The hidden value of herbariums

Duke University recently announced plans to close and re-home its century-old herbarium.

But with climate change and a looming biodiversity crisis, scientists say these preserved collections of old plants are more important than ever.

Today, On Point: The hidden value of herbariums.

Kathleen Pryer, professor of biology and director of the Duke University Herbarium.

Jacquelyn Gill, associate professor of paleoecology and plant ecology, School of Biology and Ecology and Climate Change Institute.

Joyce Onyenedum, assistant professor and principal investigator at NYU’s Department of Environmental Studies.

Susan Alberts, dean of natural sciences at Duke University.

Part I

MEGHNA CHAKRABARTI: What happens when a little-known place, home to great treasures, may soon have no home at all? That's the puzzle Kathleen Pryer is facing. She's a professor of biology at Duke University and she joins us today. Professor Pryer, welcome to On Point.

KATHLEEN PRYER: Hello. Thank you.

CHAKRABARTI: So what is this little-known place, home to great treasures that you care so much about?

PRYER: I wouldn't call it little-known. The Duke herbarium is perhaps the 6th largest university herbarium in the United States. And it is tied with Cornell. So it's very well known in the area of biodiversity research and climate change research, but it's stunning that now, it's being told it needs to find a better home.

CHAKRABARTI: Okay, so what, for those people who don't know, can you describe Duke's herbarium a little bit? First of all, what is a herbarium? And then what is in Duke's that's so unique and valuable, as you say, to science?

PRYER: So every herbarium is unique. It's a collection of dried plant materials that have been collected over time from various professors, students, researchers that have gone on explorations, and brought these treasures home. So no herbarium replicates what another herbarium has. It's unique to the history of Duke and the people who worked at the Duke herbarium.

And so our collection of 825,000 specimens is special only to, it's special to Duke. It's not replicated anywhere else.

CHAKRABARTI: And 825,000 specimens, is that the equivalent to the number of different species represented in the collection, or is it just specimens?

PRYER: No, it's just specimens.

CHAKRABARTI: Okay. So can you just give me a visual tour of what it looks like? How are these specimens stored? When you want to look at them, what do you see?

PRYER: Duke is also well known for a lemur center. And the lemur center is easy to sell when you have creatures with bushy tails and bright eyes.

When you walk into a herbarium, it is a room filled with steel cases. And each case holds about a thousand specimens. And so the Duke herbarium is in two different locations. One is the smallest part of the collection, is within the bio side building, which is slated to go under renovation in the next couple of years. And the larger part of the collection, 70% of the collection is housed in a, essentially, brand-new facility underneath a research building.

... And so when you open a case, you're faced with all these sheets that are stored in boulders. And so these plants, whenever they were pressed and dried, glued to these sheets, are stored according to a very special classification. So they're easy to find and you locate the cabinet you wish, and you go in and have a look at the material that you need to maybe describe a new species, maybe to look at the variation a species encompasses.

CHAKRABARTI: And so are they stored in books? Sheaths? What, how are they stored?

PRYER: The very earliest herbaria, about 500 years ago, were books. And today that stopped a long time ago. And today, specimens are glued on to archival sheets that are 11 by 17 inches. So a very standard sheet size, and in the left, in the right-hand corner of every sheet, is a label that tells you what the plant is or who collected it, when they collected it, where they collected it.

And so it represents a specific plant that existed in a place at a special time and point. And so it has absolutely unique history. An orchid in our collection, say Cypripedium, the pink lady slipper from North Carolina. Other herbaria may have, certainly have specimens of the pink lady slipper, but no one has our specimen.

And so when you look at material from across a breadth of herbaria, you begin to understand the variation within a species. Yeah so we'll talk more about what is going to happen to the Duke herbarium. Because its home is in peril. That's why we're having this conversation with you.

But Professor Pryer, I'd still, I would love to hear a little bit more about some of the remarkable specimens in the collection. I understand there's one called the Lady Gaga fern, is that right?

