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  • John Deutch recalls how Jimmy Carter left his mark on energy researchThis link opens in a new windowJan 3, 2025

    John Deutch was a young chemistry professor at the Massachusetts Institute of Technology (MIT) when he joined President Jimmy Carter’s energy team shortly after the Georgia Democrat took office in January 1977. And for the next 3 years Deutch had a front-row seat to history as Carter, who died on 29 December 2024 at age 100, worked to make the country less dependent on imported oil and in the process reshaped the direction of federal energy research.

    Within 6 months Deutch would become the founding director of the Office of Energy Research at the newly created Department of Energy (DOE), the successor to the Atomic Energy Commission (AEC) and the short-lived Energy Research and Development Administration (ERDA). It was led by his political mentor, economist James Schlesinger, who had been secretary of defense under former President Gerald Ford and who had extensive Washington, D.C., experience in both foreign and domestic policy.

    DOE was created “to take a broader approach to an important national issue, which was energy,” recalls Deutch, who spoke with Science shortly before Carter’s body was set to begin its journey from Georgia to Washington, D.C., for a 9 January funeral service.

    Schlesinger wanted the Office of Energy Research, the forerunner of DOE’s current $8 billion Office of Science, to be organized “not by fuels, but by the pathway of innovation.” Deutch’s job was to oversee early discovery, he explains, whereas a second assistant secretary managed the development of new energy technologies. The two units would also coordinate programs to maximize their potential impact.

    The structure recognized that the old saw that “scientists came up with new ideas and engineers applied them” was outdated, Deutch says. “That’s why I liked that it was called the Office of Energy Research, not the Office of Science.”

    Meeting DOE’s mandate also meant launching programs outside the legacy energy sources, notably fossil fuels and nuclear power, that had been the mainstay of DOE research under its predecessor agencies. “We felt the new department needed to fund high-quality fundamental research in emerging areas like photovoltaics and geothermal, areas that had not been traditionally strong in the prior ERDA or AEC time,” Deutch says. “For example, one of the first things I did was create a bioenergy section.”

    At the start, Deutch says he faced resistance from the network of DOE national laboratories, rooted in the wartime Manhattan Project to develop and deploy the atomic bomb, that were now funded by the new office.

    “There was huge suspicion of somebody from outside the national laboratories becoming head of the research program,” he says, “and more importantly, someone who was a chemistry person, not a physicist. They believed that physicists knew better” how to manage energy research.

    However, Deutch wasn’t fazed by those who questioned where the new agency was heading. “I had the complete support of the secretary,” Deutch explains, “and people knew that.”

    Thanks to his close ties to Schlesinger, Deutch was given a broad portfolio that included U.S. efforts to block the proliferation of nuclear weapons. He also oversaw research on synthetic fuels, an area that became a priority for the Carter administration and spawned the Synthetic Fuels Corporation, an ill-fated attempt to wean the country from its dependence on foreign oil.

    close-up of John Deutch
    John Deutch David Hume Kennerly/Getty Images

    Deutch was also part of a U.S. delegation to China led by Frank Press, Carter’s science adviser, that scouted out possible areas of scientific collaboration with China after it emerged from the cultural revolution and reached out to the West. Energy research was high on their shopping list of technologies. And soon after the bilateral agreement between the United States and China was signed in July 1979, Deutch says, DOE began funding Chinese students to come to the U.S. to earn graduate science and engineering degrees. (Last month, despite the rising tensions between the superpowers, the two countries agreed to another 5-year extension of that original agreement.)

    Although the Carter administration tried hard to get people in the U.S. to conserve energy and to find alternatives to foreign oil, including putting solar panels on the White House, climate change was not a significant part of OER’s portfolio under Deutch. He recalls getting $20 million one year to study the effects of rising levels of atmospheric carbon dioxide. “But there was really no competence in that area within the department at the time,” he says. “And its importance was not yet clearly recognized except among a very restricted set of environmentalists.”

    Deutch says he was able to concentrate on energy policy writ large because the ERDA staff he inherited was “extremely capable, so I didn’t have to worry about the nuts and bolts.” But a big challenge was convincing national lab directors that the new department was a friend, not a foe.

    “I was looking for people who had a vision of the future of energy research, beyond their prior emphasis on nuclear weapons,” he says. “Many of them were eager to participate in the new areas. But some of them wanted the labs to continue to be what they had been. So sometimes I had to pick up the phone. And I wasn’t subtle.”

    Neither was his boss. Both men had well-earned reputations for wielding sharp elbows when pursuing what they wanted. Schlesinger used that bare-knuckled approach in getting his way on the choice of DOE’s future headquarters in Washington, D.C.

