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    Why planting tons of trees isn’t enough to solve climate change

    Trees are symbols of hope, life and transformation. They’re also increasingly touted as a straightforward, relatively inexpensive, ready-for-prime-time solution to climate change.

    When it comes to removing human-caused emissions of the greenhouse gas carbon dioxide from Earth’s atmosphere, trees are a big help. Through photosynthesis, trees pull the gas out of the air to help grow their leaves, branches and roots. Forest soils can also sequester vast reservoirs of carbon.

    Earth holds, by one estimate, as many as 3 trillion trees. Enthusiasm is growing among governments, businesses and individuals for ambitious projects to plant billions, even a trillion more. Such massive tree-planting projects, advocates say, could do two important things: help offset current emissions and also draw out CO2 emissions that have lingered in the atmosphere for decades or longer.

    Even in the politically divided United States, large-scale tree-planting projects have broad bipartisan support, according to a spring 2020 poll by the Pew Research Center. And over the last decade, a diverse garden of tree-centric proposals — from planting new seedlings to promoting natural regrowth of degraded forests to blending trees with crops and pasturelands — has sprouted across the international political landscape.

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    Trees “are having a bit of a moment right now,” says Joe Fargione, an ecologist with The Nature Conservancy who is based in Minneapolis. It helps that everybody likes trees. “There’s no anti-tree lobby. [Trees] have lots of benefits for people. Not only do they store carbon, they help provide clean air, prevent soil erosion, shade and shelter homes to reduce energy costs and give people a sense of well-being.”

    Conservationists are understandably eager to harness this enthusiasm to combat climate change. “We’re tapping into the zeitgeist,” says Justin Adams, executive director of the Tropical Forest Alliance at the World Economic Forum, an international nongovernmental organization based in Geneva. In January 2020, the World Economic Forum launched the One Trillion Trees Initiative, a global movement to grow, restore and conserve trees around the planet. One trillion is also the target for other organizations that coordinate global forestation projects, such as Plant-for-the-Planet’s Trillion Tree Campaign and Trillion Trees, a partnership of the World Wildlife Fund, the Wildlife Conservation Society and other conservation groups.

    Yet, as global eagerness for adding more trees grows, some scientists are urging caution. Before moving forward, they say, such massive tree projects must address a range of scientific, political, social and economic concerns. Poorly designed projects that don’t address these issues could do more harm than good, the researchers say, wasting money as well as political and public goodwill. The concerns are myriad: There’s too much focus on numbers of seedlings planted, and too little time spent on how to keep the trees alive in the long term, or in working with local communities. And there’s not enough emphasis on how different types of forests sequester very different amounts of carbon. There’s too much talk about trees, and not enough about other carbon-storing ecosystems.

    “There’s a real feeling that … forests and trees are just the idea we can use to get political support” for many, perhaps more complicated, types of landscape restoration initiatives, says Joseph Veldman, an ecologist at Texas A&M University in College Station. But that can lead to all kinds of problems, he adds. “For me, the devil is in the details.”

    The root of the problem

    The pace of climate change is accelerating into the realm of emergency, scientists say. Over the last 200 years, human-caused emissions of greenhouse gases, including CO2 and methane, have raised the average temperature of the planet by about 1 degree Celsius (SN: 12/22/18 & 1/5/19, p. 18).

    The litany of impacts of this heating is familiar by now. Earth’s poles are rapidly shedding ice, which raises sea levels; the oceans are heating up, threatening fish and food security. Tropical storms are becoming rainier and lingering longer, and out of control wildfires are blazing from the Arctic to Australia (SN: 12/19/20 & 1/2/21, p. 32).

    The world’s oceans and land-based ecosystems, such as forests, absorb about half of the carbon emissions from fossil fuel burning and other industrial activities. The rest goes into the atmosphere. So “the majority of the solution to climate change will need to come from reducing our emissions,” Fargione says. To meet climate targets set by the 2015 Paris Agreement, much deeper and more painful cuts in emissions than nations have pledged so far will be needed in the next 10 years.

    We invest a lot in tree plantings, but we are not sure what happens after that. Lalisa Duguma

    But increasingly, scientists warn that reducing emissions alone won’t be enough to bring Earth’s thermostat back down. “We really do need an all-hands-on-deck approach,” Fargione says. Specifically, researchers are investigating ways to actively remove that carbon, known as negative emissions technologies. Many of these approaches, such as removing CO2 directly from the air and converting it into fuel, are still being developed.

    But trees are a ready kind of negative emissions “technology,” and many researchers see them as the first line of defense. In its January 2020 report, “CarbonShot,” the World Resources Institute, a global nonprofit research organization, suggested that large and immediate investments in reforestation within the United States will be key for the country to have any hope of reaching carbon neutrality — in which ongoing carbon emissions are balanced by carbon withdrawals — by 2050. The report called for the U.S. government to invest $4 billion a year through 2030 to support tree restoration projects across the United States. Those efforts would be a bridge to a future of, hopefully, more technologies that can pull large amounts of carbon out of the atmosphere.

    The numbers game

    Earth’s forests absorb, on average, 16 billion metric tons of CO2 annually, researchers reported in the March Nature Climate Change. But human activity can turn forests into sources of carbon: Thanks to land clearing, wildfires and the burning of wood products, forests also emit an estimated 8.1 billion tons of the gas back to the atmosphere.

    That leaves a net amount of 7.6 billion tons of CO2 absorbed by forests per year — roughly a fifth of the 36 billion tons of CO2 emitted by humans in 2019. Deforestation and forest degradation are rapidly shifting the balance. Forests in Southeast Asia now emit more carbon than they absorb due to clearing for plantations and uncontrolled fires. The Amazon’s forests may flip from carbon sponge to carbon source by 2050, researchers say (SN Online: 1/10/20). The priority for slowing climate change, many agree, should be saving the trees we have.

