In this episode
- Carly and Colleen discuss recent record high temperatures in Alaska
- Colleen asks what permafrost is, and what happens when it melts
- Carly talks about the best Beyoncé songs to sing to keep bears away
Timing and cues
Interview part 1 (2:23-12:49)
Interview part 2 (13:45-21:27)
Sidelining Science Throw (21:27-21:37)
Sidelining Science (21:37-27:21)
Colleen: Carly, welcome to the "Got Science" podcast.
Carly: Thank you so much for having me.
Colleen: So you study boreal forests with a focus on preserving carbon in the boreal forest, specifically in Alaska. So can you start by giving us the definition of a boreal forest?
Carly: Yeah. So boreal forests are the forests that occur at the highest latitude, so the most northern forests that we have. They are below Arctic tundra, which typically when we think of Arctic tundra, we're thinking of small plants, shrubs. But when we move into the boreal forest, we have trees, conifers, pines, that sort of thing. But the thing that's…that unites both of those ecosystems, both tundra and boreal forest, is that both of those are underlain by permafrost, which stores a huge amount of carbon.
Colleen: So permafrost is…it's frozen soil, is that what permafrost is?
Carly: Yeah, it's a mix of soil, rocks, and ice. So basically if you think of a soil matrix that you dumped water on and completely soaked and then stuck in the freezer, that's kind of the gist of permafrost. So it has this ice and water component, and in some places, these ice wedges. But yes, mostly soil.
Colleen: In the warmer seasons, I mean, does it melt or is it supposed to stay frozen all the time?
Carly: For permafrost, the standard definition is that it has to be frozen for at least two years. So you have continuous permafrost and discontinuous permafrost. And continuous is what it sounds like where it's all permafrost all the time essentially. And then in discontinuous areas, you have areas of continuous permafrost that are frozen year-round, with patches that may thaw out depending on the season.
But in all permafrost areas, typically you have a small portion, perhaps a foot or two, that are going to thaw out every summer, and that's the active layer. And one of the things that we've seen with climate warming is that that active layer's thickening every year.
Colleen: How thick is it?
Carly: It can be anything from a few meters thick to, you know, 2000 feet.
Colleen: Does the permafrost, with the changing of seasons, I mean, does the top part of it melt? Is it supposed to melt?
Carly: Yeah, definitely. So there is a specific part, maybe two or three feet or so that thaw every summer and that's the active layer. The active layer has been thickening in recent years though, and that's one of the major consequences that we've seen in the Arctic with the warming that we've seen there.
Colleen: Why is there more carbon in the soil in a boreal forest?
Carly: So carbon has accumulated over hundreds of thousands of years in some places in these ecosystems. So it's a very slow-growing ecosystem. But that also means that decomposition is really slow. So when we're thinking about the carbon cycle, carbon comes into the ecosystem when trees and plants are taking CO2 out of the atmosphere, and then that is transferred below ground into the soil in leaf parts and roots, etc. When there's no decomposition that can put that back into the atmosphere, that carbon is going to accumulate in the soil over time.
And so in these high-latitude ecosystems where it's really cold and very dark a lot of the time, what you're going to see is the accumulation of that carbon that's coming into the soil year after year. And a lot of it is now locked away as permafrost.
Colleen: You're studying wildfires in Alaska, both as a Kendall Science Fellow here at UCS and also at Woods Hole Research Center. Tell me a little bit about that.
Carly: Wildfires are a natural occurrence in Alaska, even before the onset of climate change. A lot of them in the boreal forest specifically are started by lightning. So a lightning strike will ignite a fire in one of these forests. And because it's typically during the summer, when things maybe have dried out, that fire can spread very quickly.
And so in Alaska, compared to other states that we see in the lower 48, they often have the highest acreage of burned area of any state. This year, they've already passed a million acres. We're really only partway through the fire season at this point. So it's a big part of the Alaskan ecosystem and it's a natural part too. These are fire-adapted ecosystems. So they're used to having fire come through. But as the climate has continued to change, the fires are coming through more frequently. They're happening more often, and they're often burning deeper and more severely into the organic layer, the active layer that I mentioned before that thaws out.
Colleen: And that's the part that concerns you.
Colleen: So tell me about that.
Carly: The active layer, like all soil, has carbon in it. But in this case, because of the slow decomposition that we talked about earlier, it's got a lot more carbon than other soils, and so it can easily burn. And in some cases, fires that are roaring through the boreal forest can burn down to the mineral soil, which is almost like a chocolate ice cream type texture. So it can take almost all of the organic horizon off of the soil. And that contributes a huge amount of carbon, a huge pulse of carbon with each fire that burns into the atmosphere.
Colleen: What’s happening in Alaska with the recent high temperatures, temperatures up to 90?
