Coastal Douglas-fir (CDF) forests and the diverse collection of ecological communities characteristic to the shores of the Salish Sea are globally rare. They are influenced by a unique interaction between climate, topography and geography, and while some CDF species can be found across borders, the combination of communities found on southern BC’s coast are found nowhere else in the world.
In this article, landscape ecologist Jan Kirkby (M.Sc., R.P. Bio) demystifies the CDF classification, explains the importance of CDF protection, and provides recommendations for individual conservation action.
What is the CDF? What are some of its defining characteristics?
The terms ‘CDF’ and ‘CDF Zone’ are usually used as abbreviations for the Coastal Douglas-fir Biogeoclimatic Zone. It is a designation of BC’s Biogeoclimatic Ecosystem Classification (BEC), which includes zone, subzone, and variant. The CDF Zone’s full name is even more of a mouthful–the Coastal Douglas-fir Moist Maritime Subzone. The CDF Zone is rich in biodiversity and home to a vast array of species, many of them at-risk and some of which are endemic to BC.
The CDF Biogeoclimatic Zone includes the low-lying portions of the southeast coast of Vancouver Island, much of the Gulf Islands, and narrow sections of the Lower Mainland and Sunshine Coast. This zone is one of the two smallest (and most threatened) biogeoclimatic zones in BC, occupying only 0.3% of BC’s land base (the other of the smallest biogeoclimatic zones in BC is the Bunchgrass (BG) Biogeoclimatic Zone in BC’s Southern Interior)1,4.
The term ‘CDF’ when talking about the Coastal Douglas-fir Biogeoclimatic Zone doesn’t just refer to the Douglas-fir tree or solely to the forest ecosystems of the CDF Zone, but the confusion is likely because Douglas-fir is generally the dominant or co-dominant tree species in forest stands and woodland ecosystems in this zone. However, ‘CDF forests’ or ‘forest ecosystems in the CDF Zone’ is a more accurate way to refer to the forests in the CDF Zone, because there are also many unforested ecosystems within the CDF Zone. These include estuaries and wetlands, beaches, dunes, and rocky headlands, grassland and shrub communities, wet meadows, and more.
Almost all of the ecological communities associated with the above broad ecosystem types in the CDF Zone (both forested and non-forested) are considered endangered or threatened by the BC Conservation Data Centre2. These include the increasingly rare and fragmented Garry oak and associated ecosystems, of which less than 5% remain in near-natural condition3. Unfortunately, the CDF Zone, the rarest of the 16 different biogeoclimatic zones in BC, is also the zone with the greatest threats to biodiversity4.
How have the ecosystems in this region changed over time?
The CDF Zone is located in BC’s coastal lowlands, which combined with their beauty, biological and ecological diversity, and mild, Mediterranean-type climate, are precisely the areas that humans find most attractive for living and working. The CDF Zone has experienced intense and escalating development pressure over decades, with many intact, natural ecosystems now completely converted to human use. Add to that the ecosystem fragmentation and degradation from deforestation, fire suppression, ditching, draining, and dredging of intact natural wetlands, invasion of alien species that outcompete less aggressive native species, and further add the stresses related to our rapidly changing climate, and you get severely compromised ecosystems that may or may not be able to withstand these pressures and stresses.
How does the fragmentation of forests impact stability and resiliency?
Fragmentation of forests reduces movement corridors that enable species movement by both plants and animals. Landscape connectivity is especially important given climatic changes that force species to shift or migrate—they need contiguous habitats and wildlife corridors in order to adapt and maintain populations. Fragmentation reduces species richness, compromises ecosystem functions such as water retention and filtration, and allows non-native species that are much better adapted to disturbed landscapes to dominate the ecosystem.
Research has also found a fascinating ‘wood wide web’ of mycorrhizal networks that connect trees and transfer the moisture and nutrients they need. Forest fragmentation disrupts this important fungal connection, impacting the health and resilience of remaining trees.
What do you want people to know about the CDF?
The BEC system does not exist outside of BC, so there is no so-named Coastal Douglas-fir Biogeoclimatic Zone outside of BC. There are some ecosystem types in parts of Washington state that are similar to those found in BC, but neither Canada nor BC have jurisdiction over or responsibility to conserve and protect ecosystems found in the United States. However, it’s important to realize that the CDF Zone is home to species and ecosystems that once existed in other provinces and states but are no longer found there, so there is a provincial, national, and even global responsibility to ensure their viability and long-term survival.
Are there actions individuals can take to secure a more stable future for CDF forests and associated habitats?
Since most of the land within the CDF Zone is privately owned, there are many ways that private landowners can ensure the long-term viability and health of ecosystems in the CDF:
- Learn about the CDF Zone, and about what types of species and ecosystems you have on your land and environs, learn about the roles they play, and the ecosystem services they provide.
- Learn how you can help to maintain and restore landscapes, attract and nurture wildlife, and avoid land use or alterations that compromise natural values and ecosystem function. Contact organizations like the Habitat Acquisition Trust (HAT) to find out how you can become a habitat steward.
- Plant native species on your property; participate in local invasive species removal efforts.
- Consider registering a conservation covenant on your land to ensure that its natural values and special features will be protected in perpetuity.
- Use your knowledge to influence and encourage informed, conservation-based land use decision making in your area and beyond. Participate in local land use decisions by volunteering to be a part of environmental advisory committees, local parks commissions, land conservation organizations, and more. Use your vote to give nature a voice.
- Participate enthusiastically in land acquisition and conservation efforts.
- Spend time walking, exploring, and enjoying nearby forests and other ecosystems. Take binoculars, a notebook, and your curious mind!
About Jan Kirkby
Jan Kirkby (M.Sc., R.P. Bio) is a landscape ecologist who has worked since the early 90s with Environment Canada, Canadian Wildlife Service and the BC Conservation Data Centre, Ministry of Environment. Her primary activities have been the collection, evaluation, interpretation, and practical application of biological and ecological information to facilitate and encourage scientifically defensible, ecologically sustainable land use policy and planning decisions. She works with federal, provincial, regional, and local government staff as well as non-government organizations and individuals, often in multi-agency partnership projects. She is currently Vice-Chair of the Garry Oak Ecosystems Recovery Team.
- Coastal Douglas-fir Conservation Partnership www.cdfcp.ca
- B.C. Conservation Data Centre. 2022. BC Species and Ecosystems Explorer. B.C. Minist. of Environ. Victoria, B.C. https://a100.gov.bc.ca/pub/eswp/
- Garry Oak Ecosystems Recovery Team. 2022. https://goert.ca/about/what-remains/
- Austin, M.A., Buffett, D.A., D.J. Nicolson, G.G.E. Scudder and V. Stevens (eds.). 2008. Taking Nature’s Pulse: The Status of Biodiversity in British Columbia. Biodiversity BC, Victoria, BC. 268 pp.
Are you looking for a way to make change?
You can help us. We would love for you to help us.
Protect bears, wolves, and cougars in the Great Bear Rainforest
Donations, no matter the size, take us one step closer to protecting bears, wolves and other carnivores. Help us stop commercial trophy hunting in more than a quarter of the Great Bear Rainforest.