A Braarudosphaera bigelowii cell magnified 1,000-fold.Credit: Tyler Coale
Researchers have discovered a type of organelle, a fundamental cellular structure, that can turn nitrogen gas into a form that is useful for cell growth.
The discovery of the structure, called a nitroplast, in algae could bolster efforts to genetically engineer plants to convert, or ‘fix’, their own nitrogen, which could boost crop yields and reduce the need for fertilizers. The work was published in Science on 11 April1.
New cellular ‘organelle’ discovered inside fruit-fly intestines
“The textbooks say nitrogen fixation only occurs in bacteria and archaea,” says ocean ecologist Jonathan Zehr at the University of California, Santa Cruz, a co-author of the study. This species of algae is the “first nitrogen-fixing eukaryote”, he adds, referring to the group of organisms that includes plants and animals.
In 2012, Zehr and his colleagues reported that the marine algae Braarudosphaera bigelowii interacted closely with a bacterium called UCYN-A that seemed to live in, or on, the algal cells2. The researchers hypothesised that UCYN-A converts nitrogen gas into compounds that the algae use to grow, such as ammonia. In return, the bacteria were thought to gain a carbon-based energy source from the algae.
But in the latest study, Zehr and his colleagues conclude that UCYN-A should be classed as organelles inside the algae, rather than as a separate organism. According to genetic analysis from a previous study, ancestors of the algae and bacteria entered a symbiotic relationship around 100 million years ago, says Zehr. Eventually, this gave rise to the nitroplast organelle, now seen in B. bigelowii.
Defining organelles
Researchers use two key criteria to decide whether a bacterial cell has become an organelle in a host cell. First, the cell structure in question must be passed down through generations of the host cell. Second, the structure must be reliant on proteins provided by the host cell.
By imaging dozens of algae cells at various stages of cell division, the team found that the nitroplast splits in two just before the whole algae cell divides. In this way, one nitroplast is passed down from the parent cell to its offspring, as happens with other cell structures.
A seagrass harbours a nitrogen-fixing bacterial partner
Next, the researchers found that the nitroplast gets the proteins it needs to grow from the wider algae cell. The nitroplast itself — which makes up more than 8% of the volume of each host cell — lacks key proteins required for photosynthesis and making genetic material, says Zehr. “A lot of these proteins [from the algae] are just filling those gaps in metabolism,” he says.
The discovery was made possible thanks to work by study author Kyoko Hagino at Kochi University in Japan, who spent around a decade fine-tuning a way to grow the algae in the lab — which allowed it to be studied in more detail, says Zehr.
“It’s quite remarkable,” says Siv Andersson, who studies how organelles evolve at Uppsala University in Sweden. “They really see all these hallmarks that we think are characteristic of organelles.”
Upgraded plants
Understanding how the nitroplast interacts with its host cell could support efforts to engineer crops that can fix their own nitrogen, says Zehr. This would reduce the need for nitrogen-based fertilizers and avoid some of the environmental damage they cause. “The tricks that are involved in making this system work could be used in engineering land plants,” he says.
“Crop yields are majorly limited by availability of nitrogen,” says Eva Nowack, who studies symbiotic bacteria at the Heinrich Heine University Düsseldorf in Germany. “Having a nitrogen-fixing organelle in a crop plant would be, of course, fantastic.” But introducing this ability into plants will be no easy feat, she warns. Plant cells containing the genetic code for the nitroplast would need to be engineered in such a way that the genes were transferred stably from generation to generation, for example. “That would be the most difficult thing to do,” she says.
“It’s both a pleasure and very impressive to see this work build up to what is certainly a major stepping stone in understanding,” says Jeffrey Elhai, a cell biologist at Virginia Commonwealth University in Richmond, Vriginia.
Every year for six years, Laureen Wamaitha hoped that her fields in Kenya would flourish. Every year, she’d see drought wither the crops and then floods wash them away. The cycle of optimism and loss left her constantly anxious, and she blamed climate change. “You get to a situation where you have panic attacks because you’re always worried about something,” she says.
Medical student Vashti-Eve Burrows, meanwhile, saw powerful hurricane Dorian rage through the Bahamas in 2019 and now she is fearful about the future of the country, an island archipelago that is vulnerable to sea-level rise and storms. “Will there even be a Bahamas in maybe 20 to 30 years?” she says.
Wamaitha and Burrows are part of a growing chorus of people speaking up about the impacts of climate change on mental health. Climate change is exacerbating mental disorders, which already affect almost one billion people and are among the world’s biggest causes of ill health. A global survey in 2021 found that more than half of people aged 16–25 felt sad, anxious or powerless, or had other negative emotions about climate change1. Altogether, hundreds of millions of people might be experiencing some type of negative psychological response to the climate crisis.
What happens when climate change and the mental-health crisis collide?
Scientists say the topic has been sorely neglected, but is leaping up the research agenda. “I’ve seen an explosion of research in the last five years for sure. That’s been very exciting,” says Alison Hwong, a psychiatrist and mental-health researcher at the University of California, San Francisco. The growing severity of heat, hurricanes and other impacts mean “it’s impossible to ignore”, she says.
Researchers want to unpick the many pathways by which climate change affects mental health, from trauma caused by hurricanes, floods, droughts and fires to ‘eco-anxiety ’— a chronic fear of environmental doom. Studies on methods that can help people prevent or manage these problems are also needed, although some work suggests that climate action and activism might help.
A seam of climate injustice is exposed by the research. Young people are likely to experience the greatest mental burden from climate change that older generations have caused. Groups of people that already experience poverty, illness or inequalities are most at risk of deteriorating mental health. “Climate change exacerbates already existing economic situations, where it’s the poorer people who are feeling even worse,” says Jennifer Uchendu, a researcher, climate activist and founder of SustyVibes, an environmental group based in Lagos, Nigeria.
Mental-health toll
The fact that climate change affects people’s mental health is not surprising: what’s new is the attention the issue is attracting — and the myriad ways that scientists are documenting its varied and sometimes shocking effects.
It is well known that extreme weather events and disasters can have an immediate traumatic impact — as well as “a long tail of mental-health conditions like post-traumatic stress disorder, anxiety, depression, substance abuse,” says Emma Lawrance, who studies mental health at Imperial College London. Also taking a mental-health toll in vulnerable countries are less sudden — but nonetheless devastating — disruptions caused by global warming’s impacts, such as forced migration, loss of livelihoods, food insecurity and community breakdown.
Research on how climate-change impacts, such as drought, affect mental health is growing.Credit: Simone Boccaccio/SOPA Images/LightRocket via Getty
There is evidence that directly experiencing higher temperatures can worsen mental health. A 2018 study of suicide data from the United States and Mexico over two or more decades showed that suicide rates rose by 0.7% in the United States and 2.1% in Mexico, with a 1 °C increase in average monthly temperature2. The researchers projected an extra 9,000–40,000 suicides by 2050 in the two countries if no action was taken against climate change. Other work has shown that higher temperatures are linked to poor sleep — which can in turn contribute to mental distress3.
Studies also suggest that people with existing mental illness are at greater risk of dying during extreme heat4, but “understanding why that is and what we can do to stop it is really unexplored”, Lawrance says. One potential explanation is that some psychiatric drugs can interfere with the body’s response to heat5.
Eco-anxiety goes global
Another striking field of research examines how the awareness of climate change and its impacts can lead to concern or distress, a phenomenon sometimes called eco-anxiety, eco-distress, climate grief or solastalgia (distress linked to environmental change). In a 2018 survey, 72% of people aged 18–34 said that negative environmental news stories affected their emotional well-being, such as by causing anxiety, racing thoughts or sleep problems (see go.nature.com/3vbbt7p). A 2020 survey6 in the United Kingdom found that young people aged 16–24 reported more distress from climate change than from COVID-19.
A few years ago, such ‘eco-emotions’ were sometimes dismissed as fretting of the ‘worried-well’ in high-income countries, Lawrance says. But research that shows the global reach of these feelings is challenging that view. The 2021 survey1 was the biggest so far on climate anxiety and included 10,000 children and young people in 10 countries. More than 45% of respondents said that worry about climate change had a negative impact on eating, working, sleeping or other aspects of their daily lives. Reports of climate change affecting people’s ability to function were highest in the Philippines, India and Nigeria and lowest in the United States and United Kingdom — contradicting the idea that eco-anxiety is just a rich-country problem (see ‘Climate anxiety around the world’).
Source: Ref. 1
For some, eco-anxiety might be linked to first-hand experience of climate-related devastation. The fact that young people in the Philippines reported some of the highest levels of worry was no surprise to John Jamir Benzon Aruta, an environmental psychologist at De La Salle University in Manila. In 2013, he saw first-hand the devastation and trauma caused in the Philippines by Typhoon Haiyan — one of the most powerful tropical cyclones ever recorded. “You see houses, communities devastated. You also see corpses all over the place,” he says. “Just witnessing the aftermath made me feel traumatized.”
