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      A year after Australia’s wildfires, extinction threatens hundreds of species

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      When Isabel Hyman heads out in coming weeks to the wilds of northern New South Wales, she’s worried about what she won’t find. Fifteen years ago, the malacologist — or mollusk scientist — with the Australian Museum made an incredible discovery among the limestone outcrops there: a tiny, 3-millimeter-long snail, with a ribbed, dark golden-brown shell, that was new to science.
      Subsequently named after her husband, Hugh Palethorpe, Palethorpe’s pinwheel snail (Rophodon palethorpei) “is only known from a single location, at the Kunderang Brook limestone outcrops in Werrikimbe National Park,” she says. Now it may become known for a different, more devastating distinction: It is one of hundreds of species that experts fear have been pushed close to, or right over, the precipice of extinction by the wildfires that blazed across more than 10 million hectares of southeastern Australia in the summer of 2019–2020.
      “This location was completely burnt,” says Hyman, who is based in Sydney. “We expect the mortality at this site could be very high and … there is a possibility this species is extinct.”
      A year after the last of the fires were doused, their toll on species is becoming increasingly clear.  Flames devoured more than 20 percent of Australia’s entire forest cover, according to a February 2020 analysis in Nature Climate Change. Even if plants and animals survived the flames, their habitats may have been so changed that their survival is at risk (SN: 2/11/20). As a result of the scale of the disaster, experts say that more than 500 species of plants and animals may now be endangered — or even completely gone. 
      A wallaby licks its burnt paws after escaping a bushfire near Nana Glen in New South Wales on November 12, 2019.Wolter Peeters/The Sydney Morning Herald via Getty Image
      Australia’s iconic koala became the poster child of the crisis as images of rescuers carrying these singed marsupials out of the flames went global: As many as 60,000 of the nation’s estimated population of 330,000 koalas perished in the fires, ecologists concluded in December in a report for World Wildlife Fund Australia. While there’s no doubt that such charismatic megafauna suffered enormously, the greatest toll is likely to have been in other groups of species, such as invertebrates and plants, which often escape the public’s attention.
      As Kingsley Dixon, an ecologist at Curtin University in Perth told the Associated Press last year: “I don’t think we’ve seen a single event in Australia that has destroyed so much habitat and pushed so many creatures to the very brink of extinction.”