    Just how many more trees might be mustered for the fight is unclear, however. In 2019, Thomas Crowther, an ecologist at ETH Zurich, and his team estimated in Science that around the globe, there are 900 million hectares of land — an area about the size of the United States — available for planting new forests and reviving old ones (SN: 8/17/19, p. 5). That land could hold over a trillion more trees, the team claimed, which could trap about 206 billion tons of carbon over a century.

    That study, led by Jean-Francois Bastin, then a postdoc in Crowther’s lab, was sweeping, ambitious and hopeful. Its findings spread like wildfire through media, conservationist and political circles. “We were in New York during Climate Week [2019], and everybody’s talking about this paper,” Adams recalls. “It had just popped into people’s consciousness, this unbelievable technology solution called the tree.”

    To channel that enthusiasm, the One Trillion Trees Initiative incorporated the study’s findings into its mission statement, and countless other tree-planting efforts have cited the report.

    But critics say the study is deeply flawed, and that its accounting — of potential trees, of potential carbon uptake — is not only sloppy, but dangerous. In 2019, Science published five separate responses outlining numerous concerns. For example, the study’s criteria for “available” land for tree planting were too broad, and the carbon accounting was inaccurate because it assumes that new tree canopy cover equals new carbon storage. Savannas and natural grasslands may have relatively few trees, critics noted, but these regions already hold plenty of carbon in their soils. When that carbon is accounted for, the carbon uptake benefit from planting trees drops to perhaps a fifth of the original estimate.

    Trees are having a bit of a moment right now. Joe Fargione

    There’s also the question of how forests themselves can affect the climate. Adding trees to snow-covered regions, for example, could increase the absorption of solar radiation, possibly leading to warming.

    “Their numbers are just so far from anything reasonable,” Veldman says. And focusing on the number of trees planted also sets up another problem, he adds — an incentive structure that is prone to corruption. “Once you set up the incentive system, behaviors change to basically play that game.”

    Adams acknowledges these concerns. But, the One Trillion Trees Initiative isn’t really focused on “the specifics of the math,” he says, whether it’s the number of trees or the exact amount of carbon sequestered. The goal is to create a powerful climate movement to “motivate a community behind a big goal and a big vision,” he says. “It could give us a fighting chance to get restoration right.”

    Other nonprofit conservation groups, like the World Resources Institute and The Nature Conservancy, are trying to walk a similar line in their advocacy. But some scientists are skeptical that governments and policy makers tasked with implementing massive forest restoration programs will take note of such nuances.

    “I study how government bureaucracy works,” says Forrest Fleischman, who researches forest and environmental policy at the University of Minnesota in St. Paul. Policy makers, he says, are “going to see ‘forest restoration,’ and that means planting rows of trees. That’s what they know how to do.”

    Counting carbon

    How much carbon a forest can draw from the atmosphere depends on how you define “forest.” There’s reforestation — restoring trees to regions where they used to be — and afforestation — planting new trees where they haven’t historically been. Reforestation can mean new planting, including crop trees; allowing forests to regrow naturally on lands previously cleared for agriculture or other purposes; or blending tree cover with croplands or grazing areas.

    In the past, the carbon uptake potential of letting forests regrow naturally was underestimated by 32 percent, on average — and by as much as 53 percent in tropical forests, according to a 2020 study in Nature. Now, scientists are calling for more attention to this forestation strategy.

    If it’s just a matter of what’s best for the climate, natural forest regrowth offers the biggest bang for the buck, says Simon Lewis, a forest ecologist at University College London. Single-tree commercial crop plantations, on the other hand, may meet the technical definition of a “forest” — a certain concentration of trees in a given area — but factor in land clearing to plant the crop and frequent harvesting of the trees, and such plantations can actually release more carbon than they sequester.

    Comparing the carbon accounting between different restoration projects becomes particularly important in the framework of international climate targets and challenges. For example, the 2011 Bonn Challenge is a global project aimed at restoring 350 million hectares by 2030. As of 2020, 61 nations had pledged to restore a total of 210 million hectares of their lands. The potential carbon impact of the stated pledges, however, varies widely depending on the specific restoration plans.

    In a 2019 study in Nature, Lewis and his colleagues estimated that if all 350 million hectares were allowed to regrow natural forest, those lands would sequester about 42 billion metric tons (gigatons in chart above) of carbon by 2100. Conversely, if the land were to be filled with single-tree commercial crop plantations, carbon storage drops to about 1 billion metric tons. And right now, plantations make up a majority of the restoration plans submitted under the Bonn Challenge.

    Striking the right balance between offering incentives to landowners to participate while also placing certain restrictions remains a tricky and long-standing challenge, not just for combating the climate emergency but also for trying to preserve biodiversity (SN: 8/1/20, p. 18). Since 1974, Chile, for example, has been encouraging private landowners to plant trees through subsidies. But landowners are allowed to use these subsidies to replace native forestlands with profitable plantations. As a result, Chile’s new plantings not only didn’t increase carbon storage, they also accelerated biodiversity losses, researchers reported in the September 2020 Nature Sustainability.

    The reality is that plantations are a necessary part of initiatives like the Bonn Challenge, because they make landscape restoration economically viable for many nations, Lewis says. “Plantations can play a part, and so can agroforestry as well as areas of more natural forest,” he says. “It’s important to remember that landscapes provide a whole host of services and products to people who live there.”

    But he and others advocate for increasing the proportion of forestation that is naturally regenerated. “I’d like to see more attention on that,” says Robin Chazdon, a forest ecologist affiliated with the University of the Sunshine Coast in Australia as well as with the World Resources Institute. Naturally regenerated forests could be allowed to grow in buffer regions between farms, creating connecting green corridors that could also help preserve biodiversity, she says. And “it’s certainly a lot less expensive to let nature do the work,” Chazdon says.

