Science Friday - What Lichen Tell Us About Ecology, Air Quality, And More

Episode Date: January 9, 2025

Last October, Ira Flatow took a trip to the World Forestry Center in Portland, Oregon, for a daylong exploration of lichen—the fuzzy growths often found on trees, roofs, and gravestones. Ira sat down in front of a sold-out room with Dr. Hannah Prather, postdoctoral researcher and visiting assistant professor of biology at Reed College, and Dr. Jesse Miller, lead botanist for the Washington Natural Heritage Program. From their crucial role in ecosystems as indicators of air quality to their striking colors and forms, we’ve really taken a lichen to these amazing organisms.Transcripts for each segment will be available after the show airs on sciencefriday.com.  Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Did you ever notice the lichen growing on the surface of trees while you're on a hike? They're actually more important than you might think. If we lost some of the lichens in our forests, the casual observer might not notice, but the forest would notice. It's Thursday, January 9th, and you're listening to Science Friday. I'm SciFri producer, D. Peter Schmidt. Today, we're listening back to a live event Ira Flato taped near the end of last year in Portland, Oregon, a place where lichens are everywhere. Let's listen.

This is Science Friday. I'm Ira Plato, live with OPP from the World Forestry Center in Portland, Oregon. Thank you. You know, we can decide wherever we want to go to. We take the show on the road. And when we come to a place like Portland, we have to think, what can we find there that is unique, that we can't find anywhere else in the country? And who are the local experts who can help us see the world in a different way?

So you look around at the towering trees and you say to yourself, hmm, why don't we go into the woods? And that's what we did. And we went into the woods and we decided to explore the very often overlooked world of lichens. A lot of people don't know what lichens are. They are a remarkable fusion of fungi, algae, other tiny bacteria, and they thrive in the misty forests of the Pacific Northwest. And from their crucial role in ecosystems as indicators of air quality to their striking colors and forms, we've really taken a lichen. I have never heard of this joke before.

I apologize. So we're going to be joined by the few people who can tell us all about them, and let me welcome them to the show right now. Right on my left is Hannah Prather, postdoctoral researcher, and visiting assistant professor. of biology at Reed College, where she teaches about the relationship among lichens, host trees, and the surrounding ecosystem. Welcome to Science Friday. Thank you. Jesse Miller is lead botanist for the Washington Natural Heritage Program,

where he provides guidance for rare plant conservation efforts. That sounds cool. And studies effects of altered fire systems on plant and lichen communities. Welcome to Science Friday. Thanks, Sarah. I'm going to start with you, Hannah. Tell us here. got interested in Lycans because I was out there with you today and you were just in your element as we said. Yeah this is true. Oh, such a great question. You know, when I started in graduate school, I started climbing trees and there's kind of a lot more to that story. But as I was up in these big tree canopies here in the northwest, some of our towering Douglas fir, I started to notice these little plants, or what we now know is Likens, that were occupying this. And we're occupying this

really incredible three-dimensional space. And I think it was sort of through that connection from the canopy to seeing the things that were thriving and living up there that I really had a lot of curiosity to ask more questions about those organisms. Very interesting. And Jesse, as I say, you helped guide how rare plant conservation happens in Washington and Oregon. And how do lichens fit into that picture? Yeah. Well, lichens have been overlooked for a long time relative to animals, especially, but plants as well. We just haven't given very much attention to the rare lichens,

the lichens that are perhaps even on the edge of extinction. And so one of my personal and professional missions in life is to try to bring more attention to our endangered lichens. So that's been a focus of mine, especially for the last couple years, since I've been in Washington.

Okay, so let's begin by helping us to understand lichens' ecological niche. I mean, they have one, right? And of course, we say they and you were telling me Jesse that the plural of lichen is lichens right that's exactly way to say it people get it wrong yeah people say all the lichen out there like it's some amorphous mass but there are a whole bunch of different lichens out there and we need people to understand that it's very important and why are they important what is their niche in nature

sure well lichens play a lot of important roles in ecosystems um for one thing a lot of animals use lichens as a food source or nesting material. There are all kinds of invertebrates that live inside lichens. But lichens also play roles in nutrient cycling. They stabilize soil. They play roles in hydrological dynamics. So if we lost some of the lichens in our forests, the casual observer might not notice, but the forest would notice. And I know that you focus on lichens that are, quote, on the fringe, right? What do we mean by that? Yeah, well, my, background, my PhD research was looking mostly at urban lichens. So how these communities of lichens and these tall tree canopies, how they're being affected by sort of the urban condition of urbanization, the transfer

of air pollution, things like this. A second part of my work took place on the western Antarctic peninsula, a place of rapid warming on the globe. And so we were looking at lichen and bryophytes, mosses, and those communities and how they're changing really dramatically with warming effects in that area. Are they significantly different from the kinds we would find around here in Oregon? If you looked at them, you say, oh, yeah, they come from the poles, you know. Certainly. I mean, Antarctica is a beautiful flora. There's certainly things that are endemic only to Antarctica, but there's also cosmopolitan species that occur everywhere.