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      Koala charisma
      Even before the fires, many vertebrate species were already on downward trends, says John Woinarski, an ecologist at Charles Darwin University in Darwin. The blazes have “exacerbated the threats that were driving the declines,” he says.
      For example, fluffy arboreal marsupials called greater gliders (Petauroides volans) had already experienced a 50 percent population decline in recent decades. The fires then burned a third of their remaining habitat along Australia’s eastern coastline. An ongoing assessment may lead to the gliders being recategorized from vulnerable to endangered.
      Overall, 49 vertebrates that previously were not endangered now qualify for being listed as threatened under Australia’s guidelines for that designation, researchers reported in July in Nature Ecology and Evolution. That shift alone would increase the tally of nationally protected nonmarine vertebrate species by about 15 percent, from 324 to 373.
      Another 21 already threatened vertebrates had more than 30 percent of their ranges burned, and some may now qualify for being reassessed to higher categories of threat, the authors found. One species that may need to be recategorized is the koala (Phascolarctos cinereas), with some state’s populations that were hardest hit under consideration to be upgraded from vulnerable to endangered. 
      A koala named Paul recovers from his burns at an ICU in November 2019 after being rescued by volunteers following weeks of bushfires across New South Wales and Queensland.Edwards/Getty Image
      Besides the impact on koalas, the WWF Australia report suggests that as many as 3 billion individual mammals, birds, reptiles and frogs died or were displaced during the crisis. Though those figures are astounding, the impacts on lesser-studied groups such as invertebrates and plants may have been even greater.
      “Many of those have much smaller ranges [than vertebrates], which means they are going to be even more impacted when a big fire goes through,” says James Watson, a conservation scientist at the University of Queensland in Brisbane and an author of the Nature Ecology and Evolution paper on vertebrates. “I am willing to bet that there’s many species … that may disappear forever.”
      Invertebrate impact
      In February, more than 100 biologists convened the first of several online workshops to assess whether 234 Australian invertebrates now need to be added to the International Union for the Conservation of Nature’s Red List — a global who’s who of threatened species. 
      Snails, similar to many invertebrates, are particularly susceptible to wildfires, as they are unable to outrun flames and can’t survive intense heat, Hyman notes. Many also have small ranges that were completely incinerated, leaving no survivors that can recolonize the burned area.
      “A snail can’t do much to escape,” she says. “You could expect more than 90 percent mortality in a high-intensity bushfire.” In October, Hyman’s team published one of the first papers quantifying the impacts on invertebrates in New South Wales in the Technical Reports of the Australian Museum Online.
      The Palethorpe’s pinwheel snail (Rophodon palethorpei) has not yet turned up in searches following the wildfires, but other snail species did survive.Vince Railton, Queensland Museum
      Their surveys showed that 29 species in the state — including dung beetles, freshwater crayfish, flies, snails and spiders — had their entire ranges burned. Another 46 species had at least half their known habitat within the fire zones. These 75 species were among the 234 under consideration for adding to the IUCN Red List during the biologists’ first online workshop.
      “We’ve gathered together 230-odd species that are believed to now be of concern. These include a range of different taxa from land snails to millipedes to arachnids to insects, and this 230 is growing rapidly,” says Jess Marsh, an arachnologist at Charles Darwin University who was one of the conveners of the workshop. “I expect it will massively increase.”
      Some of the spiders she studies were the first to be added to that list. She’s already spent several months on South Australia’s Kangaroo Island hunting without luck for the Kangaroo Island assassin spider (Zephyrarchaea austini). Dependent on leaf litter suspended in the understory, and restricted to just a few locations that were razed in early 2020, she suspects that the species may be extinct.
      Spiders on Kangaroo Island such as this assassin spider (Zephyrarchaea austini) may now be extinct after most of their habitat was razed in early 2020.M.G. Rix and M.S. Harvey/ZooKeys 2012
      “There’s no understory vegetation left, let alone any leaf litter suspended in it, so that species is really hanging in the balance,” says Marsh.
      Generally, the species being considered for recognition as endangered had more than 50 percent of their ranges burned, lived in flammable parts of the habitat and have little ability to disperse to other areas. More than 150 of the 234 species being urgently assessed had their entire range burned. And it’s not just the flames themselves that are problematic; so is the reshaped environment following fires. Millipedes, for example, are very vulnerable not only to fire but also to drying out in the reduced shade and shelter of the post-fire environment.
      “A lot of invertebrates are very susceptible to desiccation, and need cover and humidity to survive a hot summer, which are obviously lacking following the fire,” Marsh says. “Taking into account all of the threats … we could be looking at significant numbers going extinct.”
      Rooted in place
      Lost vegetation hasn’t just put animals in danger. Many plants themselves may also be at risk, though experts have yet to compile an official list.
      Rachael Gallagher, a plant ecologist at Macquarie University in Sydney, has been prioritizing endemic plant species — those found nowhere else on Earth — that are in most urgent need of conservation for the Australian government. Perhaps surprisingly, she’s particularly worried about some trees that actually depend on fire to survive. Eucalypts known as alpine ash (Eucalyptus delegatensis) and mountain ash (E. regnans), for instance, are typically killed by fire and then regenerate from surviving seeds in the aftermath. Australia has many trees that must complete their entire life cycle from germination through to reproductively mature adult before the next major bushfire passes through (SN: 2/11/20). For some species, this may take 15 to 20 years.
      Some trees in Australia, such as this mountain ash (Eucalyptus regnans), depend on fire for their lifecycle, but recent wildfires may have been too much too soon.station96/iStock/Getty Images Plus
      The problem now is that climate change has increased the frequency of fires to the degree that many of these plants are unable to reach adulthood and set seed before the next fire passes through, meaning they may be lost from these ecosystems (SN: 3/4/20).
      The fires burned 25–100 percent of the ranges of 257 species of plants for which “the historical intervals between fire events across their range are likely to be too short to allow them to effectively regenerate,” Gallagher says. These species, which have some degree of fire tolerance, are at “increased risk of extinction.” These include shrubs and trees such as the granite boronia (Boronia granitica), Forrester’s bottlebrush (Callistemon forresterae), dwarf cypress pine (Callitris oblonga) and the Wolgan snow gum (Eucalyptus gregsoniana).
      Found, not lost
      Nevertheless, as researchers head out into the field to assess what’s lost, what they are sometimes finding are glimmers of hope. “Australian plants are remarkably resilient and there’s been regeneration in places where nobody thought there would be,” Gallagher says.
      One species that survived against all the odds is the Gibraltar Range waratah (Telopea aspera), a drought-resistant shrub with leathery leaves and bright red flowers. “This species has a very small range, being specialized to granite outcrops in one mountain range, which was burnt during the fires,” she says. “However, it has been noted as resprouting after the fires by park rangers and, in the absence of another fire in coming years, is likely to be able to recover.”
      Several animal species that were thought to be in grave peril following the fires that burned nearly half of the 4,400-square-kilometer Kangaroo Island have survived better than expected too (SN: 1/13/20). In the particularly badly burned reserves of the western end of the island, tiny marsupial carnivores called Kangaroo Island dunnarts (Sminthopsis aitkeni) are frequently appearing on camera traps. Swiftly erected predator-exclusion fences now protect survivors from feral cats.
      Tiny marsupials known as Kangaroo Island dunnarts (Sminthopsis aitkeni) have fared much better than other animals, appearing frequently on camera traps.Australian Wildlife Conservancy
      Similarly, large flocks of the glossy black-cockatoo (Calyptorhynchus lathami) have adapted by moving to unburned areas with food trees, says Karleah Berris of Natural Resources Kangaroo Island, who heads the crew that manages the endangered birds. Better news yet, a surprising number of birds bred and fledged young in mid-2020. “The important thing now is to protect what is left from fire until the burnt areas regenerate,” she says. “But I think, at present, all signs are that they are coping.”
      Hyman says that, hearteningly, her team found handfuls of survivors of some snail species during several surveys in New South Wales in late 2020. The snails turned up in small patches of unburned habitat, sometimes at the bottom of gullies or in deep leaf litter around the bases of large trees. And that gives her hope that other snail species may have held on in other, larger unburned patches with greater numbers of survivors.
      “But the question then becomes, what sort of recovery can they make from that?” she says. “Whether they can recover and breed up and start to move back into surviving areas again perhaps depends on how dry the weather is in coming years and if there are more fires.”
      She’s still hoping that a handful of Palethorpe’s pinwheel snails may have clung on against all the odds. “My husband is on tenterhooks wondering if his snail is still there or not,” she says. More