    The original plan was for DOE to occupy ERDA’s current location near the city’s Union Station. “But Jim hated that building,” Deutch explains. “So one day we drove around Washington and he found the building that he wanted just off the National Mall.”

    The building, named after the first secretary of defense, James Forrestal, was then occupied by the U.S. Army Corps of Engineers and other military units. But that didn’t stop Schlesinger, Deutch recalls.

    “He went back to his White House office, which was just next door to Carter, dictated a two-line memo that said this building will be switched from the Department of Defense to the Department of Energy. And Carter signed it.”

    Harold Brown, then defense secretary, “went crazy,” Deutch adds. “He didn’t like that Jim hadn’t given him a heads-up. But that was the point. It sent a signal that he, Schlesinger, had more influence with Carter than Brown.”

    That influence eventually waned. Carter fired Schlesinger in August 1979 as part of a wholesale purge of his Cabinet. (Schlesinger died in 2014 at age 85.) Deutch rose to the fourth-ranking position at DOE under Carter and 2 decades later would return to Washington, D.C., as CIA director under former President Bill Clinton. Today, at age 86, he is emeritus professor at MIT after serving as chemistry department chair and provost.

  • Fish implanted with tumor cells could help oncologists quickly personalize cancer treatmentsThis link opens in a new windowJan 3, 2025

    Can oncologists make better cancer treatment decisions if they consult fish? A clinical trial set to start this month in Portugal aims to find out. Led by developmental biologist Rita Fior of the Champalimaud Foundation, the 5-year study is the first randomized trial in which patients will receive drugs that have been tested beforehand in zebrafish embryos implanted with the patients’ cancer cells. Retrospective studies have shown that so-called zebrafish avatars could have identified successful treatments if they had been deployed in advance, and Fior and colleagues now want to determine whether that ability can benefit patients.

    “Everybody is looking for something that is more predictive” of how therapies will affect patients’ tumors, says stem cell biologist Leonard Zon of Harvard Medical School, who isn’t connected to the trial. A menagerie of other cancer avatars already exists—including mice, fruit flies, and cell cultures—all meant to serve as personalized testbeds for treatments. But all have limitations. If the new study shows the fish have “a high predictive value, people will be all over this,” Zon says.

    Differences in patients’ tumors—features such as their genetics, metabolism, and growth potential—can make selecting the right treatment vexing for oncologists. Because several roughly equivalent options can be available, patients may have to endure one noxious therapy after another to settle on a treatment that helps. Genomic analysis can sometimes winnow the choices, but even when a patient’s cancer carries mutations that point to a specific treatment, there’s no guarantee it will respond.

    Seeking a better alternative, Fior’s lab has been studying zebrafish avatars for almost a decade. Researchers isolate cancer cells from a patient, fluorescently tag them in the lab, and transplant them into the transparent zebrafish embryos, which naturally grow outside the mother. Fior and colleagues can add cancer drugs to the fishes’ water or deliver doses of radiation, and then observe the fluorescent tumor cells to gauge whether the patient’s cancer is likely to be sensitive to the same treatments. Equally important, by revealing options that probably won’t work, avatars might spare patients from potentially toxic but futile therapies.

    The fish made a splash after Fior and her colleagues reported in 2017 that the avatars would have foretold the results of chemotherapy in four out of five people treated for colorectal cancer. In a 2024 report in Nature Communications , the scientists described generating avatars for a larger group of 55 patients and putting the fish on the same type of chemotherapy the people received. For 50 of the patients, the fish “predicted” the outcome of treatment. An added benefit, Fior says, is that avatars can reveal key characteristics of tumors’ such as whether they are likely to metastasize. Other labs have reported similarly promising findings with zebrafish avatars.

    The fish face rivals, including cancer cells taken from a patient and grown in a dish. Cancer researcher Diana Azzam of Florida International University and her colleagues reported in 2024 in Nature Medicine that this approach only required 9 days to deliver a verdict for blood cancers and 10 days for solid tumors. Unlike fish, however, cancer cells in simple cultures don’t dwell in the natural environment of the body. “They are missing a lot of the components that we know regulate tumor biology and drug response,” says cancer biologist Alana Welm of the University of Utah.

    Fruit flies are another potential treatment oracle, thanks to a technique developed by fly geneticist Ross Cagan, now at the University of Glasgow, and colleagues. Whether fruit flies naturally develop tumors is controversial. So instead of transferring cancer cells from a patient, the researchers genetically modify a fruit fly larva to carry key mutations from that person’s tumor. They can then test drugs to determine whether they thwart the mutations’ effects. The approach is efficient: From a single genetically altered fly, Cagan and his colleagues could quickly breed 400,000 avatars for each patient, enabling them to test a wide array of treatments and providing strong statistical support for the results.

