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The imminent closure of Duke University’s herbarium sparked an outcry in the natural sciences community. But the loss to climate science could be even worse.
Kathleen Pryer did not watch March Madness this year.
That isn’t unusual in and of itself — Pryer describes herself as “not a basketball person,” though that might still raise a few eyebrows this time of year at Duke University, her place of employment. But the professor of biology has been a bit distracted lately. For the past few months, she’s been on defense, fending off a loss of her own: the pending closure of the school’s herbarium.
A herbarium (or plural, herbaria) is a collection of preserved plants, typically dried and mounted on sheets of rigid paper. The oldest existing collection in the world, the Gherardo Cibo herbarium in Rome, dates back to the mid 1500s; many U.S. collections are well over a century old. Browsing digitized herbaria online, one can easily get sucked in by their unintended whimsy; though the preserved plants are scientific specimens, traditionally collected by botanists to be used in the study of taxonomy during Western biology’s golden age of naming things, the pages remind me more of the pale, beautiful botanical illustrations in my childhood copy of Thumbelina.
Duke’s herbarium turns 103 this year and contains 825,000 specimens, making it one of the largest collections in the country. But back in mid-February, Susan Alberts, Duke’s dean of natural sciences, sent an email to Pryer, who curates the herbarium, and four other associated faculty members to inform them that “it’s in the best interests of both Duke and the herbarium to find a new home or homes for these collections.”
Though there had long been rumblings about the future of Duke’s herbarium — calls for “strategic plans,” hand-wringing about funds, worry about hiring new staff — the news came as both a shock and a slap in the face to the faculty, chief among them Pryer. “It’s some kind of little stinky plot,” she told me, adding, “I didn’t just roll over when it happened. I reached out to absolutely everybody I could think of.”
The news of Duke’s herbarium closure ricocheted through the tight-knit natural sciences community. Mason Heberling, an associate curator in the Section of Botany at the Carnegie Museum of Natural History, told me it should be a “wake-up call” for other researchers. The Duke herbarium is prestigious and hardly a “languishing collection,” he explained; researchers and faculty can easily slip into taking their herbaria for granted. “I’ve realized now that a huge part of my job as a curator will need to be explaining why these collections are important,” he said.
Swiftly, botanists and curators came to Duke’s defense. Opinion pieces and quotes decrying Duke’s decision appeared in the pages of The New York Times and Science. A petition went up on Change.org urging the school to reconsider its decision. Online fora burbled with discontent. “This may be the single worst thing to ever happen to Southeastern botany,” one post on Reddit read, with 64 additional comments piling on the administration for being “profit-obsessed business assholes.” “They could probably fund the entire thing with the salary of one head [basketball] coach,” grumbled another commenter.
The criticism of Duke’s decision is rooted in both a romantic nostalgia about herbaria — the same way you might feel fondly about hand-painted globes or cabinets of curiosities — and a very modern sense of scientific urgency. Researchers have only recently started leveraging the collections as invaluable pieces of data in the greater picture of climate change. “Herbaria are, in many ways, one of our best places to understand nature across space, time, and species,” Charles Davis, the curator of vascular plants at the nation’s largest private herbaria, at Harvard University, told me. “These collections are snapshots of events and occurrences in space and time that you just can’t easily replicate anywhere else. In fact, I would argue it’s impossible.”
Think of it this way: Worldwide, there are about 3,600 herbaria located in 193 different countries that collectively hold about 400 million specimens. Botanists estimate as much as half of the planet’s undiscovered flora could be found in herbaria backlogs. Barbara Thiers, the editor of the Index Herbariorum, a digital guide to the world’s collections, told me that when she was the director of the New York Botanical Garden Herbarium, “we had a huge room filled with unidentified species; I think there were 35,000 or 40,000 specimens in there.” That wasn’t for lack of effort — Thiers said that for many of the plant groups, there simply aren’t any working experts or published literature for curators to consult.
