Douglas-fir (abbreviated as Fd) is one of the most prevalent and valuable tree species in British Columbia. The CCISS model predicts warmer temperatures will facilitate increased suitability of Fd throughout much of its current range and expansion of suitable range at higher elevations and further north, especially on mesic and drier sites. Fd is predicted to become less suitable in the hottest and driest sites, i.e. valley bottoms of the Southern Interior.
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 Douglas-fir management.
Douglas-fir (Fd) is native to the Pacific and Cordilleran regions of Western North America. In BC there are two varieties, interior Douglas-fir (Pseudotsuga menziesii var. glauca) found throughout the Central and Southern Interior and coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) found along the south coast and Vancouver Island. It is most common in the montane zone, but also occurs in the submontane zone and to a lesser extent subalpine zone (Klinka et al., 2000).
Fd is best adapted to cool/warm temperate and cool (warm) mesothermal climates (Klinka et al., 2000), occurring from the humid maritime coastal climate to the semi-arid continental climate of the interior. The distribution of Fd in the interior of BC represents its northernmost latitudinal range, limited by cold temperatures. Fd is also limited by high-elevation and forest-grassland transitions (Griesbauer & Green, 2010).
The growth response of Fd to climate varies over the species’ broad geographic and climatic range. Fd populations growing in relatively warm and dry climates are limited by growing season precipitation and water availability (Case & Peterson, 2005; Griesbauer & Green, 2010; Watson & Luckman, 2002), with trees on drier stands having greater sensitivity to drought conditions (Adams & Kolb, 2005). Meanwhile, Fd populations growing in high-elevation wet and cold climates are limited by snowfall, and cold annual and winter temperatures (Case & Peterson, 2005; Griesbauer & Green, 2010).
Fd has a wide ecological amplitude, but is most commonly found on moderately dry to slightly dry sites with medium soil nutrients (Klinka et al., 2000). Fd is found on a variety of soil types, but grows best on deep well-drained, sandy loams where moisture in the soil is plentiful.
Fd is commonly a pioneer species that regenerates after forest fires, logging or other disturbances, forming single-species even-aged stands. It is also found in un-even aged stands or in mixed-species stands, often with western hemlock, western redcedar, trembling aspen, ponderosa pine, lodgepole pine, or western larch (Klinka et al., 2000). Fd is a major component in old-growth forests in boreal, cool temperate and cool mesothermal climates.
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 1961-90 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.
*Notes on terminology: 1) The historical reference period is sometimes referred to as the “baseline” or simply “historical” or “reference” period. 2) Edatope refers to the combination of relative soil nutrient regime (SNR) and soil moisture regime (SMR) at a given site which align with distinct site series in a given biogeoclimatic unit. Here we provide three of the possible edatopes as examples: the B2 edatope representing nutrient-poor and relatively dry (subxeric) sites; the C4 edatope representing nutrient-medium and moisture-average (mesic) sites; and the D6 edatope representing nutrient-rich and relatively moist (hygric) sites.
The pie chart to the right depicts the distribution of the total environmentally suitable area for Fd in BC by biogeoclimatic (BGC) zone, based on the climate of the historical reference period (1961–1990).
On the coast, Fd is most abundant in the southern Coastal Western Hemlock (CWH) zone, especially on mesic to wet sites, where it grows alongside western redcedar, grand fir, and bigleaf maple (Egan, 1999). It also occurs in the Coastal Douglas-fir (CDF) zone, which is characterized by Fd, often with grand fir.
In the interior, Fd is a key species in the southern subzones of the Interior Cedar-Hemlock (ICH) and Sub-Boreal Spruce (SBS) zones, where it is abundant on warm, dry and rich sites. Fd dominates the Interior Douglas-fir (IDF) zone, where open canopy, un-even aged stands of Fd are common. It can also be found in the Montane Spruce (MS) and the lower southern 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.
Douglas-fir (Fd) is projected to persist within 70–90% of its historically suitable range under climate change. In addition the climatically suitable range of Fd is projected to expand over time into an area 0.75-2 times the size of the historical range. The projected expansion of Fd’s suitable area is driven by warming temperatures, for example portions of the Engelmann Spruce–Subalpine Fir (ESSF) and Montane Spruce (MS) zones becoming warmer and therefore more suitable for Fd.