PRYER: Yes, indeed it is the home to the lady. 15 years ago, my lab group was very intent on listening to her music in the lab while we were looking at herbarium specimens, processing them for extracting their DNA and that sort of thing. And I hadn't heard of her, but watched her on the Grammys in 2010, and she appeared in a costume that was so remarkable in that it looked exactly like the sexual stage of a fern gametophyte. And ferns are what I study.

And so I began to understand more about her music and what she stood for and so we named a group of ferns that is endemic to Southeastern United States and Central America. It was a group of ferns that needed a new name. And we gave it the name Gaga because of her voice as a champion for justice, for compassion and right to individual expression.

CHAKRABARTI: That's a beautiful story. And is there also a genetic component here? Because in terms that you were extracting DNA and looking, obviously, at what the DNA revealed. And please correct me if I'm wrong, but I understand that there was also like maybe a section of DNA that was GHEA.

PRYER: So that was the most unexpected part. Was that as DNA is made up of four nucleotides, ACGT, and they occur in random order.

But when we had the sequence data, all aligned at 1 point in a certain gene, there was a molecular signature where the nucleotides G, A lined up for all 19 species of the Gaga fern. And so the closest relatives and that area did not spell out Gaga. They spelled out something else. And so that was taken as a signal to us that we were doing the right thing.

CHAKRABARTI: I love that. I love that story. So let me ask you, what brought you, what made you fall in love with botany and the study of plants and took you to a place where you began, you were the director of, you are still the director of the Duke University Herbarium.

PRYER: I grew up in northern Quebec in Canada, surrounded by nature.

So I've always been fond of going out in the woods and looking at things. And my undergraduate career at McGill University, I was focused on becoming an animal behaviorist. Because I was thrilled with Jane Goodall and her stories and you could major at the time in animal behavior, which I signed up for.

But in my senior year, I took a botany course and the whole trajectory of my life changed. I found my people.

CHAKRABARTI: What is going to happen to Duke's herbarium? When I said earlier that it could soon no longer have a home, what has Duke said it wants to do with this collection?

PRYER: I don't think it really knows. So Duke is celebrating its 100th centennial and this collection is the same age as the university. It's a collection that's been built over a hundred years and it's very well-known across the world for the diversity of plants that we have, not only from a regional area, but also from a global perspective. Especially the neotropics. And it suddenly, we have been taking good care of it for 100 years and we are seeing now as not no longer being a place that should be a steward of such a treasure. It should go somewhere else. And this is rather unbelievable, because it really doesn't need much in order to survive.

The collection I told you about, the 70% of the collection that is in the newer facility, cost a million dollars to refurbish and that money came from NSF and Duke 15 years ago. And that collection is on a mobile carriage system, like you have in library, so you can compact the rows, and the plants are perfectly happy there.

They don't need watering. They just are safe and secure. And it's really a puzzle to us why that facility, which people who visit us marvel at. And wish that they had something so spectacular, that we have to go. And there is no place where it can go, where it could be accepted in its entirety at the present.

And so the idea of it being rifled through and bits and pieces sent to various places, it's actually quite horrific to us.

CHAKRABARTI: So to be clear, Duke is saying that it no longer, the university no longer feels that it's the best place for this herbarium and the implication there being that the space that the herbarium occupies may be better suited for other purposes.

We'll hear from some quotes from a university representative a little bit later in the show, but it really brings home this question, like in modern science, in a modern university, like there's costs and benefits to everything a university undertakes. And how to best balance that is now being played out with the story of Duke University's Herbarium, and we'll have a lot more when we come back. This is On Point.

Part II

I'd like to introduce Jacquelyn Gill into the conversation now. She's associate professor of paleontology and plant ecology at the University of Maine School of Biology and Ecology and Climate Change Institute.

And Professor Gill, I said that wrong. It's paleoecology, but welcome to On Point.

JACQUELYN GILL: Thank you. Thanks for having me and for having this conversation.

CHAKRABARTI: Here's the thing, to speak frankly, to most of our listeners, the concept of an herbarium may be, although very fascinating, remote. So I'd like to really ground the importance of this kind of science in the lives of just you and me and everyday people, right? What would be your argument for continuing to do the kind of science that is done with the plant samples in a herbarium like Duke's?

