Most T cells only work in the person who made them. Your T cells fight threats by responding to molecular fragments that belong to a pathogen — but only when these molecules are bound with markers that come from your own tissues. Your influenza-fighting T cells can’t help your neighbor, and vice versa.

“However, we all have T cells that do not obey these rules,” says LJI Professor and President Emeritus Mitchell Kronenberg, Ph.D. “One of these cell types is mucosal-associated invariant T (MAIT) cells.”

Now Kronenberg and his LJI colleagues have uncovered another MAIT cell superpower: MAIT cells can recognize the same markers whether they come from humans or mice. Kronenberg calls this finding “astounding.” “Humans diverged from mice in evolution 60 million years ago,” he says.

This new research, published in Science Immunology, sheds light on the genes and nutrients that give MAIT cells their fighting power. The findings are an important step toward one day harnessing these cells to treat infectious diseases and improve cancer immunotherapies.

“Because MAIT cells are the same across individuals, they could more easily be used in cell therapies, where, in principle, my MAIT cells could be given to you,” says Kronenberg.

The new study also opens the door to exploiting MAIT cells to improve cellular therapies. “If we could make normal T cells more like MAIT cells, maybe we could make them act faster and more vigorously to combat any type of infection or cancer,” says study co-first author Gabriel Ascui, a UC San Diego graduate student in LJI’s Kronenberg Lab.

Why MAIT cells are special

Kronenberg was initially interested in MAIT cells because of their unexpected response speed. Typical T cells need a few days to develop in the thymus and only adapt to fighting new threats after leaving the thymus — and after several days of stimulation from a pathogen. MAIT cells are much faster because they can respond to more generic markers of infection, rather than hunting for very specific tissue-type markers. For MAIT cells, a red flag is a red flag, no matter who is waving it.

This broad specificity makes MAIT cells similar to the immune system’s first-responder cells, such as macrophages and neutrophils, which make up the “innate” immune system. “MAIT cells have this ‘innate-like’ characteristic,” says Ascui. “They’re like your first line of defense.” In fact, MAIT cells tend to gather in tissues like the lungs and intestines, where the body is under constant threat from airborne and foodborne pathogens.

The new study shows that MAIT cells don’t just recognize a range of markers within one person. Instead, these odd T cells can “see” markers shared between humans — and even between species. Scientists call these kinds of shared markers “conserved.” There has been no reason for the markers to change over the eons, so they remain the same across related species.

But just because these MAIT cells look the same between species, doesn’t mean they fight pathogens — or make energy — in exactly the same ways.

Why look at mouse cells?

Comparing human and mouse MAIT cells is important for guiding future studies where mice can serve as useful animal models to study exactly how these cells combat pathogens.

Kronenberg, Ascui, and their colleagues used single-cell sequencing and other tools to compare differences in gene expression pathways between human and mouse MAIT cells. The scientists found that mice have two different kinds of MAIT cells, which produce different inflammatory molecules, called cytokines. One kind of MAIT cell, which the scientists call MAIT1, produces a lot of a cytokine called interferon-gamma. The other kind of the MAIT cell, called MAIT 17, produces a lot of a cytokine called interleukin-17.

A recent Nature Cell Biology study from the Kronenberg Lab, co-led by LJI Instructor and Immunometabolism Core Director Tom Riffelmacher, Ph.D., shows that after a bacterial infection, MAIT1 and MAIT17 cells persist but become super-charged, or capable of having greater protective function for months. These cytokines help the MAIT cells take aim at different threats. MAIT1 cells target viruses such as influenza, while MAIT17 cells are better at targeting bacteria.

In the new study, the team found that MAIT cells from both species are more capable of taking up and storing fat, compared with typical T cells. This finding suggests MAIT cells are more dependent on this nutrient for energy. This discovery is also in line with previous work in the Kronenberg Lab showing that some MAIT cells depend on fat to fight pathogens. The key difference between the species was that human MAIT cells can produce interferon-gamma and IL-17, but not evidently by separate cell populations.

