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    Epic blazes threaten Arctic permafrost. Can fire-fighters save it?

    Fire season is approaching in the massive Yukon Flats National Wildlife Refuge in east Alaska, where fires have long been allowed to burn unchecked unless they threaten human life and property. But as climate change increases the frequency of these fires, the land’s overseers are changing course. Working with scientists, refuge managers have designed a pilot programme to parachute elite firefighting teams into remote areas to quash infernos — to protect not people but permafrost.The forests and tundra of the Denmark-sized refuge cloak a deep layer of permafrost, frozen ground that holds enormous quantities of carbon across the Northern Hemisphere. After fires remove vegetation and soils, however, that frozen ground often begins to thaw, releasing its stores of carbon dioxide and other greenhouse gases into the atmosphere. New research1 suggests that the resulting emissions, from both the fires themselves and the subsequent permafrost thaw, could be on par with those of a major global economy over the course of this century. This could effectively reduce by up to 20% the amount of carbon dioxide that humanity can emit and still meet its goal of limiting global warming to 1.5 °C above preindustrial levels. The research has not yet been peer reviewed.These numbers suggest that a rethink of longstanding fire policies in high-latitude boreal forests — where recovery after frequent fires could take decades if it happens at all — might be needed, says Brendan Rogers, an earth-systems scientist with the Woodwell Climate Research Center in Falmouth, Massachusetts. The pilot programme at Yukon Flats represents a test of that idea in an area where permafrost is particularly vulnerable.“What we’re talking about is aggressive attacks on fires when they ignite in these areas,” Rogers says. Once such fires get going, he adds, it’s often too late. “That carbon is lost.”Earth ablazeThe proposal to suppress boreal fires to help fight climate change follows years of increasingly frequent and intense conflagrations that have raged across northern forests and Arctic peatlands. According to estimates, the wildfires in Canada’s boreal forests last year released more than three times as much carbon dioxide as the entire country emitted from burning fossil fuels. Officials at Yukon Flats, for example, say that the frequency of major fires on the refuge has quadrupled since 1988.
    Why are the Canadian wildfires so bad this year?
    A rise in fire frequency can have cascading effects on the ecosystem, and thus carbon, says Xanthe Walker, an ecologist at Northern Arizona University in Flagstaff, who has studied the effect of fires on permafrost. Historically, boreal forests have burnt once every 70–120 years, she says, which gives the black-spruce forest that dominates the ecosystem enough time to regenerate and rebuild carbon in the soil. More-frequent fires can burn ‘legacy’ carbon that has accumulated over centuries2 and can also kill off the black spruce (Picea mariana). That provides an opening for leafy deciduous trees, which do not promote the kind of carbon-rich soils that insulate permafrost.Emissions winFire suppression could help to stave off some of these effects, buying humanity time to address the climate crisis. In a 2022 paper3, researchers at Woodwell and the Union of Concerned Scientists, a non-profit organization in Cambridge, Massachusetts, found that fire-suppression efforts in Alaska tend to reduce the total area burnt. Their calculations suggest that investing in fire suppression could reduce carbon emissions at a lower cost than that of many technologies for reducing industrial emissions. With an investment of around US$700 million annually in suppression over the next decade, Alaska alone could reduce carbon emissions by up to 3.9 billion tonnes of carbon dioxide through mid-century. That is more than the annual greenhouse-gas emissions of the European Union.