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      ‘Green’ burials are slowly gaining ground among environmentalists

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      Despite “green” burials becoming increasingly available in North America, some older eco-conscious adults remain unaware of the option when planning for their deaths, a small study hints.
      Green burials do not use concrete vaults, embalm bodies or use pesticides or fertilizers at gravesites. Bodies are buried in a biodegradable container like a pinewood or wicker casket, or a cotton or silk shroud. Proponents of the small but growing trend argue it is more environmentally friendly and in line with how burials were done before the invention of the modern funeral home industry.
      But when researchers asked 20 residents of Lawrence, Kan., over the age of 60 who identify as environmentalists if they had considered green burial, most hadn’t heard of the practice. That’s despite the fact that green burial had been available in Lawrence for nearly a decade at the time. More than half of the survey participants planned on cremation, because they viewed it as the eco-friendliest option, the team reported online January 26 in Mortality.
      In 2008, Lawrence became the first U.S. city to allow green burials in a publicly owned cemetery. Several years later, at a meeting of an interfaith ecological community organization in the city, sociologist Paul Stock of the University of Kansas in Lawrence and his colleague Mary Kate Dennis noticed that most of the attendees were older adults. These people “live and breathe their environmentalism,” says Dennis, now a social work researcher at the University of Manitoba in Canada. “We were curious if it followed them all the way through to their burials.”