When mice live like us

The scientists needed to know — was this difference in human and mouse MAIT cells linked to genetic differences or to our different habitats? Lab mice, such as those cared for at LJI, are housed in ultra-clean vivariums. Their food is blasted in an autoclave to kill pathogens, and their water, toys, and cages are kept as sterile as possible.

Kronenberg and Ascui were curious — do mice living in less-controlled environments show differences in MAIT cell function? The team collaborated with UC San Diego scientists to study MAIT cells from mice kept in so-called “dirty” or less sterile conditions, similar to a pet store environment. Their research suggests MAIT cells from these mice have even more in common with human MAIT cells, especially when it came to having more MAIT1 cells, which produced more interferon-gamma than lab mouse MAIT1 cells.

“Pet stores aren’t dirty in the conventional sense,” says Kronenberg. “But part of the idea is that the ‘dirty’ mice are living in an environment — with more microbes and immune system challenges — that’s a little closer to human environments.”

The team also compared MAIT cells found in different parts of the body, such as the blood, thymus (where T cells, including MAIT cells, develop), and the lung and spleen (where MAIT cells camp out). They discovered that MAIT cells still in the thymus look very similar between humans and mice (“dirty” or not); however, MAIT cells from the lungs and blood are more different between humans and lab mice.

MAIT cells from the “dirty” mice fell between the two groups, adding to the evidence that more natural-like environments change how MAIT cells develop and learn to target disease.

“Environmental, as well as genetic differences, shape the species differences in these cells,” says Kronenberg.

What does this mean for clinical research?

The new study gives scientists a sort of answer key, a list of genetic signatures to tell MAIT cells apart depending on the species and tissues they come from. Going forward, the team is interested in whether they can prompt typical T cells to express similar genetic signatures.

“If we could make normal cells more ‘innate,’ like MAIT cells, perhaps we could improve T cell therapy for cancer,” says Ascui. “That’s one avenue we’re looking at.”

Kronenberg is also interested in whether scientists can modify MAIT cells to actually decrease levels of IL-17 in the body. Although IL17 helps fight infections, some T cells produce IL-17 against the wrong targets, triggering harmful inflammation and even autoimmune disease.

“There are cases where IL-17 can be a bad actor,” says Kronenberg. “So although there are cases where we might want to induce more MAIT17 cells, expand their population, but we’d also like to find ways to prevent them from arising in situations where they might not be what we want.”

Additional authors of the study, “Transcriptomes and metabolism define mouse and human MAIT cell populations,” include co-first authors Shilpi Chandra and Thomas Riffelmacher, and Ashu Chawla, Ciro Ramírez-Suástegui, Viankail C. Castelan, Gregory Seumois, Hayley Simon, Mallory P. Murray, Goo-Young Seo, Ashmitaa L. R. Premlal, Benjamin Schmiedel, Greet Verstichel, Yingcong Li, Chia-Hao Lin, Jason Greenbaum, John Lamberti, Raghav Murthy, John Nigro, Hilde Cheroutre, Christian H. Ottensmeier, Stephen M. Hedrick, Li-Fan Lu, and Pandurangan Vijayanand.

“I’m hopeful that policymakers will rely on this work as motivation and support for the scale-up of beneficial fire as a key strategy in preventing wildfire catastrophes,” said study co-author Michael Wara, director of the Climate and Energy Policy Program at the Stanford Woods Institute for the Environment. “Beneficial fire is not without its own risks — but what our study shows is just how large and long-lasting the benefits are of this crucial risk reduction strategy.”

Significant risk reduction

The study, which focused on California, comes almost exactly five years after the state suffered its deadliest wildfire on record, the Camp Fire. Hotter weather and a history of fire suppression have allowed the build up of tinder-dry trees and brush, which fuel increasingly destructive wildfires. It wasn’t always that way. For millennia, Indigenous people allowed wildfires to burn, and intentionally applied fire to the land for reasons ranging from ceremony to subsistence. As a result, pre-colonial forests across California contained less fuel for hungry flames and were better able to retain moisture — keys to fire and drought resilience.

It’s no secret that wildfire-prone regions need to shift from a single-minded focus on suppression to one that includes much more controlled burning and forest resilience. Previous Stanford-led research has shown that California alone needs fuel treatments — whether prescribed burns or vegetation thinning — on about 80,000 square kilometers or nearly 20% of the state’s land area.