    Indeed, massive tree-planting projects may also be stymied by pipeline and workforce issues. Take seeds: In the United States, nurseries produce about 1.3 billion seedlings per year, Fargione and colleagues calculated in a study reported February 4 in Frontiers in Forests and Global Change. To support a massive tree-planting initiative, U.S. nurseries would need to at least double that number.

    A tree-planting report card

    From China to Turkey, countries around the world have launched enthusiastic national tree-planting efforts. And many of them have become cautionary tales.

    China kicked off a campaign in 1978 to push back the encroaching Gobi Desert, which has become the fastest-growing desert on Earth due to a combination of mass deforestation and overgrazing, exacerbated by high winds that drive erosion. China’s Three-North Shelter Forest Program, nicknamed the Great Green Wall, aims to plant a band of trees stretching 4,500 kilometers across the northern part of the country. The campaign has involved millions of seeds dropped from airplanes and millions more seedlings planted by hand. But a 2011 analysis suggested that up to 85 percent of the plantings had failed because the nonnative species chosen couldn’t survive in the arid environments they were plopped into.

    A woman places straw in March 2019 to fix sand in place before planting trees at the edge of the Gobi Desert in China’s Minqin County. Her work is part of a private tree-planting initiative that dovetails with the government’s decades-long effort to build a “green wall” to hold back the desert.WANG HE/GETTY IMAGES PLUS

    More recently, Turkey launched its own reforestation effort. On November 11, 2019, National Forestation Day, volunteers across the country planted 11 million trees at more than 2,000 sites. In Turkey’s Çorum province, 303,150 saplings were planted in a single hour, setting a new world record.

    Within three months, however, up to 90 percent of the new saplings inspected by Turkey’s agriculture and forestry trade union were dead, according to the union’s president, Şükrü Durmuş, speaking to the Guardian (Turkey’s minister of agriculture and forestry denied that this was true). The saplings, Durmuş said, died due to a combination of insufficient water and because they were planted at the wrong time of year, and not by experts.

    Some smaller-scale efforts also appear to be failing, though less spectacularly. Tree planting has been ongoing for decades in the Kangra district of Himachal Pradesh in northern India, says Eric Coleman, a political scientist at Florida State University in Tallahassee, who’s been studying the outcomes. The aim is to increase the density of the local forests and provide additional forest benefits for communities nearby, such as wood for fuel and fodder for grazing animals. How much money was spent isn’t known, Coleman says, because there aren’t records of how much was paid for seeds. “But I imagine it was in the millions and millions of dollars.”

    Coleman and his colleagues analyzed satellite images and interviewed members of the local communities. They found that the tree planting had very little impact one way or the other. Forest density didn’t change much, and the surveys suggested that few households were gaining benefits from the planted forests, such as gathering wood for fuel, grazing animals or collecting fodder.

    But massive tree-planting efforts don’t have to fail. “It’s easy to point to examples of large-scale reforestation efforts that weren’t using the right tree stock, or adequately trained workforces, or didn’t have enough investment in … postplanting treatments and care,” Fargione says. “We … need to learn from those efforts.”

    Speak for the trees

    Forester Lalisa Duguma of World Agroforestry in Nairobi, Kenya, and colleagues explored some of the reasons for the very high failure rates of these projects in a working paper in 2020. “Every year there are billions of dollars invested [in tree planting], but forest cover is not increasing,” Duguma says. “Where are those resources going?”

    In 2019, Duguma raised this question at the World Congress on Agroforestry in Montpellier, France. He asked the audience of scientists and conservationists: “How many of you have ever planted a tree seedling?” To those who raised their hands, he asked, “Have they grown?”

    Some respondents acknowledged that they weren’t sure. “Very good! That’s what I wanted,” he told them. “We invest a lot in tree plantings, but we are not sure what happens after that.”

    It comes down to a deceptively simple but “really fundamental” point, Duguma says. “The narrative has to change — from tree planting to tree growing.”

    The good news is that this point has begun to percolate through the conservationist world, he says. To have any hope of success, restoration projects need to consider the best times of year to plant seeds, which seeds to plant and where, who will care for the seedlings as they grow into trees, how that growth will be monitored, and how to balance the economic and environmental needs of people in developing countries where the trees might be planted.

    “That is where we need to capture the voice of the people,” Duguma says. “From the beginning.”

    Even as the enthusiasm for tree planting takes root in the policy world, there’s a growing awareness among researchers and conservationists that local community engagement must be built into these plans; it’s indispensable to their success.

    “It will be almost impossible to meet these targets we all care so much about unless small farmers and communities benefit more from trees,” as David Kaimowitz of the United Nations’ Food and Agriculture Organization wrote March 19 in a blog post for the London-based nonprofit International Institute for Environment and Development.

    For one thing, farmers and villagers managing the land need incentives to care for the plantings and that includes having clear rights to the trees’ benefits, such as food or thatching or grazing. “People who have insecure land tenure don’t plant trees,” Fleischman says.

    Fleischman and others outlined many of the potential social and economic pitfalls of large-scale tree-planting projects last November in BioScience. Those lessons boil down to this, Fleischman says: “You need to know something about the place … the political dynamics, the social dynamics.… It’s going to be very different in different parts of the world.”

    The old cliché — think globally, act locally — may offer the best path forward for conservationists and researchers trying to balance so many different needs and still address climate change.

    “There are a host of sociologically and biologically informed approaches to conservation and restoration that … have virtually nothing to do with tree planting,” Veldman says. “An effective global restoration agenda needs to encompass the diversity of Earth’s ecosystems and the people who use them.”

