Western redcedar (abbreviated as Cw) is a species with high ecological, cultural, and economic value. The CCISS projections for Cw reveal a complex pattern: potential expansion of suitability upwards in elevation and into more northern areas, and localized declines in low-elevation and drought-prone regions.
While the CCISS tool offers valuable insights into broad-scale trends, summarized here by species, suitability projections must be interpreted with caution. Many areas of projected change are also areas with high uncertainty in climate predictions. Furthermore, factors such as soil texture, drainage, land-use history, forest health pressures, and biotic interactions (e.g., competition or browsing) can strongly influence actual outcomes on the ground. These nuances emphasize the importance of pairing climate tools with on-the-ground knowledge and site-specific judgement when planning future western redcedar management.
Western redcedar (Cw) is native to the Pacific Northwest of North America, with a broad geographic range extending from northern California, through Oregon, Washington, and British Columbia, into southeastern Alaska. Eastward, it extends as far inland as the western slopes of the Rocky Mountains in Montana and Idaho.
Cw is best adapted to climates with abundant precipitation and high humidity but can tolerate a range of conditions. In BC, Cw is most commonly found in cool and cold mesothermal climates on the coast and in montane continental cool temperate climates in the interior wet belt (Klinka & Brisco, 2009). The species grows across a wide variety of soil types, but is most productive on fresh to moist, nutrient-rich soils (Klinka & Brisco, 2009).
In British Columbia, Cw is found in two distinct populations: a coastal population, and an interior population. Approximately 81% of the province’s mature Cw volume is found in the coastal population (Klinka & Brisco, 2009). These two populations are ecologically distinct due to differences in climatic regimes, topography, and associated vegetation, but genetically, they are quite similar (Klinka & Brisco, 2009). It is common for Cw to co-occur on mesic and wet sites with western hemlock (Tsuga heterophylla) throughout its range in BC.
Species environmental suitability during the reference period (1961–1990)In the maps below, each colour represents the species environmental suitability during the historical reference period* of 1961–1990 as determined by expert ratings. Green represents a high suitability (E1 rating), blue represents moderate suitability (E2), yellow represents low suitability (E3), and white indicates areas that are unsuitable for the species. See CCISS Documentation tab > Methods > Environmental Suitability Ratings for more detailed definitions and information on the expert rating process.
*Note on terminology: The historical reference period is sometimes referred to as the “baseline” or simply “historical” or “reference” period.
The pie chart to the right depicts the distribution of the total environmentally suitable area of Cw in BC by biogeoclimatic (BGC) zone, based on the climate of the historical reference period (1961–1990).
On the coast, Cw is most abundant in the Coastal Western Hemlock (CWH) zone, especially on mesic to wet sites, where it grows alongside Douglas-fir, grand fir, and bigleaf maple (Egan, 1999). It also occurs, though less frequently, in the Coastal Douglas-fir (CDF) zone and in the lower elevation of the Mountain Hemlock (MH) zones, where it tends to be subdominant or scattered.
In the interior, it is a key species in the Interior Cedar-Hemlock (ICH) zone, particularly in the wetter subzones of southeastern and central British Columbia, and in the Interior Douglas-fir (IDF) zone, although typically as a minor component. It can also occasionally be found in the wetter subzones of the Sub-Boreal Spruce (SBS), Montane Spruce (MS), Ponderosa Pine (PP), and lower Engelmann Spruce – Subalpine Fir (ESSF) zones (Government of British Columbia 2025).
On this page, you will find a visual and interpretive synthesis of the environmental suitability projections calculated using the Climate Change Informed Species Selection CCISS tool, including:
Proportion of the historic range that the species is predicted to remain environmentally suitable (i.e. persist) or become newly suitable (i.e. expand) by site type (edatope).
Predicted mean changes in environmental suitability across its geographic range in BC, by future time period and site type (edatope).
Predicted shifts in total suitable area over time across the province and by biogeoclimatic (BGC) zone.
Overall, western redcedar (Cw) is projected to persist within about 40–60% of its historically suitable range, while its suitable range is projected to expand over time, to be about 1–1.5 times larger than the historically suitable range. Expansion of Cw’s suitable area is projected to be driven by higher temperatures expected under increased warming scenarios, particularly in wetter site types (D6).
Notes on interpretation of persistence and expansionPersistence (x-axis) and expansion (y-axis) are subtly different in how they relate to the historical range of the species. Persistence describes the change in environmental suitability within the species historical range. While Expansion describes the change in environmental suitability outside of the species historical range. Calculated as follows:
\[ \text{Persistence (\%)} = \frac{\text{future suitable area within historical range of suitability}} {\text{historically suitable area}} \times 100 \] \[ \text{Expansion (\%)} = \frac{\text{future suitable area outside historical range of suitability}} {\text{historically suitable area}} \times 100 \]