A tiny figure in a red jacket walks through tall trees, a bright green forest.

Trees naturally migrate, but with climate change they are having a hard time keeping up.

Stephani Gordon / OPB


With the help from wind or local wildlife, forests have managed to migrate naturally with changing temperatures, gradually moving to more hospitable areas. However, as climate change continues, forests are unable to adapt quickly enough. Brad St. Clair is a Research Geneticist with the U.S. Forest Service looking into what’s known as assisted migration. He joins us with details on his work in Medford and the future of forests.

The following transcript was created by a computer and edited by a volunteer.

Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. Can we move our forests in time to save them? That’s the headline of a new article in Mother Jones by the journalist Lauren Markham. She focused on the plight of trees which are in a kind of race that it doesn’t seem like they can win on their own. Trees naturally migrate with the help of wind and birds and squirrels. They take root wherever they can thrive. The problem now is their natural migration can’t keep up with the changing climate. So forest scientists say it’s time to help them out. Brad St. Clair is one of those scientists. He’s a Research Geneticist with the U.S. Forest Service based in Corvallis. He was featured in the Mother Jones article and he joins us now. It’s good to have you on Think Out Loud.

Brad St. Clair: Thank you. It’s good to be here.

Dave Miller: So I mentioned that this is a kind of race that trees seem to be losing. Can you give us a sense for the average pace of a forest migration naturally and the pace that they would need to actually keep up if they’re going to keep up with climate change.

Brad St. Clair: Yeah, that’s true. Forests, we know from the Paleo botanical literature that forests in the past when glaciers have receded and so forth have migrated at about a rate of about 200-400 meters per year. But with the rate of climate change, the estimates are the trees would have to migrate about 10 times faster. About 3000 to 5000 km. per year to keep up with the climate change.

Dave Miller: Could they even do that given the way we humans have chopped up and developed land for roads and for farms and for exurbia.

Brad St. Clair: Yeah, that is one issue, but there’s still a lot of contiguous land up and down in the national forests and things and other land ownership. So I think it’s possible, particularly when you’re moving between climates in elevation where it might be a shorter distance, but in other places you’re correct that fragmentation could be an issue.

Dave Miller: So, this gets us to assisted migration, meaning taking saplings or seeds and planting them in different places higher up to get to a higher elevation or further north to get to a cooler or wetter place. Can you give us a sense for how it actually would work in practice?

Brad St. Clair: Well, in the, I’ll give you a little bit of background about how it has worked in the past. In the past we have generally moved things, moved tree populations within what we call seed zones, which are basically a geographic area where we put a line on a map and there’s elevation bands in there that say, well we should not move things beyond this line. But the problem is the climate has changed and this is based on the idea that things are locally adapted, that they’re adapted to the locations where they come from. The problem is that’s no longer true, as the climates change, they become increasingly maladaptive. So we could, I think part of it is that we need to take the focus away from geography and focus on climate. So the approach is to match the climate to which trees are adapted, based on where they came from, with the assumption that they are adapted to the climate in which they evolved and match it to the climate in the future, but also keep in mind that it needs to be adapted to the short term, also.

Dave Miller: If it’s going to survive in the next five years... In other words, it might be great 100 years from now, but can it survive if you plant it there today?

Brad St. Clair: That’s correct. So we can’t move things too far from a warmer to a cooler climate, for example uphill, as you said, because we don’t want that, we want them to be adapted and not get cold damage in the short term, but we’re hoping that we can move them far enough that they will be adapted to the warmer climates in the long term.

Dave Miller: But it seems like the only way to do this successfully is if you have a pretty good sense for what the climate of a particular place is going to be like over the next 1 to 100 years or 400 years. And if you know which kinds of trees are likely to thrive in those places. How much confidence do you and other forest scientists have right now, given just how many variables are in the mix?

Brad St. Clair: Well, that’s why we do research. And so there’s two types. We’re looking at the climatic niche of the species and the climatic niche of the populations within species, and the climatic niche of the species is looked at by something called species distribution models, which are not, that do have some issues because they’ve just taken to affect climate mostly and there may be some other factors that we have to keep in mind when we move things, but we also have to keep in mind that populations within species are adapted at a finer scale than the species as a whole. And that’s kind of some of the research that I and others are doing to look at that relationship between how different populations from within a species grow and survive and maybe reproduce relative to the climate in which they evolved and what happens when you move them to a different climate?


Dave Miller: Well, this gets to I think work you’ve done in, among other places in southwestern Oregon near Medford. Can you describe some of the stands of trees that you planted there back in 2009?

Brad St. Clair: Yeah. So this is a study we have called the seed source movement trial and it’s basically, we do provenance tests where we take a whole bunch of seed sources and we plant them all together in one location. So the differences we see are predominantly due to genetics because they’re kind of all growing in the same environment. And we do this at several places. It’s also called a reciprocal transplant study, so that we move seeds or plant material from, for example, Washington coast down to the hot, dry climate of Medford and vice versa. And when we move things from Washington coast down to Medford, we start to see that there could be some issues because we move them too far from a wet climate to a dry climate.