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      That the majority of participants in the new survey leaned towards cremation aligns with national trends. Cremation recently surpassed traditional burial as the most popular death care choice in the United States. In July 2020, the National Funeral Directors Association projected the cremation rate that year would be 56 percent compared to 38 percent for casket burials. By 2040, the cremation rate is projected to grow to about 78 percent while the burial rate is estimated to shrink to about 16 percent.
      Cremation’s growing popularity can be traced to a number of factors, including affordability and concerns about traditional burial’s environmental impacts. But cremation comes with its own environmental cost, releasing hundreds of kilograms of carbon dioxide into the air per body.
      The preference for green burial, meanwhile, is small but growing. The Green Burial Council was founded in 2005 to establish green burial standards by certifying green burial sites. Now 14 percent of Americans over age 40 say they would choose green burial, the NFDA reports, and around 62 percent are open to exploring it.
      For those who go the green burial route, there now are a variety of commercially available choices. More adventurous options include a burial suit designed to sprout mushrooms as the body decomposes, an egg-shaped burial pod that eventually grows into a tree and human composting (SN: 2/16/20) — a one- to two-month process that turns the body into soil. In 2019, Washington became the first and only U.S. state to legalize human composting. 
      Conservation burial cemeteries take the green burial concept a step further by doubling as protected nature preserves. To date, the Green Burial Council has certified over 200 green burial sites and eight conservation burial sites in North America.
      Such initiatives showcase a growing awareness that death care choices can have a positive impact on ecosystems, says Lynne Carpenter-Boggs, a soil scientist at Washington State University in Pullman and a research advisor for the Seattle-based human composting company Recompose. But, she cautions, there is still little formal research comparing the environmental impacts of different death care choices.
      Stock and Dennis think this lack of research, coupled with a general lack of awareness of green burial as an available choice, could be the reason why many of the environmentalists they spoke with weren’t yet considering it. But as the option becomes more widely available, Dennis says, “it will be interesting to see how that shifts.” More

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      Climate change helped some dinosaurs migrate to Greenland

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      A drop in carbon dioxide levels may have helped sauropodomorphs, early relatives of the largest animal to ever walk the earth, migrate thousands of kilometers north past once-forbidding deserts around 214 million years ago.
      Scientists pinpointed the timing of the dinosaurs’ journey from South America to Greenland by correlating rock layers with sauropodomorph fossils to changes in Earth’s magnetic field. Using that timeline, the team found that the creatures’ northward push coincides with a dramatic decrease in CO2, which may have removed climate-related barriers, the team reports February 15 in Proceedings of the National Academy of Sciences.
      The sauropodomorphs were a group of long-necked, plant-eating dinosaurs that included massive sauropods such as Seismosaurus as well as their smaller ancestors (SN: 11/17/20). About 230 million years ago, sauropodomorphs lived mainly in what is now northern Argentina and southern Brazil. But at some point, these early dinosaurs picked up and moved as far north as Greenland.
      Exactly when they could have made that journey has been a puzzle, though. “In principle, you could’ve walked from where they were to the other hemisphere, which was something like 10,000 kilometers away,” says Dennis Kent, a geologist at Columbia University. Back then, Greenland and the Americas were smooshed together into the supercontinent Pangea. There were no oceans blocking the way, and mountains were easy to get around, he says. If the dinosaurs had walked at the slow pace of one to two kilometers per day, it would have taken them approximately 20 years to reach Greenland.

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      But during much of the Late Triassic Epoch, which spans 233 million to 215 million years ago, Earth’s carbon dioxide levels were incredibly high — as much as 4,000 parts per million. (In comparison, CO2 levels currently are about 415 parts per million.) Climate simulations have suggested that level of CO2 would have created hyper-arid deserts and severe climate fluctuations, which could have acted as a barrier to the giant beasts. With vast deserts stretching north and south of the equator, Kent says, there would have been few plants available for the herbivores to survive the journey north for much of that time period.
      Previous estimates suggested that these dinosaurs migrated to Greenland around 225 million to 205 million years ago. To get a more precise date, Kent and his colleagues measured magnetic patterns in ancient rocks in South America, Arizona, New Jersey, Europe and Greenland — all locales where sauropodomorphs fossils have been discovered. These patterns record the orientation of Earth’s magnetic field at the time of the rock’s formation. By comparing those patterns with previously excavated rocks whose ages are known, the team found that sauropodomorphs showed up in Greenland around 214 million years ago.
      Vertebrate fossils from the Late Triassic have been found at a number of sites around the world, some of which are marked (black dots) on this map showing how the continents were arranged about 220 million years ago. New dating of rocks at sites in South America and Greenland pinpoint when long-necked dinosaurs known as sauropodomorphs migrated north.Dennis Kent and Lars Clemmensen
      That more precise date for the sauropodomorphs’ migration may explain why it took them so long to start the trek north — and how they survived journey: Earth’s climate was changing rapidly at that time.
      Around the time that sauropodomorphs appeared in Greenland, carbon dioxide levels plummeted within a few million years to 2,000 parts per million, making the climate more travel-friendly to herbivores, the team reports. The reason for this drop in carbon dioxide — which appears in climate records from South America and Greenland — is unknown, but it allowed for an eventual migration northward.
      “We have evidence for all of these events, but the confluence in timing is what is remarkable here,” says Morgan Schaller, a geochemist at Rensselaer Polytechnic Institute in Troy, N.Y., who was not involved with this study. These new findings, he says, also help solve the mystery of why plant eaters stayed put during a time that meat eaters roamed freely.
      “This study reminds us that we can’t understand evolution without understanding climate and environment,” says Steve Brusatte, a vertebrate paleontologist and evolutionary biologist at the University of Edinburgh, also not involved with the study. “Even the biggest and most awesome creatures that ever lived were still kept in check by the whims of climate change.” More