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    The world wasted nearly 1 billion metric tons of food in 2019

    The world wasted about 931 million metric tons of food in 2019 — an average of 121 kilograms per person. That’s about 17 percent of all food that was available to consumers that year, a new United Nations report estimates.
    “Throwing away food de facto means throwing away the resources that went into its production,” said Martina Otto, who leads the U.N. Environment Program’s work on cities, during a news conference. “If food waste ends up in landfills, it does not feed people, but it does feed climate change.”
    Some 690 million people are impacted by hunger each year, and over 3 billion people can’t afford a healthy diet. Meanwhile, lost and wasted food accounts for 8 to 10 percent of global greenhouse gas emissions. Reducing food waste could ease both of those problems, according to the Food Waste Index Report 2021 published March 4 by the U.N. Environment Program and WRAP, an environmental charity based in the United Kingdom.
    Researchers analyzed food waste data from 54 countries. Most waste — 61 percent — came from homes. Food services such as restaurants accounted for 26 percent of global food waste while retail outlets such as supermarkets contributed just 13 percent. Surprisingly, food waste was a substantial problem for nearly all countries regardless of their income level, the team found. “We thought waste was predominantly a problem in rich countries,” Otto said.
    While the report is the most comprehensive analysis of global food waste to date, several knowledge gaps remain. The 54 countries account for just 75 percent of the world’s population, and only 23 countries provided waste estimates for their food service or retail sectors. The researchers accounted for these gaps by extrapolating values for the rest of the world from countries that did track these data. The report does not differentiate between potentially edible wasted food and inedible waste such as eggshells or bones.
    Otto recommends that countries begin addressing food waste by integrating reduction into their climate strategies and COVID-19 recovery plans. “Food waste has been largely overlooked in national climate strategies,” Otto said. “We know what to do, and we can take action quickly — collectively and individually.” More

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    ‘Green’ burials are slowly gaining ground among environmentalists

    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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    Plastics are showing up in the world’s most remote places, including Mount Everest

    Minuscule shreds and threads of plastic are turning up all over, including in the snow on Mount Everest.
    “We’ve known that plastic is in the deep sea, and now it’s on the tallest mountain on Earth,” says Imogen Napper, a marine scientist at the University of Plymouth in England and a National Geographic Explorer. “It’s ubiquitous through our whole environment.”
    Plastic plays an increasingly large role in our lifestyles: Globally, the use of plastics has shot up from around 5 million metric tons in the 1950s to more than 330 million metric tons in 2020. As they’re used and cast away, these plastic products shed tiny particles. The broken-down bits of bags, bottles and other consumer plastics, each smaller than 5 millimeters, can harm animals, such as marine crabs that get plastics stuck in their gills (SN: 7/8/14). They may also mess with ecosystems (SN: 1/31/20).
    Here are some of the most extreme places where microplastics have been found.

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    Atop the world’s tallest mountain
    All of the 11 snow samples that Napper’s team analyzed from Mount Everest contained plastic, the researchers report November 20 in One Earth. “I had no idea what the results were going to look like … so that really took me aback,” says Napper.
    The highest concentration of microplastics — 119,000 pieces per cubic meter — was in snow from Everest Base Camp, where climbers congregate, but plastic pieces also appeared at a spot 8,440 meters above sea level, near the 8,850-meter summit. The scientists also found plastics in three of eight samples of stream water from Everest. Perhaps the finding should not have been so surprising: Hundreds of people attempt to summit the mountain each year, leaving piles of trash behind. The majority of the microplastics found were polyester fibers, likely originating from climbers’ equipment and clothes.
    In the deepest ocean depths
    Plastic pollution in the sea goes far deeper than the floating Pacific garbage patch (SN: 3/22/18). Scientists have fished plastic fibers and fragments from the guts of critters dwelling in ocean trenches around the Pacific Rim. Of 90 crustaceans analyzed in a 2019 study, 65 contained microplastics, with the deepest coming from 10,890 meters down in the Mariana Trench. In another study, a sampling of water in the Monterey Bay suggests that plastic debris is accumulating below the surface and is most prevalent at 200 to 600 meters deep (SN: 6/6/19).
    Animals are ingesting microplastics in the deepest parts of the sea. In the guts of amphipods (one shown, left) collected from nine sites on the Pacific Rim’s trenches, researchers found plastic fragments, including microfibers (right) found in a critter from 10,890 meters deep in the Mariana Trench.A.J. Jamieson et al/Roy Soc Open Society 2019
    Blowing in the wind
    Carried through the air, microplastics can make their way to remote areas such as a meteorological station in the Pyrenees Mountains (SN: 4/15/19). On average, an estimated 365 microplastic particles per square meter per day rained down on that site during the study period, about as much as falls from the sky in some cities. Simulations of wind directions and speed suggest the plastic fragments traveled at least 95 kilometers before landing at the site.
    Embedded in Arctic ice
    A 2018 study reported millions to tens of millions of microplastic pieces per cubic meter from melted Arctic ice cores. The research team identified 17 types of plastic, including some used in packaging materials and others used in paints or fibers. Another 2020 report found lower concentrations for sea ice cores, ranging from 2,000 to 17,000 plastic particles per cubic meter. The 2020 study also found that water beneath ice floes held between 0 to 18 microplastic particles per cubic meter. 
    In our guts
    A 2019 study estimates that an average American consumes between 39,000 and 52,000 pieces of microplastic a year. Researchers came up with this number by drawing on previous studies that had surveyed plastic pieces in tap and bottled water and in certain food items, such as fish, sugar, salt and alcohol. More

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    How planting 70 million eelgrass seeds led to an ecosystem’s rapid recovery

