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Trees in the US Are Moving North, West to Escape Climate Change

As man-made climate change is forcing human populations to migrate inland, inanimate life forms on Earth are also trying to escape changing weather patterns.

Trees in the Eastern United States are moving north and west because of rising temperatures and changing rainfall patterns, according to a new study by Science Advances, published Wednesday.

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Scientists examined 86 species of trees in the Eastern US and found that 73% experienced a westward shift, while 62% experienced a poleward shift during the past 30 years. On average, abundance centers moved more than 25 miles (45 kilometers) west and 20 miles (33 kilometers) north.

Changes in precipitation had a greater effect on trees than temperature, at least in the short term, the study said. The poleward shift had been predicted as trees prefer consistent temperatures, but scientists didn’t foresee how changing rainfall patterns would cause a greater westward migration, thanks to an increase in precipitation in the central US coinciding with a decrease in the southeast.  

Trees migration US environment climate changeLeft: Changes in temperature across the eastern U.S. between the recent past (1951–1980) and the study period (1981–2014). Right: Changes in precipitation.
Image: Science Advances

Trees aren’t physically uprooting themselves and moving. Rather, saplings are thriving in new areas that are more hospitable as older trees are dying. Lead author Songlin Fei of Purdue University said to think of it as a line of people from Atlanta to Indianapolis: though nobody moves, if more people join the Indianapolis end and those at the Atlanta end leave, the center is going to shift.

Some species experienced massive migrations. The scarlet oak, for instance, has moved more than 127 miles to the northwest from the Appalachians, Fei told the Associated Press.

The shift could cause certain species of trees to go extinct in some forests, according to the study.

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Forests are crucial for the survival of more than 2 billion people around the world, according to World Wildlife Fund. They provide habitats for humans and animals and natural resources, not to mention oxygen. Furthermore, they prevent soil erosion and flooding, and help reduce climate change by absorbing carbon dioxide in the atmosphere.      

Even so, 46-58 thousand square miles of forest are lost each year.

The study accounted for people cutting down trees and planting new ones, but acknowledged other non-climatic factors could have contributed to tree species shifts (like fires, invasive species, and conservation efforts).

“Nevertheless, we observed clear broad-scale evidence of the impact on climate change on forest tree spatial dynamics, where changes in mean annual precipitation alone explained about 19% of the variability in species abundance change,” the study said.

“Management actions to increase forest ecosystem’s resilience to climate change should consider the changes in both temperature and precipitation.”

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