GILL: It's a great question. And I'm really glad that you asked, because I think it's really important that we be able to explore the usefulness of these kinds of collections, they might seem dusty and old.

And some of these samples might have been collected 100 or 200 or more years ago. But they are really the focal point of cutting-edge science, especially as we are confronted with a biodiversity crisis and the climate crisis. And the impacts of climate change on plant communities, especially rare or sensitive plant communities.

And if you think about a herbarium specimen, this pressed plant is not just a snapshot of what an ecosystem looked like in time, or maybe where we might have found a plant growing that we can then compare with today. But it also contains a wealth of information that is constantly being unlocked as new scientific techniques and technologies emerge.

So I might be able to look at a herbarium and say, okay this particular rare plant species used to grow on the top of Katahdin here in Maine, but now 200 years later, it's disappeared. That's a puzzle. That's a mystery. That's concerning. And the herbarium specimen is not only useful as a sort of, pre and post comparison, the specimen itself might actually unlock the clues as to why that species has disappeared, maybe it's something unique to that species.

Maybe it's something about its habitat and all of the information that comes along with that pressed plant is vital to unlocking some of the most critical questions that we have today.

CHAKRABARTI: Okay. That's really interesting. So Professor Pryer, let me go back to you because Professor Gill really hit on something, which I'll be honest, that came to my mind.

I'm a great lover of science and the natural sciences, without a doubt. But in thinking about a herbarium, it really conjures up the image of, I don't know, Darwin at the Galapagos collecting his samples. It conjured up a kind of science of the 19th century. But hearing Professor Gill, there's a direct connection, though, to the kinds of discoveries that you feel are critical for the 21st century.

Professor Pryer, would you agree with that?

PRYER: Absolutely. And to follow up on what Professor Gill said, these specimens, as science evolves and new technologies come online, the usefulness of herbarium collections is expanded. And to the degree that today herbaria across the world are seeing a revolution in their usefulness. Because you can extract DNA from 200-year-old specimens.

You can use machine learning to identify patterns of insect herbivory through time. There almost seems limitless what these specimens that were once just collected to be of representation of what was growing somewhere at one time. Now it was able to unlock answers to a diversity of questions that we had no idea would be possible now. So long ago.

CHAKRABARTI: Here's a question that comes from a resolute, I'm an urban gardener myself, so I don't know all that much about plants beyond the ones that I'm trying to keep alive in my condo. But Professor Gill, another thing I'm wondering is for species that end up becoming lost due to climate change or habitat destruction, in an herbarium, is it possible to, I don't know, extract DNA or seed information or anything useful from the preserved samples of those disappeared species in order to grow them again?

Or is that not what a herbarium could do?

GILL: So what you've just proposed was the topic of a recent paper that I just read a couple of weeks ago that really proposed the idea that herbarium specimens could be the sort of hidden trove of information that could enable the de-extinction of plants.

And when we think about de-extinction, we're usually thinking about things like the passenger pigeon or the woolly mammoth. We could have a whole conversation about that topic, but in terms of plants, which tend to be, we talk about this phenomenon of plant blindness, right?

Plants are thought of by many people as the backdrop rather than the focal point of our interests and our hobbies. Although I think that is very much changing. If you've ever spent any time on TikTok, plants are having a moment, right?

CHAKRABARTI: They are, for sure.

GILL: Yeah. And so there is some interest in potentially using herbarium specimens as a way to recapture lost biodiversity.

Whether that's something that will play out in the coming decades remains to be seen, and there are a whole set of ethical questions around de-extinction that definitely need to be addressed. But even aside from that, these specimens do capture information about the genetic diversity of plants that we know can be very important for their persistence.

CHAKRABARTI: I see. Okay. To be clear, Duke University is not at all saying that they wish for the destruction of Duke's Herbarium. That is not their intent. According to them, it simply is no longer, that Duke is no longer the best home for the collection. That's what they say. And they're seeking to re-home it in some other institution or institutions.

