SCOTT DETROW, HOST:
All around the world, people and ecosystems are being challenged by a changing climate. Look no further than the extreme temperatures that have scorched parts of the U.S. in recent weeks. But it's not just hotter summers that we should be worried about. It's warmer temperatures year-round that are changing life in all kinds of ways. In Minnesota, for example, warmer temperatures, drought and disease have all been putting stress on native tree species there, like paper birch and red pine. And while some trees are dying as a result, others are adapting to a hotter climate. Peter O'Dowd went deep into the woods of Minnesota to report this story.
UNIDENTIFIED PERSON: Give us a shove.
(SOUNDBITE OF BOAT REVVING)
PETER O'DOWD, BYLINE: It is a blustery spring day in Minnesota, and this tiny fishing boat is burdened with the weight of a few thousand baby trees and too many grown men. We're on McDougal Lake in the Superior National Forest. The wind is pushing whitecaps over the bow. As we chug toward an island in the middle of the lake, it's obvious why we're here. On shore, the charred remains of a white pine forest are scattered everywhere.
This spot, a couple of years ago, 2021, burned in a fire. And this crew is walking through the snags and the brush of this island, planting tiny little trees, raising up a tool that looks like an axe slamming into the ground and then putting a plug of a tree in the ground before moving on to do it again.
LAURA SLAVSKY: We're planting these trees today. But literally in 200 years, they could be the big trees that we see around. It's just hard to wrap your head around what that means.
O'DOWD: The Nature Conservancy's Laura Slavsky is managing this crew. And what it means is that every surviving tree will suck up and store planet-warming carbon from the atmosphere for centuries.
SLAVSKY: And this year, we're slated to plant about 1,400,000 trees.
O'DOWD: Does that seem like a lot to you or not?
SLAVSKY: Once you hear a million, people think it's great. And then I feel like it's really hard to picture what that actually looks like. So now that I've gotten to see a couple years of us doing this, I'd say it's quite a few trees.
O'DOWD: One of them is right here at our feet.
So it's so tiny.
SLAVSKY: Yeah.
O'DOWD: How old is that?
SLAVSKY: It was grown in a greenhouse for one year.
O'DOWD: The seed that grew this baby white pine was collected about 200 miles south of here. Slavsky says that distance is enough to make its genes just a little bit different from the white pine that grows here naturally.
SLAVSKY: So as the climate's warming, there's going to be more stresses on the trees that are growing in these areas. And taking a species - even though it does grow here - taking it from further south, that's more adapted to warm temperatures, potentially a drier climate. So they're predicted to do better. Without a helping hand, I think the forest will see a lot more stresses and mortality in the trees that are here.
O'DOWD: What Slavsky just described is something known as forest assisted migration. Some people in Minnesota believe it is the key to reversing the effects of climate change.
JULIE ETTERSON: There are just graveyards of dead and dying birch trees, and there's nothing coming up in the understory.
O'DOWD: Julie Etterson is a professor at the University of Minnesota Duluth. She had a hunch that a hotter climate might benefit a different kind of tree. So a while back, she took a few species of oak from the warmer southern regions of Minnesota and planted them in the north. Every year, she tracked their progress.
ETTERSON: To figure out whether or not the more southern population was doing better. And it was. There's significantly higher survival and better growth when they are transplanted into a climate that matches where they used to live.
O'DOWD: Etterson's work laid the foundation for assisted migration evangelists like David Abazs.
DAVID ABAZS: These trees are the best chance to help us have a surviving forest canopy in what we call now the north woods.
O'DOWD: Abazs helped start a group called the Forest Assisted Migration Project. He's recruiting seed collectors and farmers to grow what he calls climate-smart trees. It's part of a bigger goal to reforest a million acres in the state in the next two decades. Today we're visiting one of those growers.
STEFAN MEYER: So over here, these, you'll see, are all the new red oaks that were just planted this spring.
O'DOWD: Stefan Meyer runs the 3 Oaks Forest Farm in Kettle River. His high-tunnel greenhouse is hot enough to pull the sweat right off your brow.
OK. Dumbest question in the world - they come from an acorn?
MEYER: They come from an acorn. Yes.
O'DOWD: Oh, there it is.
MEYER: It looks just like that. And they've been gathering them from as - how far south in Minnesota?
ABAZS: Oh, Twin Cities, down even to south of the Twin Cities.
O'DOWD: Abazs says once Meyer's trees reach a year old, he'll sell them to groups like The Nature Conservancy.
ABAZS: If we don't do this, according to the scientists and all the models that I've looked at, we're looking at prairies moving all the way up to Duluth. So we're looking at a great transformation because guess what? Trees can't walk as fast as climate change.
O'DOWD: But there is a risk to moving plants around. A tree that's not native to the forest might carry a new disease or grow so well that it becomes an invasive species. Abazs uses a traffic signal metaphor to describe this problem. He says the safest climate-adapted trees to plant in Minnesota are the ones that are already here, like Meyer's oak trees with the southern Minnesota genetics. He calls those green trees.
