Eastern forests not adapting quickly to climate change

Many Eastern tree species aren't migrating northward as climate change models say they will, says a new study led by Duke University researchers. That could be bad news for the trees' long-term survival.

The ranges of 59 percent of the 92 species analyzed appear to be contracting on both their northern and southern ends, while 16 percent seemed to move to the south. More concerning to researchers was that only 21 percent are shifting northward.

That raises the prospect of climate change stranding some species in increasingly inhospitable surroundings. "It's kind of like pulling the climate out from from under it," said ecologist James Clark of Duke's Nicholas School of the Environment.

Models show that, as the climate warms, many tree species would lose ground on the southern end of their ranges as adults die and seeds fail to sprout. Their northern boundaries would expand as dispersed seeds find happier conditions. See some examples at this U.S. Forest Service site.

But that's not happening for many species, despite warm zones in parts of the East shifting up to 60 miles north. The researchers found no evidence that tree ranges are changing fastest where climate has changed the most. They don't believe differences in seed sizes or their ability to be dispersed account for their findings.

The study did find evidence that some species are migrating to higher elevations, as models also predict.

Clark and his colleagues, funded by the National Science Foundation, based their work on decades of data from the U.S. Forest Service's Forest Inventory and Analysis program. They compared tree distributions in more than 43,000 plots in 31 states.

Kai Zhu, a doctoral student of Clark, was lead author of the study with co-authors Christopher Woodall, a Forest Service researcher in St. Paul, Minn., and Clark. The article was published in the current issue of the journal Global Change Biology.