Distribution of tree species
A shift in climate conditions could result in changes in tree species distribution and forest composition.
Climate determines the distribution of tree species and shapes the composition of forests. Changes in climate drive changes in the distribution of tree species, which, in the long term, can affect ecosystem processes and the types of wood fibre available to the forest industry. The migration capacity of trees varies across species but, in general, a shift in species distribution is a slow process.
Climate conditions have already shifted, affecting the distribution of certain tree species in Canada. In the last 50 years, changes have occurred in plant hardiness zones. The climate in an area where a tree species currently lives and reproduces is likely to shift to new locations. In Canada, the rate of projected climate change is expected to be 10 to 100 times faster than the ability of trees to migrate, resulting in impacts on forest health and productivity.
- Why the distribution of tree species is important
- What has changed
- The outlook
- Adaptation tools and resources
Read how tree species distribution and its indicators are defined
Why the distribution of tree species is important
Tree species distribution shapes forest composition and affects ecosystem processes and wood supply.
The distribution of tree species is highly dependent on climate. Changes in climate affect the distribution of plant species and result in changes in forest composition. Tree species differ in the way they interact with their environment (water and nutrient cycling, competition, etc.). Changes in species composition may therefore affect several ecosystem properties. Forest composition also determines the wood fibre types available to the forest industry.
A tree starting to grow today in its current climate suitability zone may experience very different climate conditions when it comes to maturity. Some tree species may not be able to migrate or adapt fast enough to a rapidly changing climate, resulting in impacts on forest health. Forest management needs to take into account shifting climate suitability zones. Careful selection of seed sources and species can contribute to maintaining healthy and productive trees in this changing climate.
What has changed
Climate conditions have shifted and changes in the range and local abundance of certain tree species have occurred.
Climate change has already altered the geographical range of certain tree species. In Canada, tree species migration is a slow process and precise data on past tree species distribution is limited. Assessing past changes in the location of tree species is therefore challenging. However, it is possible to report on past changes in the climate conditions that are relevant to species distribution.
Plant hardiness zones identify the location of environmental conditions under which a species or variety of plant can successfully survive and grow. The updates of the original Plant Hardiness Zones Map indicate changes in the hardiness zones that are generally consistent with changes in climate. These changes are most pronounced in western Canada (Figure 1).
Figure 1 – Original (1931–1960; left) and updated (1961–1990; centre and 1981-2010; right) Canada’s Plant Hardiness Zones Maps
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The outlook
Figure 2 – Current (1971–2000) versus projected (2071–2100) climate suitability zone of trembling aspen (Populus tremuloides) in Canada under the Representative Concentration Pathway (RCP)Footnote* 8.5 assuming continued emissions increases
Note: Climate suitability zones were modelled using the Canada’s Plant Hardiness Site interactive mapping tool
Larger image [245 Kb]
Shifts in climate conditions are expected to outpace tree species migration capacity.
Climate change projections suggest that the climate prevalent in the area where a tree species currently lives and reproduces (i.e., climate suitability zone) will shift to new locations (Figure 2). However, it is difficult to forecast whether tree species will be able to adapt to new climate conditions or to migrate to follow these displacements. The capacity to migrate varies across tree species (see: Vulnerability of Canadian forest tree species to climate change).
In the medium term, the relative proportion of species within a forest could change, but radical changes in forest composition are not expected. Available records on past tree migration rates in response to natural changes in climate give an indication of the potential migration capacity of tree species.
The rate of projected climate change is unprecedented and, overall, is expected to be 10 to 100 times faster than the ability of trees to migrate in Canada. This discrepancy may result in species becoming maladapted, less productive and more vulnerable to insects and diseases.
How tree species distribution and its indicators are defined
The distribution of a species is the area in which it naturally lives and reproduces during a defined time. Since trees are immobile organisms, it may be decades before noticeable shifts in the distribution of tree species due to changing climate can be detected.
Precise data on past tree species distribution is limited, making the assessment of past changes challenging. Indicators that are related to the distribution of species can be backcasted to estimate how climate conditions relevant to species distribution have changed. Plant hardiness zones identify the location of environmental conditions under which plant species can successfully survive and grow. Well known to gardeners, these zones can be used for assessing past changes.
Projecting future distribution is also difficult, because of uncertainty about the capacity of tree species to adapt to new climate conditions and to migrate in order to follow their suitable climate condition. However, temporal and spatial changes in climate suitability zones (or climatic niches) can be modelled. The climate suitability zone is the current climate across the current distribution of a species. Climate suitability zones can be delineated using different modelling approaches based on projected climate data. These models are based on the assumption that present distributions of tree species are in equilibrium with the current climate conditions. They do not project the future distribution of species, but rather where the climate conditions in which the species currently lives and reproduces are expected to prevail in the future.
For this project, past changes in the distribution of individual tree species were not assessed directly. Rather, plant hardiness zones were used to estimate changes in climate conditions related to species distribution. The original Plant Hardiness Zones Map was based on 1931–1960 climate data. The updated maps used data from 1961–1990 and 1981–2010, and different interpolation techniques. The comparison of the zones between the three time periods (1931–1960, 1961–1990 and 1981-2010) shows changes that are consistent with climate change.
The baseline information on species distribution was estimated using its current climatic suitability zone that is based on the climatic reference period (1971–2000). Future tree distribution was not directly estimated. Projected climate suitability zones were modelled using the Canada’s Plant Hardiness Site interactive mapping tool. This tool goes beyond a single hardiness zone map and enables the projection and mapping of the future climate suitability zones for more than 3,000 individual plant species.
