Global warming is expected to have strongly negative effects on many species. One way these effects might be reduced is if species can change their geographical ranges as climate changes; if species can migrate to cooler places such as higher latitudes or elevations as temperature rises, they may be able to stay in the same climate by changing place. However, the preliminary research for this project shows that species of trees in the eastern U.S. have not moved northward. The project will test two alternative hypotheses to explain this, both based on whether young and adult trees differ in their ability to tolerate a wide range of environmental conditions. Researchers will expand a current species distribution model to include more explicit effects of juvenile and adult responses to temperature, and use data from a national forest inventory and climate measurements to compare the abundances of juveniles and adults.
Anticipating the impacts of climate change on U.S. forests is an important issue for forest managers and for the nation as a whole. Results from this project will help plan strategies for maintaining forest productivity and for substitutions of alternative land uses. The project will also strengthen collaboration between Duke University and the USDA Forest Service, and train a Ph.D. student and an undergraduate student.
This project aims to understand how eastern US forests respond to climate change. We analyzed decades of data from USDA Forest Service’s Forest Inventory and Analysis program. We found that instead of shifting geographic distributions to higher latitudes, the majority of tree species are staying in place – but speeding up their life cycles. We have published our results in the peer-reviewed journal Global Change Biology (Zhu et al. 2014). Many climate studies have predicted that tree species will respond to global warming by migrating via seed dispersal to cooler climates. However, by studying the climate requirements of the trees at different life stages, we found that there is no consistent, large-scale northward migration taking place. This adds to a growing body of evidence, including one of our previous studies (Zhu et al. 2012), that climate-driven migration is occurring much more slowly than predicted. We are among the first to show that most trees are responding through faster turnover – meaning they are staying in place but speeding up their life cycles in response to longer growing seasons and higher temperatures. This unexpected change on eastern US forests may be an early sign of climate change impacts, before large-scale migrations. Our finding has far-reaching consequences for biodiversity and carbon storage. Throughout the project, we collaborated closely with scientists across ecology, forestry, and statistics at Duke University and USDA Forest Service. We hired a student assistant to handle the massive forest inventory database. We disseminated our research findings to diverse groups through organized sessions at scientific meetings: Ecological Society of America (August 2013, Minneapolis, MN) and American Geophysical Union (December 2013, San Francisco, CA). Our results also received wide media coverage. References Zhu, K., C. W. Woodall, and J. S. Clark. 2012. Failure to migrate: lack of tree range expansion in response to climate change. Global Change Biology 18:1042-1052. Zhu, K., C. W. Woodall, S. Ghosh, A. E. Gelfand, and J. S. Clark. 2014. Dual impacts of climate change: forest migration and turnover through life history. Global Change Biology 20:251-264.
