Habitat and Migration Dynamics of North American Tree Species Under Climate Change

Aim

We model and map the climatically suitable habitats and migration potential of 326 tree species by combining forest inventories of the United States, Canada and to a lesser extent, Mexico, with the goal of providing a continental perspective of species ranges and migration potential to facilitate better forest stewardship under a changing climate.

Location

United States, Canada, and Mexico.

Major Taxa Studied

Tree species.

Methods

We use a multi-model ensemble technique to assess climatic habitat suitability under current and future climates, and a migration model to compute colonisation likelihoods to simulate end of century tree species migration. We combine and synthesise these outputs to provide various products relevant to range-wide assessment of tree species.

Results

For 326 tree species, we provide maps of: current habitat suitability, future habitat suitability under SSP2-4.5 and SSP5-8.5 scenarios, and combined habitat suitability and colonisation likelihoods for the end of the current century. In addition, we provide synthesis outputs of (a) climate and topographic statistical range assessments, (b) maps of potential differences in species richness from current to future climates, (c) assessment of model performance, (d) climate-topographic variable-importance groupings and (e) climatic disequilibrium trends across genera.

A continent-wide assessment of both individual and combined species responses showed evidence of climatic disequilibrium for species with smaller ranges, a projected potential reduction in species richness in the middle and lower mid-continental regions, and an increase across the southeastern, northeastern, and northwestern regions of the continent. Also, we found habitat suitability of most eastern species were mainly driven by moisture, while western species showed strong associations with heat and moisture.

Main Conclusions

Our study provides, for the first time, a baseline for understanding the overall continental dynamics of shifting climatic habitats and migration potential of tree species across their entire range, facilitating improved management of North American forested ecosystems.