    In the world’s largest seagrass restoration project, scientists have observed an ecosystem from birth to full flowering.
    As part of a 20-plus-years project, researchers and volunteers spread more than 70 million eelgrass seeds over plots covering more than 200 hectares, just beyond the wide expanses of salt marsh off the southern end of Virginia’s Eastern Shore. Long-term monitoring of the restored seagrass beds reveals a remarkably hardy ecosystem that is trapping carbon and nitrogen that would otherwise contribute to global warming and pollution, the team reports October 7 in Science Advances. That success provides a glimmer of hope for the climate and for ecosystems, the researchers say.
    The project, led by the Virginia Institute of Marine Science and The Nature Conservancy, has now grown to cover 3,612 hectares — and counting — in new seagrass beds. By comparison, the largest such project in Australia aims to restore 10 hectares of seagrass.
    The results are “a game changer,” says Carlos Duarte. “It’s an exemplar of how nature-based solutions can help mitigate climate change,” he says. The marine ecologist at King Abdullah University of Science and Technology in Thuwal, Saudi Arabia is a leader in recognizing the carbon-storing capacity of mangroves, tidal marshes and seagrasses.
    The team in Virginia started with a blank slate, says Robert Orth, a marine biologist at the Virginia Institute of Marine Science in Gloucester Point. The seagrass in these inshore lagoons had been wiped out by disease and a hurricane in the early 1930s, but the water was still clear enough to transmit the sunlight plants require.
    A researcher collects seeds from a restored seagrass meadow in a coastal Virginia bay.Jay Fleming
    Within the first 10 years of restoration, Orth and colleagues witnessed an ecosystem rebounding rapidly across almost every indicator of ecosystem health — seagrass coverage, water quality, carbon and nitrogen storage, and invertebrate and fish biomass (SN: 2/16/17).
    For instance, the team monitored how much carbon and nitrogen the meadows were capturing from the environment and storing in the sediment as seagrass coverage expanded. It found that meadows in place for nine or more years stored, on average, 1.3 times more carbon and 2.2 times more nitrogen than younger plots, suggesting that storage capacity increases as meadows mature. Within 20 years, the restored plots were accumulating carbon and nitrogen at rates similar to what natural, undisturbed seagrass beds in the same location would have stored. The restored seagrass beds are now sequestering on average about 3,000 metric tons of carbon per year and more than 600 metric tons of nitrogen, the researchers report.

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    Seagrasses can take a hit. When a sudden marine heat wave killed off a portion of the seagrass, it took just three years for the meadow to fully recover its plant density. “It surprised us how resilient these seagrass meadows were,” says Karen McGlathery, a coastal ecologist at the University of Virginia in Charlottesville.
    She believes the team’s work is more than just a great case study in restoration. It “offers a blueprint for restoring and maintaining healthy seagrass ecosystems” that others can adapt elsewhere in the world, she says.
    Reestablished eelgrass beds off Virginia not only store carbon efficiently, they also support rich biodiversity, such as the seahorse seen here.VIMS
    Seagrasses are among the world’s most valuable and most threatened ecosystems, and are important globally as reservoirs of what’s known as blue carbon, the carbon stored in ocean and coastal ecosystems. Seagrasses store more carbon, for far longer, than any other land or ocean habitat, preventing it from escaping to the atmosphere as heat-trapping carbon dioxide. These underwater prairies also support near-shore and offshore fisheries, and protect coastlines as well as other marine habitats. Despite their importance, seagrasses have declined globally by some 30 percent since 1879, according to an Aug. 14 study in Frontiers in Marine Science.
    “The study helps fill some large gaps in our understanding of how blue carbon can contribute to climate restoration,” says McGlathery. “It’s the first to put a number on how much carbon restored meadows take out of the atmosphere and store,” for decades and potentially for centuries.
    The restoration is far from finished. But already, it may point the way for struggling ecosystems such as Florida’s Biscayne Bay, once rich in seagrass but now suffering from water quality degradation and widespread fish kills.  Once the water is cleaned up, says Orth, “our work suggests that seagrasses can recover rapidly” (SN: 3/5/18).
    McGlathery also believes the scale of the team’s success should be uplifting for coastal communities. “In my first years here, there was no seagrass and there hadn’t been for decades. Today, as far as I can swim, I see lush meadows, rays, the occasional seahorse. It’s beautiful.” More

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    Invasive jumping worms damage U.S. soil and threaten forests

    What could be more 2020 than an ongoing invasion of jumping worms?
    These earthworms are wriggling their way across the United States, voraciously devouring protective forest leaf litter and leaving behind bare, denuded soil. They displace other earthworms, centipedes, salamanders and ground-nesting birds, and disrupt forest food chains. They can invade more than five hectares in a single year, changing soil chemistry and microbial communities as they go, new research shows. And they don’t even need mates to reproduce.
    Endemic to Japan and the Korean Peninsula, three invasive species of these worms — Amynthas agrestis, A. tokioensis and Metaphire hilgendorfi — have been in the United States for over a century. But just in the past 15 years, they’ve begun to spread widely (SNS: 10/7/16). Collectively known as Asian jumping worms, crazy worms, snake worms or Alabama jumpers, they’ve become well established across the South and Mid-Atlantic and have reached parts of the Northeast, Upper Midwest and West.
    Jumping worms are often sold as compost worms or fishing bait. And that, says soil ecologist Nick Henshue of the University at Buffalo in New York, is partially how they’re spreading (SN: 11/5/17). Fishers like them because the worms wriggle and thrash like angry snakes, which lures fish, says Henshue. They’re also marketed as compost worms because they gobble up food scraps far faster than other earthworms, such as nightcrawlers and other Lumbricus species.

