Duke team wins top prize in mathematical modeling contest
Of all the math competitions for college students, the annual Mathematical Contest in Modeling (MCM) is one of the biggest. And this year, Duke’s team took home a coveted top prize.
Undergraduates Erik Novak, ’24, Nicolas Salazar, ’23, and Enzo Moraes Mescall, ’24, represented the Blue Devils at this year’s contest, a grueling 4-day event where teams of undergraduates use their mathematical modeling skills to solve a real-world problem. The results are finally in, and the Duke team was chosen as one of the top 22 outstanding winners out of more than 11,200 teams worldwide.
Their task: to analyze some of the challenges facing a nature reserve in Kenya known as the Maasai Mara. This region is named for the local Maasai people, a tribe of semi-nomadic people who make a living by herding cattle. It’s also teeming with wildlife. Each year, more than a million wildebeests, zebras and gazelles travel in a loop from neighboring Tanzania into Kenya’s Maasai Mara Reserve and back, following the seasonal rains in search of fresh grass to eat.
Some 300,000 safari-goers also flock to the area to witness the massive migration, making it a major player in Kenya’s billion-dollar tourism industry. But protecting and managing the land for the benefit of both wildlife and people is a delicate balancing act.
The reserve relies on tourism revenue to protect the animals that live there. If tourism slumps — due to political unrest in Kenya, or the COVID-19 pandemic — desperate communities living around the park resort to poaching to get by, threatening the very wildlife that tourism depends on.
Poachers aren’t the only problem: wild animals such as lions, leopards and elephants sometimes venture into human settlements in search of food. Conservationists must strike a balance between protecting these animals and managing the dangers they pose by raiding crops or killing valuable domestic livestock.
Tourism is a mixed blessing, too. While safari-goers bring money into the region, they can also disturb the animals and pollute the Mara River, and off-road drivers can erode the soil with their jeeps.
The mission facing the Duke team was to identify ways to mitigate such conflicts between wildlife and people.
This year’s contest ran over a single weekend in February. Camped out on the third floor of Perkins library, the team of three worked 12 hours a day, fueled by a steady supply of Red Bull and poke bowls. During that time, they built a model, came up with budget and policy recommendations, and wrote a 25-page report for the Kenyan Tourism and Wildlife Committee, all in less than 96 hours.
They built a mathematical model consisting of a system of six ordinary differential equations. According to the model’s predictions, they said, it should theoretically be possible to increase the reserve’s animal populations by about 25%, reduce environmental degradation by 20%, nearly eliminate retaliatory lion killings, and cut poaching rates in half — all while increasing the average yearly flow of tourists by 7.5%.
“They did not win that contest, but they took everything they learned and look what they did with it. I’m very proud,” said assistant professor of mathematics and biology Veronica Ciocanel, who coached the team and co-organized the Triangle competition.
In addition to finishing in the top 0.1% of competitors, the Duke team got three additional awards for their performance; the Mathematical Association of America (MAA) award, the Society for Industrial and Applied Mathematics (SIAM) prize, and an International COMAP Scholarship Award of $10,000.
The problems in these contests tend to be much more open-ended than typical coursework. “We didn’t know what the solution was supposed to be or what tools to use,” Novak said.
Modeling, computation and coding skills are certainly important, Ciocanel said. “But really what matters more is practice, teamwork, and communicating their results in a written report. Students who have a solid course background don’t need to do anything else to prepare, they just need to be creative about using what they know from the courses they already took.”
“Use what you have and work well together,” Ciocanel said. “That I think is the most important thing.”
Amid fracturing arctic ice shelves, late September tempests, floods, droughts, jumping wildfires, a few decades of quick extinction and species blinking out like the quiet collapse of distant supernovae, our climate crisis has begun to displace humans en masse.
68.5 million people were forcibly displaced by climate change and disasters in 2017. By 2021, that number grew to 89.3 million people. In 2022, we reached 100 million.
In a series of articles for the San Francisco News entitled “The Harvest Gypsies,” John Steinbeck described the 1930s Dust Bowl migrants in California’s Central Valley, uprooted by drought and crumbling wheat, then later novelized in the American classic Grapes of Wrath.
Steinbeck wrote, “The new migrants from the dust bowl are here to stay. They are the best American stock, intelligent, resourceful; and, if given a chance, socially responsible. To attempt to force them into a peonage of starvation and intimidated despair will be unsuccessful. They can be citizens of the highest type, or they can be an army driven by suffering to take what they need. On their future treatment will depend the course they will be forced to take.”
Co-sponsored by Duke Center for International Development (DCID) and the Center on Modernity in Transition (COMIT), the lecture is part of the larger Rural Transformations speaker series, highlighting rural perspectives in the discourse around development. This objective embodies COMIT’s research as well as their cognizance of “modernity as an age of transition towards a future world society—one that will emerge not through the universalization of any existing way of life, but rather through the sustained, creative, and complexly interacting contributions of all the diverse cultures and peoples of the world.”
The Dust Bowl, McLeman pointed out, is a quintessential example of climate migration, conjuring Dorothea Lange’s depression-era photojournalism and 8th grade US history. More recently, this phenomenon has been exemplified by hurricanes Katrina, Ike, Harvey, Irma, Sandy, Ida, Hugo, Andrew, Ian, and Maria (just to name a few) with similar, though smaller scale effects.
As McLeman and Bermeo acknowledged, climate-catalyzed movement is highly dependent on complex interactions between environment, society, economy, and politics, including a myriad of non-ecological factors like “land tenure, social networks, [and] access to government programs.”
Their research on the demographic composition and rates of climate-migration answers a number of questions: who is disproportionately affected by climate change? Who is migrating? And who is participating in policy decisions?
December 2022, the Biden Administration announced a $135 million investment for relocation and adaptation planning for Native American tribes severely impacted by environmental crises, such as “coastal and riverine erosion, permafrost degradation, wildfire, flooding, food insecurity, sea level rise, hurricane impacts, potential levee failure and drought.”
In less than a lifetime, one such tribe, the Jean Charles Choctaw Nation in Terrebonne Parish, Louisiana, witnessed nearly their entire island sink into swampy silt.
On their tribal website, they write: “For our Island people, [Isle de Jean Charles] is more than simply a place to live. It is the epicenter of our Tribe and traditions. It is where our ancestors survived after being displaced by Indian Removal Act-era policies and where we cultivated what has become a unique part of Louisiana culture.
Today, the land that has sustained us for generations is vanishing before our eyes.”