But the 2021 survey documented widespread distress that went beyond those who were immediately affected by extreme climate events. Around 75% of respondents said that climate change made them think the future is frightening and 56% said that it made them think that humanity is doomed. People who felt their government was failing to act on climate issues were more likely to feel eco-distress.
Are we all doomed? How to cope with the daunting uncertainties of climate change
Climate change isn’t the first existential crisis that humanity has faced. But researchers point out that it is different from some other threats: it is happening now rather than being a future risk, such as a nuclear war; it’s affecting the entire globe at once; and many people feel angry that they have to bear the brunt of climate change that other people have caused.
Feelings of eco-anxiety are not necessarily a sign of dysfunction. “If you are under immediate threat, it is a realistic, rational, healthy survival instinct to react by being anxious or to experience fear,” says Elizabeth Marks, a clinical psychologist at the University of Bath, UK, and one of the survey’s lead authors. It could even be harmful to think of these feelings as a disorder. “If we think of it as a diagnosable condition, that risks placing the blame on the individual as having an unhealthy response,” she says. That said, some people might become so impaired by their eco-distress that they would benefit from psychological help.
Social media is being used to monitor negative feelings linked to climate change. In 2023, Kelton Minor, a research scientist at Columbia University’s Data Science Institute in New York and Nick Obradovich, a climate mental-health researcher at the Laureate Institute for Brain Research in Tulsa, Oklahoma, reported an analysis of more than eight billion posts on Twitter (now known as X) that appeared between 2015 and 2022 from people who had opted to share their geolocation data. (The analysis was part of a wider report on health and climate change7.) The researchers analysed the tweets for positive words (such as good, well, new and love) and negative ones (bad, wrong, hate and hurt), and linked them to climate data from the tweeters’ locations. Perhaps unsurprisingly, the team found that heatwaves and extreme rainfall increased negative feelings and decreased positive ones compared with control days without extreme weather in the same place and time of year. They also found that these negative reactions became worse over the years (see ‘Eco-anxiety on social media’).
Source: Ref. 7
Beyond the Western view
The full effects of climate change on mental health are hard to measure. A combination of factors, including the stigma around mental health and lack of access to health-care services, mean that many people with mental-health concerns go undiagnosed. When Wamaitha talked to her family in Kenya about how worried she was, they’d say: “It’s not a big deal, it’s part of life,” she says. Anxiety and depression are barely recognized as disorders in her region, she says. Mental-health services are scarce and older people just “think that you’re very sensitive” because they survived droughts in the past. In the 2021 survey, nearly 40% of young people worldwide said their concerns about climate change had been ignored or dismissed.
Climate change is also a health crisis — these 3 graphics explain why
Researchers are particularly worried that countries and regions that experience the harshest effects of climate change are where the least climate mental-health research has been done. In her studies, Uchendu found that most research was Western-centric. “Not a lot of people were talking about these issues in Africa,” she says. In 2022, she started the Eco-anxiety in Africa Project, which, in collaboration with the University of Nottingham, UK, has documented the emotional turmoil that heat and erratic weather has created for people living in five African cities.
Another question researchers have is how context and culture affect climate anxiety. Some studies have shown that “connection to country” — through cultural practices such as hunting and gathering food — is important to the mental health and well-being of some Aboriginal Australians and Torres Strait Islander communities8, says Michelle Dickson, who studies the mental health of Indigenous Australians at the University of Sydney, Australia. But rising sea levels, drought and bushfires threaten those practices. Tools used in health-care settings “rarely take into account the important cultural values that underpin Indigenous mental health”, says Dickson, who is a Darkinjung/Ngarigo Australian Aboriginal.
Dickson is now co-leading a project to empower communities to design their own climate action plans — allowing researchers to test whether doing this could improve people’s mental health.
Heatwaves — such as one that hit New Delhi in 2022 — can worsen mental disorders and are linked to increased negative feelings.Credit: Kabir Jhangiani/Pacific Press/LightRocket via Getty
Overcoming eco-distress
Addressing climate-fuelled mental-health conditions will be a colossal task when mental-health care globally is already poor: only around 3% of people with depression receive adequate treatment in low- and lower-middle-income countries, and 23% in high-income countries9. Lawrance says that many communities are finding their own ways to cope, but that the effectiveness of these efforts is rarely studied and shared. “There’s a massive gap around evaluation,” she says.
Some evidence suggests that taking action to combat climate change can help people to manage eco-anxiety. “There does seem to be an argument for supporting people to take collective action,” says Marks, such as joining campaign groups with like-minded people. It’s also important to “recognize that I feel this way because I care”, she says. “These climate emotions are actually something to be honoured and allowed, not pushed away.” Marks also suggests that some people who are feeling eco-distress limit the amount of time they spend ‘doom-scrolling’ through climate news.
Extreme heat harms health — what is the human body’s limit?
Researchers are starting to take collective action themselves. Last month, the Connecting Climate Minds project, one of the most ambitious research efforts in the field of climate-related mental health10, released a series of regional ‘research and action’ priorities, including, for example, to understand how climate change compounds the stress of wars, violence and disease epidemics in sub-Saharan Africa. The project includes researchers, policymakers and people with first-hand experience of climate change. Uchendu says that in one of the meetings, someone joining remotely was standing in flood water in their room. “It was mind-blowing,” she says.
Wamaitha, who along with Burrows is one of many people who shared their experiences with Connecting Climate Minds, has turned some of her concerns into action. Last year, after trying and failing to grow drought-resistant crops, she quit farming and is now working at a non-governmental organization in Bura, Kenya, that is focused on poverty relief. She is earning enough to study for a master’s degree in public health, and she raises awareness of global health on the social-networking site LinkedIn. But she is anxious about the future and worries about whether to have children. “I don’t think I am in a good environment to be able to bring kids into this particular place,” she says. “That is the saddest thing when I think about it.”
Burrows, who is studying medicine at the University of the West Indies in Saint Augustine, Trinidad and Tobago, says she chooses to be positive and does small things to help the environment, such as walking instead of driving. She says that she prays that wealthy countries and companies “will really, truly understand what is happening and not just say smooth words to try to pacify us in the moment”. They should act to “help the smaller countries and the world at large”, she says.
“It makes your heart want to skip a beat — and you cannot really describe it to someone who hasn’t experienced it in person,” said Lynnice Carter on Monday, after watching the total solar eclipse that crossed North America. Carter, a retired educator from Blue Springs, Mississippi, travelled about 230 miles (370 kilometres) to Heber Springs, Arkansas, to see the much-anticipated celestial event from the ‘path of totality’, the track from Sinaloa, Mexico, to New Brunswick, Canada, where the Moon completely blocked the Sun’s face.
Carter wasn’t alone in making time for the eclipse. Millions viewed the phenomenon from watch sites along the path of totality, where people picnicked, listened to music and donned inexpensive eclipse glasses that helped them to see the main event safely. Some researchers celebrated in their own way — by chasing the eclipse in aeroplanes or with high-resolution cameras on the ground. Although more than a few were disappointed by cloud-filled skies in some locations, others were dazzled by the fiery activity they could see within the Sun’s outer atmosphere, or corona. Here, Nature chats with casual observers and solar researchers alike to hear about what they saw — and what they learnt.
Crowds gathered on the National Mall in Washington DC to watch the eclipse on 8 April.Credit: Kent Nishimura/Getty
Some marveled over the science that they could see by eye:
The last time a total solar eclipse passed over North America was 2017, but it was during a solar minimum — a period of weak activity occurring every 11 years on the Sun when there are fewer sunspots and plasma eruptions. This time around, viewers experienced a solar maximum, when structures in the Sun’s corona are at their most fiery. “This one was just so much brighter, and so much prettier! It was just awesome,” said Alice Beverly, who journeyed from Tulsa, Oklahoma, to Heber Springs to watch.
Astronomers have long observed ‘shadow bands’ during total solar eclipses. These as-yet-unexplained phenomena are alternating segments of light and dark that pass over the ground in the moments just before and after the full eclipse. One hypothesis is that they are caused by turbulence in the atmosphere as the sliver of light from the eclipse passes through. Viewers like Kelley Boyett were particularly excited to see them. “I researched a lot, and brought a white posterboard to see the little crescents and shadow bands. The coolest thing was the shadow banding — it looked like racing water across the posterboard.” Boyett, a postal office worker, travelled from Bronson, Texas, to a watch site in Heber Springs for the festivities.
Others made the most of a cloud-covered sky:
“I was disappointed, not so much for myself — since it was my fourth eclipse — but for my sister and her husband for whom this was going to be the first time,” said Jim Klimchuk, a solar physicist at NASA Goddard Spaceflight Center in Greenbelt, Maryland, who travelled to San Antonio, Texas, to view the eclipse. “During totality, it got dark. [Automatic] streetlights and building lights came on. And then for about five seconds, we could see the corona [amid the clouds]. No details at all, but we could see the brightness around the disk. That was very exciting.”
