Why are trees moving west?

In a recent study published in Science Advances, ecologists report that more and more trees are popping up west of where they'd typically grow. It's as if part of American forests are actually shifting slightly westward.

Trees don't actually get up and move, of course. But "new trees tend to sprout farther north and west while the trees that are farther south and east tend to die off, shifting the geographic center of where trees live," according to the Associated Press.

It's long been documented that many plants and animals move north as the climate warms, but this is a finding that has some researchers scratching their heads. The authors hypothesize it has to do with moisture, not temperature.

MPR's Cathy Wurzer spoke to Lee Frelich, director of the University of Minnesota Center for Forest Ecology — who was not an author on the paper — about what may be happening.

Click on the audio player above to hear their conversation.