However, until now, studies assessing the beneficial effects of prescribed and low-intensity fires have been limited to relatively small areas, such as a single wilderness area or watershed. For this paper, the researchers reviewed 20 years of satellite monitoring of wildfires across more than 100,000 square kilometers of California forests.

The team — fire policy experts, public health scientists, and statistical and machine learning researchers — harmonized multiple state-wide datasets on fuel characteristics and fire behavior, including fire intensity (measured by the amount of energy released) and fire severity (measured by the ecosystem impacts of large fires). Previous studies have shown that prescribed fires and unplanned low-intensity wildfires have similar risk-reduction effects. Both remove surface fuels and smaller diameter trees, thereby helping forests achieve a more fire-resilient mix of trees and preventing fires from growing too intense. Both also leave tree canopies intact due to relatively low flame heights.

The authors measured the protective effect of low-intensity fires using a method that assembled unburned areas into a synthetic landscape closely resembling the burned landscapes’ attributes, such as weather patterns, elevation, vegetation type, and disturbance history. This approach allowed them to assess how these burned landscapes might have evolved had they not burned in that same year — and compare these counterfactuals to their actual evolution throughout time.

Using this approach, the researchers were able to quantify the reduced risk of high-intensity fires after a low-intensity fire burns in a forestland, and then see how long the protective effect lasts. They found that low-intensity fire in mixed conifer forests in California initially provides a 60% reduction in risk of catastrophic fire, and this effect lasts at least six years but diminishes over time. They also found a smaller but still significant reduction in risk in oak-dominated forests.

Good timing

Policymakers could use the study’s results as a foundation for future evaluation of wildland fuel treatments by comparing the quantified benefits to potential costs and risks associated with its implementation. The timing is good: The U.S. Forest Service has proposed treating nearly 200,000 square kilometers (about 50 million acres) over the next decade through a mixture of fuel treatment strategies. California has proposed increasing the amount of land it treats for wildfires to 2,000 square kilometers (about 500,000 acres) annually.

To be effective, wildland fuel treatments, including prescribed burning, have to be ongoing, periodic maintenance rather than a one-time intervention for forests that are adjacent to communities or critical infrastructure, the researchers write. The risk mitigation benefit of low-intensity burning will depend heavily on careful selection and targeting of the intervention to provide maximum protection for people, communities, and ecosystems.

“This study exemplifies how data science can contribute to climate mitigation through a highly multidisciplinary collaboration,” said study lead author Xiao Wu, an assistant professor of biostatistics at Columbia University who worked on the paper as a Data Science Fellow at Stanford. “Wildfires present substantial threats to both our ecosystems and human well-being. As scientists, our constant goal is to find practical solutions.”

Wara is also senior director of policy for the Sustainability Accelerator at the Stanford Doerr School of Sustainability.

Coauthors of the study include Erik Sverdrup, a postdoctoral scholar in Stanford’s Graduate School of Business; Michael Mastrandrea, associate director of policy at the Sustainability Accelerator, research director of the Climate and Energy Policy Program and a senior research scholar at the Stanford Woods Institute for the Environment; and Stefan Wager, an associate professor of operations, information and technology in Stanford’s Graduate School of Business and an associate professor of statistics (by courtesy) in Stanford’s School of Humanities and Sciences.

The study was funded by Stanford Data Science and the National Institutes of Health.

In a new Science Advances publication, the JILA team — along with collaborators from universities in Sweden, Greece, and Germany — probed the spin dynamics within a special material known as a Heusler compound: a mixture of metals that behaves like a single magnetic material. For this study, the researchers utilized a compound of cobalt, manganese, and gallium, which behaved as a conductor for electrons whose spins were aligned upwards and as an insulator for electrons whose spins were aligned downwards.

Using a form of light called extreme ultraviolet high-harmonic generation (EUV HHG) as a probe, the researchers could track the re-orientations of the spins inside the compound after exciting it with a femtosecond laser, which caused the sample to change its magnetic properties. The key to accurately interpreting the spin re-orientations was the ability to tune the color of the EUV HHG probe light.