    Smoke billows from fires burning in the Yukon Flats National Wildlife Refuge in eastern Alaska.Credit: NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC

    The idea that governments can or should attempt fire suppression in remote boreal forests has encountered some scepticism, owing in part to the scale of the challenge. Fires also play an important part in the ecosystem, and research shows that suppression efforts allow fuel to build up in many forests, contributing to increasingly intense fires4.Still, because of the looming climate crisis, many researchers say that the suppression efforts at the Yukon Flats might be worthwhile. “Stopping fires across the boreal forests is an impossible feat, but targeted suppression in areas that are vulnerable seems like a great strategy,” says Walker.A refuge for permafrostThe pilot project at Yukon Flats began last year in eight areas covering nearly 650,000 hectares of land. Those zones account for 19% of the refuge and include 40% of the land underlain by a uniquely vulnerable type of permafrost called Yedoma, which contains deep ice wedges that often melt after fires. This causes the land to collapse, exposing ancient carbon to microbes whose activity releases greenhouse gases.The target areas contain some 1.1 billion tonnes of carbon, which, if released, would be equivalent to around seven years of emissions from US coal burning.
    Indigenous youth must be at the forefront of climate diplomacy
    Yukon Flats refuge manager Jimmy Fox says that he decided to move forward with the project after consulting with scientists and firefighters. He also involved Indigenous communities that own some 1.2 million hectares of land in the refuge in the discussion. These communities have voiced concerns about wildfire smoke and the negative effects of the fires on water quality and on the land used for hunting, berry picking and other subsistence activities.Under the pilot programme, firefighters will be deployed on fires that start early in the season and have the potential to burn for several months. Firefighters will engage only if they determine that they can put out the fires within three days, so as to minimize costs and the use of firefighting resources.Fox notes that Yedoma permafrost zones that burned decades ago and then collapsed is slowly beginning to recover as vegetation thickens and produces carbon-rich soils that once again insulate the ice below. But with rising temperatures and increasing fire frequency, he says, the danger is that these areas will reach a tipping point at which point recovery would no longer possible.Ultimately, the goal is to hold fires to a more historic level. It could be a few decades before scientists can determine whether the effort pays off, Fox warns, “but we have to try”. More

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    Want to make a difference? Try working at an environmental non-profit organization

    Now a research scientist at The Nature Conservancy’s Nachusa Grasslands, Elizabeth Bach used her passion for the prairie to chart her career path.Credit: Dee Hudson

    As a graduate student, Shradda Dhungel studied how air pollutants move through the Himalayan valleys in Nepal — her home country. That practical experience led her in an unexpected direction: working at an environmental non-governmental organization (NGO).After earning her PhD in environmental science at the University of Virginia in Charlottesville in 2017, Dhungel taught undergraduates physical science and ecology at the Fashion Institute of Technology in New York City. Through teaching, she realized that she loved sharing scientific knowledge with the public. Eventually, Dhungel concluded that she wanted her work to have a practical impact on people and policymaking.So, in 2021, she applied for a postdoctoral position at the Environmental Defense Fund (EDF), a science-led environmental organization in New York City. She now works to mitigate global and regional levels of methane, to help inform policymaking and encourage efforts to curb emissions of the greenhouse gas.Working for the EDF, Dhungel’s applied research directly helps people and the planet, which she says is her calling. (Dhungel finished her EDF postdoctoral programme earlier this month and is now looking for a full-time scientist position at other climate-focused non-profit organizations.)Dhungel is among a small but relatively stable cohort of graduate students who have left academia for the non-profit sector. Data from the US Survey of Earned Doctorates show that, of all individuals awarded a PhD in 2021 or 2022, 6.5% — most of whom studied science or engineering — left academia for non-profit organizations. Many scientists working at NGOs wanted to see their work make a difference in communities and the environment, and have the ability to influence policy at early career stages.“There is a chance for me to contribute something quite tangible,” says environmental engineer Kashif Shaad, who is based in Singapore but works at Conservation International, an NGO in Arlington, Virginia.Researchers are key to the work of science-focused environmental non-profit organizations, which often conduct projects for or in partnership with other groups. Scientists help to deliver evidence to inform policymaking and turn findings into practical solutions, says Rebecca Shaw, chief scientist at the World Wildlife Fund (WWF), an international wildlife-conservation organization in Washington DC. Non-profit organizations need a strong supply of highly trained scientists to help find and apply solutions to global environmental challenges, from climate change and plastic pollution to biodiversity crises.For a scientist, daily work at an environmental non-profit group can be similar to that in academia, but there are key differences in the application process, climbing the career ladder and publishing research.

