An ecological approach to climate change-informed tree species selection for reforestation

Abstract Accounting for climate change in reforestation practices has the potential to be one of the most efficacious adaptation strategies for maintaining future forest ecosystem services. There is a rich literature projecting spatial shifts in climatic suitability for tree species and strong scientific evidence for the necessity of assisted migration. However, there has been limited translation of this research into operational reforestation, due in part to mismatches to the information needs of practitioners. Here, we describe a practitioner-focused climate change informed tree species selection (CCISS) model to support reforestation decisions in British Columbia (BC). CCISS projects the climate change redistribution of bioclimate units from the multi-scaled Biogeoclimatic Ecosystem Classification (BEC) system with machine-learning for 90 modelled futures. It leverages the reforestation knowledge from BEC to make site-specific species projections of reforestation feasibility with climate change uncertainty metrics. We present 21st-century feasibility projections for a comprehensive set of tree species native to western North America. Some general trends are evident: augmentation of the number of feasible species in sub-boreal regions due to the rapid expansion of feasibility for temperate species; attrition at low elevations in southern BC due to declines in the feasibility of native species with little compensation by non-native species; and turnover at mid-elevations as declining feasibility for subalpine species is compensated by uphill expansion of climatic feasibility for submontane species. Edaphic (soil) factors are important; feasibility declines are higher on relatively dry sites than on wetter sites for most species. Our analysis emphasizes that changes in feasibility are species-specific, spatially variable, and influenced by edaphic site factors. By employing the multi-scaled BEC system that currently informs operational reforestation, CCISS facilitates translation of research into actionable guidance for practitioners.