So to that point, I just want to hear a bit from a member of Duke's administration. This is Susan Alberts, professor of biology and dean of natural sciences at Duke. So as her position as dean, she's got an important role to play here. And she says that by rehoming the herbarium, Duke University is actually protecting a valuable collection.

SUSAN ALBERTS: I'm really intrigued and puzzled and a little discouraged by the idea that the relocation of the Duke herbarium is being taken as a negative statement about its value. Because I have to assure you that, for us, who are making this decision and trying to make this happen, it is actually quite the opposite.

We recognize the irreplaceable nature, the incredible value of this collection. It is the case that we believe we are not the right stewards of it anymore. And that's very different than saying the herbarium doesn't have value.

CHAKRABARTI: Professor Pryer, would you like to respond to that?

PRYER: Yes, I believe that the herbarium is a resource that truly is in support of Duke University's mission of knowledge in service to society.

Another example of that on the campus would be the Rubenstein Rare Book Library. I have no doubt that Duke recognizes the value, the fact that it wants to give it away to another institution, to me, appears to say that Duke no longer wants to be a leader in biodiversity and climate change crises.

That sort of research that are really immediate threats confronting humanity right now. And so why Duke would want to retreat and gift the collection to any other institution makes no sense. Because for 100 years, the community has known about the wealth of specimens that are here and have borrowed the material, have come to visit the material, in great numbers.

And it's unclear what other priorities are taking the place of these sorts of questions that the herbarium is capable of answering.

CHAKRABARTI: It's really interesting that you mentioned a rare book library. Because I can understand the metaphor very clearly, right? It could be a collection of, I don't know, hundreds or thousands of rare books that not everyone goes to visit, but it's a uniqueness and importance to the continuing of human knowledge.

No university would question that. Point well taken, Professor Pryer, but it's interesting because libraries were also an analogy that Professor Alberts, the Dean of Natural Sciences at Duke, that was a metaphor that she used as well.

ALBERTS: They both represent a repository of irreplaceable information that needs to be preserved for posterity.

But libraries are completely central to the endeavors of literally every single student, faculty member and research on any campus. Which in Duke's case is about, let's say, 20,000 people. In contrast, the herbarium is much more like what we call in universities a research core. It certainly has some features of a library, but it also just serves a really small portion of the community, a handful of students and faculty. Now this in no way diminishes the value of the herbarium, but there's simply no rational world in which this point won't be considered in a discussion about the best place to house it.

CHAKRABARTI: Professor Gill, I know that you're at the University of Maine and not Duke University faculty, so I want to just draw this out to a slightly higher level to talk about something that all colleges and universities face.

Now, at the risk of getting too much Inside Baseball regarding campus politics. There, in my mind, there's no doubt that colleges and universities in this country, especially, are the homes to where new knowledge, new understanding, clarity about the world, discoveries about our universe, especially in the sciences, are made, right?

It will, they will always be the engines of that, more so even than the private sector. The private sector is a secondary level of discovery, in my opinion, right? But, to that point, since nobody is talking about destroying the 825 samples in Duke's herbarium. I really wonder, from your point of view as an ecologist, does it matter where the science is done, for the good of humanity?

Suppose the collection ends up elsewhere, but the science that you talked about earlier is still done there. Does it matter to the rest of us?

GILL: I think it does, and I think that the impact, as a I'm trained as a geographer and so I have been drilled with the importance of place-based research. And one of the, I think, really important aspects of the Duke herbarium is that it is very much widely recognized as a repository of very particular kinds of information, they have certain types of taxa or species that are housed there that they're an expert in. And there are staff and faculty who have expertise in those collections that won't necessarily follow the collection if it gets parsed up.

But also, it's a hub of biodiversity information for the southeast of the United States, which is a biodiversity hotspot. We have a lot of species in the southeastern U.S. that are not found anywhere else, and they are some of the most threatened species that we have when we look at the impacts of land use change, and climate change.

And this idea that when I look at an institution like Duke, which is a much more well-endowed institution than the public university that I work at. And when an institution with an $11.6 billion endowment as of 2023 says that they are concerned about this collection to the point that they want to farm it out to other institutions.