    Kenneth Davidson gained skills during his PhD field work at the San Lorenzo Protected Forest (pictured) in Colón, Panama, that prepared him for work at the non-profit organization American Forests.Credit: Kenneth Davidson

    Many researchers in this sector still present their work at conferences and publish manuscripts in journals, but publications and citations are not their principal measure of success. More important is delivering solutions to policy partners, such as local governments or foundations, and helping to create real-world change.Adapting to non-profit work“I’m still a researcher. I still want to get publications out there. But working with local partnerships is paramount,” says Kenneth Davidson, who last year earned a PhD in plant physiological ecology at Brookhaven National Laboratory in Upton, New York. He now works at American Forests, a forest-conservation organization in Washington DC.Salary ranges can be similar to those for academic posts or slightly higher or lower, depending on the position and size of the organization. But, Davidson adds, NGOs provide more job security than academia for early-career scientists, and offer more flexibility. “Being able to start earning and saving right out of grad school was a huge draw to a non-academic path,” he says.To successfully transition to non-profit work, academics must shift their mindset, recognizing that their research must always have practical applications for real-world challenges. At an NGO, science is not done just in the pursuit of knowledge.“You’re really listening deeply to the issues at hand, and the struggles people are having. You’re developing questions and analyses to address those challenges,” explains Shaw.Environmental non-profit groups come in many sizes and flavours, and the roles for scientists can differ depending on the organization’s scope and mission. Some positions have a strong research focus; others are more involved in policy development or conservation practice. The WWF, a large global organization, employs 27 full-time scientists in its US office alone — most of whom have a PhD. It also has scientists in its other offices, including 16 in the United Kingdom. It offers three postdoctoral fellowships in its US science team and provides funding for PhD candidates and postdocs from Latin America, the Caribbean, Asia and Africa through a capacity-building programme. The WWF runs a broad array of research projects — ranging from how to transition to renewable wind and solar energy sources without harmful ecological impacts, to investigating the shifts in food production and dietary patterns needed to ensure that all people have access to healthy food. By contrast, American Forests, which is smaller in size and scope, employs around 30 scientists in total, 6 of whom have PhDs.Dhungel found that applying for her postdoctoral position at the EDF was different from the academic hiring process. Instead of submitting a written research proposal, she went through two rounds of interviews and gave a presentation about her previous work and relevant experiences to an audience not limited to just scientists.

    Environmental scientist Shradda Dhungel found her stride working at the Environmental Defense Fund on applied research that helps the planet.Credit: Shradda Dhungel

    Davidson says that, after completing his PhD, it took him a few tries before he understood how to adapt his job-seeking strategies and applications to NGOs. He noticed that networking processes were different. For example, in academia, open positions often circulate through word of mouth and on social-media platforms such as X (formerly known as Twitter). Applicants also often approach principal investigators through e-mail, introducing themselves and providing links to their publication lists.By contrast, finding non-profit positions involves searching for advertisements on jobs boards and LinkedIn, a professional networking site, says Davidson. He quickly spruced up his previously sparse LinkedIn profile. Davidson also tailored his CV to highlight sought-after skills and experiences in the non-profit sector, in particular ‘soft skills’ related to interacting and collaborating with others.“It’s the same educational background and the same research, but just the way that I describe things had to shift completely,” he says. For example, for an academic audience, Davidson focused more on the scientific details of his research; for an NGO, he emphasized his experience partnering with other non-profit organizations and the practical applications of his work.It took Davidson about six months to land his job at American Forests, where he models ecosystem carbon flux to help the Oregon Department of Forestry assess forest carbon and comply with emissions reporting requirements. Showing how your research is relevant to policy or environmental practice is crucial to getting your foot in the door, Davidson says.Also, candidates who can demonstrate experience in collaborating with partners outside academia will go further, says Davidson. For example, during the fourth year of his PhD programme, he spent a summer working on a project for Black Rock Forest, a non-profit research organization in Cornwall, New York, where he looked at how the associations between leaf traits and water-use efficiency vary across a growing season. The project was separate from his PhD, but ultimately contributed a chapter to his thesis — and probably strengthened his job applications, he says. This experience also showed him what working for a non-profit organization is like.Elizabeth Bach, an ecosystem-restoration scientist at the global non-profit The Nature Conservancy (TNC), who is based in Franklin Grove, Illinois, took a different approach. Even while pursuing her PhD in ecology and evolutionary biology at Iowa State University in Ames in 2010–14, she knew that she didn’t want a conventional academic career.