Because the climate is changing so fast, many plants in herbaria will go extinct before they’re formally discovered and named, a process known as a “dark extinction.” “It’s a very sobering feeling to touch the leaves of a tree that doesn’t exist anymore,” Erin Zimmerman, an evolutionary biologist and author of the forthcoming book Unrooted: Botany, Motherhood, and the Fight to Save an Old Science, told me, recalling coming across such a specimen in an herbarium while doing her own research. She likened herbaria to a library, but in her description I also heard echoes of a church: “The specimens are sometimes very old; you have to be very gentle with them, which just adds to the sense of holding something precious,” she went on.
Dwindling biodiversity is only the most obvious way herbaria are critical to 21st-century science. “Phenology, whether it’s when plants flower or when birds migrate, is one of the most important signals of climate change response,” Davis, the Harvard curator, said. Still, our long-term datasets aren’t very robust; research on how plants are changing with warming climates typically dates back only 25 to 30 years, tends to concentrate on the U.S. and Western Europe, and centers on easily observable phenomena, like the leafing out of woody trees. Researchers can turn to herbaria for centuries-old records of where certain plants grew and when they flowered, helping to bridge gaps in our understanding.
Heberling, of the Carnegie Museum of Natural History, tracks environmental changes in his research, but he didn’t start using herbaria until well after he’d obtained his Ph.D. Only then did he realize “herbarium specimens are incredible archives of the past,” he told me.
“You can look at the tiny pores, the stomata, on the leaves” of a plant in a herbarium and “see how that has changed over time with increased carbon dioxide,” Heberling said. Scientists have even used this method to create CO2 records.
Admittedly, climate science is still a relatively cutting-edge use case for the herbarium; according to Davis’ research, “global change biology” remains one of the least popular ways to leverage herbaria, well behind “taxonomic monographs” and “species distributions” that still dominate the field. Still, “there are things that, five to 10 years ago, I’d never even imagined we’d be doing today with herbarium specimens,” he told me.
As a result, Duke’s herbarium closure has made some question the university’s commitment to climate research — something that Alberts, the school’s natural sciences dean, emphatically refuted when I raised the question with her. She told me that a rough search revealed that only 23 of the 2,000 papers published by Duke researchers over the past few decades on climate change contained the word “herbarium” anywhere in them. “With my knowledge about all of the climate change research that’s been going on at Duke, the herbarium is not really central to whether or not Duke studies climate change,” she said.
For her part, Pryer has bristled at the administration’s insinuations that the herbarium is of limited use to students and faculty on campus. “You don’t measure a collection by who uses it,” she told me. “As I’ve been naughty enough to say, it’s not a toilet. People outside — the global community — uses it. That’s how you measure its value; things like 90 refereed publications a year [across all disciplines] cite the Duke collections.” Pryer can quickly tick off the climate projects that have come through the herbarium’s halls, including her recent supervision of a local high schooler’s research paper that found the pink lady’s slipper is flowering in the area 17 days earlier than it used to.
Duke is “not an appropriate home for a herbarium that is this large and valuable” for a number of reasons, according to Alberts, ranging from the need to hire new faculty to manage it (Pryer and several of her colleagues are approaching retirement) to the collection’s current building needing renovations. “I have had people email me saying, ‘I know you have enough money, I know you have the facilities.’ I’m like, ‘I’m sorry, you should tell me who you’re talking to, because we don’t,’” Alberts said. She added that she plans to be personally involved in finding the right home for Duke’s herbarium over the next several years.
After all, it’s not like the potential untapped climate records in the Duke collection are being destroyed (though both Pryer and Davis told me they’ve had deans wonder aloud if they could be, since many herbaria are now digitized). The goal is only to move the collection somewhere where it might be better utilized.
Thiers, though, said this is exactly what makes the natural science community so alarmed. As the collection is split up, ideally, the Index Herbariorum would record where Duke’s specimens get sent so scientists can still find them. But when new collections absorb the materials, curators will weed out duplicates, sending unneeded pages elsewhere — at which point specimens can fall between the cracks. “Before you know it, individual specimens will be lost,” Thiers said. “I can almost guarantee that as these secondary moves happen, people will not keep up with the database records.”