Climate migration in America, however, is not contained within and between states. In the past decade alone, Bermeo’s research points to a significant increase in migration from Central America to the US as well as novel patterns of family unit migration to the southern border (as opposed to a predominantly individual, male demographic in previous years). She attributes two recent droughts to this out-migration, disproportionately displacing rural communities whose livelihoods are integrally tied to subsistence farming and year-to-year crop yield.
“People leave their homes because of climate but leave their countries for other reasons,” Bermeo explained. A large percentage of climate-migration is “inter-state,” i.e. a rural coastal community is forced to move inland (but still within their country) because of dangerous erosion.
In Central America, however, there is a distinct relationship between the incidence of drought and violence. Environmental stress has catalyzed a mass exodus from rural areas, increasing urbanization, yet these cities (particularly those in Honduras, Guatemala, and El Salvador) often rank globally among the most violent, based on year-to-year per capita homicide rates.
With high levels of urban corruption and gang affiliation, it is often difficult for rural “outsiders” to find employment in the cities, leaving them unable to compensate economically for a season of crop failure. This conflict is further exacerbated by large proportions of young workers in these populations.
Despite deep-seated political polarization, climate-migration is adaptive.
McLeman described migration generally as “neither good nor bad… something that people sometimes do and always have done… [But] in North America, we lose sight of the fact that it is normal human behavior… it’s the circumstances under which it occurs that creates the challenges.”
When migration is voluntary, when people have access to social safety nets, are able to remit money to their families back home, and to mobilize legally across borders, migration is beneficial for the migrant, the migrant’s family, and the receiving community (which often benefits by filling labor demands). Often, the ramifications of immigration portrayed in the media (crime, destitution, etc.) are exacerbated by the lack of legality, social networks, and “gray markets.”
Bermeo acknowledged that the most effective mechanisms of decreasing undocumented migration are those that increase legal pathways. Historically, when the US has increased the number of visas allocated to Central American immigrants, illegal immigration subsequently decreased.
The panelists agreed: in order for both the migrating and receiving communities to benefit, we must prioritize the dignity of migrating individuals.
Though conversations surrounding climate change feel threateningly existential, Bermeo and McLeman described ways in which climate adaptation can be manageable. When migrants and rural communities are excluded from conversations and subsequent policy-making, not only do they benefit less from the proposed and funded interventions, but other communities (perhaps at less imminent risk from climate change) will still suffer from this missing insight.
Here, I return to the Jean Charles Choctaw Nation. Despite the appearance of a successful relocation project, the tribal council released a press statement in 2022, condemning the state of Louisiana. Elder Chief Albert Naquin spoke on the issue:
“If you believe that the resettlement of Isle de Jean Charles was successful, you’re headed in the wrong direction.” The memo added that, “Moving people while trampling upon our Tribe’s inherent sovereignty and rights to self-determination and cultural survival must not be viewed as a ‘success’ for future public climate adaptation investments.”
The mass movement of climate-migrants, from Indigenous to rural communities, represents a loss of autonomy, of land integral to identity, and often of home.
Still, Schewel’s Rural Transformation project advocates for the prioritization of these communities, rejecting the notion of passive policy-making and, instead, endorsing their active participation. Her project is indicative of how we must approach climate change adaptation: with empathy, education, and inclusion.
In a conversation with DCID, Schewel put it best: “[R]ural places are often treated as an afterthought… Some of the most promising advances in sustainable and equitable development are taking place in rural contexts, where a diversity of actors are striving to transform food systems, incorporate local knowledge, strengthen climate resilience, and widen participation in the development process.”
The DCID article ends with key insights from Schewel that encompass the Climate Change, Adaptation and Migration discussion and bear repetition: “As more focus is going towards migration, this is a project that will take very seriously the constraints on rural livelihoods and the motivations of migrants who leave rural places, while offering forward-looking solutions to advance our understanding of what it would mean to build more sustainable and flourishing rural futures.”
There are many ways to think of North Carolina. It was the 12th U.S. state to enter the Union. It is bordered by Virginia, Tennessee, Georgia, and South Carolina. North Carolina’s capital city is Raleigh, and it has an estimated population of 10,698,973. These are all facts, but they tell only part of the story: the human side of it.
Naturalist Tom Earnhardt offers other ways to view North Carolina: the state contains the oldest forest in the eastern United States, with trees up to 2,700 years old. It has 17 river basins, and some of its rivers show evidence of fishing weirs used by indigenous tribes hundreds of years ago. And from the Atlantic coast in the east to the Appalachian mountains in the west, North Carolina is home to thousands of native plants, animals, and fungi. There are 3,000 species of moths alone in North Carolina, and “Every one is essential; not one is optional.”
“North Carolina,” Earnhardt says, “is still one of the most biodiverse and extraordinary places on the planet.”
Earnhardt is a naturalist, photographer, writer, and attorney. He wrote and produced the show “Exploring North Carolina,” a series of dozens of episodes about North Carolina’s biodiversity, geography, and history. Earnhardt recently visited Duke to speak at the Nasher Museum of Art.
One inspiration for his talk was the ongoing Nasher exhibit “Spirit in the Land,” an exploration of ecology, culture, and connection to the natural world. “Art in its many forms,” Earnhardt says, “tells a story of love, loss, and renewal.”
Earnhardt has spent much of his career balancing caution and hope. We are facing environmental crises, including climate change and biodiversity loss. Earnhardt believes it’s important for people to know that, but he has put a lot of thought into how to get that message across. Earnhardt has learned that it can help to “tell it as though it was your best friend or brother who needed to hear an important story.” Science alone isn’t always enough. “To hear bad news of any kind is not easy,” Earnhardt says, “and people want to hear it from people they know, people they trust or can relate to.”
The stories he tells aren’t always easy to hear, but they are important. We need to know — whether on a local, state, national, or international scale — what exactly we stand to lose if we continue on a path of environmental destruction. Many species are becoming more scarce, Earnhardt says, “but we still have them.” They can’t be protected once they’re gone, but many of them are still here and can still be preserved. The goal for all of us should be to keep it that way.
North Carolina, Earnhardt says, is at “the epicenter of the temperate world.” The state has a range of climates and habitats. It marks the northernmost native range of the American alligator, while coniferous forests in the North Carolina mountains resemble boreal forests of the northern U.S. and Canada. North Carolina, according to Earnhardt, contains “whole ecosystems that other states only dream about.”
Eastern North Carolina is characterized by beaches, salt marshes, and other coastal ecosystems. Here you can find “wildflowers that grow in salty sand” and painted buntings, multicolored songbirds unlike any other in North America. On four occasions, he’s even seen manatees in North Carolina.