I have to ask, who has the resources to take those on? No one institution does. And so that means the specimens are going to get carved up and farmed out, maybe, to a bunch of different institutions who probably don't have the same level of resources that Duke does. And one thing I would just point out is I don't know how many times you've moved across the country, but whenever, I don't usually end up with arriving in my new home with all of the things that I left, right?

There's a lot of chaos. Things get lost. No matter how careful you are, things get damaged. And a lot of these specimens are completely irreplaceable and the information that they have with them would be lost. And so I think it's not just about whether the science can be done. It's certainly harder to do.

If I have to send a graduate student to six different institutions, that's six times the amount of time and six times the amount of resources that it would take for me to just send them to one, right? So there's an efficiency element here. But also, I think it comes back down to the question of what is the central mission of a university and what do universities value?

And if you can't invest in a world-renowned biodiversity collection, then I think that says something pretty stark about your values.

CHAKRABARTI: Okay, so you mentioned Duke's endowment, which is $11.6 billion. We turned that question to Professor Susan Alberts, again, who's the Dean of Natural Sciences at Duke, and she very much pushed back against using the endowment as a way to measure what the university can do, because she said it's important to understand that while that multi-billion endowment may exist, that money is promised to very many parts of the university.

ALBERTS: It generates about $500 million a year. And honestly, like Duke spends about $225 million a year in student financial aid. And so then you start thinking about, that helps, it helps highlight a university like Duke has many different responsibilities. Moral, fiscal, societal. And there is just no, unfortunately, there's no world in which those kinds of responsibilities don't sometimes conflict.

CHAKRABARTI: Professor Jacquelyn Gill, I want to take that one step further. We've only got a minute left in this segment. But the other thing that's skirting around this conversation is that universities also have to make a very important decision about where to fund things so that the return to the university is as maximized as possible.

And I think there's an argument to be made that the space that the herbarium might be taking up, Duke sees is better used for other types of science that maybe could attract more funding, could produce more supposedly needed research for today. That kind of thing. What do you think about that?

GILL: I think that if we're going to do this kind of census, we should do it honestly. And I would love to see numbers on the actual numbers of students that go through that herbarium as work study students or in their classrooms. When I talk to people about the closure of this herbarium, the vast number of scientists that I spoke with, who were really upset about this, got their start as undergrads in herbarium.

So how do you measure the impact of this location, this resource, as a pipeline to our scientific workforce, right? There's so much more that happens in herbaria, or that is engendered by herbaria, that happens well outside the boundaries of the university. And if we're going to do that math, then let's do it, it's extending as far as we can.

Part III

CHAKRABARTI: I want to move now to how an herbarium inspired a young scientist of today and just listen to what she just went out and did a couple of days ago.

JOYCE ONYENEDUM: (LEAVES CRUNCHING) Oh! Oh, it's a skunk cabbage! Oh no way! (LAUGHS) This is amazing!

CHAKRABARTI: So that's New York University botanist Joyce Onyenedum. She was out on a beautiful early spring day last Friday in Rockefeller State Park Preserve in New York, just an hour outside of lower Manhattan.

ONYENEDUM: We found something beautiful. Early spring signs, skunk cabbage we've got here.

Running along this creek, there's a bunch of them just emerging. Got these big leaves that look like lettuce! And they come furled, they unfurl, and then accompanying that is a huge, red pointy space, which is a modified leaf that has a purple and red molting design to it. Inside of it is the cluster of flowers.

So this is a pretty iconic thing to see. I'm really excited. I'm really excited to see this actually. Definitely got to be collected. So I'm going to get my plant press.

CHAKRABARTI: Professor Onyenedum grew up on nearby Long Island, and now she's returned to New York City, where she investigates the evolution of climbing plants. The skunk cabbage specimen she's collecting is bound for the New York Botanical Garden Herbarium.

ONYENEDUM: Ok, let’s get this thing collected … I need a newspaper, let’s see if I have anymore. Awesome, I have some more.