Carly: Yeah. Alaska has been experiencing a record heat wave. So the highest temperatures in Anchorage and several other cities that have ever been recorded. And this heat wave is consistent with the climatic warming that we've seen across the state. And while climate and weather are different, they can be symptomatic of each other.
So in Alaska we've been seeing record temperatures like those in Anchorage that reach 90 degrees. And one of the complicating factors, when I'm thinking about my own work and these high temperatures, is that by drying out these ecosystems, they may be increasing the risk of fire, which as we know, is part of this cycle that starts by releasing heat-trapping gases and furthering climatic warming.
Colleen: So how are wildfires in Alaska managed? Are they managed differently than in the lower 48?
Carly: Yeah. So there's an entire system that's specific to Alaska for fire management. So the state is separated or categorized, rather, into four different zones that determine how resources and personnel are allocated to fight any fire. So we have fires that are in critical zones, that are near population centers or other values at risk, where when a fire starts in one of those regions, it's going to be attacked with a huge amount of resources to really put that fire out as quickly as possible. Where on the other end of the spectrum, you have fires and lands that are in limited areas, where they're not necessarily receiving the same amount of resources as a fire in the critical zone might be, because it could be several hundred thousand acres of forest, which not that that's not worth protecting, but in terms of maintaining the natural ecosystem…
Colleen: They might just let it burn.
Carly: Exactly. I guess the one thing that distinguishes fire management in Alaska from fire management in the lower 48 is that the historic fire management that has created a lot of the problems that we're seeing, especially in California, just doesn't exist. There is no analog in Alaska. We haven't been managing forests and suppressing fires as intensely in Alaska as we have in California. And so I think that's a really important distinction in fire management strategies and history.
Colleen: So in order to keep, or in order to minimize forest fires so we're not releasing all of this extra carbon into the air, what sorts of strategies would work better in Alaska?
Carly: When it comes to fighting fire in Alaska, we can do more with management and implement different types of strategies to manage that fire. But in Alaska, there…we also need to just be fighting climate change generally. We need to be reducing our emissions of heat-trapping gases like carbon dioxide and methane. Because in Alaska, a lot of those same gases are coming out of the ecosystem when they burn.
Colleen: I mean, I know that wildfires in the west, there's a lot of forest management, like clearing out the underbrush and that…those sort of strategies. I imagine Alaska is huge and it's wilderness. It seems like those types of practices wouldn't really be practical.
Carly: And I think those are challenges with some of those preventative strategies, regardless of the ecosystem. Right? Implementing something like the mechanical thinning, like you're talking about, where you go through and remove some of the understory or some of the dead brush that you have there. One of the challenges with that is you can do that on a large area, but there's no guarantee that then that area is going to burn in the years when that treatment is effective.And so in a state like Alaska where that's magnified because it's such a huge landscape, although there have been people that have been doing research and testing out some of those treatments, the viability of them at a large scale is pretty low.
Colleen: Recently, the governor of Alaska has slashed funding for research into ecosystems at the University of Alaska. How is that going to impact the work that that really needs to happen?
Carly: The University of Alaska collects a lot of important data about how Arctic and boreal ecosystems are changing. And so with the deep cuts like those by the governor recently, that data might not be collected anymore. So these longitudinal data sets that we've collected over years and years may suddenly be capped at 2019. And so there could be huge consequences for our understanding of how these ecosystems, and especially the one that we have domestically in Alaska, is going to be changing as our climate continues to warm. Not to mention that the University of Alaska Fairbanks is the true, like, leading Arctic research university in the United States. And so to have their budget cut in the way that the governor has is going to be a huge loss to the Arctic research community, both here and abroad.
Colleen: So tell me about some of the research that you've been doing at the Woods Hole Research Center.
Carly: What we're trying to understand is if we can use fire management as a strategy to reduce overall emissions from the United States. So, like I mentioned, there are huge amounts of these heat trapping gasses that are coming out of these fires as they burn in Alaska, as they burn through that active layer, which even further melts the permafrost, which is, you know, happening all over the world. But my research specifically is trying to understand if we can manage fire differently such that we reduce the amount of those greenhouse gases.
And so, as an example, in 2004, which was one of the largest fire years on record, the amount of heat-trapping gases that were released from all the fires in Alaska were about equal to the emissions that came from the entire state of Florida burning fossil fuels. So these are a huge contribution to overall atmospheric CO2 and methane concentrations. But unlike some of the other challenges in Alaska, like melting permafrost, we actually know how to fight wildfire. And so for us, it presents an opportunity that's more viable than some of those other strategies for reducing emissions.
Colleen: How do you do the research? Are you on the ground? Or do you just use computer data?