“Travelers from around the world vacation here and raise their families in the summer,” Earnhardt says—and he’s not talking about humans. Many shorebirds and sea turtles lay their eggs on North Carolina’s beaches. Human disturbance, including artificial lighting and crowded beaches, can put their babies in danger. Minimizing light pollution near beaches, especially during turtle nesting season, and staying away from nesting shorebirds can help.
Moving farther west, we can find savannas of grasses and pine trees. “You drive past this, and people go, ‘ho hum, a pine barren.’” To that Earnhardt says, “Look a little closer.”
These pine barrens are home to some of North Carolina’s 80 species of orchid, like the white-fringed and yellow-fringed orchids. “Look at them from all angles,” Earnhardt urges, “because from up above it becomes a sunburst… for those who watch.”
Be one of those who watches.
North Carolina rivers, forests, and swamps are also home to many wildlife species. Forests around Black River contain “huge buttresses of tupelo that hold the world together” and bald cypresses that have been alive for 2,700 years. The early years of these now-ancient cypress trees coincided with the fall of the Assyrian Empire and the establishment of the first emperor of Japan. Many centuries later, they are the oldest trees in eastern North America.
They are also in danger. “If seas rise three feet,” Earnhardt says, “there will be enough pressure to flood these [trees]…. We could lose them.” But “they are worth saving.”
Still farther west are the Appalachian mountains, another biodiversity hotspot. North Carolina is home to 60 species of salamanders, many of which live in the mountains. The southern Appalachians and western North Carolina contain more salamander diversity than anywhere else on the planet. One species that lives here is the American hellbender, a two-foot-long denizen of mountainous streams.
Despite increasing human development, North Carolina is still rich in flora and fauna. “We have wild places,” Earnhardt says. North Carolina has more than 450 bird species, over 30 native pitcher plants, 20 freshwater turtles, and 38 snakes—“and they’re all good neighbors,” Earnhardt adds.
North Carolina has pink and yellow lady slippers and ten-foot-tall Turk’s Cap lilies; crayfish and thousands of mushrooms; native azaleas and insects that depend on them. It has Earnhardt’s “new favorite bird,” the swallow-tailed kite, and vultures, “the clean-up crew: not optional.” That’s a refrain throughout Earnhardt’s talk. “Nothing I’ve shown you tonight is optional,” he says.
“Both in banking and nature,” Earnhardt says, “when we make too many withdrawals and not enough deposits… there’s a deficit.” There are too many creatures we have already lost. The eastern cougar. The Carolina parakeet. The passenger pigeon. Too many more. There are still others that are threatened or endangered but not yet gone. “We humans tend to forget the failures and close calls,” Earnhardt says. While talking about biodiversity loss, he references a quote by biologist E.O. Wilson: “This is the folly our descendants are least likely to forgive us.”
So what can be done? To preserve biodiversity, we have to consider entire ecosystems, not just one endangered animal at a time. “We are part of the natural world, part of links and chains and pyramids,” Earnhardt says, and humans too often forget that. Everything is connected.
He recalls visiting entomologist Bill Reynolds’s lab and noticing crickets hopping across the floor. “Don’t step on the transmission fluid!” Reynolds warned. He was referring to the crickets and to insects more broadly. Like transmission fluid in cars, insects are essential to making sure the systems they are part of run smoothly. Insects serve crucial roles in food webs, pollination, and decomposition. Studies show that they are declining at alarming rates.
“We are at a crossroads,” Earnhardt says. “Our transmission fluid is low, and we have made too many withdrawals from the bank of biodiversity.” Still, he emphasizes the importance of not giving up on wildlife conservation. Given a chance, nature can and will regenerate.
Despite all our past and current failures, conservation also has remarkable success stories. The brown pelican is one North Carolina resident that almost went extinct but has since “come back in incredible numbers.” The bald eagle is another. Its population plummeted in the 20th century, largely due to the insecticide DDT as well as habitat loss and hunting. By 2007, though, after intensive conservation efforts, it had rebounded enough to be removed from the endangered species list. Until about 1980, Earnhardt had never seen a bald eagle in North Carolina. Today, Earnhardt says, “I see them in every county.”
“Everyone’s going to have to fly in the same direction,” to preserve North Carolina — not to mention the rest of the world — at its best and wildest, Earnhardt says. But individual actions can make a difference. He suggests planting native flowers like milkweed and coneflower, both of which are good food sources for pollinators. And if you choose to plant ornamentals like crepe myrtle, “Treat that as a piece of art in the yard and then plant the rest as native.”
Lady Bird Johnson, a former first lady and conservation advocate, once said that “Texas should look like Texas, and Mississippi like Mississippi.” Choosing native plants can be a powerful way to help native wildlife in your own yard. “If you plant it,” Earnhardt says, “they will come.”
One audience member asks, “How do you recommend that we recruit non-believers?” It’s a conundrum that Earnhardt has put a lot of thought into. “It takes time, and it takes patience,” he says. “Some of my best friends are not full believers, but I work on them every day.”
According to a recent NPR/Ipsos poll, nearly 70% of Americans believe that U.S. democracy is “in crisis and at risk of failing.” Two out of every three respondents also agree that U.S. democracy is “more at risk” now than it was a year ago.
These fears are not unfounded. For the past three years, the United Nations Human Development Report has issued increasingly grave warnings for the state of the world. The warnings focus specifically on the Anthropocene, rising inequality, and growing polarization, conveying themes of both uncertainty and hope.
“People should be able to live their lives at their full potential,” Dr. Conceição began. “When you look at the world and see how people are living their lives compared to how they should be living their lives, you get the need for human development.”
First introduced in 1990, the Human Development Report focuses on improving the quality of human life, rather than just the economy in which human beings live. The report emphasizes three pillars: people, opportunity, and choice. “Living life to your full potential is essentially about human freedom,” Dr. Conceição said. It is these freedoms that are at risk as the conditions in the Human Development Report worsen.
“We need to dig more deeply into why we aren’t taking action,” Conceição maintains. He explains that current efforts to spark change are too factual. Governments and corporations are focused too heavily on raising awareness and should pivot to trying to take tangible steps.
Political division is also a major source of stagnation, as those who lie on either side of the spectrum tend to be more insecure in their views of the future. Because of these obstacles, it requires a “more complex and unusual way of trying to understand these problems.”
The report has citizens from around the world concerned about potential declines in the quality of well-being. But Dr. Conceição asserts that the reports are meant to communicate hope.