Persistence (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. Expansion describes the change in environmental suitability outside of the species historical range. Calculated as follows:
\[\text{Persistence (\%)} = \frac{\text{future suitable area within historical range of suitability}} {\text{historically suitable area}} \times 100\] \[\text{Expansion (\%)} = \frac{\text{future suitable area outside historical range of suitability}} {\text{historically suitable area}} \times 100\]
Overall, the CCISS model predicts warmer temperatures will facilitate increased suitability of Fd across the province. Additionally, the total area suitable for Fd is projected to increase. However, large areas of the hottest/driest portions of Fd’s historical range are projected to become unsuitable.
The suitable range of Fd is projected to expand (yellow shades on the map) into previously unsuitable areas at higher elevations and more northern latitudes, especially on mesic (C4) and drier (B2) site types. This is most likely to occur east of the coast transition, in the Central Interior, Sub-boreal Interior, in the Boreal Plains, and on Haida Gwaii. Increasing or expanding Fd suitability (blue or yellow shades on the map) throughout much of the interior is driven by a shift to Interior Douglas-fir (IDF) and Interior Cedar Hemlock (ICH)-like climate conditions. However, cold air and frost is likely still a hazard for Fd in these areas.
The CCISS model predicts a loss or decline of Fd suitability (black or red shades on the map) at low elevations in the Okanagan Valley, Central Interior, Rocky Mountain Trench, and Chilcotin River Valley on C4 and D6 site types, driven by warmer temperatures creating drought conditions in these low elevation valley bottoms. The climate in these areas is predicted to become more characteristic of Bunchgrass (BG) ecosystems and therefore will not support Fd.
See the CCISS Tool Documentation for more information on how BGC projections work and the sources of error.
Key to BGC zones: CCISS Documentation > Definitions
Key to BGC zones: CCISS Documentation > Definitions
Key to BGC zones: CCISS Documentation > Definitions
Fd’s total suitable area is projected to expand across BC over the 21st century, driven by increases in suitable area in the ESSF, SBS, and CWH. Additionally there are smaller increases in suitable area in the SBPS, MH, BWBS, MS, and ICH. This broad pattern is offset by a decrease in the suitable area in the hottest and driest zones; the IDF, CDF, BG, and PP (which represent a smaller area proportionally).
Many mapped subzones within the Sub-Boreal Spruce (SBS) zone in the Skeena Region are projected to become warmer, shifting towards Interior Douglas-fir (IDF)-like climate or warmer and wetter, shifting towards Interior Cedar–Hemlock (ICH)-like climate in the future. These climates are suitable for Fd and expand the total suitable area for Fd. Similarly, on the Chilcotin Plateau, Sub-Boreal Pine–Spruce (SBPS) units are projected to shift towards IDF-like climate. The Engelmann Spruce–Subalpine Fir (ESSF) occurs on all major mountains surrounding the interior plateau (found above the MS, SBS, ICH and BWBS zones) and historically supported small populations of Fd in the warmer ESSF subzones (e.g., ESSFdh1). Warming temperatures are the likely driver of increases in suitable area for Fd projected into the ESSF zone. Fd is also projected to become suitable in a greater portion of the Coastal Western Hemlock (CWH) zone, as this area becomes warmer and drier, shifting to climates of warmer/drier CWH and Coastal Douglas-fir (CDF) subzones which are climatically suitable to Fd.
The loss of environmentally suitable area in the IDF zone is driven by a shift to Bunchgrass (BG)-like climates, which does not support Fd. These broad patterns are similar across the medium/mesic (C4) and poor/subxeric (B2) site types.
Note that the D6 edatope (rich/hygric site type) makes up a small area proportionally to the total range of Fd in BC, an order of magnitude less than the area occupied by Fd on C4 or B2 sites. Historical suitability is low (E3) on most D6 sites, therefore decreases in suitability associated with the projection of warmer climates often result in a loss of Fd suitability. The total area suitable to Fd is projected to decrease or be lost in the CDF, SBS, IDF, ESSF, and ICH, while there is an increased projected area in the CWH, MH and MS. It is also possible that these projected decreases in Fd suitability on wet rich sites are an artefact of the BGC projection method and site series crosswalk, with many fewer D6 sites containing Fd, compared to the C4 and B2 edatopes (see CCISS tool documentation for more information). Use caution when interpreting a loss of Fd suitability on wet/rich sites where Fd was historically suitable.
