May 22, 2017 I Brett Tingley

America’s Trees Are Mysteriously Migrating West

While melting Arctic and Antarctic sea ice gets most of the attention when discussing the effects of climate change on our fragile planet, changing temperatures and weather patterns are currently causing a host of unforeseen and mysterious phenomena. A new study out of Purdue University shows that some of these effects go against our expectations of how the natural world responds to rising global temperatures. According to the study published in Science, trees throughout the United States have been moving steadily westward over the last three decades. While the idea of a great American Entmoot sounds awesome, the reality is less exciting and a lot more depressing.

The migration patterns fluctuate among various tree species.

Like most of the ecological changes brought about by climate shifts, this arboreal migration is in response to rising average temperatures and the secondary effects those higher temperatures cause. The resulting shift in tree populations could have unknown consequences on fragile American ecosystems:

In summary, trees in the eastern United States have experienced prominent westward and northward shifts in response to climate change and successional processes.[...] The resultant divergent spatial shifts among various groups can have significant ecological consequences and possible extinction of certain evolutionary lineages in some forest communities.

In a press release accompanying the study, Purdue University professor Songlin Fei says that while many tree species have been found to migrate north, he and his colleagues were surprised to find that the majority of tree species have been moving west in response to climate change.

Most of the species studied were found to move west, north, or northwest.

Fei and his fellow researchers believe that changes in precipitation patterns brought about by a warming planet are to blame for these migrations, although this remains a hypothesis:

[...] We did see some northward shift as we had anticipated. But we also found many trees have been moving westward because of changing climate. When analyzing the impact of climate change, precipitation had a much stronger near-term impact on forests instead of temperatures. It is not future predictions. Empirical data reveals the impact of climate change is happening on the ground now. It’s in action.

However damning their data might sound, Fei and his colleagues speculate that only about 20% of the migration can be attributed to man-made climate change. Other factors could be at play including land use, wildfire frequency, or the impact of pests and arboreal diseases.

The researchers suspect changes to both temperature and precipitation are to blame.

Granted, human activity has contributed to many of those as well. While this study is only a beginning in understanding climate change’s impact on tree populations, the data reveals that the various forces at work in the natural world are much more interconnected and mysterious than we realize.

Brett Tingley

Brett Tingley is a writer and musician living in the ancient Appalachian mountains.

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