Combining US and Canadian forest inventories to assess habitat suitability and migration potential of 25 tree species under climate change

Abstract

AimTo evaluate current and future dynamics of 25 tree species spanning United States and Canada.LocationUnited States and Canada.MethodsWe combine, for the first time, the species compositions from relative importance derived from the USA’s Forest Inventory Analysis (FIA) with gridded estimates based on Canada's National Forest Inventory (NFI‐kNN))‐based photo plot data to evaluate future habitats and colonization potentials for 25 tree species. Using 21 climatic variables under RCP 4.5 and RCP 8.5, we model climatic habitat suitability (HQ) within a consensus‐based multimodel ensemble regression approach. A migration model is used to assess colonization likelihoods (CL) for ~100 years and combined with HQ to evaluate the various combinations of HQ + CL outcomes for the 25 species.ResultsAt a continental scale, many species in the conterminous United States lose suitable climatic habitat (especially under RCP 8.5) while Canada and USA’s Alaska gain climate habitat. For most species, even under optimistic migration rates, only a small portion of overall future suitable habitat is projected to be naturally colonized in ~100 years, although considerable variation exists among species.Main conclusionsFor the species examined here, habitat losses were primarily experienced along southern range limits, while habitat gains were associated with northern range limits (especially under RCP 8.5). However, for many species, southern range limits are projected to remain relatively intact, albeit with reduced habitat quality. Our models predict that only a small portion of the climatic habitat generated by climate change will be colonized naturally by the end of the current century—even with optimistic tree migration rates. However, considerable variation among species points to the need for significant management efforts, including assisted migration, for economic or ecological reasons. Our work highlights the need to employ range‐wide data, evaluate colonization potentials and enhance cross‐border collaborations.

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

“…Lack of propagules of warm-adapted species within most of the boreal range impeded potential AGB recovery from boreal conifer decline. In fact, thermophilous species migration towards more northern, suitable conditions will be strongly outpaced by the northward shift of the isotherms even under moderate forcing (Brice et al 2019; Prasad et al 2020). Considering their limited dispersal abilities, we projected that thermophilous species would colonize sites only few tens of km north of their actual northern range (Suppl.…”

“…Mat S2), compromising their potential expansion within the boreal forest. Notwithstanding the increased disturbance rates, thermophilous species are therefore less likely to extensively compensate AGB losses by boreal species by introducing a significant “migration lag” within the boreal forest (Taylor et al 2017; Prasad et al 2020).…”

Effects of future climate change on birch abundance and their pollen load

“…As a result, certain tree species that currently act as major allergen sources like birch may dwindle or disappear in some areas as their range contracts northward, although they may also expand their distribution into areas of higher elevation (Dyderski et al, 2018). Such displacements do not happen straight away, however, as there is a lag due to species plasticity favouring population persistence and dispersion capability as well as species competence limiting migration rates (Prasad et al, 2020). Although, it has been suggested that, due to intraspecific variations, warm margin populations are the most vulnerable to climate change (Fréjaville et al, 2020).…”

Assisted Migration Field Tests in Canada and Mexico: Lessons, Limitations, and Challenges

“…While assisted migration has received significant attention as a climate change adaptation strategy [88,89], diversification of forestry practices (e.g., use of alternative silviculture systems, planting more tree species, prioritizing harvest in areas of high risk of distur-bance) and genetic diversification in particular have also been proposed to buffer some of the uncertainty in climate change projections [1,31,90]. Crop diversification is commonly practiced by farmers to mitigate uncertainty associated with crop prices and variability in production due to pest outbreaks and extreme weather [91], and portfolio diversification is widely used by investors to stabilize returns from fluctuating markets [92].…”