Climate change is pushing U.S. trees north and west

This way, please.
Image: alan copson/Travel Libra/REX/Shutterstock

Climate change is uprooting trees across the eastern United States.

Dozens of species are shifting west and north of their usual locations as average temperatures and rainfall patterns change, researchers found.

Oak, maple, and other deciduous trees are primarily heading westward as they follow changes in moisture availability, according to a new study in the journal Science Advances. Evergreens like firs and pines are shifting northward in search of cooler climes.

“It is not future predictions,” Songlin Fei, the study’s lead author and a Purdue University professor, said in a press release.

“Empirical data reveals the impact of climate change is happening on the ground now,” he said. “It’s in action.”

Image: Songlin Fei

Tree movement can have a profound impact on forest ecosystems.

Soil, insects, animals, and other plants all depend on trees for shelter and sustenance. Trees themselves rely on this complex web for nutrition and seed-spreading. If these woody wonders pack up and move, the delicate system can be thrown off balance.

For birds, such shifts add insult to injury. Springtime conditions have grown more variable and unpredictable in North America, making it harder for songbirds to time their migrations and secure the best nests and food supplies for their chicks, a separate report found this week.

The tree study is based on an analysis of U.S. Forest Service data gathered between 1980 and 2015. It encompasses 86 tree species between Maine and Minnesota, and as far south as Florida.

Image: Songlin Fei

Over the 35-year period, the mean annual temperature in the eastern U.S. increased by about 0.16 degrees Celsius on average, or 0.29 degrees Fahrenheit. Northern areas saw the greatest temperature increases, researchers said.

Precipitation patterns also changed, particularly in the southern region, where increasing temperatures helped lead to widespread droughts, according to the Palmer Drought Severity Index.

Climate scientists attribute such changes at least partly to human-caused global warming.

As greenhouse gas concentrations in the air reach new highs, land and sea temperatures are ticking up, affecting weather patterns and spurring extreme events such as heat waves, floods, and droughts. All of these can overwhelm the ability of plants and animals to cope.

Image: Songlin Fei

Previous studies on how climate change affects trees have generally shown a strong correlation between changes in temperature and shifting tree ranges. But this new study revealed that precipitation also plays a significant role in tree movement.

Fei said the westward shift of deciduous trees was among researchers’ most surprising findings.

“When analyzing the impact of climate change, precipitation had a much stronger near-term impacts on forests instead of temperatures,” he said.

What’s less clear is how these changes will affect the sustainability and biodiversity of forest ecosystems, though Fei said further research will focus on this area.

“We want to know if there is a community breakdown among groups of species resulting from climate changes,” he said.

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