    In 2019 and 2021 papers, Cagan and colleagues reported using the approach for two patients, one with a rare salivary gland tumor and one with metastatic colorectal cancer. In both cases, the fly avatars uncovered new drug combinations that temporarily halted tumor growth, although neither person was cured. The researchers also started a clinical trial, but the COVID-19 pandemic disrupted it.

    Mouse avatars have also reached clinical trials, but it can take months to grow tumors and test treatments in mice. Welm says the verdict isn’t in for any of these approaches. “We are still waiting for the data.”

    Zebrafish advocates contend that their avatars offer a unique combination of benefits. Azzam notes that similar to cell cultures, they deliver quick results—within 10 days. “Time is very important for clinical decision-making,” she notes.

    Zebrafish are more similar to humans than cell cultures, and far cheaper to raise than mice. The small, transparent embryos are also easier to analyze, says Sofia de Oliveira, a molecular biologist and immunologist at the Albert Einstein College of Medicine. “You can visualize the whole animal under the microscope,” she explains, and easily search its tissues for metastases.

    In the clinical trial, Fior and her team will test that promise by sieving cancer cells from the fluid that builds up in the abdomen of people with metastatic breast or ovarian cancer and is usually drained as part of treatment. “We are not doing an extra procedure on the patients,” she says. The cells will then be implanted in the fish embryos. Instead of testing experimental drugs, as many other clinical trials do, the study will determine which combination of approved treatments works best. Half of the patients will receive medications suggested by the zebrafish results, and the other half will receive the treatment picked by their doctors without any fish input.

    When it comes to acceptance by oncologists, zebrafish avatars are still swimming against the tide. “In my experience, clinicians are still a little bit resistant to working with zebrafish,” says molecular geneticist Kathleen Claes of Ghent University, whose lab has been studying the avatars. But she says the study “could be groundbreaking if it can prove the added value for that group of patients where the next options are not clear.” Cancer biologist and oncologist Richard White of the University of Oxford agrees. “Oncologists are data driven. If you give them the data, they will go for it.”

  • Migrating bats surf warm winds to soar hundreds of kilometersThis link opens in a new windowJan 2, 2025

    Bats are one of the most widespread mammals on Earth, with many undertaking seasonal migrations in pursuit of balmy weather or bountiful food sources. Yet scientists know relatively little about migrating bats’ comings and goings. A new effort involving tiny transmitters and a network of low-power sensors is changing that. According to a study out today in Science , the mouse-size bat known as the common noctule ( Nyctalus noctula ) surprisingly takes advantage of tailwinds across Europe to travel more than 1000 kilometers across to find good breeding grounds , adjusting its timing depending on the weather.

    “It’s a great advance,” says Liam McGuire, a physiological ecologist at the University of Waterloo who was not involved with the work but who studies bat migration. “It’s been really tricky to get any good coverage distancewise for small animals.”

    The new work may help researchers figure out what might be done to protect bats from wind turbines . “As we know from monarch butterflies, knowing how when and where animals migrate is crucial to any conservation efforts,” says Michael Ryan, an evolutionary biologist at the University of Texas at Austin who was not involved with the work.

    Biologists have tried many approaches to learning about bat movements. Monitoring traditionally tagged individuals only gives researchers data on where the bats start and stop their journeys. Others have tried using drones , or weather radar and uncovered bats’ flight paths to some degree. Charlotte Roemer, a conservation biologist at France’s National Museum of Natural History, and colleagues have compiled ultrasonic recordings of bats from 60 collaborators across 30 countries to determine migration routes.

    But none of those approaches provide detailed looks at entire journeys. So, researchers at the Max Planck Institute of Animal Behavior (MPG) have developed a 1-gram sensor that’s small enough for a noctule, which weighs half as much as a golf ball, to easily carry. Attached by temporary surgical glue, tags stay attached for up to 2 weeks, and over this time, each records the bat’s acceleration as well as temperature, 1440 times a day, and summarizes and sends out these data daily.

    Originally, the team envisioned using an antenna on the International Space Station to receive and relay data from tags, but the Russian-Ukraine conflict ended that collaboration . Instead, behavioral ecologist Edward Hurme and his colleagues at MPG took advantage of what’s called the Internet of Things, a widespread, interconnected network of computers, smartphones, and other devices that could be tapped to detect the tag’s daily summaries. The tags ping near the network’s nearby sensors to pinpoint the bat’s location every minute.

    Of 125 bats tagged in Switzerland over 3 years, Hurme and his team got good data from 71. The researchers had expected the bats would take a pretty consistent, direct route as they headed to northern Germany, Poland, and the Czech Republic, but the tags showed “there isn’t really a corridor” he notes. The bats took off in many directions but generally headed northeast, flying up to 383 kilometers per night, at speeds ranging from about 13 to 43 meters per second. Although the journeys only took about 2 days, the bats left anywhere between April and June, the team reports. And although the tag often didn’t last long enough to reveal the bats’ final destinations, they do provide evidence that the animals “do not all migrate in the same way,” notes Roemer, who was not part of this study.