    Rebecca Shaw, chief scientist at the World Wildlife Fund, says that non-profit work requires researchers to find practical applications of science to address real-world challengesCredit: WWF-US/Rebecca Drobis

    “I absolutely love the tallgrass prairies of the Midwest,” she says, which is where she grew up. Her passion for this at-risk ecosystem helped to chart her career path. At the end of her PhD programme, she looked for postdoctoral opportunities that would give her applied-science experience. In 2014, she became a postdoc at the Illinois Natural History Survey at the University of Illinois Urbana-Champaign, where she catalogued and studied the diversity and ecology of the state’s fauna and flora to help inform management of natural resources.“It was a foot in the academic world and a foot in the world of applied science,” she says.Two years later, she began a second postdoctoral programme, with a stronger focus on science policy, at the Global Soil Biodiversity Initiative, an international collaboration to inform the public and policymakers on soil health, based at Colorado State University in Fort Collins.In 2018, her earlier applied-science and policy experiences landed her at her dream job at the TNC, she says. She leads a research programme at the Nachusa Grasslands nature preserve in Illinois, examining tallgrass-prairie restoration ecology. Bach’s research focuses on how soil and life below ground support tallgrass-prairie ecosystems through plant and soil interactions and nutrient and carbon cycling. She advises others who want to work at a non-profit organization to deliberately build up relevant technical skills through postdoctoral programmes and other opportunities, such as volunteering.Perks of the non-profit pathScientists working in the non-profit sector will typically spend less time in the laboratory than will those in academia, but this can depend on the job and the organization, says Shaw. Dhungel says her workdays at the EDF are spent doing research and analysing data, mirroring her academic days. By contrast, Bach’s job involves hands-on land management at the nature preserve, including helping to coordinate prescribed fires and making decisions about planting new prairies and protecting existing ones, in addition to running a research project.Dhungel enjoys other perks in her non-profit position. Even as a postdoc, she can work with external partners and contribute directly to policymaking. She feels that, if she had an academic position, this wouldn’t happen until much later career stages.And although environmental NGOs use cutting-edge science for practical applications, such as developing policies or conservation practices, the work is still intellectually stimulating, says Davidson. The applied science that non-profit groups pursue is often what attracts researchers to join their cause.Shaad loves that his job entails working with and learning from local communities and conservation practitioners. “There are so many passionate people on the ground. I get to learn from them and place that in my own universe of thinking about things,” he says.In 2015, Shaad completed a postdoctoral programme at Conservation International, where he helped to develop a system to judge the health of freshwater ecosystems in Jakarta. He has been at the organization ever since, and now heads a freshwater-conservation programme. Shaad was drawn to researching water issues after growing up in Bhopal, India, in the aftermath of a toxic gas leak in 1984 from US firm Union Carbide’s pesticide plant, which killed thousands and contaminated the area’s groundwater.He earned his PhD in environmental engineering at Swiss Federal Institute of Technology (ETH) Zurich and says that transitioning to non-profit work involves a “steep learning curve”. It helps to be humble and to talk to people who have built knowledge and expertise through non-academic routes, he advises.Leaving academia can be scary and difficult to explore openly, owing to fear of losing support from supervisors, says Shaw. “Academia can make you feel very bad for not choosing it,” she says. But, she advises, if your heart isn’t in it, then “just make the leap”. More

