The 19th century idea of Manifest Destiny — that U.S. settlers were destined to expand across North America — might not be a notion exclusive to humans. A new study has shown that the trees which make up many of the forests in the Eastern portion of the U.S. are steadily migrating north and, surprisingly, out west, reports Phys.org.

If the trend continues, it could one day change the composition of western forests to look more like eastern forests. Some sections of eastern forests, on the other hand, could be shifting to something else entirely.

The main reason for the change appears to be a shift in climate. The Southeast is getting generally drier and the West is getting gradually wetter. For instance, the range of the eastern white pine has picked up and moved more than 80 miles west since the early 1980s. Meanwhile, the scarlet oak has moved more than 127 miles to the northwest from the Appalachians in that same time period. Now the tree is more common in the Midwest.

"This analysis provides solid evidence that changes are occurring," wrote U.S. Forest Chief Michael Dombeck. "It's critical that we not ignore what analyses like these and what science is telling us about what is happening in nature."

You might not think of forests as moving entities, but subtle shifts in what grows at a forest's borders can mean big geographic changes over time. Researchers considered a number of factors that might be at fault for these particular changes, and determined that the biggest culprit was likely climate change. As the climate warms, the northern movement of vegetation into colder regions was to be expected. The movement west was a bit of a surprise, however.

The study shows how climate change is as much a lateral movement as a horizontal one, dramatically altering our landscape in unexpected ways. Those living on these climate borderlands might one day find their wooded surroundings unrecognizable when compared against memory.