There is also a worst-case scenario everyone seemed nervous to mention: that Duke’s collection, in whole or in part, will end up in storage somewhere. Herbarium specimens are extremely susceptible to insect damage and must be kept in expensive, climate-controlled cabinets and rooms. “If they’re putting boxes in a storage storeroom someplace, they’ll be worthless in no time,” Thiers warned. The unidentified plants and uncollected climate data — all of it could be lost. And the cruelest part? Scientists wouldn’t even know what they are losing; it’s a dark extinction of a dark extinction.
When I spoke with Alberts, she said there were no updates on the administration’s plans for the herbarium. She expressed sympathy, though, for the faculty who oppose the administration’s decision. The herbarium “is their life’s work, and it’s important that they have a voice in this process,” she said.
Pryer is determined to keep fighting, even if this isn’t exactly how she’d pictured spending her golden years at Duke. “It’s having an impact on my research and on my health,” she told me. “It’s been pretty unrelenting. I’m anxious for something to resolve.”
She looked tired. There was a faculty meeting later in the day, and she hoped she’d be able to get more clarity about the administration’s decision then. “I don’t want this to go on forever,” she said. “But I also don’t want there to be a decision that makes Duke look insane.”
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On Alaska’s permitting overhaul, HALEU winners, and Heatmap’s Climate 101
Current conditions: Kansas, Oklahoma, and Arkansas brace for up to a foot of rain • Tropical Storm Juliette, still located well west of Mexico, is moving northward and bringing rain to parts of Southern California • Heat and dryness are raising the risk of wildfire in South Africa.
The Trump administration has started the process to roll back logging protections from more than 44 million acres of national forest land. On Wednesday, U.S. Secretary of Agriculture Brooke Rollins proposed undoing a 25-year-old rule that banned building roads or harvesting timber on federally controlled forest land, much of which is located in Alaska. “Today marks a critical step forward in President Trump’s commitment to restoring local decision-making to federal land managers to empower them to do what’s necessary to protect America’s forests and communities from devastating destruction from fires,” Rollins said in a statement. “This administration is dedicated to removing burdensome, outdated, one-size-fits-all regulations that not only put people and livelihoods at risk but also stifle economic growth in rural America.”
Environmental groups slammed the proposal for jeopardizing wildlife habitats and putting waterways at risk. “Communities depend on clear water filtered by roadless areas, animals depend on the unfragmented habitat that can only exist where there are no roads, and anglers depend on clean water in the streams where trout and salmon swim,” Ellen Montgomery, the director of Environment America’s great outdoors campaign, said in a press release. “We cannot let these essential forests be carved up by roads, obliterated by chainsaws, and contaminated by mines.”
Heatmap’s new Climate 101 series aims, as Heatmap deputy editor Jillian Goodman explained, to be “a primer on some of the key technologies of the energy transition.” That includes “everything from what makes silicon a perfect material for solar panels (and computer chips), to what’s going on inside a lithium-ion battery, to the difference between advanced and enhanced geothermal.”
This might be especially helpful for those still trying to find their way into the climate conversation, but we hope there’s something here for everyone. For instance, did you know that contemporary readers might have understood Don Quixote’s “tilting at windmills” to be an expression of NIMBYism? Well, now you do!
The federal Permitting Council signed a first-of-a-kind memorandum of understanding to work together with Alaska’s government to streamline permitting on critical infrastructure projects across the state. First established in 2015, the agency was designed to improve transparency and speed up the greenlighting of infrastructure approvals. But it had yet to forge such a close pact with an individual state. “Our team is ready to work with Governor Dunleavy to bring Alaska back into the energy spotlight, ending the neglect of the Biden Administration and bringing Alaska’s incredible natural resources to the rest of the world,” Emily Domenech, the Permitting Council’s executive director, said in a statement.