So it's kind of an interesting blend. We were out in the forest. You were showing us lichen, and people are asking, could this lichen grow differently if there weren't air pollution? Does air pollution affect the growth of lichen? Yes. And many of us might have heard of this sort of lichens can be this canary in the coal mine, right? They're these bio-indicators, something that's naturally in an environment, but can also give us a lot of information about the condition of that environment. So we know that lichens respond pretty

quickly to things like air quality, pollutants. And one of the main ways that we see this is in the morphology, so the size of the lichen. Likens don't have protective mechanisms like vascular plants do. They don't have a waxy outer surface or stomata that can regulate sort of gas and surface exchange. And so because of that, they're these little sponges in the environment. So when things land on them, they actually absorb that fairly easily if they're hydrated. So the morphology is kind of one way that they can limit the surface area, exposure to pollution. So often in urban areas, we will see lichens that are tolerant of urban conditions. And if they aren't tolerant, they might shrink their size down so that they have less of that surface area touching the pollution.

Just so you're nodding in agreement. Yeah, absolutely. And when you go out to a forest with really high air quality, you know, many miles out of the city, you see a whole suite of lichens that you won't see in the city or in any other more polluted areas. So it's really, and then here in urban areas, we actually see lichen species that are indicators of air pollution. species that actually become more abundant in polluted areas. So there's a whole story to read on the landscape out there. And I know that you study the effects of wildfires on Lichen, right? I mean, is that mean just the heat effects,

or is it the smoke and everything that they leave behind? Yeah, it's a lot of different effects. So there are direct effects. I mean, Lichens often burn up in fires. That's one of the most obvious conclusions, but not a huge shocker there. But, you know. I hate it when that happens.

But there are all kinds of indirect effects as well. Fires change the landscape. They might change a forested landscape to an open grassland, and all those forest lichens are not going to recolonize unless a forest grows back some decades or centuries later. But it's really important to recognize that their fire can burn in many different ways. We have what we call low severity fires. fires that don't remove most of the trees and other vegetation, and high severity fires that

do remove most of the vegetation, and high severity fires typically have much stronger effects on the lichens. Hannah, do people walk past lichens and just never know that they're looking at them? Oh, absolutely. Likens are really good at being very cryptic, right? And so they often are sort of these kind of scummy, scummy things that are on your roof or your driveway. You've probably all have tried to scrape them off. I won't judge. But yeah, so they occupy a pretty unique part of the landscape. They like to grow on other things. So we'll see them on

trunks of trees, on rocks, even on buildings, maybe even on your car if it's been parked in the northwest for a while. So it's very common that people overlook these little organisms. Well, what makes them different from just moss that we see growing all over the place? What makes it not a lichen? Yeah, good question. So moss is in lichen. And Likens actually like to hang out in the same types of habitat.

So especially in the Northwest, we have a lot of moisture in our systems. So we see both often really together. So one of the sort of key indicators I always kind of tell my students when we're talking about the difference between lichens and mosses is that mosses are ancient plants. So they always have a stem and leaves. That's one good way to notice them. They also have a little bit greener of a color overall versus lichens are built of fungi. So they often have these really different morphologies that can look a lot of different ways flat like a leaf or sort of threaded like a little shrub.

Do they share the same space as the moss? Oh, absolutely, yeah. So is it like a symbiotic thing going on there? No, I wouldn't say there's any sort of symbiotic relationship. I would say it's more of they thrive in the same types of environmental habitats. There is a lot of work in the Northwest looking at stratification of these species across in really tall canopies. For example, we used to have a research canopy crane located here in the Northwest where we did a lot of the preliminary research looking in tall trees to see how these things stratify with gradients of light and moisture. And so what we know is that mosses often like to be in the moisture low layers, low light layers of a canopy or of a forest.

And lichens do kind of like to be in the higher bits where there's more high light and a lot of drying as well. And also do we find them on rocks? Can you see, Jesse, you see them on rocks everywhere? Oh, absolutely. Some of the very best lichens are on rocks. Is that right? I mean, lichens will grow on almost anything that holds still. So, rocks, trees.

