Aim

Species distribution models typically project climatically suitable habitat for trees in eastern North America to shift hundreds of kilometers this century. We simulated potential migration considering species’ life history and traits for 10 tree species and their ability to track climatically suitable habitat.

Location

Eastern Canada, covering ~3.7 million km²

Methods

We simulated migration-constrained range shifts through 2100 using a hybrid approach combining projections of climatically suitable habitat based on two Representative Concentration Pathways (RCP4.5, RCP8.5) for three time periods and two species distribution modelling approaches with process-based models parameterized using data related to dispersal ability and generation time. We developed a unique ‘migration kernel’ that uses seed dispersal traits and observed migration velocities to obtain kernel shape and dispersal probabilities. We then calculated lags between the migration-constrained range limits obtained through simulations and limits of climatically suitable habitat.

Results

All species demonstrated northward range shifts at the leading edge of their simulated distribution through 2100, but the magnitude and rate of that shift varied by species and time period. Climatically suitable habitat limits were found to be north of simulated distribution limits across both RCPs, with lags increasing through time. On average, the simulated distribution that remained within climatically suitable habitat showed higher decreases under RCP8.5 than RCP4.5, with large areas of the rear edge of the simulated distribution becoming partially or completely climatically unsuitable for many species.

Main conclusions

Climatically suitable habitat limits projected for 2100 far exceeded migration-constrained range limits for all 10 species, particularly for temperate species. This study underlines the limited extent to which species will track climate change via natural migration. Integrating observed migration velocities, seed dispersal and generation time with SDM outputs allows for more realistic evaluations of tree migration ability under climate change and may help orient forest conservation and restoration efforts.

Raster files of outputs from simulations of tree species migration in Eastern Canada at a resolution of 25m. Simulations were conducted over 90 years, corresponding to the time period 2011 to 2100. Climatically suitable habitat was projected for 3 time periods (2011–2040; 2041–2070, 2071–2100) using 2 SDM approaches.

Species and species codes:

• ABIBAL = Abies balsamea
• ACERUB = Acer rubrum
• ACESAC = Acer saccharum
• BETALL = Betula alleghaniensis
• BETPAP = Betula papyrifera
• PICMAR = Picea mariana
• PINSTR = Pinus strobus
• POPTRE = Populus tremuloides
• QUERUB = Quercus rubra
• THUOCC = Thuja occidentalis

Species distribution models used: ANUCLIM or Maxent

RCPs used: RCP 4.5, RCP 8.5

GCM: Canadian Earth System Model (CanESM2)