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    Hello puffins, goodbye belugas: changing Arctic fjord hints at our climate future

    Far north of the Arctic Circle lies a fjord on the front lines of climate change. Geir Wing Gabrielsen has been visiting this inlet, located on the northwest side of the Norwegian archipelago Svalbard, since 1981, when he first came to study the behaviour of Arctic birds. It used to be that each year when the ecotoxicologist would arrive in May or June — springtime in Svalbard — he could count on one thing: that the fjord would still be locked in ice.But all of that has changed.The Arctic is warming four times as fast as the rest of the world owing to climate change. And because of a quirk of ocean currents, the fjord, called Kongsfjorden, is warming even faster (see ‘Current situation’). So much so that, since 2006, it no longer freezes over — even when the Sun sets during the winter months, between October and February.

    Source: Buchholz, F., Buchholz, C. M. & Weslawski, J. M. Polar Biol. 33. 101–113 (2009).

    This has completely reshaped the fjord’s ecosystem, according to a study in Polish Polar Research published in January1. Arctic mammals such as beluga whales (Delphinapterus leucas) and ringed seals (Phoca hispida) that once called the fjord home have left. Meanwhile, more southerly animals including Atlantic puffins (Fratercula arctica) and Atlantic mackerels (Scomber scombrus) have moved in. And new habitats have popped up along the shoreline where sea ice once suffocated plant growth.For researchers such as Gabrielsen, at the University Centre in Svalbard, these changes are met with a sense of loss. But they are also viewed as an opportunity. The fjord “will provide information about how the Arctic will be in the future”, Gabrielsen says. And it could help to answer the big questions of which species will survive the shifting climate in the Arctic, and how.“It’s incredible that I — in my time — have been able to see such dramatic changes,” he says.

    As shown in this photo from April 2005, Kongsfjorden used to freeze over enough during springtime for students and researchers to safely walk on it.Credit: Kim Holmén

    Vanishing IceKongsfjorden, meaning ‘king’s fjord’, is arguably the best-studied Arctic fjord in the world. Norway established its first Arctic research station there in the 1960s in what was then the mining community of Ny-Ålesund. Since then, 11 other nations, including Germany, China and India, have set up camp there.The density of research activity in the fjord has made it possible to track its environmental changes in detail. The eastern reach of Svalbard is pummeled by an Arctic current that keeps its frigid temperatures stable. Meanwhile, the western reach — where Kongsfjorden sits — is exposed to an offshoot of the Atlantic Gulf Stream. As a result, the fjord’s winter water temperature rose from 0.3 ºC in 2004 to 4 ºC in 2017. The most obvious effect of the warmer water hitting Kongsfjorden is the rapid retreat of its glaciers, says Kai Bischof, a marine biologist at the University of Bremen in Germany.

    A view of Ny-Ålesund from April 2023 showing the fjord free of sea ice.Credit: Lisi Niesner/Reuters

    “If you go there, like me, every other year, you can really see the changes,” Bischof adds. He remembers how, in the 1990s, a retreating glacier revealed a surprise: a piece of land once covered in ice and marked on maps as a peninsula turned out to be an island. Scientists can now comfortably motor around it in boats. “The rate of change is accelerating,” Bischof says.Out with the old, in with the newKongsfjorden has become something of a pilgrimage for politicians seeking to understand global warming. Both former UN secretary general Ban Ki-Moon and former US secretary of state John Kerry have toured the fjord. The rapidly changing landscape makes it “a place where you can really experience the changing climate through your eyes”, says Bischof.The fjord has already taught researchers that the Arctic is susceptible to tipping points. When it failed to ice over in 2006, it “was a great wake-up call”, Gabrielsen says.But determining how exactly climate change will scramble the fjord’s ecosystem is a bit more difficult.Researchers have so far recorded the effects on some species. For instance, ringed seals have mostly left the fjord because, without any sea ice in which to build their dens during the spring, their pups were exposed to predatory birds. In 2023, scientists recording the living symphony of the fjord also noted that the frequency of whale songs had diminished, compared with Svalbard’s northeast coast2.