Marcel Corchado-Albelo, a solar physicist at the University of Colorado Boulder, spent the week leading up to the eclipse in Eagle Pass, Texas, visiting various schools as part of a public-outreach programme. On the morning of the eclipse, the approximately 400 people that gathered to watch at a student activity centre were “very nervous”, Corchado-Albelo said. Clouds loomed. The sun would peek from behind the clouds occasionally, and every time, “people were screaming”, he added. In the end, though, their fortune turned — the clouds parted as totality approached. And everyone screamed again.
Bright red spots called prominences appeared along the solar disk during the total eclipse.Credit: Sumeet Kulkarni/Nature
Researchers grabbed data that they can’t wait to analyse:
One thing many observers were mesmerized by during the eclipse was the appearance of bright red spots protruding from the solar disk. These are called prominences — worm-like filaments of plasma. One in particular, along the southern edge of the Sun, “looked like it was potentially lifting off”, said Amir Caspi, a solar physicist at the Southwest Research Institute in Boulder, Colorado, who travelled to Dallas, Texas, to watch the eclipse with his family.
Total solar eclipse 2024: how it will help scientists to study the Sun
Caspi leads 35 teams of citizen scientists that captured images of the eclipse from stations distributed along the path of totality. By recording images using identical telescopes and cameras, the project — called Citizen Continental-America Telescopic Eclipse, or Citizen CATE — aims to observe how structures within the corona evolve over time.
“A majority of our teams were able to get great data. But there were a few that got clouded out completely,” Caspi said. The citizen scientists are currently uploading their data — as much as tens of gigabytes per site — onto servers where it will be analysed to make an hour-long ‘film’ of the corona. Caspi expects the consolidated results to be available within the next month.
Another scientist closely watching structures in the corona was Cooper Downs, an astrophysicist at research and product-development firm Predictive Science in San Diego, California. He is part of a team that has spent the past few weeks predicting where in the corona features such as streamers will appear, with the idea of honing the firm’s solar model. Streamers are densely packed spikes of plasma pointing away from the solar core. “My initial impressions were pretty positive,” Downs said. “I saw these two streamers, one was really bright on the top left and another to the south.” Downs is now comparing the simulations generated before and during the eclipse with images taken by astrophotographers. “When you do the detailed comparison, you start seeing some discrepancies”, which should motivate revisions to the model, he told Nature.
A dairy worker in Texas has become infected with a strain of avian influenza similar to that infecting dairy cattle in several US states.Credit: Adam Davis/EPA-EFE/Shutterstock
Researchers are closely monitoring the spread of a worrisome strain of avian influenza to cattle — and one person — at farms in six US states.
These infections represent the first widespread outbreak of bird flu in cows. The outbreak is concerning because humans frequently come into contact with cattle on farms, giving the virus ample opportunity to spread to people, says Daniel Goldhill, an evolutionary virologist at the Royal Veterinary College in Hatfield, UK.
Health officials have said that the overall threat to people remains low, for now, but they are watching the situation unfold closely. “There’s always a worry that viruses will surprise us,” Goldhill says. “We don’t know what they’ll do next.”
Scientists are scrambling to assess how well candidate vaccines and antiviral drugs will work against the circulating strain and to update diagnostic kits for identifying infections in people quickly. They are also trying to understand whether the cows were infected by birds or another source, and are on alert for any changes in the situation that could raise the risk for people.
“There are a lot of questions and, so far, not a lot of answers,” says Florian Krammer, a virologist at Icahn School of Medicine at Mount Sinai in New York City.
Where was the virus found previously, and what’s happening now?
In 1996, the influenza strain called H5N1 was first detected in birds in China. It has been spreading ferociously in birds since 2021, killing hundreds of millions of domestic and wild birds around the world. It has also occasionally infected mammals, including seals and bears, which have become “accidental hosts” of what is mostly an avian virus, says Kanta Subbarao, director of the World Health Organization (WHO) Collaborating Centre for Reference and Research on Influenza in Melbourne, Australia.
Bird flu outbreak in mink sparks concern about spread in people
In the past two weeks, health officials have detected H5N1 in cows from 16 herds across six states — a number that is likely to increase as US surveillance is stepped up. Researchers have previously documented1 sporadic infections of cows with flu viruses closely related to H5N1, but no widespread outbreaks had been detected until now.
The more mammalian species the virus infects, the more opportunities it has to evolve a strain that is dangerous to humans, Goldhill says. One dairy worker in Texas has been infected, but the US Centers for Disease Control and Prevention (CDC) reports that the person is recovering. The worker’s only symptom was eye inflammation, and viral levels in their nose were low, suggesting that they don’t have a respiratory infection, according to the CDC.
The virus infecting the worker is closely related to the strains found in dairy cattle in Texas, with one notable distinction: the worker’s variant has a mutation that is linked to more-efficient spread in mammals. Goldhill says the presence of the mutation in the human sample was not surprising; it has appeared many times, including in foxes2 and cats3 infected with H5N1.
Is the virus spreading between cows, and why does that matter?
A key question for researchers is how the cows are getting infected. The answer will be important for controlling H5N1’s spread to other farms and people. “This is a controllable situation, we just have to understand how this virus is getting around,” says Richard Webby, a virologist at St. Jude Children’s Research Hospital in Memphis, Tennessee.
Avian flu freezes coastal bird research in South Africa
Of particular interest is whether the virus is passing from infected cows to uninfected ones, because that would suggest the virus has become more adept at transmission in mammals. Given that the virus has been detected at several farms across the United States, epidemiological data make it “pretty clear now we’re seeing cow-to-cow spread”, and that wild birds are not necessarily involved in viral spread in the farms, says Webby. But there aren’t enough viral sequences of animals infected later in the outbreak for genomic data to confirm cow-to-cow spread, he says.
If the virus is spreading between cows, it will be important to work out precisely how, Webby says. Evidence so far suggest that virus levels are highest in the animals’ milk, according to a report in Science. That suggests that H5N1 might not be spreading between cows through the air, a transmission pathway that would be difficult to control and could allow for relatively quick spread, Webby says. If cows are becoming infected by touching contaminated surfaces, such as milking machines, the virus would be transmitted more slowly than if it is airborne.
Gathering evidence to address these questions could help to answer why infections have only recently cropped up in cattle, and only in the United States, despite the virus’s global spread in the past few years. Marion Koopmans, a virologist at Erasmus University Medical Center in Rotterdam, the Netherlands, wonders whether there is something unique about how cattle are kept in the region, for example, or whether the virus has gained new abilities to persist in the environment. Addressing these questions will offer insights into how widespread bird-flu infections could be in cattle globally, she says. It will be important for health officials outside the United States to start looking for evidence of overlooked outbreaks, Krammer says.
What would increase concern among researchers?
Scientists say that, although bird flu is unlikely to spread widely in people, they are closely monitoring samples of H5N1 globally for mutations known to signal that it is becoming better at spreading in mammals. The virus has not spread widely in humans in part because it can’t readily enter the cells that line the nose and mouth. But it would be problematic if the virus developed mutations that would help it to gain entry to these cells, Goldhill says.
Krammer says he would look specifically for changes to the section of the viral genome that encodes a type of enzyme known as a polymerase. A portion of this enzyme is known to be “a hotspot for adaptation to mammals”. Researchers are also looking out for mutations that would make the strain less susceptible to antiviral drugs, says Webby.
The animal that no virologist wants to see a flu outbreak in, is the pig. Pigs host many influenza A viruses, making them a ‘mixing vessel’ in which strains of avian and mammalian viruses can mix and match and become more efficient at transmitting to people, says Krammer.
What do we know about how well existing vaccines and drugs will work against this strain?
The WHO maintains a list of candidate vaccines that provide protection against H5N1 and that could be mass-produced. And some countries, including the United States, maintain a small stockpile of vaccine doses should they need to vaccinate at-risk populations, such as front-line workers.
The CDC has reported that the viral strain isolated from the infected person is closely related to two strains targeted by a candidate vaccine. Webby says that his team has confirmed in laboratory studies that the WHO vaccines can protect against viral samples collected from cows early in the outbreak, and they will continue to test new samples as the outbreak progresses. Specifically, the vaccine includes antibodies produced against a human H5N8 virus isolated in Russia and an avian H5N1 virus isolated in the United States. They can “recognize this cow virus very, very well”, says Webby.
It would be useful to get more information on how much immunity these candidate vaccines produce against the circulating strain, especially because people don’t have pre-existing protection against H5N1 and closely related viruses, says Subbarao.
The church at Ntarama, a 45-minute drive south of Rwanda’s capital, Kigali, is a red-brick building about 20 metres long by 5 metres wide. Inside are features seen in Catholic churches around the world: pews for congregation members, an altar, stained-glass windows and a cross adorning the entrance. Then there are the scars of the unimaginable: piles of blood-stained clothing hanging along the walls and glass cabinets containing more than 260 human skulls, many fractured or shattered, some with rusted weapons still penetrating them. Nearby, wooden sticks and roughly carved clubs lean against the altar.