    Common noctule bat with ICARUS TinyFoxBatt tag getting ready to fly out of researcher's hand.
    A 1-gram transmitter, with the antenna sticking out, tracked this common noctule for about 12 days. Christian Ziegler/Max Planck Institute of Animal Behavior

    Hurme and his team also incorporated weather data—wind speed and direction, as well as air pressure, cloud cover, rain, and air temperature—into their analysis. As a result, he says, “we are starting to understand the environmental conditions” that prompt bats to head off on their spring migration. (After breeding, the bats return to Switzerland to hibernate.) They seem to anticipate warming conditions, which allow them to “surf” on the air being pushed ahead of the front.

    Being able to predict when bats will start to migrate could eventually help wind turbine managers know when and where to temporarily adjust the machines to minimize bat strikes, Hurme says.

    “This technology revolutionizes the tracking of bat movements and will surely help researchers answer many questions about migration,” Roemer says. “The possibilities are very exciting.”

    The findings complement a study published last month in Movement Ecology that found that a different migrating bat species, Nathusius’s pipistrelle ( Pipistrellus nathusii ), also surfs warm fronts as it crosses the English Channel into Europe . Doing so more than doubles the animals’ speed, that research team concluded.

    For “many folks in the general public, their vision [of bats] is of some animals piling out of the cave at dusk, sucking some blood, eating some mosquitoes, and then returning,” Ryan says. “But their lives are much more complicated than that.”

  • Better care urged for animal remains tied to Indigenous peoplesThis link opens in a new windowJan 2, 2025

    Boulder, Colorado— As a master’s student in museum studies at the University of Colorado (CU) Boulder, Chance Ward opened a drawer one day in 2021 and found a jumbled bag of horse bones, many broken into bits or ground into dust. Ward is Lakota and an enrolled citizen of the Cheyenne River Sioux Tribe, and he and other Lakota consider the horse sacred—“an animal I see as my brother,” he says. “It was upsetting to see [so little] care for them.” The experience was so jarring that for his thesis, Ward explored ways for museums to more thoughtfully care for animal remains that have cultural ties to Indigenous communities.

    Now, his work forms the basis of a paper, due out this month in Advances in Archaeological Practice , in which scientists, tribal elders, and preservation officers outline recommendations for the care of animal remains in anthropological collections. Curators should closely study animal remains for any links with Indigenous nations or communities, and researchers should involve those groups when remains are culturally significant, Ward says. Although animals don’t typically fall under the Native American Graves Protection and Repatriation Act (NAGPRA), which enables Indigenous peoples in the United States to reclaim human remains and funerary objects, he and others say curators should consider returning some remains.

    The work feeds into a museum movement toward culturally informed curation and collaborative care of collections. “This is such a timely paper, given how much energy we’ve seen in the space of ethical curation in the last decade or so,” says Alex Fitzpatrick, a zooarchaeologist at London’s Science Museum. “I’ve always found a frustrating discrepancy in how people and animals are treated, so it’s really exciting to see a group of authors get together and actually put up a plan.”

    Museums contain thousands of masks, jewelry, clothing, and other ceremonial items crafted from animal materials. And millions more animal specimens have never been inventoried, which “drives the true tally much, much higher,” says co-author William Taylor, a zooarchaeologist at CU Boulder who was Ward’s master’s thesis adviser.

    The glut of unprocessed material—dubbed a “curation crisis” by museum professionals— underpins the paper’s most pressing recommendations: for curators to tally, identify, and properly house animal remains that may have cultural ties. For archaeologists, this may mean partnering with zoological experts. “Creating a world in which animals in museums are cared for in a culturally connected way requires first caring about identification,” says co-author Jimmy Arterberry, a Comanche Nation tribal historian and elder. Then we “can flag items for return or create opportunities for communities with ties to these remains to provide meaningful context for their care.”

    The report also recommends careful tracing of how animal remains have been treated from the moment of their discovery. That’s because animals unearthed during archaeological excavations often get stored with ordinary zoological specimens, severing cultural links that might make them eligible for repatriation, says Kristen Barnett, an Indigenous ( Unangax̂ ) scholar and archaeologist at the University of British Columbia who was not involved in the study. How museums handled those remains also matters, because in past decades, wool textiles, pelts, bones, and feathers were treated with pesticides that may make the objects unsafe to handle today. Today, noninvasive techniques such as near-infrared spectroscopy can reveal traces of chemicals such as arsenic and cyanide. Disclosing any risks is vital to building trust with communities with cultural ties to the remains, the authors say.

