DURHAM, N.C.
T his wildflower bloomed in the low pine woods along North Carolina’s Tar River. The blossom, called a pink lady’s slipper, was plucked nearly nine decades ago — on May 16, 1936 — and stored away.
This pair of pink lady’s slippers, picked roughly three decades later, in 1962, were in full bloom a few days earlier, on May 12.
These from 1997 had blossomed by mid-April, a full month earlier than their counterpart 60 years before.
By poring over nearly 200 of these pressed orchids, collected by botanists between 1886 and 2022 and stored in drawers at Duke University’s herbarium and elsewhere, scientists found that the flowers are now blooming 12 days earlier on average than they did 150 years ago. At this rate, the orchids may eventually bloom before bees are fully out and about, cutting the chances that pollen catches a ride to other pink lady’s slippers and that plants procreate.
“The pink lady’s slipper is one of those iconic spring flowers that once you see it, you never forget it,” said Kathleen Pryer, the Duke biology professor who runs the herbarium. “It makes you happy each time you bump into it.”
These sorts of dried plant specimens are one of the few ways to track the speed and scope of how humans are transforming the planet for plant life.
In the midst of a worldwide biodiversity crisis, one that could wipe out up to a million species of plants and animals, herbaria captured the plant world before the onslaught of climate change, habitat loss and other human activity was fully apparent. Understanding how plant species’ ranges and physical characteristics have changed over time offers insights into what lies ahead for plants — and for humans.
The Duke Herbarium is one of the biggest in the country, stretching back more than a century and covering the southeastern United States, a biodiversity hot spot where many species are disappearing. The collection sheds light on the past lives of an unusually large number of species, allowing scientists armed with new genetic and computing tools to compare them with their descendants growing today.
Now the collection’s future is uncertain. Earlier this year, Duke announced plans to shut down the world-renowned herbarium, citing the high cost of maintaining the roughly 850,000-specimen collection of plants, fungi and algae. University administrators say they intend to keep the collection intact and find a new home for it within the next three years, though critics worry that there are few institutions able to absorb a collection of its size.
Susan Alberts, Duke’s dean of natural sciences and one of the university administrators who decided to move the herbarium, acknowledged that the collection is “an incredibly valuable and precious resource,” but said it is time for Duke to find it a new home and invest university resources elsewhere.
“It’s a zero-sum game,” Alberts said. “Nobody has infinite resources.”
The pending closure has led to outcry from plant curators around the world, who say the loss threatens scientists’ knowledge of biodiversity. “Having a premier, prestige university like Duke de-committing to this resource — it’s just shocking, honestly,” said Charles Davis, a biology professor who curates vascular plants at Harvard University’s herbaria.
For Kathleen Pryer, the loss is personal. As director of the Duke Herbarium and steward of this botanical treasure trove, she has spent most of her life tending to plants collected over a century around the world — flowers fastened to paper, mosses tucked in tiny envelopes, cacti stored in tiny cardboard boxes. This is where she has sought to inspire generations of budding botanists, and even where she met her husband. Duke’s herbarium will be the largest closed or relocated in U.S. history.
“This is killing me,” she said.
Plant trove
These dead-plant libraries can feel like a relic of an old way of doing science — akin to tromping through the wilderness to hunt animals for taxidermy. The first herbaria sprouted up in Europe during the Renaissance to train medical students and catalogue the unfamiliar plants explorers brought back from their travels.
Today, there are some 3,600 registered herbaria worldwide, and that number is growing. But many are smaller than Duke’s, said Barbara Thiers, a former director of the New York Botanical Garden’s herbarium, and most of that growth is happening abroad. The creation of new plant collections does not compensate for the loss of old ones with records stretching back more than a century, which allow researchers to see if a species’ range and blooming patterns are changing over the years.
Some prominent U.S. universities, such as Stanford and Princeton, have ditched natural history collections as scientists were increasingly studying the inner workings of cells under microscopes rather than focusing on the whole organism. In 2017, the University of Louisiana at Monroe moved its plant and fish collections to make room for sports facilities.
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Today, plant curators say technological advances mean herbaria are going through a renaissance of their own. Advances that have drastically lowered the cost of computing and genetic sequencing have opened up opportunities that are not available with other plant records, like field notes and illustrations. Researchers are trying to discover new species by writing AI programs to scan plant libraries and probe the secrets of evolution by extracting DNA from decades-old specimens.
The fern below, for example, was part of a DNA study in which Pryer and her colleagues uncovered a bizarre example of plants performing genetic engineering on themselves by acquiring a light-detecting gene from a distantly related plant called a hornwort that may have allowed them to thrive in dark forests.
This other fern was part of another one of Pryer’s DNA studies showing how two plants separated by 60 million years of evolution were able to interbreed — a feat akin to an elephant mating with a manatee or a human hybridizing with a lemur.
The research revamped scientists’ understanding of how long two species could be separated but still mate.