Ntarama is the site of one of the many massacres that occurred during the 1994 genocide against the Tutsi in Rwanda — one of the worst atrocities of the late twentieth century. Starting on 7 April that year, in 100 days of horrifying violence, members of the Hutu ethnic group systematically killed an estimated 800,000 Tutsi — or more than one million, according to the Rwandan government and other sources. The killers ranged from militias to ordinary citizens, with neighbours turning on neighbours. Many moderate Hutu and some of the Twa minority group were also killed.
Rwanda: From killing fields to technopolis
More than 5,000 Tutsi were murdered at Ntarama, among them babies, children and pregnant women, many of whom were raped before they were killed, says Evode Ngombwa, site manager at the Ntarama Genocide Memorial, one of six sites in Rwanda that commemorate the atrocity. “People used money to bribe the perpetrators so that they could choose the way of being eliminated. Instead of killing them with machetes, they could choose to be shot,” says Ngombwa as he walks me through the church. With more remains being found each year, about 6,000 people are now buried there in mass graves.
This month, Rwanda and the world begin commemorations to mark 30 years since the start of this atrocity. The genocide is now one of the most studied of its kind. Researchers from social and political scientists to mental-health specialists, geneticists and neuroscientists have investigated the event and its aftermath in a way that hadn’t been possible for previous atrocities.
This work is especially important now in light of violent crises in several parts of the world, including in Ukraine, Israel and Gaza, Sudan and the Democratic Republic of the Congo. Although there is debate about whether these conflicts meet the definition of genocide, some share similar characteristics. Research conducted into atrocities such as the genocide in Rwanda can help to inform responses and longer-term approaches to healing.
Despite the difficulties of these studies, researchers say that they are working towards developing a theory of genocide and the conditions that spur mass violence. They are providing guidance for first responders, as well as those involved in peacebuilding and supporting survivors of other systematic mass murders and of war. Some of their approaches have been used in other conflicts. And the research on Rwanda is offering lessons for how scholars can improve studies of similar events.
At a vigil in April 2019, young Rwandans commemorate the 25th anniversary of the genocide.Credit: Yasuyoshi Chiba/AFP/Getty
“Genocide studies are important,” says Phil Clark, an international-politics researcher at SOAS, part of the University of London, who has studied Rwanda for more than two decades. “If we can start to understand why and how genocides happen, and especially if we can compare genocides across the world, we should ideally be able to build a general theory of how these terrible events are even possible.”
One of the lessons emerging from Rwanda is the importance of involving — and supporting — local researchers, whose work, language skills and access to traumatized communities can be essential for understanding the roots of violence and the best techniques for reconciliation. This can be difficult — in Rwanda’s case because the genocide wiped out almost its entire academic community. Now, through programmes aimed at elevating local scholars’ voices, their work is finally reaching a wider audience.
Patterns of violence
Before 1994, the field of genocide studies was dominated by the Holocaust — the systematic killing of 6 million Jewish people by Nazi Germany during the Second World War. “It’s only in the last 20 years that other genocides have entered the discussion,” says Clark. But research on Rwanda didn’t start immediately. “It was only maybe 10–15 years after the genocide that scholars started to really interrogate this question of what drove hundreds of thousands of everyday civilians to participate in mass violence.”
Scholars say that it’s important not to forget the genocide’s strong link to colonialism in Rwanda. In the early 1900s, Belgian colonizers began formally dividing Rwandan people into social classes: Hutu, Tutsi and Twa. Designations were often based on pseudoscientific ideas, including phrenology and arbitrary observations, such as how many cattle a person owned. Ethnic tensions between Hutu and Tutsi intensified over the decades and several massacres of Tutsi occurred in the period leading up to 1994. This set the stage for a descent into genocide — a legal term that is defined by the perpetration of certain crimes that are intended to destroy a particular group, and is codified by the United Nations’ 1948 Genocide Convention.
Each genocide is unique, says Timothy Longman, a political scientist at Boston University in Massachusetts, who first went to Rwanda in 1992 and returned in 1995 as a researcher with Human Rights Watch, an international non-governmental organization that was one of the first to investigate the event. “But there also are some common patterns,” he says. Researchers can learn a lot from studying cases such as Rwanda, the Holocaust and other genocides, he says. “It helps you to prevent violence from happening elsewhere.”
One of the main scientific contributions of studies so far are the insights from mental-health researchers, many of whom were on the ground in the immediate aftermath. Over the past three decades, they have documented the initial trauma of an entire country and the slow recovery of survivors and their children, many of whom are prone to being retraumatized. With few available resources, Rwanda had to build up its mental-health services and it has gained unique experience in responding to the atrocity’s aftermath.
Source: Y. Kayiteshonga et al. Rwanda Mental Health Survey 2018 (Govt of Rwanda, 2021).
At the Rwanda Biomedical Centre (RBC) in Kigali, the nation’s main health organization, Jean Damascène Iyamuremye recalls his experience of 1994. “I witnessed everything that happened.” Iyamuremye was a 28-year-old training to be a medical assistant, but the genocide spurred him to specialize in mental health. He was among the first medical staff supporting survivors. “We were like firefighters,” says Iyamuremye, who is now director of the psychiatric unit in the RBC’s mental-health division, which oversees countrywide services.
The first care came mostly from outsiders. Non-governmental organizations provided psychological interventions such as counselling for the survivors, most of whom had experienced physical violence as well as unimaginable emotional trauma from the mass killings they’d witnessed. After the genocide, 96% of Rwandans experienced post-traumatic stress disorder (PTSD) as a result of the extreme violence1.
It took time for the country to develop its own mental-health resources. In 1994, Rwanda had only one psychiatrist, Naasson Munyandamutsa, who was living in Switzerland at the time and lost most of his family in the violence. Munyandamutsa returned quickly to Rwanda to work at the country’s sole psychiatric hospital, where he began training mental-health responders and psychiatrists.
While Munyandamutsa, who died in 2016, led the training of practitioners in Rwanda, many Rwandans went overseas to train. But about half didn’t return, says Iyamuremye.
It wasn’t until 2014 that Rwanda had its own school of psychiatry, at the University of Rwanda in Kigali. Even now, the country has only 16 psychiatrists, 13 of whom graduated from that facility, to serve a fast-growing population of 13.5 million.
Evidence-based interventions for survivors, such as counselling, cognitive behavioural therapy and medication, have continued — but people still bear significant mental scars from their experiences (see ‘Complex consequences’). In Rwanda’s most comprehensive mental-health survey yet, conducted by the RBC in 2018, about 28% of genocide survivors reported PTSD symptoms, compared with 3.6% of the general population (see ‘Trauma’s long shadow’).
Sources: Ref. 1; A. Eytan et al. Int. J. Soc. Psychiatr.61, 363–372 (2015); Y. Kayiteshonga et al. Rwanda Mental Health Survey 2018 (Govt of Rwanda, 2021).
Long-term support for survivors is important, because many can become retraumatized. For example, media reports about violence in nearby parts of the Democratic Republic of the Congo can bring back memories, says Iyamuremye. And yearly commemorations that last from April to July, called kwibuka in the national language, Kinyarwanda, bring challenges. “You will see people who fall, who are agitated, who cry” because what they experience triggers a memory, says Iyamuremye.
For this year’s commemorations, the RBC and other organizations have trained 5,000 responders around Rwanda to support distressed people. But Iyamuremye and his colleagues have learnt that the commemorations themselves can be therapeutic: they give people the opportunity to talk about their trauma and support each other.
And researchers have found that even people who weren’t alive during the genocide are suffering. “Intergenerational trauma is a challenge and a reality in Rwanda. This needs to be targeted with strong, strong interventions,” says Iyamuremye.
Trauma across generations
At the Rwanda Military Hospital on Kigali’s outskirts, Léon Mutesa, a physician and, for a long time, the nation’s only geneticist, is seeing mothers and babies at his paediatric clinic. Mutesa, who directs the Center for Human Genetics at the University of Rwanda, was the first to explore the effects of Rwandans’ trauma at the genetic level. As an undergraduate in the early 2000s, Mutesa saw that children born to women who had been pregnant in 1994 also exhibited signs of trauma. During commemorations, the children expressed symptoms such as PTSD, depression, anxiety and hallucinations from an event that they hadn’t experienced.
Inspired by studies of Holocaust survivors2, Mutesa devised a small study to investigate whether the trauma from the genocide had left epigenetic marks on individuals’ DNA through the addition of methyl groups to certain regions.
In that study3, conducted in 2012, Mutesa’s team sampled blood from women who were pregnant in 1994 and their children, as well as control participants who weren’t exposed to the genocide. The team found evidence that genocide survivors and their children bore similar epigenetic marks on certain sections of DNA.
Geneticist Léon Mutesa has studied DNA markings in genocide survivors and their children.Credit: AP Photo
Hoping to start a larger study, Mutesa collaborated with Stefan Jansen, a Belgian neuroscientist who had been at the University of Rwanda since 2011. In 2017, the pair, with US partners, won funding from the US National Institutes of Health to extend their investigations.