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    But when it comes to ecology, the worms have more worrisome traits. Their egg cases, or cocoons, are so small that they can easily hitch a ride on a hiker’s or gardener’s shoe, or can be transported in mulch, compost or shared plants. Hundreds can exist within a square meter of ground.  
    Compared with Lumbricus worms, jumping worms grow faster and reproduce faster — and without a mate, so one worm can create a whole invasion. Jumping worms also consume more nutrients than other earthworms, turning soil into dry granular pellets that resemble coffee grounds or ground beef — Henshue calls it “taco meat.” This can make the soil inhospitable to native plants and tree seedlings and far more likely to erode.
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    Asian jumping worm species thrash furiously, unlike the more placid movements of other earthworm species. The jumping worms can also slime and shed their tails as defense mechanisms.
    To date, scientists have worried most about the worms’ effects on ground cover. Prior to a jumping worm invasion, the soft layer of decomposing leaves, bark and sticks covering the forest floor might be more than a dozen centimeters thick. What’s left afterward is bare soil with a different structure and mineral content, says Sam Chan, an invasive species specialist with Oregon Sea Grant at Oregon State University in Corvallis. Worms can reduce leaf litter by 95 percent in a single season, he says.
    That in turn can reduce or remove the forest understory, providing less nutrients or protection for the creatures that live there or for seedlings to grow. Eventually, different plants come in, usually invasive, nonnative species, says Bradley Herrick, an ecologist and research program manager at the University of Wisconsin–Madison Arboretum. And now, new research shows the worms are also changing the soil chemistry and the fungi, bacteria and microbes that live in the soils.
    Invasive jumping worms can clear a forest of leaf litter in just a couple of months, as these pictures taken in Jacobsburg State Park near Nazareth, Pa., in June 2016 (left) and August 2016 (right) show.Nick Henshue
    In a study in the October Soil Biology and Biochemistry, Herrick, soil scientist Gabriel Price-Christenson and colleagues tested samples from soils impacted by jumping worms. They were looking for changes in carbon and nitrogen levels and in soils’ release of carbon dioxide, which is produced by the metabolism of microbes and animals living in the soil. Results showed that the longer the worms had lived in the soils, the more the soils’ basal metabolic rate increased — meaning soils invaded by jumping worms could release more carbon dioxide into the atmosphere, says Price-Christenson, who is at the University of Illinois at Urbana-Champaign.
    Relative amounts of carbon and nitrogen in soils with jumping worms also shifted, the team found. That can affect plant communities, Herrick says. For example, although nitrogen is a necessary nutrient, if there’s too much, or it’s available at the wrong time of year, plants or other soil organisms won’t be able to use it. 
    The team also extracted DNA from worm poop and guts to examine differences in microbes among the jumping worm species, and tested the soils for bacterial and fungal changes. Each jumping worm species harbors a different collection of microbes in its gut, the results showed. That’s “a really important find,” Herrick says, “because for a long time, we were talking about jumping worms as a large group … but now we’re learning that [these different species] have different impacts on the soil, which will likely cascade down to having different effects on other worms, soil biota, pH and chemistry.”  
    The finding suggests each species might have a unique niche in the environment, with gut microbes breaking down particular food sources. This allows multiple species to invade and thrive together, Herrick says. This makes sense, given findings of multiple species together, but it’s still a surprise that such similar worms would have different niches, he says.    
    Scientists have been working hard to get a good handle on the biology of these worms, Henshue says. So the newly discovered soil chemistry and microbiology changes are “thoughtful” and important lines of research. But there’s still a lot that’s unknown, making it hard to predict how much farther the worms might spread and into what kinds of environments. One important question is how weather conditions affect the worms. For example, a prolonged drought this year in Wisconsin seems to have killed off many of the worms, Herrick says. Soils teeming with wriggling worms just a few weeks ago now hold far fewer.
    Perhaps that’s a hopeful sign that even these hardy worms have their limits, but in the meantime, the onslaught of worms continues its march — with help from the humans who spread them. More

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    What we know and don’t know about wildfire smoke’s health risks

    Acrid smoke continues to pollute skies in the western United States. On some recent days, the air quality in Portland, Seattle, San Francisco and Los Angeles has been so hazardous, it’s ranked among the worst in the world. 
    It’s hard to predict when the smoke will fully clear. And with some parts of the West  having faced a week or more of extremely polluted air, the unusual, sustained nature of the assault is increasing worries about people’s health.
    There’s plenty of evidence that air pollution — a broad category that includes soot, smog, and other pollutants from sources such as traffic, industry and fires — can harm health. The list of medical ailments associated with exposure to dirty air includes respiratory diseases, cardiovascular disease and diabetes (SN: 9/19/17).
    Most of what’s known about the hazards of wildfire smoke has to do with particulate matter, the tiny bits of solids and liquids in polluted air. Wildfires are especially good at producing particles in a size range that can be dangerous to health. It isn’t clear yet if what fuels wildfire smoke — be it vegetation, a mix of trees and structures, or other human-made sources — affects the toxicity of particulate matter.
    A growing body of evidence points to a range of risks to health during or soon after wildfires, such as increased trips to the emergency room for chronic lung conditions. But there are many more questions than answers about the long-term risks for people struggling to cope with day upon day of polluted air, and facing longer and fiercer fire seasons each year due to climate change (SN: 8/27/20).
    Science News spoke with scientists about what’s in the air, the health risks and what more we need to learn.
    What’s in wildfire smoke?
    Wildfire smoke is a complex mixture of gases and particles that is similar to cigarette smoke but without the nicotine, says physician John Balmes of the University of California, San Francisco, who studies the effects of air pollution on health. “It has the same kind of mixture of nasty small particles and irritant gases.”
    The precise chemical makeup of the smoke varies by fire. It depends on “the type of fuel burned — including structures, intensity of the fire, atmospheric mixing, and distance or age of smoke,” says Tania Busch Isaksen, who studies public health effects of wildfire smoke at the University of Washington in Seattle.
    “Generally speaking, it’s a mixture of carbon dioxide, carbon monoxide, nitrogen oxides, particle matter — fine to coarse — hydrocarbons and other organic compounds,” she says. “Fine particulate matter, PM2.5, is what we are primarily concerned about when we consider impacts on health” (SN: 7/30/20).
    Those particles are 2.5 micrometers across or smaller, or about one-thirtieth the width of a human hair (SN: 8/22/18). Common in air pollution produced not only by wildfires, but also by power plants and cars, these particles are so tiny that they can be inhaled deeply into the lungs. There, they can trigger inflammation and possibly seep into the bloodstream.
    Can you see how much PM2.5 is in the air?
    No. These particles are so tiny and difficult to see that “even if the air seems clear, PM2.5 could be at levels that are dangerous,” says Perry Hystad, an environmental epidemiologist at Oregon State University in Corvallis. In the United States, the most reliable gauge of PM2.5 is the Air Quality Index, or AQI, which is based on data from air quality monitoring stations that measure the concentrations of pollutants in the air.
    The U.S. Environmental Protection Agency developed the index to grade levels of common air pollutants, such as ozone, PM2.5  and carbon monoxide. On a scale from 0 to 500, higher numbers indicate dirtier air. The EPA assigns AQI scores to different types of pollution based on studies of each contaminant’s health effects.
    The EPA considers scores up to 100 — indicating an average 35.4 micrograms of particulate matter per cubic meter of air over 24 hours  — generally safe. Scores from 101 to 200 may pose particular risk to people in sensitive groups, such as children and those with heart or lung diseases. Those people are advised to limit or avoid prolonged or vigorous outdoor activity. Above 200, everyone should cut down on physical activity outside. At scores 300 or above, with at least 250.4 micrograms of PM2.5 per cubic meter of air, everyone should avoid going outside.
    Smoke blanketing the western United States has created hazardous, and at times off-the-chart, levels of pollution in many places. For instance, on the morning of September 17, areas of Oregon near Portland showed PM2.5 AQI levels up to around a hazardous 380. In regions of central California northeast of Fresno, AQI levels reached a staggering 780.
    “Especially under conditions that we’re experiencing here in the western United States, it would be wise to check the AQI on a daily basis,” says Kent Pinkerton, a biologist at University of California, Davis.