    Once curators understand something about the history of remains, they can add that information to records for other scholars and descendant communities, says Jane Anderson, a legal scholar and anthropologist at New York University. She co-founded an organization called Local Contexts to help curators and Indigenous communities attach traditional knowledge and biocultural information to digital records. That context can shape how objects are handled and displayed. For example, Cheyenne and Arapaho tribes successfully requested that a Sun Dance buffalo skull housed at the Smithsonian Institution’s National Museum of Natural History be stored facing east and upside down to signal that it is ceremonially inactive.

    Taylor, who is also the curator of archaeology at the Museum of Natural History at CU Boulder, says the recommendations could extend to remains that have no known connection to human cultures, but may still be important to Indigenous peoples, including remains in natural history or teaching collections. But because the new approach will require staff, time, and money—resources in short supply at museums—he recommends focusing on animal remains with clear links to Indigenous communities. His own experiences show how this can be done.

    In 2022, Taylor got state funds to rehouse a collection of 200 bison skulls associated with a mass hunting event near Kit Carson, Colorado, roughly 11,000 years ago. The Lakota have cultural connections to the site, so the museum invited a delegation of Lakota elders to perform a blessing and share suggestions for the skulls’ care. The team grouped the herd in storage as it would have been in life, and commissioned new fiberglass molds that better support the skulls while leaving them accessible to handling or viewing. The team also scanned some skulls to create 3D models for Indigenous people who want access for cultural or research purposes but are unable to travel. “Having done some of this engagement work, I can already see all the things I would have done differently, but that uncertainty—or fear over potential costs—is no excuse not to engage,” Taylor says.

    At the moment, Indigenous communities rely on the good faith of institutions to repatriate animal remains. There have been some success stories, such as the voluntary repatriation of Big Medicine , a white buffalo sacred to the Confederated Salish and Kootenai Tribes. In 2022, the Montana Historical Society returned custodianship of the mounted remains to the tribes upon their request. But some museum professionals want a broader policy solution, such as updating NAGPRA to include animal remains; others urge scientists to take responsibility for returning remains—or perhaps not collect them at all.

    For example, archaeologists like Barnett and Sara Gonzalez of the University of Washington aim to leave sites they excavate largely intact. Gonzalez, who studies Indigenous food systems in western North America, sometimes finds animal remains during digs. Rather than collecting material, she maps and studies each item in place, employing low-impact methods such as ground-penetrating radar. “My goal is that when we have completed our research, I’m holding nothing,” she says.

    Ward is now the NAGPRA compliance officer for the state of Colorado and has broad discretion to determine which of the state’s roughly 225,000 artifacts are eligible for repatriation. Many, such as a ceremonial whistle made from an eagle’s bone, are outside NAGPRA’s purview, but Ward knows they hold special meaning. He hopes that one day, after human ancestors have been fully repatriated, museums will move on to other categories. “Even though these items may not fall under NAGPRA, I have the knowledge and the duty of care, so I pull them aside,” he says.

  • Farmers are abandoning land worldwide. What should happen to it?This link opens in a new windowJan 2, 2025

    Tyurkmen, Bulgaria— People in this small village didn’t know what to think when Gergana Daskalova showed up and moved into her grandparents’ former house. Ambitious young people generally flee this sleepy village. Few return for long.

    Yet Daskalova, a fellow in the Georg August University of Göttingen’s Department of Conservation Biology, is determined to live at least part time in the place where she spent childhood summers. Along with all the fond memories, it’s become a research site. She’s studying what happens to ecosystems when people vanish.

    The population of Tyurkmen has fallen by about 80% over the past century. Many of the houses stand empty, with collapsed roofs and teetering walls. Shrubs and small trees are taking root in former gardens.

    Beyond the village lies open land. On much of it, crops no longer grow, and sheep no longer graze. The plots of land are owned by heirs who live far away. “Every generation, it becomes more complicated to do anything with that land,” Daskalova said as she stood on a hill and took in the view in September 2024. “My family has fields that we inherited from my grandparents,” she said. “But I don’t know where they actually are.”

    Fallow fields are now covered with opportunistic grasses. Thorny shrubs and wild plum trees are taking root. Stands of an invasive tree called Tree of Heaven are spreading fast.

    When Daskalova was growing up in the half-abandoned village, such scenes were simply the backdrop of ordinary life. “I had to leave my village and do my education abroad to realize that, ‘Oh, other people don’t see this every day,’” she said. The abandonment of rural land “is happening behind the scenes. Most people have no idea that it’s occurring.”

    In reality, it’s surprisingly common. “This is a worldwide phenomenon,” says Peter Verburg, a land use researcher at the Free University Amsterdam. Global trade in food has fueled the clearing of forests in Brazil and Bolivia for agriculture, but elsewhere it has sidelined small farms with rocky soil, steep hills, or scarce water. “People give up because they cannot compete,” Verburg says.