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      A drop in CFC emissions puts the hole in the ozone layer back on track to closing

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      Good news for the ozone layer: After a recent spike in CFC-11 pollution, emissions of this ozone-destroying chemical are on the decline.
      Emissions of trichlorofluoromethane, or CFC-11, were supposed to taper off after the Montreal Protocol banned CFC-11 production in 2010 (SN: 7/7/90). But 2014 to 2017 saw an unexpected bump. About half of that illegal pollution was pegged to eastern China (SN: 5/22/19). Now, atmospheric data show that global CFC-11 emissions in 2019 were back down to the average levels seen from 2008 to 2012, and about 60 percent of that decline was due to reduced emissions in eastern China, two teams report online February 10 in Nature. 
      These findings suggest that the hole in Earth’s ozone layer is still on track to close up within the next 50 years — rather than being delayed, as it would have been if CFC-11 emissions had remained at the levels seen from 2014 to 2017 (SN: 12/14/16).
      One group analyzed the concentration of CFC-11, used to make insulating foams for buildings and household appliances, in the air above atmospheric monitoring stations around the globe. The team found that the world emitted about 52,000 metric tons of CFC-11 in 2019 — a major drop from the annual average of 69,000 metric tons from 2014 to 2018. The 2019 emissions were comparable to the average annual emissions from 2008 to 2012, Stephen Montzka, an atmospheric chemist at the U.S. National Oceanic and Atmospheric Administration in Boulder, Colo., and colleagues report.

      The new measurements imply that there has been a significant decrease in illicit CFC-11 production within the last couple of years, the researchers say, probably thanks to more rigorous regulation enforcement in China and elsewhere.
      Another group confirmed that emissions from eastern China have diminished since 2018 by analyzing air samples from Hateruma, Japan and Gosan, South Korea. The region emitted about 5,000 metric tons of CFC-11 in 2019, which was about 10,000 metric tons less than its average annual emissions from 2014 to 2017 and was similar to the 2008 to 2012 average. That analysis was led by Sunyoung Park, a geochemist at Kyungpook National University in Daegu, South Korea.

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      The recent downturn in CFC-11 pollution shows that “the Montreal Protocol is working,” says A.R. “Ravi” Ravishankara, an atmospheric scientist at Colorado State University in Fort Collins not involved in either study. When someone violates the treaty, “atmospheric sleuthing” can uncover the culprits and spur countries to take action, he says. “China clearly took action, because you can see the result of that action in the atmosphere.” 
      Montzka cautions that it might not always be so easy to point the finger at rogue emitters. “I think we got lucky this time,” he says, because atmospheric monitoring sites in Asia were able to trace the bulk of illegal emissions to eastern China and monitor the situation over several years. Many places around the world, such as in Africa and South America, lack atmospheric monitoring stations — so it’s still a mystery which countries besides China were responsible for the recent rise and fall of CFC-11 emissions. More

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      Three things to know about the disastrous flood in India