“In the past, people haven’t done this color tuning of HHG,” explained co-first author and JILA graduate student Sinéad Ryan. “Usually, scientists only measured the signal at a few different colors, maybe one or two per magnetic element at most.” In a monumental first, the JILA team tuned their EUV HHG light probe across the magnetic resonances of each element within the compound to track the spin changes with a precision down to femtoseconds (a quadrillionth of a second).

“On top of that, we also changed the laser excitation fluence, so we were changing how much power we used to manipulate the spins,” Ryan elaborated, highlighting that that step was also an experimental first for this type of research.

Along with their novel approach, the researchers collaborated with theorist and co-first author Mohamed Elhanoty of Uppsala University, who visited JILA, to compare theoretical models of spin changes to their experimental data. Their results showed strong correspondence between data and theory. “We felt that we’d set a new standard with the agreement between the theory and the experiment,” added Ryan.

Fine Tuning Light Energy

To dive into the spin dynamics of their Heusler compound, the researchers brought an innovative tool to the table: extreme ultraviolet high-harmonic probes. To produce the probes, the researchers focused 800-nanometer laser light into a tube filled with neon gas, where the laser’s electric field pulled the electrons away from their atoms and then pushed them back. When the electrons snapped back, they acted like rubber bands released after being stretched, creating purple bursts of light at a higher frequency (and energy) than the laser that kicked them out. Ryan tuned these bursts to resonate with the energies of the cobalt and the manganese within the sample, measuring element-specific spin dynamics and magnetic behaviors within the material that the team could further manipulate.

A Competition of Spin Effects

From their experiment, the researchers found that by tuning the power of the excitation laser and the color (or the photon energy) of their HHG probe, they could determine which spin effects were dominant at different times within their compound. They compared their measurements to a complex computational model called time-dependent density functional theory (TD-DFT). This model predicts how a cloud of electrons in a material will evolve from moment to moment when exposed to various inputs.

Using the TD-DFT framework, Elhanoty found agreement between the model and the experimental data due to three competing spin effects within the Heusler compound. “What he found in the theory was that the spin flips were quite dominant on early timescales, and then the spin transfers became more dominant,” explained Ryan. “Then, as time progressed, more de-magnetization effects take over, and the sample de-magnetizes.”

The phenomena of spin flips happen within one element in the sample as the spins shift their orientation from up to down and vice versa. In contrast, spin transfers happen within multiple elements, in this case, the cobalt and manganese, as they transfer spins between each other, causing each material to become more or less magnetic as time progresses.

Understanding which effects were dominant at which energy levels and times allowed the researchers to understand better how spins could be manipulated to give materials more powerful magnetic and electronic properties.

“There’s this concept of spintronics, which takes the electronics that we currently have, and instead of using only the electron’s charge, we also use the electron’s spin,” elaborated Ryan. “So, spintronics also have a magnetic component. The reason to use spin instead of electronic charge is that it could create devices with less resistance and less thermal heating, making devices faster and more efficient.”

From their work with Elhanoty and their other collaborators, the JILA team gained a deeper insight into spin dynamics within Heusler compounds. Ryan said: “It was really rewarding to see such a good agreement with the theory and experiment when it came from this really close and productive collaboration as well.” The JILA researchers are hopeful to continue this collaboration in studying other compounds to understand better how light can be used to manipulate spin patterns.

Cardiovascular disease, which refers to all diseases of the heart and circulation, is the number one cause of mortality globally. In 2021, it was responsible for one in three deaths (20.5m), with coronary heart disease alone the single biggest killer. Since 1997, the number of people living with cardiovascular disease across the world has doubled and is projected to rise further.

In this study, researchers at UCL analysed data from six studies, encompassing 15,246 people from five countries, to see how movement behaviour across the day is associated with heart health, as measured by six common indicators*. Each participant used a wearable device on their thigh to measure their activity throughout the 24-hour day and had their heart health measured.

The researchers identified a hierarchy of behaviours that make up a typical 24-hour day, with time spent doing moderate-vigorous activity providing the most benefit to heart health, followed by light activity, standing and sleeping compared with the adverse impact of sedentary behaviour.