“We found that those mothers who were exposed had around 24 differentially methylated regions, which is really high compared to the control group,” says Clarisse Musanabaganwa, a medical research analyst at the RBC who was part of Mutesa and Jansen’s team. The team found that many of the methylated regions were the same in mothers and in the children that they were pregnant with during the genocide4,5. The research indicates a way in which trauma can transcend at least one generation, and the researchers suggest that lasting effects could be passed down through multiple generations through a mechanism of epigenetic inheritance.
But the idea of multigenerational epigenetic inheritance is controversial. Many scientists are sceptical about whether methylation marks on DNA in humans can be inherited.
“I’m not aware of any really convincing case where the transgenerational inheritance — inheritance of methylation patterns — has been demonstrated,” says Timothy Bestor, a molecular biologist in Gaylordsville, Connecticut, who holds an emeritus position at Columbia University in New York City.
But Mutesa and Jansen are seeing some practical benefits of their work. When the scientists discussed with study participants that their trauma could influence their children, they saw the participants’ resilience increase. For instance, if survivors’ children were performing poorly in school, parents now saw a possible reason. The researchers could support children with psychotherapy. “They could now understand why this is happening to their children,” says Mutesa.
Biological studies also have a broader importance, says Jansen. “We want to evidence that, and have that recorded for history: this is what happened.” The evidence helps to fight genocide denial, he says.
Beyond the epigenetic analyses, Jansen and his colleagues have strengthened methodological approaches to studying community mental health in Rwanda. These studies have informed research on conflicts elsewhere, such as in Iraq, says Jansen.
Lessons from Rwanda
The bulk of the research on the genocide in Rwanda has been in the social sciences and humanities — studying topics from reconciliation, peacebuilding and justice to the role of ethnic designations in a society after conflict. For instance, neighbouring Burundi, which experienced ethnic violence in a roughly decade-long civil war that started in 1993, chose to recognize ethnicities, whereas the Rwandan government eradicated formal ethnic distinctions after the genocide. In a global study6 that compared countries that had taken either approach after war, those that chose to recognize ethnic groups scored better on societal markers such as peace, democracy and economics.
Some of the skulls of people who were killed while seeking refuge at Ntarama in April 1994 are on display in the church.Credit: Nichole Sobecki/VII/Redux/eyevine
The growing literature on genocides has revealed that they have huge ramifications that extend well beyond the borders of the countries where they happen, say researchers.
“In terms of the scale of violence, the scale of disruption, the scale of suffering, they are enormously important events,” says Scott Straus, a political scientist at the University of California, Berkeley.
Studies had been conducted almost exclusively by Western scholars — although that’s starting to change. In the past decade, as discussions of decolonizing research began in academia, Clark started working with the UK-based Aegis Trust, which runs the Kigali Genocide Memorial. An analysis by Clark and his colleagues of 12 relevant journals showed that from 1994 to 2019, just 3.3% of studies on post-genocide Rwanda had been done by scholars from the nation (see go.nature.com/3qapae7). In 2014, with funding from the Swedish and UK development agencies, the Aegis Trust launched the Research, Policy and Higher Education (RPHE) programme, an effort to invite Rwandan scholars to submit research proposals.
“There are cultural nuances that have to be told by the very people that go through those experiences,” says Sandra Shenge, who is director of programmes at the Aegis Trust based at the Kigali Genocide Memorial, and former RPHE manager. The grants were modest — just £2,500 (US$3,150) each. But the response to the programme was amazing, says Shenge. The first call received more than 500 applications.
The aim was for Rwandan scholars to share their stories and for external researchers to provide support with advice on methodology, publishing and how best to disseminate results. These studies are collected in a resource called the Genocide Research Hub.
“The RPHE was the best thing that happened to Rwandan researchers,” says Munyurangabo Benda, a philosopher of religion at the Queen’s Foundation, an ecumenical college in Birmingham, UK. “It is the only space where Rwandan research has begun to have impact on policy.”
Photos of lives cut short by the 1994 killings are on display at the Kigali Genocide Memorial.Credit: Chris Jackson/Getty
Benda’s research7,8,supported by the RPHE, has already influenced policy. His project examined a state programme on reconciliation that had grown from a grassroots effort. His work exploring the guilt felt by children of Hutu people was inspired by the experience of his young nephew in Denmark, whose father was a Hutu. One day, his nephew’s class was studying the genocide in Rwanda and classmates asked him: “Were your family killers or survivors?” His nephew was traumatized.
The research helped to shape programmes that the Rwandan government offers for students of various ages, says Benda.
The RPHE programme also holds lessons for making the broader academic community more inclusive. According to Clark, “the problem is with journal editors and peer reviewers”, who often dismiss work from Rwanda and other countries because of preconceived ideas of quality based on where the work has been produced.
A theory of genocides
Another author whose work has been published through the Genocide Research Hub is sociologist Assumpta Mugiraneza9. From a hilltop office with views over Kigali, Mugiraneza runs an organization called the IRIBA Centre for Multimedia Heritage. Iriba means ‘source’ in Kinyarwanda, and the centre collects audio-visual archives of testimonies from the genocide and of life before 1994.
Mugiraneza says she started this work to capture Rwanda’s heritage, which was in danger of disappearing. The country’s historic oral traditions were eroded by colonization, which imposed reading and writing. As a result, Rwanda’s history is written without this richer heritage, says Mugiraneza. “Let’s go back to what we have in common: sound and image.”
Sociologist Assumpta Mugiraneza runs the IRIBA Centre for Multimedia Heritage.Credit: Carl De Keyzer/Magnum Photos
The centre, she says, is designed “to support the process of reappropriating the past”. To think about genocide, “we must dare to seek humanity where humanity has been denied”.
IRIBA’s work is extraordinary, says Zoe Norridge, who studies African literature and culture at King’s College London. “That’s the kind of work that can be done by Rwandan scholars in depth in a way that I think outsiders never really reach.”
Researchers agree that studying atrocities is a difficult undertaking. “Research involves talking to survivors who have endured unimaginable horror and putting yourself in the position to listen and hear and be empathetic,” says David Simon, who directs the Genocide Studies Program at Yale University in New Haven, Connecticut.
Still, scholars say that, through these studies, they are developing a broader understanding by identifying similarities among different genocides. These include what happened in Rwanda and the Holocaust, as well as in the genocide of the Armenian people in 1915 and of the Herero and Nama people in what is now Namibia, starting in 1904.
All of them shared common ingredients, according to researchers. The first is racializing members of society and identifying an ‘inferior’ segment of the population to be eliminated. Other factors include planning organized massacres and spreading an ideology across a whole society. The last component is the involvement of the state and its institutions, such as religious establishments and schools, as participants in the killings, says historian Vincent Duclert, who is France’s leading scholar on the 1994 genocide.
Studies in Rwanda helped to solidify the theory, says Duclert. “This pattern was really reinforced by the genocide of the Tutsi.”
Another lesson from Rwanda, say researchers, is the need to seek multiple narratives — from people inside and outside the region, and from perpetrators as well as survivors. “In 1994, and in the years immediately after, there was a very simple narrative about the Rwandan genocide being driven by ancient tribal hatreds, and that it almost explained itself away,” says Elisabeth King, who studies peace, conflict and education at New York University. Scholars, says King, have a crucial part to play in developing nuanced accounts of the complex political and social factors that underlie these events. Those explanations, in turn, can help researchers and others to understand why people commit atrocities, and could ultimately contribute to developing approaches that help to stop them.
Belongings of people killed at Ntarama, including identity cards, which showed people’s ethnicities.Credit: Ben Curtis/AP Photo/Alamy
Straus is also studying causal factors shared by different genocides, and why some conflicts that have the ingredients of genocide do not escalate into them — violence in Mali in the 1990s and Côte d’Ivoire in the early 2010s are two examples10.
Some scholars say that studying genocides can yield many benefits, but that stopping them from happening is ultimately a political matter decided by nations and international bodies.
Aggée Shyaka Mugabe, acting director of the Centre for Conflict Management at the University of Rwanda, is pessimistic about the extent to which studying genocides can ultimately stop them. “What we publish informs public policies,” says Mugabe, who studies transitional justice and peacebuilding11. But that doesn’t translate into something everyday people can understand, he adds.
Some have also raised concerns that it can be difficult for Rwandan researchers to study topics related to genocide freely, because of pressure from the government to follow a certain narrative on politically sensitive issues. But Mugabe rejects the idea that research done inside Rwanda isn’t useful because of the perceived political pressure. “Some of my papers have a critical aspect,” he says. “There is no police trying to tell me what to write or what not to write.”
Survivors’ stories
One concern among scholars is that there has been less focus on elevating the voices of survivors, given that judicial inquiries focused so much on perpetrators.