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      A flash flood surged down a river in India’s Himalayan Uttarakhand state on February 7, killing at least 30 people and washing away two hydroelectric power stations.
      As rescue workers search for more than 100 people who are still missing, officials and scientists are trying to unravel the causes of the sudden flood. Did a glacier high up in the mountains collapse, releasing a huge plug of frigid meltwater that spilled into the river? Or was the culprit a landslide that then triggered an avalanche? And what, if any, link might these events have to a changing climate?
      Here are three things to know about what might have caused the disaster in Uttarakhand.
      1. One possible culprit was the sudden break of a glacier high in the mountains.
      News reports in the immediate wake of the disaster suggested that the floodwaters were caused by the sudden overflow of a glacial lake high up in the mountain, an event called a glacial lake outburst flood.
      “It’s likely too early to know what exactly happened,” says Anjal Prakash, the research director of the Bharti Institute of Public Policy at the Indian School of Business in Hyderabad. Satellite images show that a section of a glacier broke off, but how that break relates to the subsequent floods is still unknown. One possibility is that the glacier was holding back a lake of meltwater, and that heavy snowfall in the region two days earlier added enough volume to the lake that the water forced its way out, breaking the glacier and surging into nearby rivers.
      This scenario is certainly in line with known hazards for the region. “These mountains are very fragile,” says Prakash, who was also a lead author on the Intergovernmental Panel on Climate Change’s 2019 special report on oceans and the cryosphere, Earth’s icy places. But, he notes, there isn’t yet much on-the-ground data to help clarify events. “The efforts are still focused on relief at the moment.”
      2. A landslide may be to blame instead.
      Other researchers contend that the disaster wasn’t caused by a glacial lake outburst flood at all. Instead, says Daniel Shugar, a geomorphologist at the University of Calgary in Canada, satellite images snapped during the disaster show the telltale marks of a landslide: a dark scar snaking through the white snow and clouds of dust clogging the air above. “You could see this train of dust in the valley, and that’s common for a very large landslide,” Shugar says.
      “WOW,” he wrote on Twitter the morning of February 7, posting side-by-side satellite shots of a dark area of possible “massive dust deposition,” contrasted against the same snowy, pristine region just the day before.

      Landslides — the sudden failure of a slope, sending a rush of rocks and sediment downhill — can be triggered by anything from an earthquake to an intense deluge of rain. In high, snowy mountains, cycles of freezing and thawing and refreezing again can also begin to break the ground apart; the ice-filled cracks can slowly widen over time, setting the stage for sudden failure, and then, disaster.
      The satellite images seem to point clearly to such a landslide, rather than a typical glacial lake overflow, Shugar says. The force of the landslide may have actually broken off that piece of hanging glacier, he says. Another line of evidence against a sudden lake burst is that “there were no lakes of any size visible” in the satellite images taken over the region.
      However, an outlying question for this hypothesis is where the floodwaters came from. It might be that one of the rivers draining down the mountain was briefly dammed by the rockfall; a sudden release of that dam could send a large plug of water from the river swiftly and disastrously downhill. “But that’s a pure guess at the moment,” Shugar says.
      3. It’s not yet clear whether climate change played a role in the disaster.
      The risk of both glacial lake outburst floods and freeze-thaw-related landslides in Asia’s high mountains has increased due to climate change. At first glance, “it was a climate event,” Prakash says. “But the data are still coming.”
      The region, which includes the Hindu Kush Himalayan mountains and the Tibetan Plateau, “has been a climate change hot spot for a pretty long time,” Prakash says. The region is often called Earth’s third pole, because the stores of ice and snow in the Himalayan watershed amount to the largest reserves of freshwater outside of the polar regions. The region is the source of 10 major river systems that provide water to almost 2 billion people.
      Climate change reports have warned that warming is not only threatening this water supply, but also increasing the likelihood of natural hazards (SN: 5/29/19). In the Intergovernmental Panel on Climate Change’s 2019 special report on oceans and the cryosphere, scientists noted that glacier retreat, melting snow and thawing permafrost are making mountain slopes more unstable and also increasing the number of glacial lakes, upping the likelihood of a sudden, catastrophic failure (SN: 9/25/19).
      A 2019 comprehensive assessment focusing on climate change’s impacts in Asia’s high mountains found that the glaciers in the region have retreated much more quickly in the last decade than was anticipated, Prakash says, “and that is alarming for us.” Here’s another way to look at it: Glaciers are retreating twice as fast as they were at the end of the 20th century (SN: 6/19/19).
      Glacier-related landslides in the region have also become increasingly common in the last decade, as the region warms and destabilizing freeze-thaw cycles within the ground occur higher and higher up on the slopes.
      But in the case of this particular disaster, Shugar says, it’s just hard to say conclusively at this point what role climate change might have played, or even what specific event might have triggered a landslide. “Sometimes there is no trigger; sometimes it’s just time,” he says. “Or it’s that we just don’t understand the trigger.”