The team modelled what would happen if an individual changed various amounts of one behaviour for another each day for a week, in order to estimate the effect on heart health for each scenario. When replacing sedentary behaviour, as little as five minutes of moderate-vigorous activity had a noticeable effect on heart health.

For a 54-year-old woman with an average BMI of 26.5, for example, a 30-minute change translated into a 0.64 decrease in BMI, which is a difference of 2.4%. Replacing 30 minutes of daily sitting or lying time with moderate or vigorous exercise could also translate into a 2.5 cm (2.7%) decrease in waist circumference or a 1.33 mmol/mol (3.6%) decrease in glycated haemoglobin.

Dr Jo Blodgett, first author of the study from UCL Surgery & Interventional Science and the Institute of Sport, Exercise & Health, said: “The big takeaway from our research is that while small changes to how you move can have a positive effect on heart health, intensity of movement matters. The most beneficial change we observed was replacing sitting with moderate to vigorous activity — which could be a run, a brisk walk, or stair climbing — basically any activity that raises your heart rate and makes you breathe faster, even for a minute or two.”

The researchers pointed out that although time spent doing vigorous activity was the quickest way to improve heart health, there are ways to benefit for people of all abilities — it’s just that the lower the intensity of the activity, the longer the time is required to start having a tangible benefit. Using a standing desk for a few hours a day instead of a sitting desk, for example, is a change over a relatively large amount of time but is also one that could be integrated into a working routine fairly easily as it does not require any time commitment.

Those who are least active were also found to gain the greatest benefit from changing from sedentary behaviours to more active ones.

Professor Emmanuel Stamatakis, joint senior author of the study from the Charles Perkins Centre and Faculty of Medicine and Health at the University of Sydney, said: “A key novelty of the ProPASS consortium is the use of wearable devices that better differentiate between types of physical activity and posture, allowing us to estimate the health effects of even subtle variations with greater precision.”

Though the findings cannot infer causality between movement behaviours and cardiovascular outcomes, they contribute to a growing body of evidence linking moderate to vigorous physical activity over 24 hours with improved body fat metrics. Further long-term studies will be crucial to better understanding the associations between movement and cardiovascular outcomes.

Professor Mark Hamer, joint senior author of the study from UCL Surgery & Interventional Science and the Institute of Sport, Exercise & Health, said: “Though it may come as no surprise that becoming more active is beneficial for heart health, what’s new in this study is considering a range of behaviours across the whole 24-hour day. This approach will allow us to ultimately provide personalised recommendations to get people more active in ways that are appropriate for them.”

James Leiper, Associate Medical Director at the British Heart Foundation, said: “We already know that exercise can have real benefits for your cardiovascular health and this encouraging research shows that small adjustments to your daily routine could lower your chances of having a heart attack or stroke. This study shows that replacing even a few minutes of sitting with a few minutes of moderate activity can improve your BMI, cholesterol, waist size, and have many more physical benefits.

“Getting active isn’t always easy, and it’s important to make changes that you can stick to in the long-term and that you enjoy — anything that gets your heart rate up can help. Incorporating ‘activity snacks’ such as walking while taking phone calls, or setting an alarm to get up and do some star jumps every hour is a great way to start building activity into your day, to get you in the habit of living a healthy, active lifestyle.”

This research was funded by the British Heart Foundation.

*The studies were part of the Prospective Physical Activity, Sitting and Sleep (ProPASS) consortium. Heart health was measured using six outcomes: body-mass index (BMI), waist circumference, HDL cholesterol, HDL-to-total cholesterol ratio, triglycerides and HbA1c.

Alongside the echidna’s rediscovery, the expedition — a partnership between the University of Oxford, Indonesian NGO Yayasan Pelayanan Papua Nenda (YAPPENDA), Cenderawasih University (UNCEN), Papua BBKSDA, and the National Research and Innovation Agency of Indonesia (BRIN), Re:Wild — made many other remarkable finds. These included Mayr’s honeyeater, a bird lost to science since 2008; an entirely new genus of tree-dwelling shrimp; countless new species of insects; and a previously unknown cave system. This was despite the difficulties posed by extremely inhospitable terrain, including venomous animals, blood-sucking leeches, malaria, earthquakes, and exhausting heat.