Sources and references for tree species distribution and its indicators
- Aitken, S.N., Yeaman, S., et al. 2008. Adaptation, migration or extirpation: Climate change outcomes for tree populations. Evolutionary Applications 1, 95–111.
- Beaudoin, A., Bernier, P.Y., et al. 2014. Mapping attributes of Canada’s forests at moderate resolution through kNN and MODIS imagery. Canadian Journal of Forest Research 44, 521–532.
- Bonan, G.B. 2008. Forests and climate change: Forcings, feedbacks, and the climate benefits of forests. Science 320(5882), 1444–1449
- Gauthier, S., Bernier, P., et al. 2014. Climate change vulnerability and adaptation in the managed Canadian boreal forest. Environmental Reviews 22, 256–285.
- Gray, L.K., Gylander, T., et al. 2011. Assisted migration to address climate change: Recommendations for aspen reforestation in western Canada. Ecological Applications 21, 1591–1603.
- Intergovernmental Panel on Climate Change (IPCC). 2013. Climate change 2013: The physical science basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK, and New York, NY: Cambridge University Press.
- Juday, G.P., Barber, V., et al. 2005. Forests, land management, agriculture. In Symon, C., Arris, L., et al. (eds.), Arctic climate impact assessment, 781–862. New York, NY: Cambridge University Press.
- Lafleur, B., Paré, D., et al. 2010. Response of northeastern North American forests to climate change: Will soil conditions constrain tree species migration? Environmental Reviews 18, 279–289.
- Lavoie, C., and Payette, S. 1996. The long-term stability of the boreal forest limit in subarctic Quebec. Ecology 77, 1226–1233.
- Leithead, M.D., Anand, M., et al. 2010. Northward migrating trees establish in treefall gaps at the northern limit of the temperate–boreal ecotone, Ontario, Canada. Oecologia 164, 1095–1106.
- McKenney, D.W., Pedlar, J.H., et al. 2007. Potential impacts of climate change on the distribution of North American trees. Bioscience 57, 939–948.
- McKenney, D.W., Pedlar, J.H., et al. 2011. Revisiting projected shifts in the climate envelopes of North American trees using updated general circulation models. Global Change Biology 17, 2720–2730.
- McManus, K.M., Morton, D.C., et al. 2012. Satellite-based evidence for shrub and graminoid tundra expansion in northern Quebec from 1986 to 2010. Global Change Biology 18, 2313–2323.
- Millar, C.I., Stephenson, N.L., et al. 2007. Climate change and forests of the future: Managing in the face of uncertainty. Ecological Applications 17, 2145–2151.
- Nathan, R., Horvitz, N., et al. 2011. Spread of North American wind-dispersed trees in future environments. Ecology Letters 14, 211–219.
- Roush, W.M. 2009. A substantial upward shift of the alpine treeline ecotone in the southern Canadian Rockies (Unpublished master’s thesis), University of Victoria, Victoria, BC.
- Seastedt, T.R., Bowman, W.D., et al. 2004. The Landscape Continuum: A Model for High-Elevation Ecosystems. BioScience 54, 111–121.
- Steenberg, J.W.N., Duinker, P.N., et al. 2013. Criteria and indicators of sustainable forest management in a changing climate: An evaluation of Canada’s national framework. Journal of Sustainable Development 6, 32–64.
- Ste-Marie, C. 2014. Adapting sustainable forest management to climate change: A review of assisted tree migration and its potential role in adapting sustainable forest management to climate change. Ottawa, ON: Canadian Council of Forest Ministers.
- Zhu, K., Woodall, C.W., et al. 2012. Failure to migrate: Lack of tree range expansion in response to climate change. Global Change Biology 18, 1042–1052.
- Zhu, K., Woodall, C.W., et al. 2014. Dual impacts of climate change: Forest migration and turnover through life history. Global Change Biology 20, 251–264.
Canadian Forest Service key contacts
Dan McKenney, Chief, Landscape Analysis and Applications, Great Lakes Forestry Centre
André Beaudoin, Research Scientist, Remote Sensing and Spatial Modelling, Laurentian Forestry Centre
Pierre Bernier, Research Scientist, Forest Productivity, Laurentian Forestry Centre
Adaptation tools and resources
Assisted migration of tree species in Canada – a web page describing the human-assisted movement of plants to more climatically suitable habitats and links to articles, reports and resources
Canada’s Plant Hardiness Site – a web application with species-specific models and maps of current and projected climate distribution for more than 3000 plant species
Forest Change Toolkit – a list of tools and resources for climate change adaptation
- Beaudoin, A., Bernier, P.Y., et al. 2014. Mapping attributes of Canada’s forests at moderate resolution through kNN and MODIS imagery. Canadian Journal of Forest Research 44, 521–532.
- Gauthier, S., Bernier, P., et al. 2014. Climate change vulnerability and adaptation in the managed Canadian boreal forest. Environmental Reviews 22, 256–285.
- Guindon, L., Bernier, P.Y., et al. 2014. Annual mapping of large forest disturbances across Canada’s forests using 250 m MODIS imagery from 2000 to 2011. Canadian Journal of Forest Research 44, 1545–1554.
- McKenney, D.W., Pedlar, J.H., et al. 2007. Potential impacts of climate change on the distribution of North American trees. Bioscience 57, 939–948.
- McKenney, D.W., Pedlar, J.H., et al. 2011. Revisiting projected shifts in the climate envelopes of North American trees using updated general circulation models. Global Change Biology 17, 2720–2730.
- Ste-Marie, C. 2014. Adapting sustainable forest management to climate change: A review of assisted tree migration and its potential role in adapting sustainable forest management to climate change. Ottawa, ON: Canadian Council of Forest Ministers.
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