Ok. It is the 15th of March, 2024, I’ve come across a skunk cabbage. Laying out the leaves one at a time, get our inflorescence, our cluster of flowers and put that down. I’m going to open one up, it’ll press better. Close my newspaper, put my specimen in the plant press. (CRUNCH)

CHAKRABARTI: Professor Onyenedum joins us now. Welcome to On Point, Professor.

JOYCE ONYENEDUM: Thank you for having me.

CHAKRABARTI: What gave you so much joy discovering that skunk cabbage?

ONYENEDUM: I love that question. As a botanist, we have trained eyes for spotting different species when we're walking around. So constantly we're identifying plants when we're walking around.

And when you see one that you don't typically see, so I live in New York City, I live in Greenwich Village, and I don't get a chance to see skunk cabbage very much. And I didn't get a chance to see skunk cabbage at all growing up. So when I get a chance to see something I am not used to, it just has this awe effect on you.

It's this funky little plant. It literally smells bad. That's why it's called skunk cabbage. It has a pointy inflorescence. It's purple. It's in the swamp. It's just a funky plant. So seeing biodiversity is always an awe inducing experience and it brings me so much joy.

CHAKRABARTI: So tell me more about then how this joy formed in you, because I understand that you really fell in love with plants actually because of family connections in Haiti?

ONYENEDUM: Sure, yeah. As you mentioned, I grew up outside of New York City and it was a sort of urban, suburban experience. Very disconnected from nature, never really thought about biodiversity whatsoever. And it wasn't until we took a family trip to Haiti in 2011, after the seven-magnitude earthquake in Haiti hit.

And we all came down to see our family. And we were in the southwest part of Haiti where my grandfather's home was, in a village called La Selle. And for the very first time, my eyes had a different precision. I was able to see colors differently. I saw the national flower and it was brighter than I ever noticed plants to be.

And for the first time I saw a pineapple plant and a pomegranate plant. And they're not just things in the grocery store, they're actually legitimate plants. And I think that stark contrast to the kind of maple London planetrees of New York sidewalks contrasted with pomegranates and red and yellow just reminded me, or actually for the first time taught me, live, there's a lot of plants in the world.

So from there, when I came back to the U.S. I became intrigued by plants and diversity, and I transferred to Cornell to study plant sciences, where I became desperate for a research opportunity. And the first opportunity I got was at a herbarium at the U. S. National Herbarium in Washington, D.C.

I had no idea what it was. I didn't know what these words meant. I just showed up that summer ready and eager to do anything. And I fell in love. It was two floors, 5 million specimens, cold, dark rooms, thousands of specimens, very quiet space. The task was to look at tens of thousands of specimens and look very carefully at the leaves to see if there's any differences in the way the veins of this species are versus the veins of that species.

And for some reason that worked for me. And that really showed me every single species is special. And so I continued on with that inspiration into my PhD and eventually as a professor, now at NYU. And I just want to give that back to people, that joy of plant collections, when you see something for the first time, realizing it's different, it's unique, it's special, and enjoying that awe moment.

CHAKRABARTI: I completely understand what you mean about seeing the spectacular biodiversity of different places firsthand, because it's one thing just living in your neighborhood and getting familiar with the plants. And especially in urban areas, the dwindling number of plants that might be in a person's neighborhood.

But years ago, on one of our trips, a family trip to India, I clearly remember where we were walking around, actually in a very rural place. And I saw growing in the wild, like cloves and jackfruit and turmeric and cardamom, like just growing. Because that's where they grew on planet Earth.

And it was deep in my pleasure and understanding of how much there is to this little planet that we are stewards of. Are you saying that, like, when people get to go into herbariums that they, that it brings that home to them even without having to go to Haiti or India, etc.?

ONYENEDUM: Oh, absolutely.

I think that's one of the major advantages of a herbarium, is that you can be transported across the world. So I study a group of plants that's from the Neotropics, Central and South America, and there's 500 species. And as a professor, we don't honestly have the time to go around the world and collect each of those 500 species.

And what can I do? I can go to a already curated archival collection of plants from all around the world, and I can collect leaves from the curated collection of a herbarium, one leaf at a time. And that really transports me to that place. The label that Professor Pryer was mentioning has all the information of the time, the locality, the observations by the scientists when they collected the specimens.