    Black-legged kittiwakes feed in Kongsfjorden.Credit: Geir Wing Gabrielsen

    Meanwhile, some opportunistic species have moved onto the scene. Atlantic mackerels were first spotted in September 2013. The Atlantic puffin, spotted occasionally in the 1980s, is now thriving in Kongsfjorden. And a 19-year survey3 of the stomach contents of black-legged kittiwakes (Rissa tridactyla) in the fjord — a type of seabird in the gull family — suggests that, since around 2006, they have started to feast on a wide array of Atlantic fish that seem to have relocated, including Atlantic herring (Clupea harengus), capelin (Mallotus villosus) and Atlantic cod (Gadus morhua).The presence of these southern migrants seems to support the hypothesis that the Arctic will become more and more similar to the North Atlantic Ocean, a process aptly called Atlantification.Arctic adaptersSome newcomers to Kongsfjorden present a challenge for researchers. Luisa Düsedau, a molecular biologist at the Alfred Wegner Institute in Bremerhaven, Germany, says that she and her colleagues now need to keep a watch out for polar bears (Ursus maritimus) as they walk the shoreline to collect specimens such as algae and kelp.

    Polar bears now come into the fjord to eat the eggs of eiders along the shoreline.Credit: Geir Wing Gabrielsen

    Once upon a time, these massive marine mammals would rarely come into the fjord. But with there being less and less sea ice — which polar bears rely on to hunt — the animals have started shifting tactics. Last summer, according to Gabrielsen, an unprecedented 20 polar bears and cubs travelled to the fjord to eat the eggs of common eiders (Somateria mollissima) and barnacle geese (Branta leucopsis) nesting along the shore.Polar bears aren’t the only new thing on the shoreline. Scientists used to have a hard time studying anything growing along the tide line because of the sea ice covering it for a large chunk of the year. They also assumed that the ice would prevent most plants from growing there, because it would scrape away anything that tried to take root. Today, thick strands of kelp and algae — some species entirely new to science, according to Düsedau — are flourishing.

    Molecular biologist Luisa Düsedau works along the tide line of Kongsfjorden, where you can now see kelp and algae, in 2021.Credit: Nele Schimpf

    “It’s like a tiny forest” that forms a home for crabs, worms, snails and many other creatures that used to live on the sea floor, says Düsedau. “It’s blooming.”The growth is a reminder that nature can adapt, she says. But she also emphasizes that it used to be difficult to know what was actually under the sea ice, especially during the harsh conditions of winter.With the shifting environment, that is changing. Researchers are trying to establish a baseline for what typically lives in the fjord so that they can systematically bear witness as the ecosystem continues to evolve.Two years ago, for instance, polar ecologist Charlotte Havermans, also at the Alfred Wegner Institute, travelled with a team to Kongsfjorden to learn whether jellyfish stayed active during the polar winter. The researchers didn’t know whether they would succeed. But upon shining their headlamps into the dark, now-uncovered water, “we saw so many jellyfish”, she says, “it was incredible”. She adds: “There were so many more species in the winter than we thought.” Not only that, but the team found jellyfish DNA in the stomachs of amphipods — tiny crustaceans — also spending the winter in the fjord. It was the first time scientists had spotted Arctic amphipods naturally feeding on jellyfish, and suggested that the jellies play a much bigger part in the winter food chain that previously thought4.

