How Will These Long-Lived Trees Adapt To Climate Change?

IRA FLATOW: Staying with our tree theme, if you had to take a guess of what type of tree lives the longest, what would you say? I’d guess the Redwood. Well, I’d be wrong. The most ancient trees actually live on mountaintops in harsh, dry climates. And they are called bristlecone pines. These trees have evolved lots of adaptations to live in rough terrains. 

But it’s going to get even tougher. Climate change is raising temperatures and pushing the trees to adapt once again. So how will these trees survive in a warmer future? That’s the topic of our latest Macroscope video, which features my next guest, Brian Smithers, Assistant Ecology Research Professor at Montana State University in Bozeman. And you can watch the video up on our website at sciencefriday.com/pine. Welcome to Science Friday. 

BRIAN SMITHERS: Thanks for having me. It’s really a pleasure. 

IRA FLATOW: You’re welcome. And when you say pine trees, a pointy Christmas tree comes to mind. But these bristle– they’re not really like a Christmas tree, are they? 

BRIAN SMITHERS: Interestingly, where they grow, protected, with plenty of water, they do. They grow nice and straight and look lovely. The problem is that happens pretty rarely where these grow. These are found throughout the Great Basin, which is a dry area, mostly kind of centered around Nevada, at the tops of mountains. And they get just beaten down by the conditions, by wind, by snow, by drought, by heat. They get them all. And so they really get gnarled and twisted and deformed by the physical conditions in which they live. 

IRA FLATOW: So they’ve had to adapt over the years to be some of the longest living trees. 

BRIAN SMITHERS: It’s part of living in that kind of a climate is you can’t grow quick and fast, like say, you mentioned a Redwood or Sequoia, where they get plenty of water. Their adaptation is to grow slowly. And a byproduct of that slow growth means they have incredibly dense wood. And that dense wood allows them to just keep on growing. They don’t get knocked over by wind. They can’t get invaded by parasites or pests. And so they just keep on trucking along. 

IRA FLATOW: So how old do they get? 

BRIAN SMITHERS: We don’t really know the answer to that. There are a couple of specimens that we have aged to over 5,000 years, which you said they were the oldest tree. They’re actually the oldest organisms on Earth that aren’t colonial in some way. 

IRA FLATOW: I’m just– I’m silent because I’m in awe. A 5,000-year-old tree. Wow. And these trees are going to need to find– I mean, you say how tough they are, but they are facing another challenge, which is climate change. With warming temperatures, they’re going to have to move up the mountain to cooler climes? 

BRIAN SMITHERS: They will. You can imagine a 5,000-year-old tree has seen quite a bit of climate change in its life. Adults are probably fine, for the near term anyway. It’s really about how will the young trees establish– how will they establish in response to climate change. Can they establish in places where the adults are found now? Or is it now too warm and, hence, too dry to establish there? Or do they need to move up slope in order for the species to keep up with climate change? 

IRA FLATOW: So when we say that they have to move up the mountain, it will be the young trees, the new trees falling– trying to take root in a different place and surviving better than their parents down the mountain. 

BRIAN SMITHERS: Correct. 

IRA FLATOW: And that’s how it actually moves. 

BRIAN SMITHERS: Adult trees are really bad at moving. 

[LAUGHING] 

It’s really about the seeds and the young that need to make that move. That’s all plants, of course. 

IRA FLATOW: Of course. I’m Ira Flatow. This is Science Friday from WNYC Studios, talking with Brian Smithers of Montana State University in Bozeman. Why do the trees need these cooler temperatures? We were just talking about these other maple trees. What about these trees? Are they– same story? 

BRIAN SMITHERS: That’s funny. I really enjoyed the conversation you were having with the prior guest. There’s a– there’s a bristlecone pine growing in front of the California State capitol in Sacramento, California. It is not known for being cool in Sacramento, California. Temperatures up to 120 degrees in the summer. That tree is doing just fine because it’s getting– it’s getting watered. 

Bristlecone pine isn’t relegated to these rough, dry, windy spots because it enjoys it. It’s there because there’s not a whole lot of competition. It’s– what it does well is grow slowly and persistently. But it doesn’t compete well with faster growing trees that are typically found further down slope. 

IRA FLATOW: And it’s interesting that you say that because isn’t there another species, a limber pine, that is competing for the same real estate? 

BRIAN SMITHERS: Yeah, that’s right. So there is a species that they sort of coexist, although limber pine is typically found a little further down slope, can handle hotter and drier temperatures. And they have, what we called leapfrogged, right over bristlecone pine and are charging up slope. In the last, say, 50 years we’ve seen this trend, where limber pine is establishing in far higher numbers than bristlecone pine is above what is usually all adult bristlecone pines. 

And so the concern is are they taking all of the good spots? Are they taking all of the available real estate up slope of where you do find these bristlecone pine trees? We don’t know the answer to that. Sorry, go ahead. 

[INTERPOSING VOICES] 

IRA FLATOW: You almost answered my question. I was going to ask is there going to be a definite winner in this race? 

BRIAN SMITHERS: There certain– I don’t know the answer to that question. There certainly looks like there is a short-term winner. And that’s limber pine. The problem with saying something like short-term is that we probably think of that as decades or something. But when we talk about trees that live for thousands of years, short-term can be 5,000, 10,000 years, multiple generations of these trees, where we will probably see a far higher abundance of limber pine in these historically, you know, pretty historically bristlecone pine forests. 

I think we won’t know the answer to your question for 10,000 years? 20,000 years? 

IRA FLATOW: All right, we’ll meet back here and talk about– 

BRIAN SMITHERS: Yeah, we’ll talk. That’s great. Yeah. I’ll enjoy it. 

IRA FLATOW: But this is one case of changes that happened due to climate change, right? 

BRIAN SMITHERS: It’s absolutely– it’s absolutely a climate change issue. But these– and a recent climate change issue. Interestingly, there are, of course, natural climate changes, which have also happened. Because these trees grow so slowly and respond to climate so slowly, they’re still actually responding to coming out of what we call the Little Ice Age, which started getting warmer around 1850. They’re still actually responding to that climate change, much less the more recent anthropogenic climate change. So it’s kind of a convoluted mess out there. 

IRA FLATOW: Well, that’s a great way to end this conversation, thinking about they’re still adjusting from 1850. Brian Smithers, Assistant Ecology Research Professor at Montana State University in Bozeman. Thank you for joining us today. 

BRIAN SMITHERS: Thanks so much. It was my pleasure. 

IRA FLATOW: And you can watch our latest Macroscope video featuring Brian and these bristlecone pines at our website at sciencefriday.com/pine.

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