People. You know, it probably means you need to live a more active lifestyle if that happens. Is that right? Because sometimes you'll see, you go through and you see these rocks in a forest, and they have patches on them, different colored patches. Is that what lichens are also sort of flat, not these big raised leafy things? Yeah, and those are crustos lichens, those really flattened lichens that are just totally sunken into the substrate. And those are actually some of the most challenging lichens to identify.

Those are the lichens that keep us up at night. Those are the kinds that people are power washing off their rocks sometimes. Yeah, you know, some people try to identify the lichens, other people just try to power wash the lichens. That's the world we live in. Why should we care? And seriously, why should we care about Lichens? They're so small. A lot of people don't see them.

Why should we care so much? Let me start with you. Sure. Well, you know, a lot of people don't even think about Likens or notice Likens in their day-to-day life, but Likens play all these roles in ecosystems that we don't see. And ultimately, we're all dependent upon the ecosystems around us. So one of my favorite examples is old growth forests

in the Pacific Northwest are inhabited by flying squirrels that eat lichens as a major part of their diet. And flying squirrels in turn are eaten by spotted owls, which are one of our great animals in the conservation history of the Pacific Northwest. So if we lost a lot of our forest lichens somehow, it would affect this whole food chain. And people see the squirrels and they see the owls, but they may not notice the lichens. We'll be right back. After this short break, This is Science Friday from WNYC Studios. Are all lichens equally safe to touch and handle? And if not, what are the features you look for that might say stay away?

Are they poisonous lichens? Boy, okay, I'll do my best. Jesse, you can jump in. I'm almost like afraid to go on statement here. No one's listening, so it's okay. Most lichens are safe to handle. I think would be a safe assumption. There are a few lichens that have sort of toxic qualities to them.

One of those is the wolf lichen. It's a chartreuse lichen. It's often on the east side forest that we'll see. And it just has known to have some poisonous qualities. So you wouldn't want to ingest it or maybe, you know, touch it a lot and touch your mouth. But for the most part, lichens are really friendly to interact with. Yeah, if you find them on the ground, you can pick them up. There's nothing.

Can you think of any other? I'm not overlooking. So it's not like possible poisonous mushrooms that you might be thinking. No. No. I think that's probably what people were thinking of. Yes, thank you for that question. Next.

Well, yeah, actually on the concept of picking up lichen, I'm a nature and forest therapy guide, and we do a lot of texture stuff, and people like to bring textures back with them, and they often bring back lichen, whether it's still attached to a stick or that they found on the ground. Are those alive? Yeah, we saw a lot of stuff today.

in the forest. A lot of lichens on sticks that were falling down. Are they alive? The answer would be yes. I mean, assuming that they are in, lichens can die. They can start to sort of degrade back into the environment. Often those look, like Jesse had mentioned, either bleached, so they've lost the algal component or they're a little bit necrotic and reddened, meaning that the fungal partner is starting to die. And that can happen fairly quickly if it's in a really wet, they fall on soil and they can kind of start to decompose back. But typically things that are epithetic, they like to grow on tree branches or up on other surfaces. If you bring those inside, they probably are still alive if they're hydrated.

They can go into that sort of dormancy period if they're dry. And they can do that again for periods of time depending on the species. Yeah. We were in the forest watching, you found a tree branch on the ground, and I have never seen a scientist get so excited about finding a tree branch. What makes that so special about that? Oh, if you're a lichenologist and you find a branch from the canopy on the ground, it's like total gold.

Like, you've hit the jackpot. Because it's really giving us this nice snippet of what we're seeing up overhead that otherwise would be really hard to access. You'd have to use ropes or some other technique to get up there. And so just on that one branch, Ira, we found, what, almost eight different species, just on a very coarse look. So there's probably many more. And you were happy a dog had and come along and just run off with the branch.

Yes. Yeah, I get it. Yes. Next question, please. I'm curious as we have a room here of people who are interested in Liken, what we can personally do to help encourage Lichen growth and conservation. I think about when I am out in nature and I'm trying to not walk off the trail and thinking about what you said about Lichen anchoring on soil to stabilize.

it. I'm also curious about cryptobiotic soils, but curious about personal responsibility, how we can help lichen and how to encourage its growth and not accidentally kill it, things like that. Any recommendations? Should you avoid walking on the lichen if you see them in the forest? Yeah, as far as those crusts that grow on the soil, we have a saying don't bust the crust. So yeah, don't walk on this crest. That's one smart move. But I think more broadly, just learning a little bit about lichens

and learning to identify some common lichens in your area is one great step forward to being a friend of the Likens and helping them. But one much more specific thing I'd suggest, the U.S. Forest Service is working on revising its umbrella management plan for all the forests in the west, the northwest, or in the northwest, the northwest forest plan.

