Go west, young tree! A study published Wednesday in Science Advances finds the trees of eastern American forests are on the move—and none too slowly, either. The study looked at 86 tree species between 1980 and 2015, Smithsonian reports. Over those 35 years, 73% of the trees saw their population centers move westward, and 62% saw them move northward. According to Science Alert, westbound trees moved by about 9.5 miles per decade; northward trees moved about 6.8 miles per decade. The trees themselves weren't moving, Groot-style; instead their population centers shifted as saplings sprouted up in new areas and trees in older areas died off, the Atlantic explains.
Scientists have long expected tree populations to move north in search of cooler temperatures as the effects of climate change increase. However, the move west was unexpected—and difficult to explain. “When the result came out that trees are moving westward, our eyeballs opened wide," study author Songlin Fei says. "Like, ‘Wow, what’s going on with this?'" Researchers hypothesize that climate change-related shifts in precipitation are causing the westward movement. The Great Plains have received much more precipitation than normal over the past few decades, while the Southeast has received much less. But, the researchers admit precipitation can only account for about 20% of the westward movement. (Newly discovered forests could cover 60% of Australia.)