Document: SAR-3-17-5

Potential changes in the distributions of tree and shrub taxa in western North America under future climate scenarios.

SHAFER, S.L.* ¹, P.J.BARTLEIN ¹ and R.S.THOMPSON ²

Dept. of Geography, Univ. of Oregon, Eugene, OR 97403, USA ¹
Earth Surface Processes Team, U.S. Geological Survey, Denver, CO 80225, USA ²

Abstract:
In order to characterize the ways in which vegetation will respond to future climate change, this study uses response surfaces to simulate the distributions of individual tree and shrub taxa in western North America under future climate scenarios. Response surfaces are local regression models that capture the relationship between geographic distributions of species and the environmental variables that limit, or are proxies for processes acting to limit, their ranges. The current geographic distributions of 78 tree and shrub taxa were defined using three bioclimatic variables: mean temperature of the coldest month, growing degree days, and a moisture index. Response surfaces were then used to simulate the distribution of suitable climate habitat for each species under present climate (1951-1980 30-yr mean) and future climate (2090-2099 10-yr mean) conditions using climate scenarios generated by three general circulation models: HADCM2, CGCM1, and CSIRO. For many species the potential range changes under each of the future climate scenarios are large. Due to interactions among the bioclimatic variables, suitable climate habitat not only shifts in a northward direction but in all directions, including southward for certain species. The potential distributions of some species become increasingly fragmented under the future climate scenarios, while other species consolidate their distributions. The magnitude of the potential range changes imply significant impacts to ecosystems and shifts in centers of species diversity in western North America.

Keywords: climate change, response surface models, western North America

This abstract is being presented at: 10:15 AM in session:
Symposium # 20: Global Change in Forests: Interactions Among Biodiversity, Climate and Land Use.