“There are whole new series of very sophisticated, highly sensitive scientific techniques that are now amenable to applying to herbarium records in ways that we’d never previously imagined,” Davis said.
Some of the most powerful work done at herbaria involves uncovering so-called “dark extinctions” — that is, the loss of species scientists didn’t even know existed. Decades can pass between when botanists bring a plant to a herbarium and when it is determined to be a new species. The only way researchers know some extinct plants once existed is through the careful detective work of herbarium curators.
“It’s the kind of thing that I lose sleep about at night,” Davis said.
Plants and people
Pryer, born in Quebec, went to college at McGill University in Montreal to study animal behavior. “I wanted to be the next Jane Goodall,” she says. But after taking a botany class, she flipped to plants. “That switch went on and it was like, ‘These are my people, this is my thing,’ and I never looked back.”
She came to Duke to pursue her doctorate in large part because of its herbarium. Aside from a six-year stint at Chicago’s Field Museum, Pryer has been here ever since. She teaches an undergraduate class about the importance of plants in society, called “Plants and People,” with her husband, Michael Windham.
“We disclose it to students now when we teach,” Pryer said during a tour of the herbarium. “We may act like an old married couple...”
“...because we are!” said Windham, who curates the herbarium’s flowers, ferns and other vascular plants.
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The pair said that many of their students are pre-med. “Even though we say doctors used to be botanists first, because they had to know their plants to be able to cure, they’re like, ‘Yeah, whatever,’” Pryer said.
Recently, Pryer had some luck getting a young mind interested in plants. Kylie Dumaw, a Raleigh-area high school student, had read some of her research on genetics and reached out about helping at the herbarium.
As a ballerina, Dumaw was drawn to the pink lady’s slipper. Along with Pryer and Windham, she is one of the researchers who pieced together the flower’s blooming history.
“In high school, you hear the word ‘research,’ but I had no idea what that would entail,” said Dumaw, who is planning to present her findings about the orchid at a botany conference in June.
“This herbarium can be used by so many different people for so many different purposes,” she added. “I wouldn’t have been able to do any of this if it weren’t for the herbarium.”
Where to root a plant collection
Alberts, the Duke dean behind the decision to transfer the collection, said she knows how important Duke’s plant collection is — both in and outside the university — to understanding nature’s diversity. “It’s really important that we think about it as relocating rather than closing,” said Alberts, who researches baboons. “We see this as an incredibly valuable and precious resource.”
But there are several reasons to relocate the herbarium now, according to Alberts.
Several of its scientists, including Pryer, are near retirement. One of the buildings housing the collection is old and needs repairs, so a big portion will need to be put in storage somewhere else. “That creates a huge problem for hiring any faculty to study the herbarium in the short term,” Alberts said.
It would take a $25 million endowment for Duke to keep the herbarium, she added. Alberts said she did not know yet what Duke will do with the 9,500 square feet of office space on campus it now occupies. She thinks these sort of plant collections are better kept by museums rather than academic departments.
“That’s what natural history museums are for,” she said. “This is not a debate about the value of the herbarium.”
Pryer, who was in the middle of discussions with a Duke alum interested in donating $1 million to the herbarium when she learned of the university’s plans, said there is “no substantiation” to that $25 million price tag. To boot, she and other critics note, Duke could afford it with its large endowment. Getting rid of the collection “makes Duke look like it doesn’t want to be a leader in biodiversity research and climate change research,” Pryer added.
In response, Alberts said Duke’s commitment to climate research is “unchanged.” But when it comes to the herbarium, she added, “there is no way back from this decision.”
Botanists across the country have protested the decision, penning op-eds, journal articles and an online petition endorsed by six science societies that drew more than 19,000 signatures.
“We’re not just keeping these around because they’re quaint and pretty,” said Thiers, who tracks herbaria and used to run the country’s largest. “We’re just barely scratching the surface of what we can do.”
Alberts and other university administrators are committed to keeping the collection together.
But advocates for the Duke Herbarium say a collection as big as Duke’s may have to sit in storage while a new facility is being prepared, risking damage to delicate plants from insects or fungi. A relocation of this size is also prone to having specimens misplaced and lost forever, endangering future research on how plants are adapting to human-driven climate change.
None of the institutions capable of taking on Duke’s collection have yet stepped forward. “I can’t think of any that have just moved into some new facility where they could just easily incorporate that many specimens,” Thiers said.
Ever since the closure announcement, Pryer has fielded hundreds of emails from researchers, with some asking for specimens. Granting those requests would mean splitting up the collection.
“That would be really the most horrific thing that could happen,” Pryer said.
If Duke goes through with its decision, the task of packing up the specimens for their new home would fall to her and her staff. She knows how important it is to preserve the collection but can’t bring herself to send away her life’s work.
“I did not get up to my golden years here to be packing up specimens and destroying a legacy … I won’t be part of that.”
Photos by Kate Medley. Text by Dino Grandoni.