    What happens when people breathe in wildfire smoke?
    “Wildfires, through the combustion process, create lots and lots of particles” in the size range of PM2.5, says Colleen Reid, an environmental epidemiologist and health geographer at the University of Colorado Boulder. A breath of these microscopic particles can send them all the way to the alveoli, the tiny sacs where the lungs and the blood swap oxygen and carbon dioxide.
    Research in lab dishes has found that the particles can lead to inflammation and oxidative stress, in which reactive molecules that contain oxygen build up and can damage cells. The smallest pollution particles may make their way into the bloodstream, possibly causing harm to the cardiovascular system.
    The research linking PM2.5 with health generally does not consider what types of materials are burning, so “at this point we are concerned about all PM2.5 regardless of source,” says Anthony Wexler, who studies particulate pollutants at the University of California, Davis. “But the source is likely important.”
    Historically, wildfires have burned mostly plant matter. But many of the recent devastating fires in the western U.S., such as the Camp Fire that destroyed the town of Paradise, Calif., in 2018, have devoured human-made structures (SN: 11/15/18). “Houses have paint and solvents and plastics and all this other terrible stuff going up in smoke, too, which may be increasing the toxicity of the material that’s being emitted,” says Wexler. He is currently preparing an experiment to compare the toxicity of the smoke from burnt household materials with that from woody materials.
    The impact of extended exposures to wildfire smoke also needs more research. Wildfires put a lot of pollution into the air, more than what’s generally produced from industrial and traffic sources, Reid says. But it’s often for a short period of time. “What’s going on right now in Oregon and Washington and California, where they’ve had essentially a week of very unhealthy levels of air pollution, is less common,” she says.
    Recent fires in the western United States have consumed not only trees but many buildings like this one, in Butte County, Calif., which went up in flames on September 9. Some researchers are concerned that plastics and other materials in homes may make smoke more toxic.Noah Berger/Associated Press
    What are the immediate health risks from wildfire smoke?
    Breathing in smoky air can irritate the respiratory tract, leading to coughing, sore throats and itchy, watery eyes. The foul air can also cause headaches and fatigue.
    Hospital visits for lung care go up during wildfires compared to periods without them, according to studies of emergency department traffic. For instance, an increase in PM2.5 exposure related to wildfires in northern California in 2008 was associated with an increase in risk for emergency department visits and hospitalizations for asthma, Reid and colleagues reported in Environmental Research in 2016. The 2012 wildfires in Colorado were linked to a rise in emergency department visits for asthma and chronic obstructive pulmonary disease, according to a 2016 study in Environmental Health. There’s some evidence of increased trips to the hospital for cardiovascular health problems during wildfires as well.
    Medical visits for kids go up during wildfires too. During the 2017 Lilac Fire in San Diego county, visits for respiratory problems to a children’s hospital rose due to increased exposure to PM2.5, according to a 2020 study in the Annals of the American Thoracic Society.
    Children, especially the very young and those with diseases like asthma, can be more vulnerable to health effects from wildfires. “They breathe more air per minute compared to adults” to meet their physiological needs, says Marissa Hauptman, a pediatrician at Boston Children’s Hospital. That can add up to more exposure. And developing lungs “are more susceptible to injury,” she says. 
    A developing fetus may also be at risk from exposure to PM2.5. In a 2012 study in Environmental Health Perspectives, Reid and colleagues reported a slight decrease in birth weight for infants from pregnancies that occurred during the 2003 wildfires in Southern California. Mothers exposed to smoke from Colorado wildfires during the second trimester were more likely to give birth prematurely, according to a 2019 study in the International Journal of Environmental Research and Public Health. Infants born early or smaller than usual can face developmental delays.
    What’s known about long-term health risks from wildfire smoke?
    Not much. But a few studies provide some initial clues.
    One examined how wildfires that scorched large areas of Indonesia in 1997 impacted health 10 years later. This population-wide study found that males and the elderly were worse off in 2007 for health measures such as lung function, the researchers reported in Economics & Human Biology in 2017.
    In the United States, the wildfire smoke that plagued the Seeley Lake community in Montana in 2017 has parallels to the prolonged, hazardous exposures happening now in the West. The wildfires produced extremely high levels of PM2.5 from July 31 to September 18 that year; the daily average was 221 micrograms per cubic meter of air. Christopher Migliaccio, a respiratory immunology researcher at the University of Montana in Missoula, and his colleagues screened adults in the community right after the last day of increased smoke and two more times in each of the following two years.
    Compared with members of a Montana community that hadn’t been exposed to the same levels of smoke, the participants from the Seeley Lake area had poorer lung function one and two years out, Migliaccio and his colleagues reported in Toxics in August. “I thought people might be worse right after,” he says, “but it’s a little bit of a delayed response.”
    Migliaccio and colleagues had planned to screen the participants again this year, but COVID-19 got in the way. Eventually they hope to see whether, in participants that still have worse lung function, the condition is treatable or if it’s “the new normal.”
    Can a mask protect you from wildfire smoke?
    It depends on the type of mask. “Cloth masks, which are effective at preventing transmission of SARS-CoV-2 [the virus that causes COVID-19] … don’t do anything to protect the wearer from exposure to wildfire smoke,” Balmes says (SN: 6/26/20). Surgical masks provide some protection. But “an N95 is the best protection.” N95 masks are designed to filter out at least 95 percent of airborne particles.
    But N95 masks are in short supply, and those masks have not been certified for use by children as they don’t fit properly. So the best protection is to avoid exposure. “People should stay indoors as much as possible with the windows closed,” Balmes says.