Jean Pierre Sagahutu is one of those survivors. “I can’t tell you everything that happened in 1994 because it’s too hard,” he says. “I remember everything as if it were yesterday,” he says. “It’s as if I’m seeing it now.” Sagahutu survived by hiding in a septic tank for more than two months. In that time, his father and mother were killed. Originally trained as an accountant, Sagahutu began driving taxis after the genocide and worked as a ‘fixer’ for people visiting the country for projects, often interviewing génocidaires, the perpetrators of the violence against the Tutsi. “Sometimes my ears hurt, but it made me understand what the people had really done. And in the end, it became therapy.”
In 2019, he met Duclert, whom French President Emmanuel Macron had commissioned to conduct a study on France’s role in the genocide, owing in part to the French government’s support of Rwanda’s pre-genocide Hutu government. In 2021, Duclert presented his 1,000-page report12, which concluded that French authorities saw evidence of a coming genocide as early as 1990 but didn’t take enough measures to stop it.
Sagahutu takes positives from Duclert’s report, but says that scholars have more work to do: “I’d like researchers to try to learn, to really dig and find out what the real causes of the genocide were,” he says. “Because the genocide was not a game of chance, it was something that had been well prepared for a long time.”
One of the most important tools for researchers is recording the testimony of survivors, says Yolande Mukagasana, who wrote the first comprehensive survivor’s account of the genocide, which was published in French in 199713. Mukagasana, now 69, has remained a writer and activist, and is determined to keep the memory of the genocide against the Tutsi alive. As part of her work, she has talked to survivors of other genocides and mass killings and she sees similarities in these events, regardless of where in the world they happened. “The ideology of hate is the same,” she says, adding that survivors experience “exactly the same suffering”.
Yolande Mukagasana wrote the first comprehensive account of the genocide by a survivor.Credit: Chris Schwagga
In 1994, Mukagasana was a nurse and a successful Tutsi woman who ran her own health clinic. When the killings started, Mukagasana and her husband separated, hoping that their three children would be safer with him. During the months of the genocide, in which she was protected by Hutu people, she began writing her testimony on scraps such as cigarette packets.
Mukagasana’s husband and children were killed. When she reached safety at the Hôtel des Mille Collines — featured in the 2004 film Hotel Rwanda — one of the first things she wanted was a pen and paper to record what had happened.
At IRIBA, Mugiraneza knows the importance of documenting the events of 1994. But she also strives to collect evidence of life before. “The marriages. The love songs. The buildings, the proverbs, the stories — all those things that are so magnificent but are seen as trivial.”
“People negotiate a space for thinking, for giving meaning to life — which allows us to better understand what extermination and death are.”
Researchers in North America are gearing up for their chance to observe the Sun’s corona — its wispy outer atmosphere — like never before. Normally hidden to the naked eye by the Sun’s glare, the corona will be visible to millions from Sinaloa, Mexico, to Newfoundland, Canada, when the Moon blocks the solar disk during the total eclipse on 8 April. Importantly, the event coincides with the solar maximum — a period of extreme activity that occurs every 11 years. During this time, the Sun’s magnetic fields intensify, creating sunspots, fiery loops of plasma and exciting structures in the corona.
The Sun’s outer atmosphere, named for its crown-like appearance, is one of astronomy’s biggest unsolved mysteries, says James Klimchuk, a solar physicist at the NASA Goddard Spaceflight Center in Greenbelt, Maryland. For decades, scientists have been scratching their heads about why the corona, a hot plasma that extends millions of kilometres from the core, is so much hotter than the solar surface. “It’s like if you walk away from a campfire,” Klimchuk says, but instead of cooling down, you get warmer. “Why would that be?” They also have puzzled over what gives the corona its intricate structure (see ‘Crown jewels’).
Source: Nature adaptation from image provided by Nicolas Lefaudeux
Earth experiences total eclipses roughly once every 18 months. But their paths often cross remote areas, where few people can view them. The last time a total eclipse passed over North America was in 2017. Viewers along that eclipse’s ‘path of totality’ — in which the Moon completely blocks the solar disk — “wouldn’t have seen the same Sun as we’re seeing” during this one, says Marcel Corchado-Albelo, a solar physicist at the University of Colorado Boulder, who will participate in a public-outreach programme on 8 April aimed at marginalized communities in Texas. During the previous eclipse, the Sun was closer to its solar minimum.
The corona will “look much more complex” this time, Klimchuk says.
Simulating the Sun
A preview of how it might appear during the eclipse was released last month by Predictive Science, a research and product-development firm in San Diego, California. Staff members, including astrophysicist Cooper Downs, used real-time satellite data of the Sun’s surface magnetic fields and intensive supercomputer simulations to make the prediction. “The Sun is quite chaotic,” Downs says. So forecasting the corona’s appearance is as difficult as predicting cloud movement — the mention of which is a source of anxiety for eclipse chasers. Clouds could obscure the eclipse from the view of many on 8 April.
Staring at the Sun — close-up images from space rewrite solar science
The firm’s prediction shows a corona composed of several spiky, spade-like structures called streamers, in which coronal plasma is tightly confined by magnetic field lines that leave the Sun’s surface but loop back into it. Streamers glow brighter than other parts of the corona because electrons in the denser plasma scatter sunlight. The prediction also shows coronal holes, darker regions between the streamers where magnetic field lines don’t loop back into the Sun but extend into interplanetary space. The holes can create strong gusts of solar wind — charged particles accelerated by magnetic fields — that cause geomagnetic storms threatening Earth-orbiting satellites.
By comparing the locations of streamers and holes in the actual eclipse and the simulation, the firm’s scientists will be able to validate and improve their model for future applications, including space-weather forecasting, Downs says.
Photo op
Because the Moon perfectly blocks the solar disk during an eclipse — owing to the cosmic coincidence that the Sun and Moon have similar sizes when viewed from Earth — solar physicists on the ground, including Shadia Habbal at the University of Hawaii in Honolulu, will be able to study the Sun’s chromosphere next week. This thin layer of plasma just above the solar surface is home to prominences, worm-like filaments of plasma protruding into the corona. “You see them very clearly during an eclipse,” Habbal says.
Sometimes, these prominences can snap explosively to form a coronal mass ejection. During one of these events, billions of tonnes of relatively cool (about 10,000 °C) solar plasma are expelled from the solar surface and are enveloped by the corona, whose temperature can exceed 1,000,000 °C. Habbal says that because of the solar maximum, viewers have a good chance of seeing a coronal mass ejection. Eclipses provide “the best opportunity to figure out how these plasmas co-exist and interact”, she adds.
To do this, Habbal is leading a team of 40 researchers armed with high-speed cameras and high-resolution sensors to capture tiny changes in the corona during the eclipse’s minutes of darkness. The scientists will be spread across three sites in Texas and Arkansas, to maximize the chance of a cloudless observation.
Flying high
One group that is not worried about clouds is the Airborne Coronal Emission Surveyor (ACES) team. These scientists will fly in a Gulfstream V jet above the clouds, at an altitude exceeding 13 kilometres. This will put them over a layer of water vapour in Earth’s atmosphere that absorbs infrared light and would interfere with their measurements of the corona. Chad Madsen, an astrophysicist at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and an ACES participant, says the team is interested in studying one particularly long streamer in the Predictive Science forecast.
What powers the Sun’s mysterious wind? A daring spacecraft has some answers
The team will measure infrared light emitted by the streamer to determine the strength of the magnetic fields in the part of the corona where it appears and the makeup of ions along various segments of the streamer, Madsen says. (Magnetic fields in the corona directly affect the infrared light emitted by plasma.)
Their flight will chase the Moon’s shadow along the path of totality through Texas, adding 90 more seconds of observation time to the maximum of 4 minutes and 30 seconds that viewers on the ground will get.
For many corona scientists, this eclipse isn’t their first, and probably won’t be their last. But each one offers a few minutes of magic. “There’s always an anticipation — you don’t know what it’s going to look like,” says Habbal, who will count this as her twentieth total eclipse. “Every time, it’s different.”
A fertility treatment that has been used for 45 years is once again available in Alabama. Invitro fertilization (IVF) procedures in the state were halted after the Alabama Supreme Court ruled in February that embryos created using the technique have the same rights as children. A new state law protecting clinics from legal fallout has allowed IVF treatments to resume — but clinicians and scientists in the United States who are working with human embryos are not totally reassured and fear that they will face an increasing number of legal and constitutional challenges.
Physicians are especially worried that officials might cap the number of embryos that can be created in each treatment cycle, which often entails the fertilization of several eggs. Lawmakers could also ban the freezing of backup embryos, which doctors say would result in less efficient and more expensive treatments.
The fact that IVF is so popular in the United States could protect the practice to some extent, says Hank Greely, director of the Center for Law and the Biosciences at Stanford University in California. But research using human embryos — which is already restricted or even banned in some states — might be an easier target for anti-abortion advocates, some of whom contend that life begins at conception and that discarding an embryo is akin to killing a child. “From a researcher’s perspective, there’s reason to be worried,” he says.