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      Ship exhaust studies overestimate cooling from pollution-altered clouds

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      Among the biggest questions for climate change forecasters is how atmospheric aerosols shape clouds, which can help cool the planet. Now, a new study finds that one promising strategy for understanding how aerosols and clouds interact can overestimate the cooling ability of pollution-generated clouds by up to 200 percent, researchers report in the Jan. 29 Science.
      “Clouds in general, and how aerosols interact with the climate, are a big uncertainty in climate models,” says Franziska Glassmeier, an atmospheric scientist at Delft University of Technology in the Netherlands. Scientists know that aerosols — both natural, as from volcanoes, and human-caused, as from pollution — can change a cloud’s thickness, ability to scatter sunlight or how much rainfall it produces. But these complicated physical effects are difficult to simulate, so scientists have sought real-world examples to study these effects.
      Enter ship tracks. Exhaust belched out of massive cargo ships crossing the oceans can form these bright lines of clouds. The tiny exhaust particles act as cloud nuclei: Water vapor condenses on the particles to form cloud droplets, the watery stuff of clouds. Ship tracks are “this prime example where we can see this cause and effect,” Glassmeier says. “Put in particles, and you can see the clouds get brighter.” Brighter clouds means that they are reflecting even more sunlight back into space.
      Visible and measurable by satellite, the tracks offer a potential window into how larger-scale industrial pollution around the globe might be altering the planet’s cloudscape — and perhaps how such clouds might affect the climate. Satellite-derived analyses of ship tracks involve measuring the density of the water droplets in the clouds from the images, and calculating how the brightness of the clouds changes over time.

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      To assess how well ship tracks actually represent the overall impact of pollution on clouds, Glassmeier and her colleagues compared the cooling effect of ship track clouds with that of simulated pollution-derived clouds, such as might occur over a city. In particular, the researchers wanted to simulate how both the thickness and the brightness of the clouds — and therefore their cooling effect — might evolve over time, as a result of processes like rainfall and evaporation.
      The problem, the team found, is that the ship tracks don’t tell the whole story. Ship tracks are short-lived, because the source of pollution is always on the move. But industrial pollution doesn’t tend to happen in a brief pulse: Instead, there is a steady influx of particles to the atmosphere. And that difference in inputs affects how natural clouds respond over time.
      In both the ship track studies and the simulations of industrial pollution, clouds initially brighten and produce a cooling effect. That’s because, in both cases, the addition of abundant aerosol particles to the atmosphere gives water vapor numerous surfaces on which to condense, creating many small water droplets that form this brighter cloud and reflect incoming radiation.
      After a few hours, however, as a ship moves on, the ship track goes away, and the pulse of pollution ceases, Glassmeier says. The initial brief bit of cooling subsides as the preexisting natural clouds return to their original, nonpolluted state.
      But in the case of industrial pollutants, the natural clouds don’t return to their original state, the simulations show. Rather, the pollutants hasten the clouds’ demise. That’s because the tinier aerosol-seeded droplets begin to evaporate more quickly than larger, natural cloud droplets would. This increased evaporation thins the original cloud, allowing more heat through than if the pollutants never arrived. And that can ultimately have an overall warming, rather than cooling, effect on the climate, the team says.
      “There is this timescale effect that needs to be taken into account,” Glassmeier says. Relying solely on ship track data to understand all sources of pollution misses this gradual thinning effect. “I wouldn’t throw all the ship track data away; we just need to interpret it in a new way.” Current climate models tend to omit this thinning effect, she says.
      The new study is “really useful for helping to interpret aerosol-cloud relationships in satellite data,” says Edward Gryspeerdt, an atmospheric physicist at Imperial College London who was not involved in the study. It “demonstrates that the cloud response to aerosols is not instant, but evolves over time.”
      Scientists have been aware that ship tracks may not lead to cooling, says Graeme Stephens, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. For example, Stephens notes that he and others have previously found that ship tracks can speed up cloud thinning by increasing the rate of evaporation at the tops of the clouds, while at the same time suppressing rainfall, which maintains some of the cloud’s thickness. These two competing responses make determining a cloud’s ultimate fate tricky.
      But what ship tracks can do is act as “a controlled laboratory of sorts,” Stephens says. They “offer us a way to examine aerosol influences on clouds in a direct, concrete way.” More