Carly: Yeah. So for the research that I'm doing, we're using a lot of big data sets that are compiled by different government agencies. So we're using a combination of on-the-ground data sets that have been collected almost over the past century. So, databases of Alaska fires and what they're, you know, spatial extent is. We're using information about fire weather, about vegetation, a lot of which are from satellite data. And so what we're doing is we're trying to build a predictive model that can predict fire size based on things like vegetation, climate, as well as things like elevation. And in our specific research, we're incorporating these fire management zones, the critical to limited zones, that determine how a fire is fought.
Colleen: As temperatures rise, is there the possibility of extending the boreal forest into the tundra area?
Carly: Yeah, so there's definitely predicted range expansion of the boreal forest. And while that might be a positive thing in some respects, because we could get greater carbon storage above ground, an issue with that could be that we don't know what those consequences would be for the permafrost. We don't know whether or not that transition of trees growing into areas where typically there have only been these small shrubs and other, you know, prostrate plants, if that would have any impact on the permafrost.
Colleen: The one thing that I just can't, like, I can't get a visual on is when you say we can manage the fires in Alaska differently.
Carly: In Alaska, when we're talking about managing it differently, it's more about suppressing more fires in high carbon areas.
Colleen: Which I imagine is challenging because if your fire is out in the middle of the wilderness, how do you get people there to put it out?
Carly: Yeah. So there are hotshots and smokejumpers that are a big part of fighting fire in Alaska. So those are the people that are jumping out of planes into some of these burning forests to be the first on the ground to, you know, dig the trenches and make the firebreaks. But there's also a lot of aviation support in Alaska and so that can really help as well as hiking. So if you can get yourself out there, sometimes that's the best thing that you can…the best way you can get out there.
Colleen: So before we started taping, you were talking about the topography and what it’s like hiking in different parts of Alaska.
Carly: A lot of people who visit Denali for the first time, thinking it's going to be the same as hiking the Grand Canyon, are often surprised by how spongy the floor is. So the forest floor, I mean, and that's usually by virtue of the plant species that grow there and also the moss. So I know when I was walking in tundra, which is a little different than permafrost, I had someone explain it to me as walking on a mosaic of bowling balls and rotten watermelons and you never knew which you were gonna step on. And that can make the hiking itself even more challenging. I've rolled many an ankle walking in the tundra myself.
Colleen: So tell me about the time you've spent in Alaska doing research. You've been there typically not in the dead of winter, but in the milder climate.
Carly: Yes. I'm very much a fair-weather Arctic researcher, in that I've really never seen the sunset in the Arctic, if that tells you anything about the times that I've been there. So I worked at a research station that's funded by the National Science Foundation called Toolik Lake. That's up on the north slope of the Brooks Range, which is above the Arctic Circle.
And so I was interested, like you mentioned at the beginning, in soil carbon and what we can do to preserve that carbon and also what factors are changing the way that carbon is cycled in those ecosystems. So I dug a lot of cold holes.
Colleen: And so what does that mean?
Carly: Exactly what it sounds like.
Colleen: You're digging a hole in…
Carly: In the active layer and trying to understand what the microbial communities, the bacteria and fungi that are part of that soil, are doing in response to warming temperatures, in response to vegetation changes across these ecosystems that are changing so much more quickly than the rest of the world.
Colleen: So are you actually taking samples of that and then bringing it back into the lab and…?
Carly: Yeah, so for a lot of that research, we were bringing that soil back into the lab, and in some cases, doing measurements in situ, out in the field, you know, lugging equipment with us. But as you can imagine, there's a certain limit to both what you can bring with you and also what's reasonable to measure on the timescale of the summer up there.
Colleen: Did you find anything particularly surprising in any of your time out there in the field?
Carly: Oh, certainly. Almost everything was surprising to a certain extent. Yeah, one of the surprising things was that I learned that you can feel permafrost thaw by walking on the tundra. So there are areas, so it's bowling balls and rotten watermelons, but then there are also areas where it's almost like you're on a trampoline but there's still ground beneath you. There's like a bounciness to the land. And so I was taught that that was where there was permafrost failure beneath you. And that's why the ground was bouncier. So that really surprised me.
And I also saw a wolverine and that was incredibly surprising.
Colleen: Wow. How close?
Carly: It nearly ran us off the road.
Colleen: Wow. Any grizzly bears?
Carly: Only from afar. I used to sing loudly so that the bears would hear me. That's what they recommend when you're out in the field alone.
Carly: A lot of Halo, a lot of Love On Top. Really get a large vocal range there, you know, if you go through the key changes. Beyoncé's greatest hits typically.
Colleen: Well, Carly, thanks so much for joining me on the podcast.
Carly: Yeah, I hope we can talk more soon.
Sidelining Science: Shreya Durvasula
Editing: Omari Spears
Music: Brian Middleton
Research and writing: Jiayu Liang and Pamela Worth
Executive producer: Rich Hayes
Host: Colleen MacDonald