Climate change may speed up forests' life cycles

September 11, 2013, Duke University

Many climate studies have predicted that tree species will respond to global warming by migrating via seed dispersal to cooler climates. But a new study of 65 different species in 31 eastern states finds evidence of a different, unexpected response.

Nearly 80 percent of the species aren't yet shifting their geographic distributions to . Instead, they're staying in place—but speeding up their life cycles.

The Duke University-led study, published online Wednesday in the peer-reviewed journal Global Change Biology, is the first to show that a changing climate may have dual impacts on forests. It adds to a growing body of evidence, including a 2011 study by the same Duke team, that climate-driven migration is occurring much more slowly than predicted, and most plant species may not be able to migrate fast enough to stay one step ahead of rising temperatures.

"Our analysis reveals no consistent, large-scale northward migration is taking place. Instead, most trees are responding through faster turnover—meaning they are staying in place but speeding up their life cycles in response to longer and higher temperatures," said James S. Clark, H.L. Blomquist Professor of Environment at Duke's Nicholas School of the Environment.

Anticipating the impacts of this unexpected change on U.S. forests is an important issue for and for the nation as a whole, Clark said. It will have far-reaching consequences for biodiversity and .

To test whether trees are migrating northward, having faster turnover, or both, the scientists went through decades of data on 65 dominant tree species in the 31 eastern states, compiled by the USDA Forest Service's Forest Inventory and Analysis program. They used computer models to analyze the temperature and precipitation requirements of the trees at different life stages, and also considered factors like reproductive dependence of young and adult trees.

"The patterns we were able to see from this massive study are consistent with forests having faster turnover, where young trees tend to be more abundant than adult trees in warm, wet climates. This pattern is what we would expect to see if populations speed up their life cycle in warming climates," said lead author Kai Zhu, a doctoral student of Clark's at Duke. "This is a first sign of climate change impacts, before we see large-scale migrations. It gives a very different picture of how trees are responding to climate change."

The fact that most trees are not yet showing signs of migration "should increase awareness that there is a significant lag time in how tree species are responding to the ," Zhu said.

Explore further: Forests not keeping pace with climate change: study

More information: "Dual Impacts of Climate Change: Forest Migration and Turnover through Life History" Kai Zhu, Christopher W. Woodall, Souparno Ghosh, Alan E. Gelfand, James S. Clark, Published Sept. 11, 2013, in Global Change Biology DOI: 10.1111/gcb.12382

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1 / 5 (9) Sep 12, 2013
Another crap study from those believing in global (or eastern uS) warming without checking the data. The results presented could be caused by more rapid growth because of more ideal (increased) CO2 levels and/or increased rainfall.
Since no "migration" northward was found for any of the species how can Zhu come to the conclusion that there is "is a significant lag time in how tree species are responding to the changing climate" when he has not reviewed the data to see if the environment really has warmed during the study period but instead has relied on the global warming myth that it has?

The old adage, "show me a graduate student who has a "new" idea and I show you a graduate student who hasn't read the literature" surely applies. As it does to his adviser and the other authors of this misleading, poor quality paper.

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