Cemeteries Offer A Green Refuge For Urban Plant And Animal Life

11:58 minutes

a graveyard with gravestones with lichen on them
Credit: Acabashi, via Wikimedia Commons

A cemetery isn’t necessarily the first place that comes to mind when thinking about urban biodiversity and conservation, and, for a while, even ecologists wrote them off. But there’s a growing body of research that’s come together in recent years pointing to the value of these unexpected green spaces in protecting biodiversity, especially in cities where land is at a premium and green space is limited. 

Researchers even discovered a new beetle species at a cemetery in Brooklyn earlier this summer and spotted a rare salamander species in the same cemetery only a few years earlier. But it’s not just beetles and salamanders that take refuge in cemeteries. Lichen, which are an algae-fungi amalgamation, do too. 

Jessica Allen, assistant professor of biology at Eastern Washington University and an expert in New York City lichen, joins Ira to discuss the rare lichen that her research team found in a cemetery in the Bronx and why cemeteries are helping lichen to thrive in NYC. 

Further Reading

Segment Guests

Jessica Allen

Jessica Allen is an assistant professor in the Department of Biology at Eastern Washington University in Cheney, WA.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Later in the hour– myths about moths and the fascinating behaviors of this underrated night dweller. If you have a question about moths in your neck of the woods, give us a call. Our number is 1-844-724-8255, 844-725-8255. Or you can tweet us @SciFri.

But first, in cities where plants and animals compete with humans for space and survival, cemeteries offer an unexpected reprieve, right? They’re usually pretty big, a lot of green growing, not frequently visited by many people, making them ideal places for some plant and animal species to thrive and sometimes even new ones that we haven’t seen before, like a new beetle species recently discovered at Greenwood Cemetery in Brooklyn or a rare population of salamanders that researchers found in a hidden glen of the same cemetery just a few years earlier.

But you know what? It’s not just the beetles and salamanders that benefit from these unexpected green spaces. Lichen, lichen do, too. Here to tell us more about that is Jessica Allen, professor of biology at Eastern Washington University. Welcome to Science Friday.

JESSICA ALLEN: Hi, Ira. Thank you so much for having me on.

IRA FLATOW: You’re welcome. First of all, tell us exactly what a lichen is. Because I asked three different people and got three different answers.

JESSICA ALLEN: OK. That’s not unexpected necessarily. But sort of our textbook answer is that lichens are a quintessential symbiosis. So it’s a relationship between a fungus and an alga where the fungus is really making the bulk of the structure that you see and housing the algae.

So the algae are photosynthesizing and making sugars in return for this nice home. And so that’s what you probably will read if you read a textbook. But recent research has shown that lichens are a lot more complicated than that.

So in addition to that main fungus and the main alga, there are usually these really complex and diverse communities of other fungi and bacteria, maybe multiple different algae. You can often find tardigrades in there and nematodes as well. So some people have started to sort of call these miniature ecosystems, yeah, so a little bit more complicated maybe than our original textbook definition.

IRA FLATOW: Are they’re pretty hardy? Are they tough, can stand the elements?

JESSICA ALLEN: Yeah. So some lichens, definitely. Many lichens are what we would call extremophiles, so organisms that really thrive in extreme environments. So if you’ve ever traveled to the Arctic or the Antarctic, you’re bound to see lichens, or in deserts.

People have sent lichens into space. And they not only can withstand that ultraviolet radiation and that level of desiccation, but rewetting them they’re totally fine. Other scientists have grown them in growth chambers that mimic conditions on Mars. And not only are they OK, but they’re physiologically active. So often, lichens are very tolerant of these incredibly extreme conditions.

IRA FLATOW: Except they’re not tolerant of air pollution I understand, right? And that makes them a good indicator about air pollution?

JESSICA ALLEN: Yup, absolutely. So lichens are excellent indicators of air quality. And so by looking at what species of lichens exist in an area and how abundant they are, how many of each species are present in that area, we can learn a lot about what sort of air pollutants are impacting the region and get a sense of that overall air quality. And that’s why we have these air quality monitoring programs throughout North America largely run by the US Forest Service to better understand our air quality through looking at these lichens.

IRA FLATOW: Now, let’s talk about your research team heading to a cemetery in the Bronx.


IRA FLATOW: It sounds like the end of a joke somewhere. But it’s not. You were there for a good reason.

JESSICA ALLEN: Yes, absolutely. Can I give you a little bit of back story on that?

IRA FLATOW: Sure, sure.

JESSICA ALLEN: Yeah. So I started studying the lichens in New York City when I was a graduate student at the New York Botanical Garden in the Bronx. And it kind of really started during Hurricane Sandy actually, which led to a lot of downed trees and branches on the grounds of the garden. And I started collecting lichens in New York at that point.

And that kind of fed into a number of other lichen surveys in New York, especially the Macaulay Honors College BioBlitzes in Central Park and Freshkills. And eventually, I came up with this list of over 100 species of lichens in New York City. And this was really the first attempt at a comprehensive list of lichens for New York City since 1914.


JESSICA ALLEN: Yeah, which was actually conducted by, again, a New York Botanical Garden graduate student named George Wood. But at that point, I moved away. And I was working in Switzerland.

And I got a message from my friend Jenna Dorey, who was still a graduate student at the New York Botanical Garden. And she told me that she’d found this old man’s beard lichen in Woodlawn Cemetery. So this is the genus Usnea.

And at first, I did not believe her. Because I had tried to transplant Usnea to the New York Botanical Garden with James Lendemer the lichen curator there, a number of years before. And that was not successful.