And there are periodic opportunities for the public to comment on this. And one big question, so for many years, the Forest Service has safeguarded or tried to safeguard many of our rare lichens. It's kind of up in the air whether that policy will continue. So I'd encourage everyone to put in a comment and say you want to see our rare lichens continue to be a priority for management. Yeah, it takes public interest. Absolutely.

Yeah. Before I ask my question, I have a lichen joke. A fungus and an algae took a lichen to each other, and now their marriage is on the rocks. So when I taught in Alaska where glaciers had receded, we told our students that you could age how long ago where the ice had moved back, especially places where there wasn't photographic evidence, because certain species of lichen would grow on the rocks at a certain rate. I didn't know, I would, wondering if you could speak to that. I'm not sure what else to say.

It's a really cool thing. I've worked in polar ecosystems and the lichens there are incredible. I think it's a really, it's been a really neat part of my work to kind of look in areas of recent recession and see what types of species are there, what types of role they're playing, how they transform soils early on in those processes. So it's pretty fascinating. Is it surprising to see how resilient they are to live in that kind of climate? Oh, absolutely. Yeah, I think some of the interesting changes on the Antarctic Peninsula are just the change from precip from snow to rain.

And so a lot of those species aren't able to kind of handle having more liquid moisture. Interesting. Yes, step up. Okay, so I saw a video once upon a time of two lichen experts that came here to Oregon, and they were at the waterfront here in Portland and also in the gorge, talking about signs of, or like symptoms and lichens of an unhealthy air environment. So if you know anything about that, could you get into some of the basic signs of how to tell your air quality? Yeah, how do you tell air quality from the lichens? Well, I'd say one thing to notice is just the size and stature of the lichens.

In polluted places, the lichens are going to be a lot smaller. but we also have a lot of lichens that are orange in color that grow in polluted places, and these are nitrophiles or nitrogen-loving lichens, pollution-loving lichens. So when you see just a tree that's covered in orange lichens, for example, that's a sign you may be in a fairly polluted place. And when you see a tree that's covered in big, draping, three-dimensional lichens, And that's a sign that you might be in a place with better air quality. Interesting.

It's good to know that. Yes, please. So I've noticed at the Home Depot parking lot near my home where they do a lot of leaf blowing, the trees in the parking lot are just covered in lichen. And I've always wondered if it's because of the leaf blowing. It's blowing the lichen particulates up and sticking them on to the trunk. Do you have any thoughts? Wow, what an observation.

I think you could set up a really neat experiment to test this. There's grant money here for that. I fell in love with him about 12 years ago and just, I'm obsessed with him. Could that be happening? I mean, serious? Could there be an unintended consequence of leaf blowing? And is it a healthy thing to get more of them up into the tree? I think it's conceivable that there could be like in propagules getting into the leaves

and then blowing back onto the tree. Yeah, that would be a great science or nature paper, I think, if we could prove that. Talk about citizen science. Yeah, exactly right? You want a citizen science project? But we actually are still working on developing methods for, you know, I mentioned this idea that we perhaps should be establishing new populations of some of our rare lichens. And figuring out the exact methods we would use to do that remains kind of an open question.

so I'll add leaf blowers to the stack of ideas. Wow, wow. Yes, next question, please. So when I go to any bookstore and I go to the natural science section, there are dozens, if not hundreds, of books on fungi, but like two or three, if any, on lichen. So I want to know why does it seem like there is such a deficit of research and cultural significance placed on lichen as opposed to fungi.

Yeah, it needs better public relations like it. I mean, seriously, right? I mean, people don't talk about it. They talk about the moss. And that gives me, brings me to my blank check question, I ask a lot of my guess, if you had a blank check and you wanted to spend it on, researching or doing, getting public. How was the best way to spend all that money?

Is it studying Likens in a certain way or publicity for it? Jesse, let me ask you first. We were just, what don't you know that you want to know that you could spend that money on? Yeah, so we know that there are a lot of lichens that are associated with old growth forests in the Pacific Northwest, but we've, of course, lost most of our old growth forest, which used to cover the landscape. So one question I wonder about is, how suitable are some of our more mature second growth forests? And what can we do to help bring about more old growth character in some of our forests that aren't quite old growth? but are nice old stands of second growth,

and also doing experiments to try to establish new rare lichen populations in some of those stands. That would be a priority for me. How would you spend some money? I'm giving your blank check. What would you spend it on? Anyway, anything that involves working with lichens. Yeah, I hate to piggyback on jesse's,

but I think there's a real, I think just living in the Northwest and loving our forests and really seeing the beauty of an old growth forest and kind of the loss that we're looking at with increasing wildfire and the loss of Opal Creek. Oh my goodness. I really think that there's some interesting research around these types of questions that Jesse is posing. Can we somehow accelerate those conditions back to old growth? Can we somehow bring in lichens and propagate or attach them into canopies and help reestablish that biodiversity? I think there's a lot of interest in that.

