ARI SHAPIRO, HOST:
We're all familiar with migration. Wildebeests gallop across Africa. Monarch butterflies flit across the Americas. Well, what if I told you that forests migrate, too? Here's science writer Zach St. George reading from his new book "The Journeys Of Trees."
ZACH ST GEORGE: (Reading) Individual trees, as will be apparent to most people who have encountered one, don't often move around. Once a tree is rooted in one spot, it's rare for it to wind up in another. Forests, though, are restless things. Any time a tree dies or sprouts, the forest it is a part of has shifted a little. The migration of a forest is just many trees sprouting in the same direction. Through the fossils that ancient forests left behind, scientists can track their movements over the eons. They shuffle back and forth across continents, sometimes following the same route more than once, like migrating birds or whales.
SHAPIRO: Zach St. George told me it's an agonizingly slow migration as forests creep inch by inch to more hospitable places.
ST GEORGE: They produce a seed, and that seed arrives somewhere new, maybe a little bit beyond the edges of the species' current range. So the migration of a forest is communal, it's constant. It is accomplished over many generations.
SHAPIRO: So if we imagine a forest, it's not that it is sending all of the seeds to the north, it's that it's sending seeds in every direction, but the ones that go to the north thrive a little more than the ones that went to the south. And so over time, the forest marches steadily northwards. Is that right?
ST GEORGE: Yeah, that's right. So it's a question of the species succeeding more in one part of its range, becoming more abundant in one part of its range and less abundant in another part of its range.
SHAPIRO: This has happened over millennia, and climate change tends to be the driving force, pushing and pulling forests around the globe. Of course, today, climate change is speeding up, and trees can't keep up with the pace. Take California. It's getting hotter and drier, and scientists estimate that before too long, Joshua Tree National Park may not be able to sustain Joshua trees. Zach St. George describes a similar threat to Sequoia National Park during California's epic drought a few years back.
ST GEORGE: The scientists there had never seen anything like it. They worried that maybe Sequoia National Park would no longer be the place for giant sequoias. And I think at some point we will lose these ancient trees, and we will have to think about what we do with the places and do we plant new groves somewhere else.
SHAPIRO: This is known as assisted migration - humans planting trees in other places where they're more likely to thrive. But that carries risks. People can accidentally introduce insects and diseases to new places where they may wipe out entire populations of native plants and animals. So, St. George writes, there is a debate among conservationists and foresters today. Should humans help the trees escape?
ST GEORGE: I think there are going to be instances where people are probably going to step in and help species move to places they'll be more suitable in the future. So far, there are no huge movements of citizen groups moving trees north or upslope, but that's kind of one vision of the future that people I interview hope to see.
SHAPIRO: Did you end the process of writing this book more or less optimistic than when you started?
ST GEORGE: I think I ended more optimistic. You know, climate change is going to have these really dramatic effects on forests. We're going to lose a lot of forests. We're going to see species rearranged. We'll probably see more fires and droughts and millions of dead trees.
But, you know, the book is very much about trees, but it's also very much about people. And I met a lot of people in the process who sort of see these changes coming and have mourned what has been lost and what will be lost and are still continuing to try and do good and try and work towards a better future. You know, you can see these vast changes in the future and you can be worried about them, but you can still continue to do good and work in the moment for small things.
SHAPIRO: That's Zach St. George, author of "The Journeys Of Trees: A Story About Forests, People, And The Future." Thank you for talking with us today.
ST GEORGE: Thanks so much for having me.
(SOUNDBITE OF EVOLUTION OF STARS' "PRETENDING")
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.