And I even rarely see this lichen up in places like the Hudson Valley. So if she hadn’t taken a picture, I probably wouldn’t have believed her. And then the next time I visited New York, which was in mid-December, we went up to Woodlawn.

So we took the Metro North up there on a weekday afternoon. And it was rather cold, overcast day, one of those early dusk sort of winter days.

IRA FLATOW: We’re having one of those today.

JESSICA ALLEN: Yeah? I could imagine so. And we sort of started our lichen meander across the cemetery and eventually ended up at this really beautiful large, old red oak. And sure enough, there it was about the size of the fingernail on my pinky finger, this tiny fragment of an Usnea. And this is the first record of an old man’s beard lichen in New York City since 1824.

IRA FLATOW: Wow, 1824. That’s, like, 200 years almost.

JESSICA ALLEN: Basically, yup. So at that point, Abraham Halsey, a banker, had done a lichen survey of New York City and recorded it being present at that time.

IRA FLATOW: So tell us why this is such a great finding? Is it merely because it’s a rare one that you did not expect to see?

JESSICA ALLEN: Yeah. So certainly there’s that aspect.


JESSICA ALLEN: This was a completely unexpected discovery. And you know, I thought that we were getting close to having a somewhat complete list of the lichens for New York City. And this was an obvious message that we are not anywhere close.

So there was definitely that aspect of it. And I think it’s also kind of a rather hopeful finding in that we don’t really know what the full potential of diversity is in cities, in even really large densely urbanized cities like New York. It’s kind of an indication that the air quality is improving, biodiversity is returning, and that eventually the city could host a lot more species than we’re even considering at this point.

And we know that, for instance, in the ’60s and ’70s, Irwin Brodo did some surveys of lichens in New York City and especially focused on Long Island. And at that point in Brooklyn and in Queens, he only found seven species of lichens. And now, we’re back into the hundreds. And maybe the potential cap on the number of species could be a lot higher than we [AUDIO OUT] thinking before.

IRA FLATOW: So there are a lot of lichenologists who are successfully going into cemeteries? And do people look at them a little weirdly? What are you doing in a cemetery? We’re looking for like a lichen.

JESSICA ALLEN: That’s a great question. I would say that lichenologists get strange looks no matter where we go when we’re looking for lichens. Because sort of the way that we search for these generally somewhat small organisms is to stop and carefully examine.

Like if you go up to a tree, you want to look at your eye height. And then you want to look at the base of it and maybe the soil around it, look for any fallen branches. And we’re using these small magnifying glasses called hand lenses to do that.

And so we very carefully examine this one area. And then maybe move on to the next. And we’ll try to look at every single different type of rock that might be present.

Because you’ll see very different lichens on limestone versus sandstone versus granite and even things like park benches. Like the wood on park benches can often have different species of lichens than you would see on a tree, for instance. So we tend to move rather slowly and be looking very closely at different, what we would call, substrates, so different materials the lichens could be growing on.

IRA FLATOW: This lichen, the 200-year-old find, the Usnea– is it called that– how did you know it was what it was?

JESSICA ALLEN: So we could tell immediately which genus it was. But beyond that, by just looking at it, we couldn’t tell what species it was. Because it was somewhat stressed out. I think it’s sort of a little bit of an intense environment for that as Usnea to live in.

IRA FLATOW: Well, it is New York, right?

JESSICA ALLEN: Exactly. So it’s the New Yorker Usnea. So what we ended up having to do, because we couldn’t just look at it and identify it, was to take a very small fragment of it. And lichens produce all of these chemical compounds that no other organisms make.

So we did some chemical analysis on it. And it should have been producing a number of chemicals, and it wasn’t producing any. So that was not fruitful.

So then Jenna took it the next step, took the sample down to the DNA Learning Center. And we took a DNA barcoding approach, so basically sequencing a really small gene, a really small fragment of the genome, matching that up to a database of sequences. And from there, we had ended up with 100% match to Usnea mutabilis. So with that genetic data, we were able to confidently identify it to species.

IRA FLATOW: Do you ever identify a lichen and name it after the cemetery where you found it?

JESSICA ALLEN: Not yet. I have named a lichen with my colleague James Lendemer after Dolly Parton and Oprah, but nothing after a cemetery yet.

IRA FLATOW: I got to ask why. Why Dolly Parton and Oprah?


IRA FLATOW: I’ve only got a minute, so the quick answer.

JESSICA ALLEN: Yeah, they’re both just incredible women who have done so much to contribute to the world. And we found these new species in the Southeastern United States. And so really to honor their work and their contributions, we decided to do that. Because that name will likely stick with that species–

IRA FLATOW: I think so.

JESSICA ALLEN: –for a very long time.

IRA FLATOW: You’re wise beyond your years, Dr. Allen.


IRA FLATOW: Thank you. That was a great idea. Thank you for taking time to be with us today. It’s great a story about the lichens.

JESSICA ALLEN: Yeah, thank you so much, Ira. And for people who want to learn more, we’re working on a book, The Lichens Of Urban Areas Of Northeastern North America that will be a field guide. So stay tuned for that.

IRA FLATOW: We’re lichen it, Jessica. Thank you. Jessica Allen– assistant professor of biology in Eastern Washington University.

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Meet the Producers and Host

About Danya AbdelHameid

Danya AbdelHameid is Science Friday’s fall 2019 narrative podcasting intern. She’s most interested in telling stories about the complex, messy ways that science interacts with culture, history, and society, but she’s really into glaciers and ice sheets, too.

About Ira Flatow

Ira Flatow is the host and executive producer of Science FridayHis green thumb has revived many an office plant at death’s door.

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