But IVF seemed to remain protected, says Eli Adashi, a reproductive endocrinologist at Brown University in Providence, Rhode Island. “Because in so many ways you could look at IVF as a pro-life proposition, IVF was by and large left alone,” he says.
That changed after three couples in Alabama filed a lawsuit against a fertility clinic for the accidental destruction of their frozen embryos. The suit claimed that the loss violated the 1872 Wrongful Death of a Minor Act, a state law that allows family members to sue when their child dies owing to negligence.
People rally for IVF rights outside the Alabama State House after a state supreme court ruling led clinics to put IVF treatments on hold.Credit: Stew Milne/AP for RESOLVE: The National Infertility Association via Alamy
The Alabama Supreme Court ruled on 16 February that the act covers “all unborn children”, including embryos outside the uterus. The decision meant that the lawsuit was valid — and that clinics and doctors could be liable for the destruction of embryos created by fertility procedures. Clinics suspended IVF treatments, and the resulting backlash prompted lawmakers to quickly pass legislation on 6 March to provide immunity to providers and patients for the destruction of embryos.
Several states, including Alabama, have laws conferring rights to embryos. Because there is no federal law protecting IVF, state laws could potentially be targeted at the technique, which often involves discarding embryos, such as those with genetic abnormalities.
Complicated politics
The Alabama ruling was a warning shot, Greely contends. It signalled that some anti-abortion forces are now interested in protecting embryos outside the womb. If “you’ve just won this great victory in overturning Roe v. Wade, you’re going to be looking for what’s next”, he says.
Mary Szoch, the director of the Center for Human Dignity at the Family Research Council, an anti-abortion organization in Washington DC, didn’t directly answer a written question from Nature about whether anti-abortion organizations are pushing for restrictions on IVF in the United States. The council recognizes the value of the lives of children born as a result of the procedure, she says. However, “millions more lives have been lost as the result of human life being made in the laboratory”, she adds. “Society must stop viewing these embryos as mere products.”
It’s not clear how far anti-abortion groups will go to campaign to restrict IVF. These groups have consistently opposed the destruction of embryos for any reason, says Jennifer Holland, a historian at the University of Oklahoma in Norman. But they have been cautious about advocating against IVF because of concerns about whether “this erodes the kind of political support that they’ve gotten from the Republican Party”, Holland says. Many Republican leaders have openly supported IVF.
Eroding efficiency
Even if IVF is not banned, clinicians worry about the prospect of restrictions on disposal of embryos. Other countries have imposed such constraints: a law in Italy, for example, mandated that only three embryos could be produced per round of IVF, and required all embryos to be transferred “as soon as possible”. “It was very inefficient, and they finally overturned that,” says Eric Forman, a reproductive endocrinologist at Columbia University in New York City.
How much should having a baby cost?
If embryo freezing is considered legally risky, “couples will limit the number of eggs retrieved or inseminated [per treatment cycle] to avoid any frozen embryos”, says Nanette Santoro, chair of obstetrics and gynecology at the University of Colorado in Aurora. That would make each round of IVF much less efficient, she notes, which could raise the number of cycles couples undergo, drive up costs and increase exposure to risks from the procedure and fertility drugs.
Forman is also concerned with potential restrictions on genetic testing of embryos, which helps providers to select embryos that are more likely to result in a viable pregnancy and avoid certain genetic conditions. “I worry that [would] result in fewer healthy babies from this technology,” he says.
Fears of restrictions
The study of human embryos is already heavily restricted in the United States. Since 1996, federal funding for research involving the creation or destruction of human embryos has been barred. In 11 states, human embryo research is banned. For scientists, the Alabama ruling sounded an alarm about the prospect of increased constraints.
“I’m concerned, obviously, about what the consequences of this decision are going to be,” says Ali Brivanlou, an embryologist at The Rockefeller University in New York City who conducts research involving human embryonic stem cells.
He says that he understands why people might find it easier to support IVF than human embryo research. With IVF, “you’re trying to help couples to have kids who otherwise would not have kids, so it’s easier to accept why this technology is important,” he says. That doesn’t take into consideration, however, “the fact that IVF could not exist without basic research and that most other aspects of medical practice are derived from the basic research approach”.
To cope with the demand for international bandwidth almost doubling every two years, Japanese corporations NEC and NTT have successfully trialed a revolutionary submarine cable technology set to drastically enhance internet speeds under the sea.
The transoceanic-class experiment transmitted hundreds of terabits across a staggering 7,280km, a feat made possible through a sophisticated algorithm.
NEC and NTT’s innovative solution uses a 12-core multicore fiber, comprising of 12 optical signal transmission paths within a standard outer diameter optical fiber, a significant enhancement from existing single-core fiber used in submarine cables.
(Image credit: NEC/NTT)
MIMO technology
However, the addition of more cores to an optical fiber presents its own challenges. Interference, or crosstalk, occurs when optical signals leak from one core to another, leading to a degradation in communication quality. This is amplified in long-distance transmission where non-uniformity of delay and loss between signals makes accurate reception difficult.
To overcome these issues, NEC developed an algorithm for demodulating received signals using MIMO technology. This enabled accurate separation and demodulation of high-speed received signals. Concurrently, NTT developed the coupled 12-core multicore fiber optical transmission line which mitigates the effects of non-uniformity in signal delay and loss.
Moving forward, NEC and NTT say they aim to commercialize their research, potentially contributing to the realization of a high-capacity optical submarine cable system and terrestrial core network.
The research team, which recently presented its findings as a highly scored paper at the Technical Conference of OFC 2024 in San Diego, estimates that such systems could operate at hundreds of terabits per second, depending on specific cable designs, potentially heralding the advent of petabit per second class submarine cables.
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Reddit’s many ‘subreddit’ communities offer channels for discussing science and are of interest to social-media scholars.Credit: Amy Lombard/New York Times/Redux/eyevine
It has been almost 18 months since Elon Musk purchased Twitter, now known as X. Since the tech mogul took ownership, in October 2022, the number of daily active users of the platform’s mobile app has fallen by around 15%, and in April 2023 the company cut its workforce by 80%. Thousands of scientists are reducing the time they spend on the platform (Nature613, 19–21; 2023). Some have gravitated towards newer social-media alternatives, such as Mastodon and Bluesky. But others are finding a home on a system that pre-dates Twitter: Reddit.
The site was founded in 2005, originally as one all-encompassing forum where users (known as redditors) could post content such as links, texts, images and videos. Anonymous user upvote (or downvote) and comment on each other’s content, deciding on what performs well enough to reach others’ feeds.
Social media for scientists
Today, Reddit is divided into communities, called subreddits, each with volunteer moderators who review content. These subreddits have names that begin with ‘r/’ and are devoted to all sorts of subjects, such as literature, solo travel and Washington DC. Reddit is regularly irreverent: r/trees is for people to share content about marijuana, whereas r/marijuanaenthusiasts is the place to look at trees. It is sometimes dangerous — some communities have amplified conspiracy theories. And there are subreddits devoted to science, ranging from the broad r/science to more specific ones, such as r/bacteriophages.
As of December 2023, according to Reddit’s own statistics, the site had 73 million daily active users, more than 100,000 active communities and had amassed over 16 billion posts and comments. In February 2024, it was the eighth most visited website in the world, ahead of both Amazon and TikTok (see go.nature.com/3tugxbq). And on 20 March, the company floated on the New York Stock Exchange, where it was initially valued at US$6.4 billion. With most researchers now needing to pay to download useful amounts of data on X, Reddit is another option to survey the Internet hivemind. Although changes made last year threaten researchers’ ability to pull data as easily as they once did, Reddit says access to its data continues to be free for non-commercial researchers and academics.
“As the social-media landscape started changing, we really started thinking about the other spaces besides Twitter that people are using,” says Nicholas Proferes, a social media researcher at Arizona State University’s School of Social and Behavioral Sciences in Phoenix, who co-authored reviews on the use of Reddit for research1,2. Here, Nature reports on how Reddit is providing scientists with continued avenues for connecting with other researchers, gathering data and engaging with the public.
Networking and collaboration
Yvette Cendes’s journey on Reddit began in 2014. Cendes, who is currently a postdoctoral scholar at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts, found herself with some downtime during her PhD studies in astronomy, and started poking around on the platform. She came across a thread in which users were panicking over how imminent γ-ray bursts from supernovae were going to wreak havoc and kill people — something that she knew to be untrue. She resolved to jump into the comments and clear things up, and this was the start of her science-communication career.
Since then, Cendes has made a name for herself on Reddit and even created her own subreddit, with nearly 17,000 members. “It’s a very good way to get good knowledge out there,” she says.
Scientists also use Reddit to get tips and tricks from other scientists. The r/biotech subreddit features news about biotechnology innovations and career advice; r/datascience is a community specifically for data-science professionals. There’s even a subreddit devoted to electron microscopy, from which users can seek guidance on the technology.
