Vegetation vulnerability to climate change in the Rocky Mountains

Background/Question/Methods

This presentation assesses components of vulnerability of tree species and biome types to projected future climate within the Great Northern Landscape Conservation Cooperative (GNLCC) in the US Northern Rockies and the ecosystems surrounding Yellowstone/Grand Teton National Parks.  We drew on the results of five published studies and analyzed current and projected future climate suitability for 11 tree species and 8 biome types under two IPCC emissions scenarios.  We assessed components of vulnerability based on four metrics of current and projected future climate suitability.  We additionally developed habitat suitability models for dominant tree species and community types across the Greater Yellowstone Ecosystem (GYE) based on climate, water balance, soil and topographic predictors and projected habitat suitability to 2100 under IPCC MMIP5 climate scenarios.

Results/Conclusions

Results for biome types indicated largely a shift from climates suitable for alpine and subalpine conifer to climates suitable for desert scrub and grassland types. Results from the four studies of tree species indicated substantial loss of area of climate suitability for the four subalpine species by 2100. This was especially true for Whitebark pine (Pinus albicaulis). Suitable climate for this species dropped from just over 20% of the study area in the reference period to 0.5-7.0% by 2070- 2100 under the A2 scenario. The studies agreed in projecting expansion of climate suitability for some montane tree species. Importantly, the rankings of tree species vulnerability were similar among studies, scenarios, and geographic areas and indicated highest vulnerability for Whitebark pine and Mountain hemlock (Tsuga mertensiana).  Analyses within GYE found that decreasing spring snowpack and increasing late-season soil moisture deficit will decrease suitable habitat area for seven mountain forest species while increasing suitable area for sagebrush and juniper communities. For most forest species under projected climate change, their suitable habitat moved up in elevation Managing to maintain vulnerable subalpine tree species will be a particular challenge because habitat suitability tends to shift to land allocation types such as designated Wilderness where active management is dissuaded by enabling legislation.