Global Warming

American Trees Are Moving West Due to Climate Change

As the consequences of climate change strike across the United States, ecologists have a guiding principle about how they think plants will respond. Cold-adapted plants will survive if they move “up”—that is, as they move further north (away from the tropics) and higher in elevation (away from the warm ground).

A new survey of how tree populations have shifted over the past three decades finds that this effect is already in action. But there’s a twist: Even more than moving poleward, trees are moving west.

About three-quarters of tree species common to eastern American forests—including white oaks, sugar maples, and American hollies—have shifted their population center west since 1980. More than half of the species studied also moved northward during the same period.

These results, among the first to use empirical data to look at how climate change is shaping eastern forests, were published in Science Advances on Wednesday.

Trees, of course, don’t move themselves. But their populations can shift over time, and saplings can expand into a new region while older growth dies in another.

While climate change has elevated temperatures across the eastern United States, it has significantly altered rainfall totals. The northeast has gotten a little more rain since 1980 than it did during the proceeding century, while the southeast has gotten much less rain. The Great Plains, especially in Oklahoma and Kansas, get much more than historically normal.