One of the world’s most unusual mammals finally caught on film

Recorded by science only once in 1961, Attenborough’s long-beaked echidna is a monotreme: an evolutionarily distinct group of egg-laying mammals that includes the platypus. This echidna species is so special because it is one of only five remaining species of monotremes, the sole guardians of this remarkable branch of the tree of life. Echidnas are notoriously difficult to find since they are nocturnal, live in burrows, and tend to be very shy. Attenborough’s long-beaked echidna has never been recorded anywhere outside the Cyclops Mountains, and is currently classified as Critically Endangered on the IUCN Red List of Threatened Species

To give themselves the best chance of finding one, the team deployed over 80 trail cameras, making multiple ascents of the mountains, and climbing more than 11,000 meters (more than the height of Everest) in the process. For almost the entire four weeks that the team spent in the forest, the cameras recorded no sign of the echidna. On the last day, with the last images on the final memory card, the team obtained their shots of the elusive mammal — the first ever photographs of Attenborough’s echidna. The identification of the species was later confirmed by Professor Kristofer Helgen, mammalogist and chief scientist and director of the Australian Museum Research Institute (AMRI).

Dr James Kempton, a biologist from the University of Oxford who conceived of and led the expedition, said: ‘Attenborough’s long-beaked echidna has the spines of a hedgehog, the snout of an anteater, and the feet of a mole. Because of its hybrid appearance, it shares its name with a creature of Greek mythology that is half human, half serpent. The reason it appears so unlike other mammals is because it is a member of the monotremes — an egg-laying group that separated from the rest of the mammal tree-of-life about 200 million years ago.’

‘The discovery is the result of a lot of hard work and over three and a half years of planning,’ he added. ‘A key reason why we succeeded is because, with the help of YAPPENDA, we have spent years building a relationship with the community of Yongsu Sapari, a village on the north coast of the Cyclops Mountains. The trust between us was the bedrock of our success because they shared with us the knowledge to navigate these treacherous mountains, and even allowed us to research on lands that have never before felt the tread of human feet.’

A treasure trove of discoveries

Alongside searching for the echidna, the expedition carried out the first comprehensive assessment of invertebrate, reptile, amphibian, and mammal life in the Cyclops Mountains. With the support of local guides in the expedition team, the scientists were able to create makeshift labs in the heart of the jungle with benches and desks made from forest branches and vines.

By combining scientific techniques with the Papuan team members’ experience and knowledge of the forest, the team made a wealth of new discoveries. These included several dozens of insect species completely new to science and the rediscovery of Mayr’s honeyeater (Ptiloprora mayri), a bird lost to science since 2008 and named after famed evolutionary biologist Ernst Mayr.

An extraordinary finding was an entirely new genus of ground and tree-dwelling shrimp. ‘We were quite shocked to discover this shrimp in the heart of the forest, because it is a remarkable departure from the typical seaside habitat for these animals,’ said Dr Leonidas-Romanos Davranoglou (a Leverhulme Trust Postdoctoral Fellow at the Oxford University Museum of Natural History), lead entomologist for the expedition. ‘We believe that the high level of rainfall in the Cyclops Mountains means the humidity is great enough for these creatures to live entirely on land.’

The team also revealed a treasure trove of underground species, including blind spiders, blind harvestman, and a whip scorpion, all new to science, in a previously unexplored cave system. This astonishing discovery was made on one of the sacred peaks above Yongsu Sapari where the team had been given special permission to do research. People rarely tread here, and the striking cave system was chanced upon when one team member fell through a moss-covered entrance.

‘A beautiful but dangerous land’

Extremely challenging and, at times, life-threatening conditions were at the background of these discoveries. During one of the trips to the cave system, a sudden earthquake forced the team to evacuate. Dr Davranoglou broke his arm in two places, one member contracted malaria, and another had a leech attached to his eye for a day and a half before it was finally removed at a hospital. Throughout the expedition, members were beset by biting mosquitoes and ticks, and faced constant danger from venomous snakes and spiders. Making any progress through the jungle was a slow and exhausting process, with the team sometimes having to cut paths where no humans had ever been before.