“It’s precisely because we are having this level of uncertainty that this becomes even more relevant,” he said. In fact, it is this uncertainty that the report will build off of for future publications. The literature will dig deeper into novel areas of uncertainty, to figure out the best way forward.
Dr. Conceição urges students to invest in the United Nations and its initiatives, as it is crucial in creating a better outlook on the future. As Abraham Lincoln once expressed, “The most reliable way to predict the future is to create it.”
Want to get involved with the United Nations? Click here!
When it comes to balancing the needs of humans and the needs of nature, “Historically it was ‘develop or conserve’ or ‘develop or restore,’” says Carter Smith, Ph.D., a Lecturing Fellow in the Division of Marine Science & Conservation who researches coastal restoration.
However, according to Brian Silliman, Ph.D., Rachel Carson Distinguished Professor of Marine Conservation Biology, “We are having a new paradigm shift where it’s not just… ‘nature over here’ and ‘humans over here.’”
Instead, conservation initiatives are increasingly focusing on coexistence with nature and ecological resilience, according to this panel discussion of marine science experts during Duke Research and Innovation Week 2023.
Nature-based solutions — protecting and restoring natural shoreline habitats — have a proven role in protecting and restoring coastal ecosystems. According to the International Union for Conservation of Nature (IUCN), “Nature-based solutions… address societal challenges effectively and adaptively, simultaneously benefiting people and nature.”
According to Smith, nature-based solutions can “leverage nature and the power of healthy ecosystems to protect people” while also preserving biodiversity and mitigating climate change. She spoke about living shorelines as an effective and ecologically responsible way to protect coastal ecosystems.
“The traditional paradigm in coastal protection is that you build some kind of hard, fixed structure” like a seawall, Smith said, but conventional seawalls can have negative effects on biodiversity, habitats, nutrient cycling, and the environment at large. “In this case, coastal protection and biodiversity really are at odds.”
After multiple hurricanes, living shorelines had significantly less visible damage or erosion than sites with conventional hardscape protection, like seawalls.
Nicholas Lecturing Fellow Carter Smith
That’s where living shorelines come in. Living shorelines incorporate plants and natural materials like sand and rock to stabilize coastal areas and protect them from storms while also creating more natural habitats and minimizing environmental destruction. But “if these structures are actually going to replace conventional infrastructure,” Smith says, it’s important to show that they’re effective.
Smith and colleagues have studied how living shorelines fared during multiple hurricanes and have found that living shorelines had significantly less “visible damage or erosion” compared to sites with conventional storm protection infrastructure.
After Hurricane Matthew in 2016, for instance, both natural marshes and conventional infrastructure (like seawalls) lost elevation due to the storm. Living shorelines, on the other hand, experienced almost no change in elevation.
Smith is also investigating how living shorelines may support “community and psychosocial resilience” along with their benefits to biodiversity and climate. She envisions future community fishing days or birdwatching trips to bring people together, encourage environmental education, and foster a sense of place.
PhD student Stephanie Valdez then spoke about the importance of coastal ecosystems.
“Blue carbon ecosystems,” which include sea grasses, marshes, and mangroves, provide services like stabilizing sediments, reducing the destructive force of powerful waves, and storing carbon, she said. These ecosystems can bury carbon much faster than terrestrial ecosystems, which has important implications when it comes to climate change.
In the atmosphere, carbon dioxide and other greenhouse gasses contribute to global warming, but plants pull carbon dioxide out of the air during photosynthesis and convert it to carbohydrates, releasing oxygen as a byproduct. Therefore, ecosystems rich in fast-growing plants can serve as carbon sinks, reducing the amount of atmospheric carbon, Valdez explained.
Unfortunately, blue carbon ecosystems have suffered significant loss from human activities and development. We’ve replaced these wild areas with farms and buildings, polluted them with toxins and waste, and decimated habitats that so many other creatures rely on. But given the chance, these places can sometimes grow back. Valdez discussed a 2013 study which found that seagrass restoration led to a significantly higher carbon burial rate within just a few years.
Sea grasses, marshes, and mangroves provide services like stabilizing sediments, reducing the destructive force of powerful waves, and storing carbon.
PhD Student Stephanie Valde
Valdez also talked about the importance of recognizing and encouraging natural ecological partnerships within and between species. Humans have taken advantage of such partnerships before, she says. Consider the “Three Sisters:” beans, corn, and squash, which Native Americans planted close proximity so the three crops would benefit each other. Large squash leaves could provide shade to young seedlings, beans added nitrogen to the soil, and cornstalks served as a natural beanpole.
Recognizing that mutualistic relationships exist in natural ecosystems can help us preserve habitats like salt marshes. Valdez points to studies showing that the presence of oysters and clams can positively impact seagrasses and marshes. In restoration, it’s important “that we’re not focusing on one species alone but looking at the ecosystem as a whole”—from top predators to “foundation species.”
“There is hope for successful restoration of these vital ecosystems and their potential to aid in climate change mitigation,” Valdez said.
Finally, Prof. Brian Silliman discussed the role of predators in wider ecosystem restoration projects. Prioritizing the protection, restoration, and sometimes reintroduction of top predators isn’t always popular, but Silliman says predators play important roles in ecosystems around the world.
“One of the best examples we have of top predators facilitating ecosystems and climate change mitigation are tiger sharks in Australia,” he says. When the sharks are around, sea turtles eat fewer aquatic plants. “Not because [the sharks] eat a lot of sea turtles but because they scare them toward the shoreline,” reducing herbivory.
However, Silliman said it’s unclear sometimes whether the existence of a predator is actually responsible for a given benefit. Other times, though, experiments provide evidence that predators really are making a difference. Silliman referenced a study showing that sea otters can help protect plants, like seagrasses, in their habitats.
Restoring or reintroducing top predators in their natural habitats can help stabilize ecosystems impacted by climate change and other stressors.
And crucially, “Predators increase stress resistance.” When physical stressors reach a certain point in a given ecosystem, wildlife can rapidly decline. But wildlife that’s used to coexisting with a top predator may have a higher stress threshold. In our ever-changing world, the ability to adapt is as important as ever.
“I think there is great optimism and opportunity here,” Silliman says. The other speakers agree. “Right now,” Valdez says, “as far as restoration and protection goes, we are at the very beginnings. We’re just at the forefront of figuring out how to restore feasibly and at a level of success that makes it worth our time.”
Restoring or reintroducing top predators in their natural habitats can help stabilize ecosystems impacted by climate change and other stressors.