Interesting. Yeah. Okay. Next question, please. I was wondering, since lichens are three or more organisms, how you begin to sort them taxonomically and describe that evolutionary relationship that some of them might have. Jesse, let me begin? Yeah, great question. How do we define species for organisms that are inherently composed of multiple species? So the names we actually use for lichens, the scientific names,

actually refer to the fungal partners. And part of the reason for that is because pretty much every unique lichen out there is a different fungus, but many of them share the same algae. So that's why we use the names of the fungi rather than the algae. But there are

some interesting cases where that system doesn't quite work perfectly. There are cases where the same fungus can partner with two different algae and form two totally different lichens, but because we name them after the fungi, we call those two lichens the same thing. So it remains an imperfect science. Do we need different names?

Perhaps. That's something that's been talked about in the lichenological community. And I think it'll be interesting to see where we are in 20 or 30 years. Lichenological. I like that. Like that. Yes. The whole idea around symbiosis, I honestly find really romantic. And the way you're even describing those relationships and how they meet each other and how they have been. babies and all that. So I'm wondering about the, I know this is different than other people's questions, but the sense of poetry or art or the elements of that relationship inspiring some creative worlds. I will add just on your romantic notion that I did have a final project for my Likens course

last year was a Lichen outreach project where they had to spread the word on Likens and what was so great. And I had some students put together. a dance about the symbiosis, the coming together of the partners, and it was actually really incredible. Where can we see that? It's actually, I think, posted on the Reed Biology webpage. There you go. Soon to be major motion picture. Okay.

Question. I'm wondering about whether or not we see any lichens in the fossil record, and if we have any ideas about their history of evolution, kind of a different turn from the post. poetry going a little bit more hard science there. But they don't have any hard parts. Do we see them? Do we have any ideas about when and how they might have evolved? Great question. So my understanding is that there are only about 150 individual lichens that have been

found as fossils. So they really don't fossilize very well at all compared to a lot of other organisms. So that's one reason why reconstructing their ancient evolutionary history has been really difficult. But we do currently believe that Likens are hundreds of millions of years old, so they do go back a really long ways. Wow, that's good to know. Yes, sir. Hi, I'm really interested in how cities grow and change, and I'm really wondering whether there's any lessons to be learned by looking at our Likin communities and how they grow and adapt to changing environments that we can apply to the way we design our neighborhoods

in our cities. Well, great question. I think one cool example is after the Clean Air Act was passed, some likened that were no longer growing in urban areas were actually observed to come back and recolonize urban areas

because the air quality had improved so much. So, yeah, I think it's wonderful to use them as an environmental indicator as conditions change over time. Absolutely. That's great. All right. One last question for the evening for the panel here. What one thing, what one message, what one idea do you want everybody in our audience to take

home tonight about Likin? I'll start with you. Well, I, you know, one thing that I think that has really been meaningful for me in working with students and Likens is probably that just it's a great connection to nature and they're so ubiquitous. So you can go right outside your door on your city street or in a city park and find many lichens. So I really want to encourage people to just get to know the lichens in your neighborhood, get to be outside and enjoy those. This is the best lichen viewing time because we're having sort of this stormy wet weather. So it brings down lichens out of the canopy.

It brings down branches. And so it's a great way to just connect with nature, find them in your area and learn about them. Thank you, Hannah. Jesse, what do you think? Well, we, we really are living in challenging times. We are experiencing a biodiversity crisis around us, and we have to make choices collectively about how we want to address this. So my closing message to everyone is please vote. That's Jesse Miller, lead botanist for the Washington Natural Heritage Program, and Hannah Prather, postdoctoral researcher and visiting assistant professor of biology at Reed College. They spoke with us on stage at the World Forestry Center in Portland, Oregon, in an event we produced with OPP.

Special thanks to OPP's Jess Burns and SciFri's Diana Plasker. That's all the time we have for today. Lots of folks help make the show happen, including Rasha Eri-Di, Sandy Roberts, Shoshana Bucksbaum, Danielle Johnson. Coming up tomorrow, we've got really big Science Friday news to share with you. You won't want to miss it. Stay tuned. I'm SciFrii producer, D. Peter Schmidt.

Thanks for listening.