occur here.
An emerging industry in BC is Non-Timber Forest Products
. It involves the collection and sale of mushrooms, medicinal herbs, berries and floral greens. This type of harvesting can be carried out in a way that does not compromise the health or function of the forest; however, proper codes of practice, and consultation with First Nations do need to be ensured. Although it is just beginning, the industry shows promise in that many of these products fetch premium prices, and can be harvested continuously, unlike the practice of timber harvesting, where a lag time of 50 years or more is necessary for the forest to regenerate. Non-Timber Forest Products rely, for the most part, on the products of a mature forest ecosystem, such as those found in the CDF zone.
Douglas-fir is one of the most prized timber trees, and as such is valuable to the forest industry and economy of BC. Although logging has cleared much of the old-growth CDF forests, it can be practiced in a sustainable manner.
What threatens Coastal Douglas-fir ecosystems?
CDF ecosystems have been largely destroyed, fragmented and damaged by logging and urban, residential and agricultural development. As the human population continues to grow in this region, old-growth and older second growth forests continue to be cleared. Only about 0.5% of the land base formerly occupied by CDF forest is now composed of "older forest" (greater than 120 years old). Invasive species
also represent a major threat to CDF 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 Douglas-fir ecosystems in the Victoria area?
One of the best places to see a remnant old-growth CDF ecosystem is on the grounds of Royal Roads University in Colwood. Some Douglas-fir trees at this site are over 800 years old. The area has many trails that are open to the public.
Cathedral Grove, 20 km east of Port Alberni, is a smaller fragment of an old-growth CDF ecosystem, with some very large tree specimens. Thetis Lake Park
, Goldstream Provincial Park
and Gowlland Tod Provincial Park
also have some older second-growth CDF forest. East Sooke Park
is an excellent place to see Arbutus trees, second-growth Douglas-fir, and coastal bluffs, along the oceanside trail.
How can I help protect Coastal Douglas-fir ecosystems?
For information on protecting CDF ecosystems, please visit our How Can I Help
Additional Information & Links © Second image courtesy of Mary Sanseverino