Domenech — a former staffer for House Speakers Kevin McCarthy and Mike Johnson who went on to serve as a senior vice president at Boundary Stone, a firm founded by alumni of the Obama-era Department of Energy — acted as something of a Republican sage for the clean energy industry. In an interview with Heatmap’s Matthew Zeitlin after last November’s election, she urged the industry to forge closer relationships with members of the current congressional majority. “If you ask Republicans to be for or against the IRA as a whole, they’ll be against it,” Domenech said, “But Republicans think about energy as a regional issue. So instead of forcing this one size fits all approach, IRA advocates would be smart to give people room to support only the policies that make the most sense for their state or region.”
The Department of Energy selected another three companies to receive a special kind of nuclear fuel from its growing stockpile. HALEU — pronounced HAY-loo, an acronym for high assay low enriched uranium — is a reactor fuel enriched up to four times as much as traditional reactor fuel. The fuel is needed for all kinds of novel reactor designs, particularly those that use coolants other than water. Until recently, however, Russia’s state-owned Rosatom had enjoyed a virtual monopoly over its global supply. The Biden administration set aside billions for HALEU production. In April, the Trump administration selected five companies to receive some of the government-procured supply, including Westinghouse, Bill Gates’ TerraPower, and the Google-backed Kairos Power. Now the agency has picked another three:
Two firefighters battling the Bear Gulch fire on Washington’s Olympic Peninsula were arrested by federal law enforcement Wednesday. The reason for the arrests is unclear, according to the Seattle Times. Over three hours, federal agents from Border Patrol carried out an “operation on the fire,” demanding identification from members of two private contractor crews who were among the 400 firefighters battling Washington state’s largest active blaze. The Incident Management Team from the National Interagency Fire Center suggested that the action did not interfere with the efforts to tamp down the flames.
The American West is primed for wildfires right now. Following a lull in June and July, Heatmap’s Jeva Lange wrote that “the forecast for the Pacific Northwest for ‘Dirty August’ and ‘Snaptember,’ historically the two worst months of the year in the region for wildfires,” was full of warning signs, including low precipitation and abnormally high temperatures.
Living, gnawing weedwackers.Vesper Energy
The 1.36 million solar panels at Vesper Energy’s Hornet Solar farm in Swisher County, Texas, one of the United States' largest single-phase solar projects, were overgrown with vegetation. So naturally, the company brought in sheep. More than 2,000 white, wooly ovines arrived this month and were allowed to roam the facility’s six square miles. “As Texas continues to lead the nation in solar energy growth, solar grazing highlights how innovation can support rural economies, preserve farmland, and strengthen the state’s reliable energy future,” Vesper said.
Here at Heatmap, we write a lot about decarbonization — that is, the process of transitioning the global economy away from fossil fuels and toward long-term sustainable technologies for generating energy. What we don’t usually write about is what those technologies actually do. Sure, solar panels convert energy from the sun into electricity — but how, exactly? Why do wind turbines have to be that tall? What’s the difference between carbon capture, carbon offsets, and carbon removal, and why does it matter?
So today, we’re bringing you Climate 101, a primer on some of the key technologies of the energy transition. In this series, we’ll cover everything from what makes silicon a perfect material for solar panels (and computer chips), to what’s going on inside a lithium-ion battery, to the difference between advanced and enhanced geothermal.
There’s something here for everyone, whether you’re already an industry expert or merely climate curious. For instance, did you know that contemporary 17th century readers might have understood Don Quixote’s famous “tilting at windmills” to be an expression of NIMYBism? I sure didn’t! But I do now that I’ve read Jeva Lange’s 101 guide to wind energy.
That said, I’d like to extend an especial welcome to those who’ve come here feeling lost in the climate conversation and looking for a way to make sense of it. All of us at Heatmap have been there at some point or another, and we know how confusing — even scary — it can be. The constant drumbeat of news about heatwaves and floods and net-zero this and parts per million that is a lot to take in. We hope this information will help you start to see the bigger picture — because the sooner you do, the sooner you can join the transition, yourself.