Yvette Cendes discusses astronomy as a science and a career on Reddit.Credit: Floris Looijesteijn
Not everyone is as forthcoming with their names and credentials on Reddit, which can make networking a bit more challenging than on other sites, says Cendes. But the pseudoanonymity can also be beneficial. Groups such as r/labrats offer safe spaces for scientists to discuss their research or dilemmas with others of similar backgrounds (and these groups are sometimes used by science journalists looking for article ideas). The anonymity provides some protection for people to post without fear of retaliation, and to seek counsel. In one discussion, for instance, a user laments how their principal investigator published a paper based on their research without giving credit, and considers hiring legal support.
Reddit can also be a great jumping-off point for early-career scientists or those trying to pivot between specialties. Kevin Ortiz Ceballos, a graduate student at Harvard University’s Department of Astronomy, happened upon one of Cendes’ posts about how to become an astronomer back when he was in secondary school. He credits it with helping him to switch from literature to physics and eventually astrophysics. Engaging in conversations about professional astronomy before entering the field himself was a huge asset.
“The fact that Yvette made it so accessible gave me the tools I needed to take the necessary steps to study and prepare what I needed to get into astronomy grad school,” he says. The two have since connected in person, and even collaborated on a project that was recently submitted for publication.
With all of its subspaces, Reddit can be overwhelming at first. Cendes encourages potential users to take it slowly, find the communities they are most interested in and go from there — putting keywords in the search function and perusing the different subreddits that come up.
Research and analysis
The information embedded in posts and comments from Reddit’s millions of users can also be a treasure trove for researchers studying online behaviours. In 2022, NASA collaborated with master’s students at the University of British Columbia in Vancouver, Canada, to use Reddit data to locate landslides (see go.nature.com/3tlum6t). The team scraped the site for mentions of ‘landslide’, before analysing and validating relevant mentions to add to the NASA landslides database. According to the team, this verification was needed because a Reddit post about the song ‘Landslide’ by the rock band Fleetwood Mac might “give us insight about the changes and challenges of life, but it doesn’t do much for global disaster detection”.
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A 2021 review2 in Social Media + Society, co-authored by Proferes, chronicled 727 manuscripts published between 2010 and 2020, that made use of Reddit data. These studies spanned all sorts of disciplines — from computer science to medicine to social science.
One reason that Reddit is ripe for research is that there are few bureaucratic hurdles to clear compared with what’s required for other studies involving human beings. “It is a publicly accessible web forum in the US and so is not considered to be human-subjects research,” says Proferes. Institutional review boards view Reddit research as “exempt from ethical review”, he says.
However, Proferes and his co-authors emphasize the need for intentionality and sensitivity when collecting data from the site. Consider a subreddit such as r/opiates. Data on substance use are often difficult to procure from in-person interviews or other social science methods, but because of Reddit’s anonymity, people are more open to sharing such information on the platform. However, using the subreddit for research could be seen as invasive by a community that considers itself a semi-private anonymous support network. Certain communities on Reddit are also wary of scientific researchers.
The 2024 review co-authored by Proferes1 lists some of these considerations and suggests steps such as obfuscating usernames in published work and collaborating with moderators.
“Academia and data populations have a very sore history of, frankly, academics coming in and just taking,” says Proferes. The online community “is not getting any benefit whatsoever. It is very exploitative. There’s some real historical reasons, too, why folks may be highly suspicious or dubious about researchers coming in, even in these digital spaces.”
Research findings derived from Reddit posts should be shared with users, says Sarah Gilbert.Credit: Steven Shea
“It’s really easy when you’re working with these large data sets to just think of the data points in them as literal data,” says Sarah Gilbert, research director of the Citizens and Technology Lab at Cornell University in Ithaca, New York, and a co-author of the review. “Spending time in the community and learning the norms and actually reading it, it turns that data into people. It gives a better sense of who is going to be included, more like human-subject research.”
Gilbert also recommends sharing whatever published research comes out of trawling through Reddit data with those who provided the information. “Hopefully what you learnt is beneficial to the community so they can see data is used for something,” she says.
Connecting with non-scientists
Reddit can be a way for scientists to use their expertise to answer any questions the general public might have, says Cendes. She is a regular on r/space, educating users about topics such as the James Webb Space Telescope.
Kelly Zimmerman, a PhD candidate in ecology at Montclair State University in New Jersey, has connected with and educated other users on Reddit. When she started on the platform about 12 years ago, she mostly used it to find journal articles of interest on r/ecology and r/biology. But, like Cendes, she noticed how curious users were about scientific topics that were in her area of expertise, and she now often engages in discussions on subreddits such as r/whatisthisbug.
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Although she previously used X, Zimmerman thinks that Reddit provides a more engaging experience. “I felt like I was just talking into a void — there wasn’t a lot of response on Twitter,” she says.
One way for scientists to try their hand at science communication on Reddit is through ‘ask me anything’ (AMA) sessions, in which researchers answer users’ questions in their own time. Moderators pull in verified researchers to provide responses — even renowned theoretical physicist Stephen Hawking participated. (To schedule an AMA with r/askscience, you can e-mail the moderators.)
With both AMAs and general discussion forums, there is an art to making sure that information is communicated effectively and succinctly. “We’re trying to keep it as scientific as possible, but in layman’s terms, so that non-scientists can understand cutting-edge science that’s coming out right now,” says Zimmerman, who also moderates some science subreddits.
Nathan Allen, a synthetic chemist based in Milwaukee, Wisconsin, and a former moderator at r/science, likens it to writing a persuasive e-mail. “On Reddit, you have got to convince the general public that this has some general interest to them, and you’ve got to develop it and build the message and make sure people stay on point,” he says. “You get a lot of practice writing concise explanations of complicated things that people who aren’t necessarily scientists are able to digest and understand.”
When using Reddit in any capacity, Zimmerman encourages scientists to make sure to read the rules before making a post or comment, and to mind their manners, just as they would on any other social-media platform. “Be polite,” she says. “Just because you’re an anonymous username doesn’t mean you should be rude to other people.”
Jennifer Cole, a biologist and anthropologist at Royal Holloway University of London, notes that using Reddit for scientific communication is not without its problems. Moderators do a lot of work behind the scenes and often face a torrent of abuse for trying to maintain standards, says Cole. And although using people’s real names can help with credibility, it can also make academics and experts targets for harassment and abuse. Although the site does not provide support for users who experience abuse, a spokesperson for Reddit noted that the platform has policies to prohibit both harassment and the sharing of personal or confidential information, and that these policies are enforced by the internal safety teams.
It can also be used to spread falsehoods. R/conspiracy has repeatedly posted misinformation about COVID-19 and vaccines. Climate deniers are also present on the platform, although a decade ago the science forum specifically banned climate change deniers. Asked about misinformation, the Reddit spokesperson said that because Reddit is governed by upvotes and downvotes, quality and accurate information tend to rise to the top.
Interviewees agree that Reddit is at its core a social media platform, and social media has the potential to be toxic. But when scientists engage, there’s also a lot of great scientific communication and debunking of misinformation. “Don’t be afraid to talk to the people,” Zimmerman says. Those “who are not scientists are just as curious as we are. There’s nothing special about being a scientist. We are like everybody else, and sometimes folks forget that.”
This six-legged animal isn’t an insect: it’s a mouse with two extra limbs where its genitals should be. Research on this genetically engineered rodent, which was published on 20 March in Nature Communications1, has revealed a way in which changes in DNA’s 3D structure can affect how embryos develop.
Developmental biologist Moisés Mallo, at the Gulbenkian Science Institute in Oeiras, Portugal, and his colleagues were studying one of the receptor proteins, Tgfbr1, in a signalling pathway that is involved in many aspects of embryonic development. The scientists inactivated the Tgfbr1 gene in mouse embryos about halfway through development to see how the change affected spinal-cord development.
Then, Mallo’s graduate student, Anastasiia Lozovska, came to his office to tell him she’d found that one of the bioengineered embryos had genitals that looked similar to two extra hind limbs. Her finding sent the research down an unexpected path. “I didn’t choose the project, the project chose me,” Mallo says.
A 3D reconstruction of the skeleton of the genetically altered embryo shows its extra and normal limbs (magenta and turquoise, respectively).Credit: Anastasiia Lozovska et al/Nat. Comms
Researchers have long known that, in most four-limbed animals, both the external genitalia (penis or clitoris) and hind limbs develop from the same primordial structures.
When Mallo’s team looked further into the six-legged mouse phenomenon, they found that Tgfbr1 directs these structures to become either genitalia or limbs by altering the way that DNA folds in the structure’s cells. Deactivating the protein changed the activity of other genes, resulting in extra limbs and no true external genitalia.
The researchers hope to determine whether Tgfbr1 and its relatives affect DNA structure in other systems such as metastatic cancer, and in immune function. They are also examining whether the same mechanism underlies the development of the reptilian hemipenis, a double penis that, in snakes, forms from primordial organs in lieu of legs.