Dave Miller: You move them in a sense to the future, right?

Brad St. Clair: Exactly. And I’d love the first sentence of the article in Mother Jones that Lauren wrote that said, “I drove to Oregon because I wanted to see the future.”  And the future that she saw, was another term that I wish I’d thought of before: ‘arboreal apocalypse’.

Dave Miller: Well, I was going to ask you about this. I mean, this is one of the stands of the trees that you planted in Medford. Can you describe where those trees came from and what they look like?

Brad St. Clair: Well, we’re in the process of trying to figure out. I can tell you what they look like. So they came from wet dry places in the Oregon Washington coast, no wet, warm places, mild climates. And then we moved them to the hot, dry climate at two locations near Medford and Grants Pass and what appears to be happening, we’re trying to sort this out now, but it appears that they’re being attacked by, they’re drought stressed and we looked at different characteristics that might explain drought, adaptation to drought, for example, what we call specific leaf area, but they appear to be drought stressed and they’re getting attacked by a canker that is called Phomopsis and that’s followed by beetles. So they’re starting to die, they’re getting dead tops, they’re getting dead branches and eventually they might start to die. So that’s the arboreal apocalypse that Lauren was describing in her article.

Dave Miller: Correct me if if this is too much of an oversimplification, but is the basic idea that you would be really interested now in the opposite, in trees that, say Doug Firs, that have specific populations of which have done seemingly pretty well in hotter, drier places and those would be the kinds of trees that you might increasingly plant in places that are going to get hotter and drier in the coming decades. Is that the basic idea?

Brad St. Clair: Yes, that’s correct. Move things from a hot dryer climate or move things from hot dry to currently colder climate and then they will be adapted to the future when it becomes hotter and drier.

Dave Miller: One of the things that tree scientists seem to have known for decades now, but many of the rest of us are learning more recently is that forests are complex communicative societies that are not just about trees but super important underground networks, mycological networks and bugs all of which are in a kind of conversation with each other. Even trees talk to each other chemically, meaning none of this happens in a vacuum. You can’t just put a tree somewhere and expect it to thrive, necessarily. Can humans reproduce that kind of interconnected community as you’re doing artificial migration?

Brad St. Clair: That’s a very good question. It’s not my area of expertise but you know there is concern about it’s called Mycorrhizal fungi that we might need to make sure that there are native Mycorrhizal fungi that are also at those sites. It’s not clear to me how much of what we call genotype by fungi interaction there is so that there is adaptation or certain fungi or populations of fungi or genotypes of fungi are associated with certain genotypes or populations of trees. It’s not, I don’t think that’s an area of research that is not something that’s clear right now. But just in general, yes Mycorrhizal fungi are important for forests.

Dave Miller: To what extent is the seemingly growing consensus about the need to move trees? How much is that in line with the U.S. Forest Service policy and procedure, in other words can you do what you say needs to be done?

Brad St. Clair: I think we can do what needs to be done. The Forest Service manual, which is something that guides reforestation, again, this is not my area of expertise. I’m part of the research branches, it’s the National Forest branches that does the actual management, but the Forest Service manual, in the past, as I said, we’ve had these seed zones. And so the manual in the past has said, well we need to stay within these seed zones. But then they revised it a little bit, I’m not sure how long ago. And they said we need to use seedlings that are adapted to local climatic conditions, but we need to know something about that. We need to use seedlings from distant sources only if we’ve evaluated those distant sources. Well, we can’t evaluate all distant sources, but we do have the science that shows that tree populations are adapted to the local climates. So this new statement in the Forest Service manual does give us some latitude for assisted migration, but it’s not very specific about it. And that is actually I believe being reviewed right now at the Washington office for updates to what the manual might say in response to concerns about climate change.

Dave Miller: Just briefly, what’s it like to do this work when, if you’re successful or if these ideas are put in practice, you and I and probably everybody listening, we’re not going to be even alive to truly see it bear fruit. We’re talking about work that’s going to go many, many decades into the future.

Brad St. Clair: Yes. And that’s where the research branch of the Forest Service has an advantage because we can, we are not subject to short term funding and we’re able to look at things way in advance. I just finished a paper last year that looked at one of the first studies that was founded by the forest service called the Douglas Fir Energy Study. And it was planted in 1915 and 1916. So we had 100 year results from that. And so we can follow these things for quite some time. It’s still rewarding to know that we are, we may not see these results for 20 years, but it’s rewarding. First of all, we can learn stuff in short term studies in the early time, but it’s also rewarding to know that it’s out there and can be, provide some important information in the long term.

Dave Miller: Brad St. Clair, thanks for joining us today. I appreciate it.

Brad St. Clair: Yeah, thank you. My pleasure.

Dave Miller: Brad St. Clair is a Research Geneticist with the U.S. Forest Service. Tomorrow on the show, the Washington State Department of Corrections announced last week that they’re not going to use solitary confinement as punishment anymore. They found it wasn’t effective. We’re gonna get the details on the next Think Out Loud. Thanks very much for tuning in to Think Out Loud on OPB and KLCC. I’m Dave Miller. We’ll be back tomorrow.

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