    Farmers, or their children, are walking away from land in Eastern Europe, southern France, South Korea, Japan, and mountainous parts of India. It’s difficult to measure the exact extent of the trend. Land is often abandoned, then reclaimed and farmed again. But an estimated 120 million hectares have been left fallow in Europe alone since 1990. Globally, the figure since 1950 could be as high as 400 million hectares—half the area of Australia. “Abandonment will continue, I think there’s no doubt,” Verburg says. In fact, climate change is likely to accelerate it as droughts afflict more farming areas.

    The phenomenon raises thorny questions that ecologists and policymakers are now debating. What sort of nature will reclaim this land? Does it add up to environmental restoration or degradation? Should policymakers step in to steer the fate of the land or even stop it from being abandoned?

    A White Stork returns on its nest, as viewed through the window of a disintegrating  shed in Tyurkmen, Bulgaria
    In Tyurkmen, Bulgaria, storks and other animals are reclaiming land abandoned by people. Malkolm Boothroyd

    The answers can be murky. They sometimes depend less on data than on the version of nature that scientists and policymakers value most.

    “It’s a bit of a cultural war,” says Henrique Pereira, an ecologist at the German Centre for Integrative Biodiversity Research and Martin Luther University Halle-Wittenberg. Pereira has led a push in Europe to embrace land abandonment as an opportunity to let nature take its course—even if it opens the way to weeds and invasive species, as in Daskalova’s village. “I endorse ecological succession after abandonment,” he says. “I’m a ‘if you love them, set them free’ kind of person.” Other ecologists say a hands-off approach is a recipe for loss. When traditional farming disappears, they say, communities of wildflowers and birds that thrive in a mosaic of fields and meadows also vanish. The idea that vibrant ecosystems will naturally emerge instead is “an ecological fairy tale,” says Michael Glemnitz, a biodiversity researcher at Germany’s Leibniz Centre for Agricultural Landscape Research.

    ON THAT HOT LATE-SUMMER DAY in September, Daskalova stepped carefully across a rickety footbridge and climbed a grass-covered road through what’s left of Kreslyuvtsi. It’s one of 30 villages where she and her research team are counting plant species and hiding battery-powered audio recorders in trees to capture the sounds of birds and bats. For each study site that’s experiencing abandonment, the researchers have chosen a twin, another village that’s similar but is not losing people, in an attempt to isolate the effects of depopulation.

    “These changes in villages have always been something very close to my heart,” she said. “I really wanted to see, what does human migration mean for nature, for biodiversity? And what are some of the ways that we could reimagine villages in a way that is good for both people and for nature?”

    Kreslyuvtsi is officially uninhabited, one of Bulgaria’s 500 or so “ghost villages.” Like many of them, it’s located amid forested mountains.

    Daskalova walked past brick and stucco houses with red tile roofs, many of them partially hidden behind a veil of vines. Thickets of wild blackberries filled what once were gardens or orchards. “As far as we can see, it’s just brambles,” Daskalova said. “The blackberries are suppressing the growth of anything else.” A solitary walnut sapling stood amid the shrubs.

    Daskalova standing on a road in a forest. She is wearing hiking clothes and looking upward. White mist obscures the more distant road and trees, so that the road seems to disappear into the mist behind her.
    Gergana Daskalova, who has been studying the ecological consequences of land abandonment, near one of her research sites around Tryavna, Bulgaria Malkolm Boothroyd

    The version of nature that’s taking over this village, Daskalova said, is a poor substitute for what preceded it. “I think if we were to do a plant survey here right now, we might be at something around like 10 plant species, which for a mountain village is not very many,” she said. A village where people still tend gardens and herd goats might have 10 times that many plant species, and also more birds, she said.

    There’s no sign that time will break the brambles’ stranglehold, she said. Another village in this region, abandoned at least 50 years ago, remains so overwhelmed by thorny shrubs that Daskalova couldn’t even hack her way through to set up a study site there.

    The lack of human activity seems to be choking out biodiversity in mountain villages like this one, where abandonment is most advanced. In the more populous lowlands, on the other hand, where abandoned homes and fields sit alongside others where people still live and work, she has found that some wildlife prospers in the ruins. “Remnants of human infrastructure are actually quite good for biodiversity,” Daskalova says. “There will be birds nesting in houses, bats nesting in houses.”

    But these are just a few data points in a very large and messy array.

    Johannes Kamp first encountered abandoned farmland in 2003, and at the time, it felt like paradise.

