Boreal forests will be more severely affected by projected anthropogenic climate forcing than mixedwood and northern hardwood forests in eastern Canada

Abstract

Context Increased anthropogenic climate forcing is projected to have tremendous impacts on global forest ecosystems, with northern biomes being more at risk. Objectives To model the impacts of harvest and increased anthropogenic climate forcing on eastern Canada forest landscapes and to assess the strong spatial heterogeneity in the severity, the nature and direction of the impacts expected within northern forest regions. Methods We used LANDIS-II to project species-specific aboveground biomass (AGB) between 2020 and 2150 under three climate (baseline, RCP 4.5 and RCP 8.5) and two harvest (baseline harvest, no harvest) scenarios within four forest regions (boreal west, boreal east, mixedwood and northern hardwood). Results Climate change impacts within the boreal forest regions would mainly result from increases in wildfires activity which will strongly alter total AGB. In the mixedwood and northern hardwood, changes will be less important and will result from climate-induced growth constraints that will alter species composition towards more thermophilous species. Climate-induced impacts were much more important and swifter under RCP 8.5 after 2080 suggesting that eastern Canada forests might cross important tipping points under strong anthropogenic climate forcing. Conclusions Boreal forest regions will be much less resilient than mixedwood or northern hardwoods to the projected changes in climate regimes. Current harvest strategies will interact with anthropogenic climate forcing to further modify forest landscapes, notably by accelerating thermophilous species AGB gain in southernmost regions. Major changes to harvest practices are strongly needed to preserve the long-term sustainability of wood supply in eastern Canada. Adaptation strategies should be region-specific.

A framework to support the identification of critical habitat for wide-ranging species at risk under climate change

“…LANDIS-II scenarios run in Quebec, New Brunswick and Nova Scotia projected that Wood Thrush would increase in those provinces, particularly with moderate climate warming (Leston, 2022; Appendix S3). The latter results are consistent with projected increases in deciduous forest growth rates along with declines in coniferous forests (Taylor et al, 2017;Boulanger and Puigdevall, 2021). Our single Ontario land-use scenario in ALCES Online suggested a negligible increase in Wood Thrush abundance would occur between 2020-2070.…”

“…Land-use scenarios projected that populations of Canada Warbler would respond differently to timber harvest across its range: negatively in Alberta and generally positively in Nova Scotia, although we note that: 1) in the Alberta scenarios, habitat restoration and alternative harvest strategies to clear-cutting were not considered; 2) in Nova Scotia, the forested wetlands used by Canada Warbler are not generally targeted for harvest, but are not properly captured in the wetland inventory that would otherwise provide protective measures afforded to other wetlands (Nova Scotia Wetland Conservation Policy 2019). The same scenarios projected less habitat for Canada Warbler in both regions under a warming climate, consistent with projected decreases in coniferous habitats in eastern(Taylor et al, 2017;Tremblay et al, 2018;Boulanger and Puigdevall, 2021) and average forest stand age in western Canada(Cadieux et al, 2020).…”