Boreal
—REfugia in the BOREAL Ecosystem—
Birch forest with mountains in the distance.
Birch Mountains, Alberta. Photo: Scott Nielsen.
Lake with lily pads and reflections of clouds with coniferous forest along the shoreline.
Half Moon Lake, Alberta. Photo: Scott Nielsen.
North American boreal region
Northern latitudes are warming more rapidly than other parts of the planet. The North American boreal region, which spans Canada and part of Alaska, contains 16% of the world’s forests and represents a globally important carbon store. The region is dominated by coniferous forests, particularly spruce, interspersed with wetlands, mostly bogs and fens.
Aerial view of a coniferous forest.
Coniferous forest at Old Conklin Road, Alberta. Photo: Scott Nielsen.
Steep elevational gradients harbor a diversity of climates and ecosystems
Boreal mountain regions, which include parts of the Rocky Mountains, Laurentian, and
Appalachian Mountains, are characterized by steep elevational gradients and relatively high ecological diversity. Given that air temperatures decrease with increasing elevation, cooler and wetter conditions supporting boreal ecosystems will persist longer at high elevations. Rugged terrain also contains a diversity of microclimates, and more opportunities for topographically sheltered features such as north-facing slopes and steep canyons.
Across boreal interior landscapes, terrain diversity is limited to minor plateaus and hill systems with several hundred meters of elevation gain. Although topographic relief is relatively low, even small gains in elevation may be enough to maintain cooler future temperatures.
Boreal peatlands have high ecological inertia
Variety of flora with water droplets.
Boreal forest floor, Lower Athabasca Region, Alberta. Photo: Scott Nielsen.
Boreal interior lowlands are experiencing high climate velocity and may lack sufficient topographic relief to maintain boreal climates in microrefugia. But these areas contain extensive peat-forming wetlands (peatlands), which retain large quantities of water on the landscape. Depending on local hydrology and geology, peatlands may also make surrounding upland forests more resilient to drought and wildfire.
Aerial view of a lake. The shoreline is filled with lots of trees.
Cree Lake, Saskatchewan. Photo: Scott Nielsen.
Large lakes cool neighboring forests and interrupt fires
An abundance of large, deepwater lakes throughout the interior boreal region may have
moderating influences on local and regional climates, due to cooling and moist onshore breezes, which may both reduce fire occurrence and buffer local climates. Water can also act as a natural fuel break, and therefore islands and peninsulas can serve as fire refugia.
Recent publication: Climate-change refugia in boreal North America: what, where, and for how long? (Stralberg et al. 2020)
30 boreal scientists from academia, government, and NGOs convened to address climate-change refugia in the boreal region in Feb/March 2018. The resulting framework is published in a special issue of Frontiers in Ecology and the Environment.
publications
Estevo, C.A., Stralberg, D., Nielsen, S.E. & Bayne, E. 2022. Topographic and vegetation drivers of thermal heterogeneity along the boreal-grassland transition zone in western Canada: Implications for climate change refugia. Ecology and Evolution. https://doi.org/10.1002/ece3.9008.
Gilbert, N.A., Anich, N. M., Worland, M. & Zuckerburg, B. 2022. Microclimate complexities at the trailing edge of the boreal forest. Forest Ecology and Management. https://doi.org/10.1016/j.foreco.2022.120533.
Wilson, R.E. et al. 2021. Implications of Historical and Contemporary Processes on Genetic Differentiation of a Declining Boreal Songbird: The Rusty Blackbird. Diversity- Basel. https://doi.org/10.3390/d13030103.
Kato, A., Thau, D., Hudak, A.T. , Meigs, G.W., Garrett, W. & Moskal, L.M. 2020. Quantifying fire trends in boreal forests with Landsat time series and self-organized criticality. Remote Sensing of Environment. https://doi.org/10.1016/j.rse.2019.111525.
Stralberg et al. 2020. Climate‐change refugia in boreal North America: what, where, and for how long? https://doi.org/10.1002/fee.2188
Stralberg, D, Bayne, EM, Cumming, SG, Sólymos, P, Song, SJ & Schmiegelow, FKA. 2015. Conservation of future boreal forest bird communities considering lags in vegetation response to climate change: a modified refugia approach. Diversity and Distributions 21:1112-1128. https://doi.org/10.1111/ddi.12356