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      Some bacteria are suffocating sea stars, turning the animals to goo

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      The mysterious culprit behind a deadly sea star disease is not an infection, as scientists once thought.
      Instead, multiple types of bacteria living within millimeters of sea stars’ skin deplete oxygen from the water and effectively suffocate the animals, researchers report January 6 in Frontiers in Microbiology. Such microbes thrive when there are high levels of organic matter in warm water and create a low oxygen environment that can make sea stars melt in a puddle of slime.
      Sea star wasting disease — which causes lethal symptoms like decaying tissue and loss of limbs — first gained notoriety in 2013 when sea stars living off the U.S. Pacific Coast died in massive numbers. Outbreaks of the disease had also occurred before 2013, but never at such a large scale.
      Scientists suspected that a virus or bacterium might be making sea stars sick. That hypothesis was supported in a 2014 study that found unhealthy animals may have been infected by a virus (SN: 11/19/14). But the link vanished when subsequent studies found no relationship between the virus and dying sea stars, leaving researchers perplexed (SN: 5/5/16). 

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      The new finding that a boom of nutrient-loving bacteria can drain oxygen from the water and cause wasting disease “challenges us to think that there might not always be a single pathogen or a smoking gun,” says Melissa Pespeni, a biologist at the University of Vermont in Burlington who was not involved in the work. Such a complex environmental scenario for killing sea stars “is a new kind of idea for [disease] transmission.”  
      There were certainly many red herrings during the hunt for why sea stars along North America’s Pacific Coast were melting into goo, says Ian Hewson, a marine biologist at Cornell University. In addition to the original hypothesis of a viral cause for sea star wasting disease — which Hewson’s team reported in 2014 in Proceedings of the National Academy of Sciences but later disproved — he and colleagues analyzed a range of other explanations, from differences in water temperature to exposing the animals to bacteria. But nothing reliably triggered wasting.   
      Then the researchers examined the types of bacteria living with healthy sea stars compared with those living among the animals with wasting disease. “That was when we had our aha moment,” says Hewson.
      Not all sea stars are susceptible to sea star wasting disease. Species that have more structures on their surface, and therefore more surface area for bacteria to deplete oxygen, appear more likely to get severely sick compared with flatter sea stars. In this photo, an ochre sea star (Pisaster ochraceus) succumbs to the disease in Davenport, Calif., in June 2018.Ian Hewson
      Types of bacteria known as copiotrophs, which thrive in environments with lots of nutrients, were present around the sea stars at higher levels than normal either shortly before the animals developed lesions or as they did so, Hewson and colleagues found. Bacterial species that survive only in environments with little to no oxygen were also thriving. In the lab, the sea stars began wasting when the researchers added phytoplankton or a common bacterial-growth ingredient to the warm water tubs those microbes and sea stars were living in.  
      Experimentally depleting oxygen from the water had a similar effect, causing lesions in 75 percent of the animals, while none succumbed in the control group. Sea stars breathe by diffusing oxygen over small external projections called skin gills, so the lack of oxygen in the wake of flourishing copiotrophs leaves sea stars struggling for air, the data show. It’s unclear how the animals degrade in low oxygen conditions, but it could be due to massive cell death.
      Although the disease isn’t caused by a contagious pathogen, it is transmissible in the sense that dying sea stars generate more organic matter that spur bacteria to grow on healthy animals nearby. “It’s a bit of a snowball effect,” Hewson says.
      The team also analyzed tissues from sea stars that had succumbed in the 2013 mass die-off — which followed a large algal bloom on the U.S. West Coast — to see if such environmental conditions might explain that outbreak. In fast-growing appendages that help them move, the sea stars that perished had high amounts of a form of nitrogen found in low oxygen conditions — a sign that those animals may have died from a lack of oxygen.
      The problem may get worse with climate change, Hewson says. “Warmer waters can’t have as much oxygen [compared with colder water] just by physics alone.” Bacteria, including copiotrophs, also flourish in warm water.  
      But pinpointing the likely cause could help experts better treat sick sea stars in the lab, Hewson says. Some techniques include increasing the oxygen levels in a water tank to make the gas more easily available to sea stars or getting rid of extra organic matter with ultraviolet light or water exchange.
      “There’s still a lot to figure out with this disease, but I think [this new study] gets us a long way to understanding how it comes about,” Pespeni says. More