PROCEEDINGS: Index of Abstracts

ASSESSING THE ABILITY OF PLANTS TO RESPOND TO CLIMATIC CHANGE THROUGH DISTRIBUTION SHIFTS

Mark W. Schwartz

Assistant Research Scientist, Center for Population Biology, University of California at Davis, Davis, CA 95616.

Predictions of future global warming suggest northward shifts of up to 800 km in the equilibrium distributions of plant species. Historical data estimating the maximum rate of tree distribution shifts (migration) suggest that most species will not keep pace with future rates of human-induced climatic change. Previous plant migrations have occurred at rates typically ranging from 15-50 km per century. A simulation model, which incorporates the effects of forest fragmentation and habitat loss, predicts maximum potential migration responses of trees may be only 1-10 km per century, or two orders of magnitude below that required to keep pace with predicted climatic warming. These predicted migration rates suggest that plants will fail to respond adequately to even modest climatic changes. Gauging the actual response of forest species to climatic change, and then appropriately managing forest resources poses several problems. First, we do not know the distribution limits of most forest species with the degree of precision to detect migration events on a 1-10 km scale. Second, many species may become vulnerable to extinction by their inability to migrate, leaving them geographically isolated from regions within their climatic tolerance. Third, while the distributions of species can be artificially expanded if climate does warm, this is not currently part of acceptable conservation management practice. Deciding whether or not to artificially enhance species ranges forces a choice between species preservation and historical community composition models for conservation. A pressing concern for forest management is to discover how climate change, anthropogenic habitat change, and doubled CO2 interact to alter forest species performance and regeneration within habitats they currently occupy. Range edges are the first place to look for key changes in these ecological responses.