‘Though some might describe the Cyclops as a “Green Hell,” I think the landscape is magical, at once enchanting and dangerous, like something out of a Tolkien book’ said Dr Kempton. ‘In this environment, the camaraderie between the expedition members was fantastic, with everyone helping to keep up morale. In the evening, we exchanged stories around the fire, all the while surrounded by the hoots and peeps of frogs.’

An enduring legacy

Rediscovering the echidna is only the beginning of the expedition’s mission. Attenborough’s long-beaked echidna is the flagship animal of the Cyclops Mountains and a symbol of its extraordinary biodiversity. The team hope that its rediscovery will help bring attention to the conservation needs of the Cyclops, and Indonesian New Guinea more generally, and they are committed to supporting long-term monitoring of the echidna. Key to this work is NGO YAPPENDA, whose mission is to protect the natural environment of Indonesian New Guinea through empowerment of Indigenous Papuans. As part of the expedition team, members of YAPPENDA helped train six students from UNCEN in biodiversity surveys and camera trapping during the expedition.

Dr Davranoglou said: ‘Tropical rainforests are among the most important and most threatened terrestrial ecosystems. It is our duty to support our colleagues on the frontline through exchanging knowledge, skills, and equipment.’

With the team having only sorted a fraction of the material collected on the expedition, they expect that the coming months will yield even more new species. The intention is to name many of these after the Papuan members of the expedition.

Besides animal specimens, the team also collected over 75 kg of rock samples for geological analysis, which was led by the expedition’s chief geologist, Max Webb, from Royal Holloway University, London. These could help answer many questions about how and when the Cyclops Mountains originally formed. The mountains are believed to have formed when an island arc in the Pacific Ocean collided with the New Guinea mainland about 10 million years ago. Combined with the biological findings, this geological work will help the team understand how the extraordinary biodiversity of the Cyclops came to be.

About Attenborough’s long-beaked echidna:

• Attenborough’s long-beaked echidna, Zaglossus attenboroughi, is not known to live outside the Cyclops Mountains and biologists still have many unanswered questions about its habitat and ecology.
• Attenborough’s long-beaked echidna is an EDGE species: a threatened species that has few close relatives on the evolutionary tree of life. They have evolved independently of other mammals for about 200 million years.
• The echidna has cultural significance for the people of Yongsu Sapari, who have lived on the northern slopes of the Cyclops Mountains for eighteen generations. When there is a conflict within the community, rather than fighting, there is a tradition that one party goes up into the Cyclops to search for an echidna while the other party goes to the ocean to find a marlin. Both creatures were so difficult to find that it would often take decades or a whole generation to locate them, but, once found, the animals symbolized the end of the conflict and a return to harmonious relationships in the village.
• The echidna has only been scientifically recorded once, when it was discovered by Pieter van Royen — a Dutch botanist — in 1961. Since then it has only been known from reports of sightings by the Yongsu Sapari community, and indirect signs during pre-expedition work in 2022. These signs, also observed during the expedition, included ‘nose pokes,’ holes in the ground left by echidnas after using their long, slightly curved snouts to probe for underground invertebrates.

About the expedition:

• The expedition was first proposed in 2019 by James Kempton.
• Academics who collaborated closely on the expedition include Dr James Kempton (University of Oxford), Dr Leonidas-Romanos Davranoglou (Oxford University Museum of Natural History), Madeleine Foote (University of Oxford), Dr Andrew Tilker (Re:wild, Leibniz Institute for Zoo and Wildlife Research), Dr Attila Balázs (Mendel University) and Dr Max Webb (Royal Holloway, University of London).
• Cenderawasih University (UNCEN) team members and partners include Dr Suriani Surbakti, Gison Morib and Heron Yando.
• Team members and collaborators from Indonesian NGO Yayasan Pelayanan Papua Nenda (YAPPENDA) include co-founders Iain and Malcolm Kobak, and Yali Kobak, Sampari Kobak, Ezra Daniel, Ruben Penggu, Melias Heluka, Yuanis Yalak and Sili Yalak.
• The team obtained permits from Papua BBKSDA and BRIN. They were also given permission from the community of Yongsu Sapari to conduct research and collect specimens on their land during the expedition.
• This rediscovery was made possible in part by the generous support of Merton College Oxford, the Royal Geographical Society, the Scientific Exploration Society, Re:wild, Royal Holloway University, the University of Oxford, Reconyx, and private donations from Derek Williams, Chris Peri, and other generous individuals.