Smith emphasized the important role that nature-based solutions can play. Even in areas where we aren’t achieving the “full benefit of conserving or restoring a habitat,” we can still get “some benefit in areas where if we don’t use nature-based solutions,” conservation and restoration might not take place at all.
According to Valdez, “Previously we would see restoration or… conservation really at odds with academia itself as well as the community as a whole.” But we’re reaching a point where “People know what restoration is. People know what these habitats are. And I feel like twenty or thirty years ago that was not the case.” She sees “a lot of hope in what we are doing, a lot of hope in what is coming.”
“There’s so much that we can learn from nature… and these processes and functions that have evolved over millions and millions of years,” Smith adds. “The more we can learn to coexist and to integrate our society with thriving ecosystems, the better it will be for everyone.”
Fleas, tapeworms, Giardia, pinworms: Parasites are all around us. But some animals are more susceptible than others. Take the well-studied chimpanzee, for example: it’s known to host over 100 parasites. In contrast, species like the indri, a lemur only found on Madagascar, are only known to host about 10 parasites. Many other primates are so poorly studied that only one parasite has ever been recorded.
In a new study published in the Journal of Animal Ecology, we examined which traits of both primates and parasites predict the likelihood of their interactions. Using advanced techniques in social network analysis, called the exponential random graph, we were able to simultaneously test the traits of primates and parasites to determine what predisposes primates to infection and what gives some parasites a unique advantage.
For primates, larger species that are found in warmer, wetter climates are more likely to host diverse parasites, compared to smaller species living in drier, cooler climates. Further, species in the same branches of the evolutionary tree and those that live in the same geographic region are more likely to share parasites than more distantly related species found on different continents. Viruses, protozoa, and helminth worms are more likely to infect diverse primates than fungi, arthropods, and bacteria. Parasites that are known to infect non-primate mammals are also more likely to infect diverse primates.
These new results were made possible by the great advances being made in infectious disease ecology. Over the last two decades, Dr. Charles Nunn at Duke University’s Evolutionary Anthropology and Global Health departments has been working with teams of researchers to compile all published records of primate-parasite interactions. Combing through the literature, almost 600 published sources were obtained to glean which parasites are found in over 200 primates species, with over 2,300 interactions recorded. With the analytical tools in social network science mastered by Duke Sociology professor Dr. James Moody, we were able to systematically test how traits of both hosts and parasites affect the likelihood of their interaction for the first time. While many previous studies used subsets of this database and examined either hosts or parasites in isolation, we were able to make new inferences about the critical links in this unique ecological network.
This work builds on a recent study that showed how extinction of primate hosts could lead to the co-extinction of almost 200 parasite species. While at first this might seem like a good thing, in fact it could have negative impacts on biodiversity as a whole. Many parasites don’t actually cause disease or death in the hosts, and some may even have beneficial properties. We simply don’t know enough about these critical and co-evolved relationships to understand what effects host-parasite coextinctions could have in the long-term.
While it might seem strange to worry about parasite extinctions, they are actually an important part of biodiversity and ecosystem functions. Understanding how primates and parasites interact reveals new insights into coevolutionary theory, and could also contribute to the conservation of underappreciated species richness. While from a public health perspective, we’d like to see some parasites disappear, like corona and ebola viruses, from an evolutionary stance, the sheer diversity of parasites and their intimate relationships with their hosts make them fascinating and crucial components of biodiversity.
DURHAM, N.C. — Some of us live and die by our phone’s GPS. But if we can’t get a signal or lose battery power, we get lost on our way to the grocery store.
Yet animals can find their way across vast distances with amazing accuracy.
Take monarch butterflies, for example. Millions of them fly up to 2,500 miles across the eastern half of North America to the same overwintering grounds each year, using the Earth’s magnetic field to help them reach a small region in central Mexico that’s about the size of Disney World.
Or sockeye salmon: starting out in the open ocean they head home each year to spawn. Using geomagnetic cues they manage to identify their home stream from among thousands of possibilities, often returning to within feet of their birthplace.
Now, new research offers clues to how migrating animals get to where they need to go, even when they lose the signal or their inner compass leads them astray. The key, said Duke Ph.D. student Jesse Granger: “they can get there faster and more efficiently if they travel with a friend.”
Many animals can sense the Earth’s magnetic field and use it as a compass. What has puzzled scientists, Granger said, is the magnetic sense is not fail-safe. These signals coming from the planet’s molten core are subtle at the surface. Phenomena such as solar storms and man-made electromagnetic noise can disrupt them or drown them out.
It’s as if the ‘needle’ of their inner compass sometimes gets thrown off or points in random directions, making it hard to get a reliable reading. How do some animals manage to chart a course with such a noisy sensory system and still get it right?
“This is the question that keeps me up at night,” said Granger, who did the work with her adviser, Duke Biology Professor Sönke Johnsen.
Multiple hypotheses have been put forward to explain how they do it. Perhaps, some scientists say, migrating animals average multiple measurements taken over time to get more accurate information.
Or maybe they switch from consulting their magnetic compass to using other ways of navigating as they near the end of their journey — such as smell, or landmarks — to narrow in on their goal.
In a paper published Nov. 16 in the journal Proceedings of the Royal Society B, the Duke team wanted to pit these ideas against a third possibility: That some animals still manage to find their way, even when their compass readings are unreliable, simply by sticking together.
To test the idea, they created a computer model to simulate virtual groups of migrating animals, and analyzed how different navigation tactics affected their performance.
The animals in the model begin their journey spread out over a wide area, encountering others along the route. The direction an animal takes at each step along the way is a balance between two competing impulses: to band together and stay with the group, or to head towards a specific destination, but with some degree of error in finding their bearings.
The scientists found that, even when the simulated animals started to make more mistakes in reading their magnetic map, the ones that stuck with their neighbors still reached their destination, whereas those that didn’t care about staying together didn’t make it.
“We showed that animals are better at navigating in a group than they are at navigating alone,” Granger said.
Even when their magnetic compass veered them off course, more than 70% of animals in the model still made it home, simply by joining with others and following their lead. Other ways of compensating didn’t measure up, or would need to guide them perfectly for most of the journey to accomplish the same feat.
But the strategy breaks down when species decline in number, the researchers found. The team showed that animals who need friends to find their way are more likely to get lost when their population shrinks below a certain density.
“If the population density starts dropping, it takes them longer and longer along their migratory route before they find anyone else,” Granger said.