    Polar ecologist Charlotte Havermans (centre) and team sample amphipods in the water of Kongsfjorden during winter 2022.Credit: Alfred-Wegener-Institut/Esther Horvath

    Kongsfjorden is powerful because it serves as a visual reminder of the power that climate change has to reshape the world, says Gabrielsen. Some 40 years ago, “I was so fascinated” by the fjord’s beauty, he says. Now, “I have grandchildren, and I wonder if they will be able to see what I have seen”. More

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    Australia’s Great Barrier Reef is ‘transforming’ from repeated coral bleaching

    Australia’s iconic Great Barrier Reef is fundamentally changing because of repeated bleaching from high ocean temperatures brought on by climate change, according to marine biologists.“It’s not a question of reefs dying or reefs disappearing, it’s reef ecosystems transforming into a new configuration,” says marine biologist Terry Hughes, from James Cook University in Townsville, Australia.“Species like fish and crustaceans and so on — the iconic biodiversity of reefs — all depend on the structure and three dimensionality the habitat provided by corals,” Hughes says. “When you lose a lot of corals, it affects everything that’s dependent on corals.”Corals ‘bleach’ when stressed, expelling their colourful resident zooxanthellae. According to a report released on 17 April by the Great Barrier Reef Marine Park Authority – the Australian government’s reef management agency — the World Heritage-listed reef is experiencing its worst mass bleaching event on record. The Reef Snapshot said three-quarters of the entire reef is showing signs of bleaching and nearly 40 percent is showing high or extreme bleaching.The report is based on aerial surveys of 1,080 of the Great Barrier Reef’s estimated 3,000 individual reefs, and in-water surveys of a smaller number of reefs.It showed that while bleaching was observed along the entire length of the Great Barrier Reef, it was most severe in the central and southern regions.“We’ve never seen this level of heat stress across all three regions of the Great Barrier Reef,” says Brisbane-based marine biologist Lissa Schindler, from the Australian Marine Conservation Society.This is the fifth mass bleaching event on the Great Barrier Reef in eight years. Hughes warns that climate change-driven increases in ocean temperatures are making it more difficult for the Reef’s corals to recover between bleaching events. “In the last six years, we’ve settled into bleaching every other year – in 2020, 2022, and now 2024 – and that’s simply not enough time for a proper recovery,” he says.Global phenomenonThe Snapshot was one of a series of reports released this week on coral bleaching that also sounded alarm bells for reefs. The Australian Institute of Marine Science announced on 18 April that the Great Barrier Reef experienced water temperatures in parts of the southern reef at 2.5 degrees Celsius higher than historical summer peaks.Meanwhile on 15 April the United States’ National Oceanic and Atmospheric Administration declared the fourth global coral bleaching event on record, and the second in the past decade. The declaration acknowledges that the warmth of the southern hemisphere summer mirrored coral bleaching events seen in the northern hemisphere summer last year.It comes as global sea surface temperatures again broke records in 2023, associated with a strong El Niño weather pattern, recording an annual average temperature around 0.3 degrees Celsius higher in the second half of 2023 compared with 2022.“There have been very high temperatures driven by climate change all across the world, and there has been coral bleaching in many other countries,” says environmental scientist Roger Beeden, chief scientist for the Great Barrier Reef Marine Park Authority, Townsville.Hughes says the warming climate is pushing reefs to have less coral, and the mix of coral species is changing. For example, the branching and table-shaped corals are often the fastest to recover from a bleaching event because they are fast-growing, Hughes says. However they’re also very prone to bleaching and have higher levels of mortality during bleaching events.“It’s a bit analogous to a fire on land through a forest, that favours a bounce-back by flammable grasses before the trees can recover,” he says. “Ironically, that that bounce-back, that resilience, undermines the ability of the reef to cope with the next inevitable bleaching event.” Seaweeds also flourish when corals degrade.Beeden says those who live and work on the Reef are observing significant changes. “There’s historical photos that show inshore reefs that were laden with coral, and that’s very different now,” he says.He says there are an estimated 450 different species of coral on the Reef, and such diversity means there is a chance the Reef will adapt to the changing conditions, even if it changes character. “What we see within species is definitely there is variability in how they respond to stress events.”Hughes says the solution to the Great Barrier Reef’s bleaching problem is clear. “Reduce greenhouse gas emissions. Full stop.” More