ABAZS: Yellow - yield.
O'DOWD: Trees like the river birch - proceed with caution. Abazs says those are already creeping into northeast Minnesota as the climate warms.
ABAZS: And then there's the red ones. There's the northern Iowa ones that may eventually get here. But, you know, those - really let's stop and think about this.
O'DOWD: Give me an example of what a red tree...
ABAZS: Oh, like a shagbark hickory, tulip poplar, a southern species. Man, I love tulip poplar. I've lived in areas tulip poplar. Is it appropriate for our area? I don't think so. And so that's the red light.
O'DOWD: A red light that a researcher in Minnesota's Chippewa National Forest has blown right through.
BRIAN PALIK: This is our seedling trail. So what we have here are examples of everything we planted. So this is eastern white pine.
O'DOWD: Brian Palik is nine years into his own assisted migration study for the U.S. Forest Service. As we walk down this wooded path, even Palik says some of the trees he planted in this experiment are pushing the limits. There's a thriving, bitternut hickory from southern Michigan and Illinois.
PALIK: So we've moved it quite a ways.
O'DOWD: Yeah, I mean, Illinois is not close really.
PALIK: No. No, it's not close. One of the more radical species we brought in is ponderosa pine, which is native to the western U.S. This one that we're looking at is from the Black Hills in South Dakota. It's doing quite well.
O'DOWD: There's another from Nebraska and one from Montana. Palik says three-quarters of the ponderosa pine in this experiment have already died.
PALIK: But when they do survive, they grow like gangbusters. They're the fastest growing thing that we've planted out here. I used to think of some of what we're doing with assisted migration as being high risk, and it is to some extent, but less so as you start thinking about how the climate has already changed in this part of the world. And I don't think that we can sit back and wait and see what happens.
O'DOWD: Is that why you think it's necessary to push the envelope even farther than you would otherwise...
PALIK: Yeah.
O'DOWD: ...With these trees?
PALIK: Absolutely. When we're thinking about another nine-degree mean annual temperature increase in this part of Minnesota by the end of the century, we have to be looking at trees that are adapted to that. And they're probably not here right now.
O'DOWD: Nine degrees.
PALIK: Yeah. Yep. Yes.
BEN BENOIT: I think there's some trepidation, certainly.
O'DOWD: Ben Benoit was invited to come along on this tour. He's a district ranger for the Chippewa National Forest and a member of the Leech Lake Band of Ojibwe. They've been living with the bounty of these woods and waterways for generations.
BENOIT: Every fall, the wild rice grows and is harvested by tribal members throughout this whole area.
O'DOWD: And I understand that rice is in decline.
BENOIT: Right. And that is one of the fears, I think, about climate change. Like, how are those resources that are so integrated into culture and livelihood going to be affected?
O'DOWD: And it's not just the wild rice. Listen to the ovenbirds and the warblers rejoice in the canopy above us.
(SOUNDBITE OF BIRDS CHIRPING)
O'DOWD: Benoit says tribe members believe all living creatures in the forest are like relatives, including the trees. And some people are wary of unintended consequences. Think about cane toads in Australia, he says. Ninety years ago, scientists introduced the animals to control a sugarcane beetle. Today, millions upon millions of them have infested the country.
BENOIT: I think that's kind of where that trepidation is. Treating things like an experiment isn't the way that we're taught to care for, you know, our relatives in the land.
O'DOWD: What do you think your elders would think of seeing a ponderosa pine growing here?
BENOIT: I think you would find people who would understand and be supportive of that and people who wouldn't. My grandfather, for example, likely wouldn't want to see those things brought in in this way. He'd probably say, just leave it alone.
(SOUNDBITE OF WATER DRIPPING)
O'DOWD: But is there time to just leave it alone? People like Chris Dunham with The Nature Conservancy don't think so, which is why there are sprigs of new life popping up along the Baptism River and McDougal Lake.
CHRIS DUNHAM: There is definitely some poetry in this business. You know, we're leaving this legacy.
O'DOWD: Only about a quarter of the 1.5 million trees the group planted this year are from warmer areas to the south, but every one of them was chosen to help diversify the forest to make it more resilient to a changing climate.
DUNHAM: We're not just, like, sitting ducks waiting to be wiped out by climate change. We can actively go out there and do what we can do. And in our case, we feel like that means planting millions of trees, taking care of millions of trees. And we just hope that that holds.
O'DOWD: Every time a crew member strikes the earth to open up a hole, a fledgling tree goes into the ground. Given time, a few of them might grow tall enough to outlive us all.
DETROW: That was reporter Peter O'Dowd. His story about trees and the changing climate in Minnesota first aired on Here & Now, a production of WBUR Boston and NPR. Transcript provided by NPR, Copyright NPR.
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