Previous studies have made similar predictions, but the Duke team’s model could help future researchers quantify the effect for different species. In some runs of the model, for example, they found that if a hypothetical population dropped by 50% — akin to what monarchs have experienced in the last decade, and some salmon in the last century — 37% fewer of the remaining individuals would make it to their destination.
“This may be an underappreciated aspect of concern when studying population loss,” Granger said.
This research was supported in part by the Air Force Office of Scientific Research (FA9550-20-1-0399) and by a National Defense Science & Engineering Graduate Fellowship to Jesse Granger.
CITATION: “Collective Movement as a Solution to Noisy Navigation and its Vulnerability to Population Loss,” Jesse Granger and Sönke Johnsen. Proceedings of the Royal Society B, Nov. 16, 2022. DOI: 10.1098/rspb.2022.1910
As part of this year’s Energy Week at Duke, graduate and undergraduates were able to participate in a competitive “situation room” style event in which participants were split into five teams and given seventy-five minutes to create a plan for expanding EV (electric vehicle) access in Durham.
For just over an hour in a Fuqua School of Business classroom, my fellow participants and I mulled over the complexities of an issue facing municipalities across the country and produced a variety of solutions, representative of the range of specialties within each group. One more CS-minded group proposed an app to both help residents locate charging stations and help the city collect data on the use of new EV infrastructure, while another group explored the technological and price saving perks of utility pole-mounted charging stations.
The resulting ideas were reviewed by a panel of judges who covered multiple areas of EV expertise: Jennifer Weiss, Senior Advisor for Climate Change Policy at the North Carolina Department of Transportation; Matt Abele, Director of Marketing and Communications at North Carolina Sustainable Energy Association; Sean Ackley, E-Mobility Segment Lead at Hitachi Americas, Ltd.; and Evian Patterson, Assistant Transportation Director in the Durham Department of Transportation.
The goal of Duke’s EnergyWeek is to “promote collaboration, knowledge-sharing, and professional networking” for students interested in the energy sector. The situation room event was not strictly research oriented – our team rooms had windows and we were given free supper and lemonade – but it promoted the fundamentals of research: idea generation, collaboration, and outside-of-the-box thinking.
The teams were tasked with crafting a strategy that combined technical, business, marketing, and policy considerations to increase EV penetration in Durham. The teams operated under a hypothetical $10 million budget and strategies were to align with the Justice40 initiative, the federal plan to ensure that forty percent of the benefits of new clean transit jobs flow to “disadvantaged communities that are marginalized, underserved, and overburdened by pollution.”
Participants were encouraged to consider “potential barriers to EV adoption, the existing distribution of EV charging stations, and opportunities for community and business involvement” and to be creative.
My team was comprised of students from a range of scholarly backgrounds, from a freshman beginning a mechanical engineering track to a grad student at the Nicholas School with prior work and research in school bus electrification policy. For our plan, we spent little time discussing electric cars and instead focused on expanding access to electric micro-mobility and electrified public transportation.
We had many reasons for doing so. Many Durham residents don’t own cars, so the likelihood of increasing the adoption of electric cars in a timely and affordable manner seems low. Countries around the world are instead focusing on expanding e-bike access, citing, in addition to climate and affordability concerns, the desire to move away from the safety issues and traffic burden of car-centric urban design.
We saw Durham, which is expected to double in population in just twenty-five years, as a city perfectly positioned to develop around micro-mobility and robust public transportation before it’s too late and set an example for growing urban centers across the country. We used our $10 million to add bike lanes, fund electric buses, and subsidize electric bikes across income levels.
Our team placed second (no big deal!) and walked away with a full stomach and a rekindled spark to break the Duke bubble and get involved in the exciting development of the Bull City.
On a sunny Friday in September, Dr. Nicki Cagle led a herpetology walk in the Duke Forest with the Wild Ones. The Wild Ones is an undergraduate club focused on increasing appreciation for the natural world through professor-led outings. Herpetology is the study of reptiles and amphibians.
Dr. Cagle is a senior lecturer in the Nicholas School of the Environment at Duke and the Associate Dean of Diversity, Equity, and Inclusion. Along with teaching courses on environmental education and natural history, she is also the science advisor for a citizen science project focused on reptiles and amphibians, or herpetofauna, in the Duke Forest. Volunteers monitor predetermined sites in the Duke Forest and collect data on the reptiles and amphibians they find.
“We get a sense of abundance, seasonality… and how the landscape is affecting what we’re seeing,” Dr. Cagle says. There is evidence that herp populations in the Duke Forest and elsewhere are decreasing.
The project relies on transects, “a sampling design… where you have a sampling spot at various intervals” along a line of a predetermined length. In this case, the sampling spots are “traps” meant to attract reptiles and amphibians without harming them. Each site has a large board lying on the ground. “Different herps are more likely to be found under different objects,” Dr. Cagle explains, so the project uses both wooden and metal cover boards.
But why would snakes and other herps want to hide under cover boards, anyway? Reptiles and amphibians are “cold-blooded” animals, or ectotherms. They can’t regulate their own body temperature, so they have to rely on their environment for thermoregulation. Snakes might sun themselves on a rock on cold days, for instance, or hide under a conveniently placed wooden board to escape the heat.
Salamanders that use the cover boards might be attracted to the moist environment, while “snakes will tend to go under cover boards either to hide — like if they’re about to molt and they’re more vulnerable — to look for prey, or just to maintain the proper temperature,” Dr. Cagle says.
Citizen scientists typically check the boards once a week and not more than twice a week. Volunteers have to avoid checking the traps too often because of a phenomenon called “trap shyness,” where animals might start avoiding the traps because they’ve learned to associate them with pesky humans flipping the boards over and exposing their otherwise cozy resting places. By checking the traps less frequently, scientists can reduce the likelihood of that and minimize disturbance to the animals they’re studying.
Dr. Cagle gave the Wild Ones a behind-the-scenes tour of some of the cover boards. Using a special, hooked tool conveniently stashed in a PVC pipe next to the first cover board, we flipped each board over and looked carefully underneath it for slithery movements. We didn’t find any under the first several cover boards.
But then, under a large sheet of metal, we saw a tiny snake squirming around in the leaf litter. There was a collective intake of breath and exclamations of “snake!”
Dr. Cagle captured it and held it carefully in her hands. Snakes, especially snakes as young as this one, can be all too easily crushed. We gathered around to look more closely at the baby snake, a species with the adorable name “worm snake.” It was dark above with a strikingly pink underside. The pink belly is a key field mark of worm snakes. Earth snakes are also found around here and look similar, but they tend to have tan bellies.