Without further ado, here’s your Climate 101 syllabus:
Once you feel ready to go deeper, here are some more Heatmap stories to check out:
The basics on the world’s fastest-growing source of renewable energy.
Solar power is already the backbone of the energy transition. But while the basic technology has been around for decades, in more recent years, installations have proceeded at a record pace. In the United States, solar capacity has grown at an average annual rate of 28% over the past decade. Over a longer timeline, the growth is even more extraordinary — from an stalled capacity base of under 1 gigawatt with virtually no utility-scale solar in 2010, to over 60 gigawatts of utility-scale solar in 2020, and almost 175 gigawatts today. Solar is the fastest-growing source of renewable energy in both the U.S. and the world.
There are some drawbacks to solar, of course. The sun, famously, does not always shine, nor does it illuminate all places on Earth to an equal extent. Placing solar where it’s sunniest can sometimes mean more expense and complexity to connect to the grid. But combined with batteries — especially as energy storage systems develop beyond the four hours of storage offered by existing lithium-ion technology — solar power could be the core of a decarbonized grid.
Solar power can be thought of as a kind of cousin of the semiconductors that power all digital technology. As Princeton energy systems professor and Heatmap contributor Jesse Jenkins has explained, certain materials allow for electrons to flow more easily between molecules, carrying an electrical charge. On one end of the spectrum are your classic conductors, like copper, which are used in transmission lines; on the other end are insulators, like rubber, which limit electrical charges.
In between on that spectrum are semiconductors, which require some amount of energy to be used as a conductor. In the computing context these are used to make transistors, and in the energy context they’re used to make — you guessed it — solar panels.
In a solar panel, the semiconductor material absorbs heat and light from the sun, allowing electrons to flow. The best materials for solar panels, explained Jenkins, have just the right properties so that when they absorb light, all of that energy is used to get the electrons flowing and not turned into wasteful heat. Silicon fits the bill.
When you layer silicon with other materials, you can force the electrons to flow in a single direction consistently; add on a conductive material to siphon off those subatomic particles, and voilà, you’ve got direct current. Combine a bunch of these layers, and you’ve got a photovoltaic panel.
Globally, solar generation capacity stood at over 2,100 terawatt-hours in 2024, according to Our World in Data and the Energy Institute, growing by more than a quarter from the previous year. A huge portion of that growth has been in China, which has almost half of the world’s total installed solar capacity. Installations there have grown at around 40% per year in the past decade.
Solar is still a relatively small share of total electricity generation, however, let alone all energy usage, which includes sectors like transportation and industry. Solar is the sixth largest producer of electricity in the world, behind coal, gas, hydropower, nuclear power, and wind. It’s the fourth largest non-carbon-emitting generation source and the third largest renewable power source, after wind and hydropower.
Solar has taken off in the United States, too, where utility-scale installations make up almost 4% of all electricity generated.
While that doesn’t seem like much, overall growth in generation has been tremendous. In 2024, solar hit just over 300 terawatt-hours of generation in the U.S., compared to about 240 terawatt-hours in 2023 and just under 30 in 2014.
Looking forward, there’s even more solar installation planned. Developers plan to add some 63 gigawatts of capacity to the grid this year, following an additional 30 gigawatts in 2024, making up just over half of the total planned capacity additions, according to Energy information Administration.
Solar is cheap compared to other energy sources, and especially other renewable sources. The world has a lot of practice dealing with silicon at industrial scale, and China especially has rapidly advanced manufacturing processes for photovoltaic cells. Once the solar panel is manufactured, it’s relatively simple to install compared to a wind turbine. And compared to a gas- or coal-fired power plant, the fuel is free.
From 1975 to 2022, solar module costs fell from over $100 per watt to below $0.50, according to Our World In Data. From 2012 to 2022 alone, costs fell by about 90%, and have fallen by “around 20% every time the global cumulative capacity doubles,” writes OWID analyst Hannah Ritchie. Much of the decline in cost has been attributed to “Wright’s Law,” which says that unit costs fall as production increases.