Douglas-fir beetle (Dendroctonus pseudotsugae) is one of the primary killers of mature Douglas-fir (Fd) in BC and usually attacks weakened or dying trees. Occasionally the beetle populations increase to the extent that they infest and kill large numbers of healthy trees (Douglas-Fir Beetle, 2025). The beetle is most common in BC’s interior and less common in coastal forests where it rarely causes the large-scale damage seen in the interior. Trees are killed when the flow of food and water between the roots and needles is blocked by feeding larvae and by dead sapwood cells killed by the blue-stain fungus carried by the Douglas-fir beetle adults (Burleigh et al., 2014).
Fd is also attacked by western spruce budworm (Choristoneura occidentalis), a native defoliator found southern BC in the coast, montane and Columbia forest types. Population levels periodically reach outbreaks which can last up to 25 years (Western Spruce Budworm, 2025). When trees are stressed they are more likely to die. Repeated budworm defoliation causes tree mortality over large areas. Sustained attack results in complete defoliation in four to five years. Once an infestation has subsided, surviving trees take several years to regain full foliage and resume growth. Successive years of defoliation in stands may predispose trees to other insects and pathogens such as bark beetles and root disease.
Douglas-fir tussock moth (Orgyia pseudotsugata) is another defoliator of concern, found at low elevations in the warm dry areas of the Southern Interior and occasionally on the south coast. Defoliated trees may die after one or more years of severe defoliation. Douglas-fir tussock moth outbreaks can cause extensive mortality of interior Fd (Douglas-Fir Tussock Moth, 2025).
In coastal populations, Fd is affected by Swiss needle cast (Nothophaeocryptopus gaeumannii), a fungus that causes a major foliar disease (Swiss Needle Cast, 2025). Swiss needle cast has emerged as a serious concern in recent decades, with increased incidence due to warmer winters and wetter springs. It often affects young stands of Fd leading to premature foliar drop, loss of growth and occasionally mortality.
Finally, root and butt rots (for example, red ring rot [Phellinus pini], laminated root rot [Coniferiporia sulphurascens], and Armillaria root disease [Armillaria ostoyae]) are a major and increasing concern for Fd.
For more information see the Forest Guide to Tree Health.
To view forest health risk across BGC subzone by tree species and biotic factor see the “Forest Health” tab of the By-BEC Portal.
Higher summer temperatures and drought are causing reduced Fd growth, increased mortality and susceptibility to pests and pathogens. Increased Fd mortality has been observed following periods of prolonged drought and warming, associated with decreasing summer available soil water and increasing summer temperature and rising vapour pressure deficit (for example in western Oregon, Cline et al. (2025)).
These trends are driven by specific the physiological vulnerabilities of Fd. Fd has a large foliage area and fairly high water consumption at maturity compared to co-occurring conifers, making it vulnerable to a warmer drier climate (Leuschner & Meinzer, 2024). Additionally, evidence suggests that the root system of juvenile Fd is highly drought-sensitive, while drought susceptibility decreases with age, when root penetration is deeper (Leuschner & Meinzer, 2024). Tap root growth of Fd seedlings and saplings is slow, and root system remains shallow, meaning young plants are susceptible to desiccation. Consequently, seedlings may face high drought induced mortality in large open gaps or when planted on clear cuts. To mitigate these vulnerabilities, research from BC’s coastal forests suggests that a lower planting density improved the drought tolerance of Fd (Damen et al., 2025; Lukose et al., 2025).
Numerous dendrochronological studies have demonstrated that reduced Fd growth is linked to increased temperature and vapour pressure deficit (Gazol et al., 2022; Leuschner & Meinzer, 2024; Restaino et al., 2016). During severe droughts, annual radial growth can be reduced by 30 %, or more and consecutive droughts increase the negative impact on growth (Charlet De Sauvage et al., 2023; Montwé et al., 2015; Sergent et al., 2014). The hot droughts of 2015 and 2021 in the Pacific Northwest have led to growth decline, crown damage, and mortality of Fd in low-elevation regions, often linked to fungal and insect infestations (Leuschner & Meinzer, 2024).
In southern and lowland areas, Fd growth is expected to slow and pathogen/insect attack and mortality will increase (Leuschner & Meinzer, 2024). On the coast, warming winters may increase susceptibility to fungal attack (notably Swiss needle cast), causing defoliation, growth decline and mortality. Conversely, climate warming will likely promote Fd growth in the cooler and wetter areas of its range.