After a minute or two, the worm snake made a successful bid for freedom and wriggled back under the board, disappearing from sight almost immediately.
Some of the cover boards revealed other animals as well. We found a caterpillar chrysalis attached to one and several holes — probably made by small mammals — under another.
Whatever made the holes, we can safely assume it wasn’t a snake. According to Dr. Cagle, the term “snakehole” is misleading. Most snakes don’t make their own holes, though some of them do use existing holes made by other animals. One exception is the bull snake, which is known for digging.
We found a young five-lined skink sunning itself on top of one of the metal cover boards. (Thermoregulation!) Juvenile five-lined skinks are colloquially known as blue-tailed skinks, but the name is somewhat misleading — the adults don’t have blue tails at all.
The snakes we were looking for, meanwhile, were often elusive. Some vanished under the leaf litter before we could catch them. Sometimes it was hard to tell whether we were even looking at a snake at all.
“What are you?” Dr. Cagle muttered at one point, crouching down to get a better look at what was either a stick-esque snake or a snake-esque stick. “Are you an animal? Or are you just a wet something?” (Just a wet something, it turned out.)
Later on, we found at least three young ring-necked snakes (Diadophis punctatus) under different cover boards. One of them was particularly cooperative, so we passed it around the group. (“All snakes can bite,” Dr. Cagle reminded us, but “some have the tendency to bite less,” and this species “has the tendency not to bite.”) Its small, lithe body was surprisingly strong. The little snake wrapped tightly around one of my fingers and seemed content to chill there. A living, breathing, reptilian ring. That was definitely a highlight of my day.
If you’ve ever wondered if snakes have tails, the answer is yes. The official cut-off point, Dr. Cagle says, is the anal vent. Everything below that is tail. In between flipping over cover boards and admiring young snakes, we learned about other herps. Near the beginning of our walk, someone asked what the difference is between a newt and a salamander.
“A newt is a type of salamander,” Dr. Cagle says, “but newts have an unusual life cycle where they spend part of their life cycle on land… and that is called their eft phase.” As adults, they return to the water to breed.
We learned that copperheads “tend to be fatter-bodied for their length” and that spotted salamanders cross forest roads in large numbers on warm, rainy nights in early spring when they return to wetlands to breed.
Perhaps the most interesting herp fact of the day came near the end of our walk when one of the students asked how you can tell the sex of a snake. Apparently there are two ways. You can measure a snake’s tail (males usually have longer tails), or you can insert a metal probe, blunted at the end, into a snake’s anal vent. Scientists can determine the sex of the snake by how deep the probe goes. It goes farther into the anal vent if the snake is a male. Why is that? Because male snakes have hemipenes — not two penises, exactly, but “an analogous structure that allows the probe to slide between the two and go farther” than it would in a female snake. The more you know…
Disclaimer: Handling wild snakes may result in snake bites. It can also be stressful to the snakes. Furthermore, some snakes in this area are venomous, and it’s probably best to familiarize yourself with those before getting close to snakes rather than afterward. Snakes are amazing, but please observe wildlife safely and responsibly.
Lichens are everywhere—grayish-green patches on tree bark on the Duke campus, rough orange crusts on desert rocks, even in the Antarctic tundra. They are “pioneer species,” often the first living things to return to barren, desolate places after an extreme disturbance like a lava flow. They can withstand extreme conditions and survive where nearly nothing else can. But what exactly are lichens, and why does Duke have 160,000 of them in little envelopes? I reached out to Dr. Jolanta Miadlikowska and Dr. Scott LaGreca, two lichen researchers at Duke, to learn more.
According to Miadlikowska, a senior researcher, lab manager, and lichenologist in the Lutzoni Lab (and one of the Instructors B for the Bio201 Gateway course) at Duke, lichens are “obligate symbiotic associations,” meaning they are composed of two or more organisms that need each other. All lichens represent a symbiotic relationship between a fungus (the “mycobiont”) and either an alga or a cyanobacterium or both (the “photobiont”). They aren’t just cohabiting; they rely on each other for survival. The mycobiont builds the thallus, which gives lichen its structure. The photobiont, on the other hand, isn’t visible—but it is important: it provides “food” for the lichen and can sometimes affect the lichen’s color. The name of a lichen species refers to its fungal partner, whereas the photobiont has its own name.
Unlike plants, fungi can’t perform photosynthesis, so they have to find other ways to feed themselves. Many fungi, like mushrooms and bread mold, are saprotrophs, meaning they get nutrients from organic matter in their environment. (The word “saprotroph” comes from Greek and literally means “rotten nourishment.”) But the fungi in lichens, Miadlikowska says, “found another way of getting the sugar—because it’s all about the sugar—by associating with an organism that can do photosynthesis.” More often than not, that organism is a type of green algae, but it can also be a photosynthetic bacterium (cyanobacteria, also called blue-green algae). It is still unclear how the mycobiont finds the matching photobiont if both partners are not dispersed together. Maybe the fungal spores (very small fungal reproductive unit) “will just sit and wait” until the right photobiont partner comes along. (How romantic.) Some mycobionts are specialists that “can only associate with a few or a single partner—a ‘species’ of Nostoc [a cyanobacterium; we still don’t know how many species of symbiotic and free-living Nostoc are out there and how to recognize them], for example,” but many are generalists with more flexible preferences.
Lichens are classified based on their overall thallus shape. They can be foliose (leaf-like), fruticose (shrubby), or crustose (forming a crust on rocks or other surfaces). Lichens that grow on trees are epiphytic, while those that live on rocks are saxicolous; lichens that live on top of mosses are muscicolous, and ground-dwelling lichens are terricolous. Much of Miadlikowska’s research is on a group of cyanolichens (lichens with cyanobacteria partners) from the genus Peltigera. She works on the systematics and evolution of this group using morphology-, anatomy-, and chemistry-based methods and molecular phylogenetic tools. She is also part of a team exploring biodiversity, ecological rules, and biogeographical patterns in cryptic fungal communities associated with lichens and plants (endolichenic and endophytic fungi). She has been involved in multiple ongoing NSF-funded projects and also helping graduate students Ian, Carlos, Shannon, and Diego in their dissertation research. She spent last summer collecting lichens with Carlos and Shannon and collaborators in Alberta, Canada and Alaska. If you walk in the sub basement of the Bio Sciences building where Bio201 and Bio202 labs are located, check out the amazing photos of lichens (taken by Thomas Barlow, former Duke undergraduate) displayed along the walls! Notice Peltigera species, including some new to science, described by the Duke lichen team.