    Kamp was a 23-year-old bird enthusiast traveling through Kazakhstan, where state-owned agricultural enterprises had collapsed in 1991 along with the Soviet Union. Some 24 million hectares of croplands had been left to their own devices. “These abandoned fields were teeming with wildlife,” Kamp says. Foxes patrolled the steppe and the sky “was just absolutely filled with birdsong.”

    “For me, it was very emotional,” says Kamp, who’s now a conservation biologist who works with Daskalova at Göttingen. It seemed a sign of hope in a world where environmental loss is the rule.

    In the years that followed, however, grass accumulated on the fallow and ungrazed farmland, and devastating fires erupted . “We had these huge wildfires, sometimes 30,000 hectares,” Kamp says. At the same time, new agricultural enterprises showed up to reclaim some of the most productive land. Kamp wondered whether the wildlife paradise he’d witnessed would vanish completely.

    In Kreslyuvtsi, Bulgaria, vegetation is swallowing an abandoned homestead (first image) and memorial notices mark the deaths of former inhabitants (second image). (first image) MALKOLM BOOTHROYD; (second image) D. Charles/ Science

    Yet the steppe continued to surprise. When Kamp returned to Kazakhstan in the summer of 2024, he found that the danger of fire had receded. Increasing numbers of livestock and a booming population of wild saiga antelopes were keeping the vegetation in check. Meanwhile, the move to reclaim land for farming had stalled. Abandoned land that’s remote or infertile will likely stay that way, Kamp wrote in an email to Science .

    Today, Kamp can’t say whether land abandonment generally is helpful or harmful to biodiversity. “I think there are facets and nuances, but nobody knows what the answer to that question is,” he says. “I’ve changed my mind over the years, to be honest.”

    Geography and climate certainly affect the answer. Farms in the northeastern United States that went out of business between 1880 and 1930 have turned into mostly healthy forests, with only the occasional stone fence betraying the land’s past. (The idea of ecological succession, describing the step-by-step transformation of disturbed land into a vibrant forest, was based on observations of abandoned U.S. farmland.) Yet fallow fields in the arid climate of western Australia can sit almost unchanged for close to a century. “You just have slow erosion, and it’s bare ground,” Daskalova says.

    Scientists in Poland reported in Science in 2023 that up to 75% of that country’s abandoned farmland is now dominated by invasive species such as goldenrod, walnut, and boxelder maple. Goldenrod, in particular, keeps trees from taking root and reduces populations of wild pollinators and birds, the scientists wrote. Yet a researcher found rising bird populations in abandoned vineyards of southern France. And Kamp has seen “huge populations” of butterflies in a former military training area in Germany that was abandoned nearly 40 years ago—although he expects those populations to decline eventually as open spaces give way to more shrubs and trees.

    A songbird with a yellow body, brown wings, and a black head perches on a wheat plant surrounded by bright red flowers.
    Abandoned farmland can create habitat for wildlife, such as this black-headed bunting in an overgrown wheat field near Shistmantsi, Bulgaria. Malkolm Boothroyd

    In short, the picture is confusing, and researchers are trying to figure out what factors send each landscape down its particular path. There are some prime suspects: whether there’s enough rainfall to support a forest, what seeds remain in the soil, and whether diverse ecosystems exist nearby that could colonize the abandoned fields. “It’s definitely an opportunity to study,” says Emma Ladouceur, a researcher on ecological restoration at the University of Prince Edward Island.

    Besides doing fieldwork in villages of Bulgaria, Daskalova is organizing an international working group to collect and analyze ecological data from other abandoned sites around the world. “We want to quantify the different trajectories for what happens,” she says.

    But the findings won’t be able to say how abandoned land should be managed, or whether people should try to manage it at all. “Even if we are scientists, at the end of the day it’s going to be a decision based on values,” Daskalova says. Those value-based preferences, in fact, are increasingly up for debate.

    Europe’s policies on biodiversity, for example, aim to preserve centuries-old farming landscapes and ecosystems. But Pereira started to question those policies after he returned to Portugal from Stanford University. He’d been inspired by near-wilderness areas in the U.S., and wished for something similar in his home country, “someplace where we have nature working,” he says.

    In northern Portugal, where he’d carried out earlier fieldwork, he realized that traditional patterns of sheep herding and cattle ranching had collapsed, creating an opening for wilderness to return. He thought: “This is kind of a cool opportunity, you know?”

    Without animals to graze the meadows, shrubs and small trees were taking over. Once-rare wild animals, such as roe deer and wild boar, were mounting a comeback.

    Pereira took a break from academia in 2006 and served for 3 years as director of Peneda-Gerês National Park, which includes areas long used by ranchers. He decided to change the park’s strategy: Instead of fighting the retreat of farming, he’d embrace it. He drafted a new management plan for the park, designating land where animals wouldn’t graze any longer.