About the Cyclops Mountains:

• The Cyclops Mountains are one of the most inhospitable regions in the world, being rugged, steep, and dangerous, and ranging from sea level to 1,970 metres. They are dominated by two main peaks — Gunung Rara and Gunung Dafonsoro. When sailing ten leagues from the range’s northern coastline in 1768, Baron Louis de Bougainville noted ‘les deux cyclopes’, from which the mountains bear their name.
• The Cyclops Mountains are a Key Biodiversity Area, meaning that they are critical to the persistence of biodiversity and to the overall health of the planet.
• The community of Yongsu Sapari have lived in the region for eighteen generations and hold the land as sacred. They believe it is stewarded by a female spirit who can take the form of a tree-kangaroo.

The research, published in PLOS Climate, is the first systematic review to explore how and why climate change-related concerns may be impacting reproductive decision-making.

The team examined 13 studies, involving 10,788 participants, which were conducted between 2012 and 2022, primarily in Global North countries such as the USA, Canada, New Zealand, and various European countries. They found that climate change concerns were typically associated with less positive attitudes towards reproduction and a desire or intent for fewer children or none at all.

Underpinning this finding were four key factors: uncertainty about the future of an unborn child, environmentalist views centred on overpopulation and overconsumption, meeting family subsistence needs, and political sentiments.

The term eco-anxiety has rapidly entered public discourse, describing a range of negative emotional responses including fear, worry, guilt and anger as a response to climate change. In 2018, a nationally representative New York Times survey found that 33% of childfree Americans aged 20-45 cited being “worried about climate change” as a reason for not having children.

Since then, ethical concerns about the quality of life children might have in a climate-changed future have been cited as the primary rationale for individuals choosing to not have children. However, the team behind this new study wanted to understand if there was an evidence base supporting the claims that climate change concerns were causing people to change their childbearing decisions, and if so, whether any other motivating factors, aside from ethical concerns, came into play.

The new analysis found that in 12 out of 13 studies, stronger concerns about climate change were associated with a desire for fewer children, or none at all.

One of the main reasons for this was the individual’s concern for their children in a world affected by climate change. However, the review also highlighted three other factors, with a primary concern being the ecological impact of reproduction, as people feared that having children would contribute to overpopulation and overconsumption in a world with already stretched resources.

To a lesser extent, two studies in Zambia and Ethiopia also found that participants desired fewer children to meet subsistence needs during periods of declining agricultural productivity.

Finally, individuals in another study had political considerations resulting in their decision to not have children — with two participants even reporting their refusal to have children as a method of ‘striking’ until systemic change was enacted.

Interestingly, these final two themes were also raised by some participants as reasons to have a greater number of children. For example, in Zambia, participants were concerned about their ability to support their family without the household labour provided by additional children helping with domestic work, as well as water and food collection.

Lead author, Hope Dillarstone (former MSc student at the UCL Institute for Global Health, said: “Recent media attention has been paid to a growing number of individuals factoring their concerns about climate change into their childbearing plans. However, we were concerned that public discourse may have oversimplified this relationship.

“Our first-of-its-kind study shows that there is a complex and intricate relationship between climate change and reproductive choices, with differences noted both within and between countries across the world.

“Our analysis shows that not only are many people concerned about their child’s welfare growing up in a world of uncertainty, but that they are also considering the impact of having children on the environment, their family’s ability to subsist, and their politics.

“Understanding why some people choose to adjust their reproductive decisions as a result of climate change may prove instrumental for shaping public policy, showing a need for collaboration among policymakers to incorporate local-level environmental concerns within national and international climate change, mental health and sexual and reproductive health policies.”

The team are now calling for more research at the intersection of climate change, mental health, and reproductive decision-making, particularly among highly affected Global South populations where current research is lacking.