Lichens have value beyond the realm of research, too. “In traditional medicine, lichens have a lot of use,” Miadlikowska says. Aside from medicinal uses, they have also been used to dye fabric and kill wolves. Some are edible. Miadlikowska herself has eaten them several times. She had salad in China that was made with leafy lichens (the taste, she says, came mostly from soy sauce and rice vinegar, but “the texture was coming from the lichen.”). In Quebec, she drank tea made with native plants and lichens, and in Scandinavia, she tried candied Cetraria islandica lichen (she mostly tasted the sugar and a bit of bitterness, but once again, the lichen’s texture was apparent).
In today’s changing world, lichens have another use as well, as “bioindicators to monitor the quality of the air.” Most lichens can’t tolerate air pollution, which is why “in big cities… when you look at the trees, there are almost no lichens. The bark is just naked.” Lichen-covered trees, then, can be a very good sign, though the type of lichen matters, too. “The most sensitive lichens are the shrubby ones… like Usnea,” Miadlikowska says. Some lichens, on the other hand, “are able to survive in anthropogenic places, and they just take over.” Even on “artificial substrates like concrete, you often see lichens.” Along with being very sensitive to poor air quality, lichens also accumulate pollutants, which makes them useful for monitoring deposition of metals and radioactive materials in the environment.
LaGreca, like Miadlikoska, is a lichenologist. His research primarily concerns systematics, evolution and chemistry of the genus Ramalina. He’s particularly interested in “species-level relationships.” While he specializes in lichens now, LaGreca was a botany major in college. He’d always been interested in plants, in part because they’re so different from animals—a whole different “way of being,” as he puts it. He used to take himself on botany walks in high school, and he never lost his passion for learning the names of different species. “Everything has a name,” he says. “Everything out there has a name.” Those names aren’t always well-known. “Some people are plant-blind, as they call it…. They don’t know maples from oaks.” In college he also became interested in other organisms traditionally studied by botanists—like fungi. When he took a class on fungi, he became intrigued by lichens he saw on field trips. His professor was more interested in mushrooms, but LaGreca wanted to learn more, so he specialized in lichens during grad school at Duke, and now lichens are central to his job. He researches them, offers help with identification to other scientists, and is the collections manager for the lichens in the W.L. and C.F. Culberson Lichen Herbarium—all 160,000 of them.
The Duke Herbarium was founded in 1921 by Dr. Hugo Blomquist. It contains more than 825,000 specimens of vascular and nonvascular plants, algae, fungi, and, of course, lichens. Some of those specimens are “type” specimens, meaning they represent species new to science. A type specimen essentially becomes the prototype for its species and “the ultimate arbiter of whether something is species X or not.” But how are lichens identified, anyway?
Lichenologists can consider morphology, habitat, and other traits, but thanks to Dr. Chicita Culberson, who was a chemist and adjunct professor at Duke before her retirement, they have another crucial tool available as well. Culbertson created a game-changing technique to identify lichens using their chemicals, or metabolites, which are often species-specific and thus diagnostic for identification purposes. That technique, still used over fifty years later, is a form of thin-layer chromatography. The process, as LaGreca explains, involves putting extracts from lichen specimens—both the specimens you’re trying to identify and “controls,” or known samples of probable species matches—on silica-backed glass plates. The plates are then immersed in solvents, and the chemicals in the lichens travel up the paper. After the plates have dried, you can look at them under UV light to see if any spots are fluorescing. Then you spray the plates with acid and “bake it for a couple hours.” By the end of the process, the spots of lichen chemicals should be visible even without UV light. If a lichen sample has traveled the same distance up the paper as the control specimen, and if it has a similar color, it’s a match. If not, you can repeat the process with other possible matches until you establish your specimen’s chemistry and, from there, its identity. Culberson’s method helped standardize lichen identification. Her husband also worked with lichens and was a director of the Duke Gardens.
LaGreca shows me a workroom devoted to organisms that are cryptogamic, a word meaning “hidden gametes, or hidden sex.” It’s a catch-all term for non-flowering organisms that “zoologists didn’t want to study,” like non-flowering plants, algae, and fungi. It’s here that new lichen samples are processed. The walls of the workroom are adorned with brightly colored lichen posters, plus an ominous sign warning that “Unattended children will be given an espresso and a free puppy.” Tucked away on a shelf, hiding between binders of official-looking documents, is a thin science fiction novel called “Trouble with Lichen” by John Wyndham.
The Culberson Lichen Herbarium itself is a large room lined with rows of cabinets filled with stacks upon stacks of folders and boxes of meticulously organized lichen samples. A few shelves are devoted to lichen-themed books with titles like Lichens De France and Natural History of the Danish Lichens.
Each lichen specimen is stored in an archival (acid-free) paper packet, with a label that says who collected it, where, and on what date. (“They’re very forgiving,” says LaGreca. “You can put them in a paper bag in the field, and then prepare the specimen and its label years later.”) Each voucher is “a record of a particular species growing in a particular place at a particular time.” Information about each specimen is also uploaded to an online database, which makes Duke’s collection widely accessible. Sometimes, scientists from other institutions find themselves in need of physical specimens. They’re in luck, because Duke’s lichen collection is “like a library.” The herbarium fields loan requests and trades samples with herbaria at museums and universities across the globe. (“It’s kind of like exchanging Christmas presents,” says LaGreca. “The herbarium community is a very generous community.”)
Meticulous records of species, whether in databases of lichens or birds or “pickled fish,” are invaluable. They’re useful for investigating trends over time, like tracking the spread of invasive species or changes in species’ geographic distributions due to climate change. For example, some lichen species that were historically recorded on high peaks in North Carolina and elsewhere are “no longer there” thanks to global warming—mountain summits aren’t as cold as they used to be. Similarly, Henry David Thoreau collected flowering plants at Walden Pond more than 150 years ago, and his samples are still providing valuable information. By comparing them to present-day plants in the same location, scientists can see that flowering times have shifted earlier due to global warming. So why does Duke have tens of thousands of dried lichen samples? “It comes down to the reproducibility of science,” LaGreca says. “A big part of the scientific method is being able to reproduce another researcher’s results by following their methodology. By depositing voucher specimens generated from research projects in herbaria like ours, future workers can verify the results” of such research projects. For example, scientists at other institutions will sometimes borrow Duke’s herbarium specimens to verify that “the species identification is what the label says it is.” Online databases and physical species collections like the herbarium at Duke aren’t just useful for scientists today. They’re preserving data that will still be valuable hundreds of years from now.