    He soon got a call from Portugal’s director of conservation. “You cannot do that,” Pereira recalls the official saying, because it would violate the European Union’s Habitats Directive . One of Europe’s flagship conservation laws, the directive lists more than 200 habitat types that need to be preserved. About half, according to Pereira, require some sort of human management.

    They include the seminatural meadows of traditional farming communities. Such habitats can be threatened by intensive agriculture, as farmers try to grow more hay, or graze more cattle. Yet if farmers stop all grazing or mowing, they give way to shrubland or forests.

    The EU is using its agricultural subsidies as a tool to fight land abandonment, persuading farmers to keep tending such “cultural landscapes.” Landowners who fail to keep their land in “good agricultural condition” can lose their payments. Farms at higher risk of going out of business because they are in remote or mountainous areas get bigger payments.

    Sheep kick up dust as a herder leads them through the streets of Tyurkmen, Bulgaria. Traditional farming is declining in many countries, opening the door to land abandonment. MALKOLM BOOTHROYD

    Pereira found this wrong-headed. He persuaded Portugal’s conservation officials that removing cattle from parts of the park could serve a broader goal of the Habitats Directive—promoting more natural and dynamic ecosystems. (After he stepped down as park director, however, his successor decided not to adopt the proposed changes because of opposition from local cattle ranchers and shepherds.)

    Ever since, Pereira has been on a mission to change Europe’s approach to nature conservation. He co-authored a much-cited paper in 2012 arguing that land abandonment could be an opportunity to “rewild” European landscapes.

    Preserving static “museum landscapes” should not be a priority, Pereira says. In fact, “species richness” shouldn’t even be the main goal if it depends on human management, as it does at a zoo or botanical garden. Instead, he argues, conservationists should try to create conditions that allow natural ecological process to unfold, free of human control, with shifting communities of plants, herbivores, carnivores, and scavengers such as vultures adapting to disruptions such as climate change.

    The problem, though, is that natural succession can take abandoned landscapes in directions that most people find ugly—such as masses of thorny blackberries. Pereira says certain interventions, such as introducing herbivores, might “get more of these landscapes on trajectories that are seen as good for nature and people.”

    In addition, researchers are finding that it can take a very long time, perhaps centuries, for complex and dynamic ecosystems to emerge on former farmland. In fact, there’s no guarantee that they ever will.

    Pereira says he once expected to see such results within his lifetime. Now, he has come to accept that “there are many things I’m not going to see. Maybe my children, maybe my grandchildren get to see that.”

    Pereira hasn’t managed to change Europe’s policies significantly, but his views are getting increasing attention. A group called Rewilding Europe hopes to create wild reserves in 10 landscapes across the continent, from the Scottish highlands to the Danube delta. The EU recently launched a $10 million research project aimed at exploring how rewilding farmland and forests could help Europe reach its biodiversity and climate goals.

    Pereira admits that for people with ties to the land, letting nature reclaim it can be hard to stomach. In surveys, they express “a feeling of loss. A feeling of failure,” he says.

    But those feelings are sometimes mixed with others, which he’s witnessed firsthand in northern Portugal. “For instance, farmers have this fight against the wolf. You know, ‘The wolf, he’s really an enemy.’ But then a shepherd will say,”—and Pereira’s voice shifted to an awestruck whisper—“The other day I saw a wolf, and oh man, it was quite something.”

    As Daskalova walked through the village where five generations of her family lived, it’s the human losses that seemed to preoccupy her. In the doorway of one ruined house, a child’s book, with a boy’s name written inside, lay open on the ground. “Somebody poured their heart and soul into creating a home, and now it’s all collapsing,” she said. “It’s quite sad. That’s why I find it very difficult when there’s the question of, ‘Should we let abandoned land just be? Should nature claim it back?’ It’s not just birds coming in. It’s little bits of human history disappearing.”

    The landscape around Tyurkmen, Bulgaria, includes a mosaic of abandoned and still working farms. Malkolm Boothroyd

    Even the benefits for nature, which she sometimes sees in her data, may be short-lived, Daskalova said, because cheap abandoned land is ripe for exploitation. “Any conservation benefit of restored habitat on abandoned land can disappear in the blink of an eye,” she says.

    A mining company recently bought land 500 meters from the edge of Tyurkmen. It wants to blast open a limestone quarry there. Daskalova is organizing a citizens’ movement to stop it, but a village that’s already half-deserted lacks political clout. “The places that are experiencing a lot of abandonment are very vulnerable,” she says.

    Some researchers have suggested geographic targeting of EU subsidies, with funding to stop land abandonment where the consequences seem particularly damaging, while promoting rewilding in other areas. But deciding where to intervene would be daunting. Daskalova, for her part, is taking a very personal stand for villages. She’s currently renovating a house in Tyurkmen for herself, her husband, and their young son.