While construction costs have flat-lined or slightly increased recently due to supply chain issues and overall inflation, the overall trend is one of cost declines, with solar construction costs declining from around $3,700 per kilowatt-hour in 2013, to around $1,600 in 2023.
There are solar panels at extreme latitudes — Alaska, for instance, has seen solar growth in the past few years. But there are obvious challenges with the low amount of sunlight for large stretches of the year. At higher latitudes, irradiance, a measure of how much power is transmitted from the sun to a specific area, is lower (although that also varies based on climate and elevation). Then there are also more day-to-day issues, such as the effect of snow and ice on panels, which can cause issues in turning sunlight into power (they literally block the panel from the sun). High latitudes can see wild swings in solar generation: In Tromso, in northern Norway, solar generation in summer months can be three times as high as the annual average, with a stretch of literally zero production in December and January.
While many Nordic countries have been leaders in decarbonizing their electricity grids, they tend not to rely on solar in that project. In Sweden, nuclear and hydropower are its largest non-carbon-emitting fuel sources for electricity; in Norway, electricity comes almost exclusively from hydropower.
There has been some kind of policy support for solar power since 1978, when the Energy Tax Act provided tax credits for solar power investment. Since then, the investment tax credit has been the workhorse of American solar policy. The tax credit as it was first established was worth 10% of the system’s upfront cost “for business energy property and equipment using energy resources other than oil or natural gas,” according to the Congressional Research Service.
But above that baseline consistency has been a fair amount of higher-level turmoil, especially recently. The Energy Policy Act of 2005 kicked up the value of that credit to 30% through 2007; Congress kept extending that timeline, with the ITC eventually scheduled to come down to 10% for utility-scale and zero for residential projects by 2024.
Then came the 2022 Inflation Reduction Act, which re-instituted the 30% investment tax credit, with bonuses for domestic manufacturing and installing solar in designated “energy communities,” which were supposed to be areas traditionally economically dependent on fossil fuels. The tax then transitioned into a “technology neutral” investment tax credit that applied across non-carbon-emitting energy sources, including solar, beginning in 2024.
This year, Congress overhauled the tax incentives for solar (and wind) yet again. Under the One Big Beautiful Bill Act, signed in July, solar projects have to start construction by July 2026, or complete construction by the end of 2027 to qualify for the tax credit. The Internal Revenue Service later tightened up its definition of what it means for a project to start construction, emphasizing continuing actual physical construction activities as opposed to upfront expenditures, which could imperil future solar development.
At the same time, the Trump administration is applying a vise to renewables projects on public lands and for which the federal government plays a role in permitting. Renewable industry trade groups have said that the highest levels of the Department of Interior are obstructing permitting for solar projects on public lands, which are now subject to a much closer level of review than non-renewable energy projects.
Massachusetts Institute of Technology Researchers attributed the falling cost of solar this century to “scale economies.” Much of this scale has been achieved in China, which dominates the market for solar panel production, especially for export, even though much of the technology was developed in the United States.
At this point, however, the cost of an actual solar system is increasingly made up of “soft costs” like labor and permitting, at least in the United States. According to data from the National Renewables Energy Laboratory, a utility-scale system costs $1.20 per watt, of which soft costs make up a third, $0.40. Ten years ago, a utility-scale system cost $2.90 per watt, of which soft costs was $1.20, or less than half.
Beyond working to make existing technology even cheaper, there are other materials-based advances that promise higher efficiency for solar panels.
The most prominent is “perovskite,” the name for a group of compounds with similar structures that absorb certain frequencies of light particularly well and, when stacked with silicon, can enable more output for a given amount of solar radiation. Perovskite cells have seen measured efficiencies upwards of 34% when combined with silicon, whereas typical solar cells top out around 20%.
The issue with perovskite is that it’s not particularly durable, partially due to weaker chemical bonds within the layers of the cell. It’s also more expensive than existing solar, although much of that comes down inefficient manufacturing processes. If those problems can be solved, perovskite could promise more output for the same level of soft costs as silicon-based solar panels.