I can put myself in their shoes and see what they see. And we have, even at this point, digitized specimens across the world, where herbaria take images of their collections, and then we can share them across the world as well. So it brings you to the place you need to go. Of course, it's no replacement for being in the field itself, but it is an absolutely amazing resource. Because we don't all have the time to go to Haiti every week.

CHAKRABARTI: I want to just see what you think of a question that I asked a little earlier. Because while I can spend hours romanticizing about the possibilities of discovery in collections like an herbarium, the truth is that modern universities are also businesses and very political places, too.

You know that as a professor, right? And so I can definitely hear the argument we played from the Dean from Duke who, she was essentially saying, right now, for the spaces that the Duke Herbarium is in, they just don't think that the function of the university is to be a museum.

But rather, there are other things that they can do there that would serve both science, but more frankly money, in terms of funding, etc., better. So I'm just wondering how you think through that, because that is a real issue that's at play at every college and university in this country.

ONYENEDUM: Yeah, thank you for the question, these days I'm thinking about plants in the urban context, and I can see an argument for someone closing a herbarium in a city. Or because maybe it's not important, presumably not important for cities to have trees, but there is a push right now for it. Rightfully so, to greenify urban spaces.

And how are we actually supposed to do that? We need to know what plants are best suited for this environment. We need to know what plants are going to be pollution resilient, that are going to be good for mitigation of runoff of rain, especially in our coastal cities. And how are we supposed to teach our students?

That kind of stuff. We can't keep planting the same plants over and over again, that are not suited for the changing environment of urban landscapes. So the herbarium, in my context, an urban environment of New York City, is a resource for me to teach the students about the plants that can grow here, that can't grow here.

The best suited ones for their changing environment. And so ... ultimately, if we think long term, this is going to cost the city less money if they plant the right trees. And that they plant the right trees that produce shade for the citizens of New York, for example.

So I can see the argument for the sort of myopic vision of immediately what's going to have a return on investment. But I'm thinking long term about the urban environment, the landscape, and the people who are benefiting from it, the ecosystem services that the plants are providing to the people and the citizens of the urban environment.

And that is going to cost the city so much less if they do it right. And we need to teach the students how to do that.

CHAKRABARTI: I am inspired by your vision, professor, but I think the thing maybe blocking that long term vision isn't necessarily the science or the scientists doing it, but the policy makers who would have to decide to think more long term here.

Do you have a favorite plant or two, that is, or 17 or 10,000, but we'll go back to one or two that you could describe for us.

ONYENEDUM: Huh. Oh goodness, that's such a great question. And of course, I'm going to have so many answers, but I think these days ... so I study climbing plants, so I have favored towards those guys.

And I also have become very interested in urban plants. And so I have become very interested in wisterias in New York City, because they are our chosen brownstone plant. People love planting wisterias. They're very old specimens in Greenwich Village. There's right-handed ones. There's left-handed ones.

They twist right, twist left. They have big clusters of purple flowers. There's a few species around these parts. There's some natives, there's some non-natives, and they're really decorative in an environment that there could be tree line, there could be streets with no trees, but there are some vines creeping on the bricks.

There are some vines creeping on the brownstone. So these days I'm really into the wisteria.

CHAKRABARTI: Okay. So what do you think the best argument that you would provide now, for why an herbarium is important for you and your research now, but you had mentioned your students, like future botanists and ecologists.

ONYENEDUM: So in my work, I use herbaria constantly for two reasons. And the umbrella reason on top of all of that is we just want to understand the biodiversity of the world, which means we have to understand how many species there actually are and how to distinguish them from one another.

So how do we do that in a modern age? We continuously use classical techniques of using our eyes, our senses, to sense the differences between every species, but we also use sort of DNA extractions and gene sequencing in order to figure out how these are genetically different than one another. We use anatomy, meaning we cut the plants open, look at the cellular composition to see how in the interior they're actually organized differently.

And I get all of this data from working in the herbarium. So we are unable to really account for how many species are in the world and how to conserve them if we don't have the herbarium at our disposal.