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    How can people keep indoor air clean?
    “If they have central ventilation, they should turn that to recirculation,” Balmes says. That can reduce the amount of smoke that enters the home. People can also use a High Efficiency Particulate Air, or HEPA purifier to smoke-proof a single room. And those who cannot afford a HEPA cleaner can put together a makeshift purifier using a MERV-13 furnace filter and a box fan, Balmes says. “They’re not as good as the proper devices, but they do provide some protection.”
    People hunkered down indoors can also keep the air clear by not burning gas stoves or candles, or even vacuuming — which can stir up particles inside the home.
    But some people don’t have a home to escape to. King County in Washington announced on September 11 the opening of a clean air shelter for people experiencing homelessness.
    How else might wildfires be harming health?
    The toll that the wildfires have on mental health could also be significant. The past month in the Pacific Northwest has brought images reminiscent of a science fiction novel: hazy, deep orange skies that sometimes completely obscured the sun, turning day to night.
    Extreme wildfires, with the potential for long periods of time in which the air is a danger, can upend people’s lives and add to stress levels. One of the few respites to the COVID-19 pandemic — going out for a breath of fresh air — has been shut off for millions of people. And there are many that have no choice but to work or live outdoors, exposed to hazardous air. “There could be a psychological impact of that,” says Reid. “That needs to be explored.” More

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    This moth may outsmart smog by learning to like pollution-altered aromas

    Pollution can play havoc with pollinators’ favorite flower smells. But one kind of moth can learn how to take to an unfamiliar new scent like, well, a moth to a flame.
    Floral aromas help pollinators locate their favorite plants. Scientists have established that air pollutants scramble those fragrances, throwing off the tracking abilities of such beneficial insects as honeybees (SN: 4/24/08). But new lab experiments demonstrate that one pollinator, the tobacco hawkmoth (Manduca sexta), can quickly learn that a pollution-altered scent comes from the jasmine tobacco flower (Nicotiana alata) that the insect likes.
    That ability may imply that the moth can find food and pollinate plants, including crucial crops, despite some air pollution, researchers report September 2 in the Journal of Chemical Ecology. Scientists already knew that some pollinators can learn new smells, but this is the first study to demonstrate an insect overcoming pollution’s effects on odors.
    Chemical ecologist Markus Knaden and colleagues focused on one pollutant — ozone, the main ingredient in smog. Ozone reacts with flower aroma molecules, changing their chemical structure and therefore their fragrance.

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    In Knaden’s lab at the Max Planck Institute for Chemical Ecology in Jena, Germany, his team blew an ozone-altered N. alata scent from a tiny tube into a refrigerator-sized plexiglass tunnel, with a moth awaiting at the far end of the tunnel. Usually, when the moth smells the unaltered floral fragrance, it flies upwind and uses its long, skinny mouthparts to probe the tube the way that it would a blossom.
    The researchers expected that the modified scent might throw the moth off a little. But the insect wasn’t attracted at all to a flower aroma exposed to levels of ozone that are typical on some hot, sunny days.
    In addition to scent, tobacco hawkmoths track flowers visually, so Knaden’s team used that trait, along with a sweet snack, to train the moth to be attracted to a pollution-altered scent. The researchers wrapped a brightly-colored artificial flower around the tube to lure the moth back across the tunnel, despite the unfamiliar aroma. And the team added sugar water to the artificial flower. After a moth was given four minutes to taste the sweet stuff, it was attracted to the new smell when sent into the tunnel 15 minutes later, even when neither the sugar water nor the visual cue of the artificial flower was present. 
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    In the lab, researchers showed that tobacco hawkmoths can learn to drink from a fake flower whose scent has been scrambled by pollution. To train the moths to accept the altered scent, a visual cue — dressing up a tube emitting a fouled bouquet as an artificial flower — attracts the moth, and a sugar-water reward teaches the insect that it’s worth a return trip.
    Still, in an ozone-polluted environment in the wild, tobacco hawkmoths would have to be close enough to a tobacco flower to see it to learn its altered scent, and Knaden isn’t sure how often that will occur. The moths are difficult to observe in nature because they feed at twilight and are fast flyers.
    “This study is a clarion call to other scientists” to examine whether and how different pollinators might also adapt to human-driven changes to their environment, says chemical ecologist Shannon Olsson of the Tata Institute of Fundamental Research in Bangalore, India, who wasn’t involved with the work.
    Although the results suggest that some adaptation by insects to pollution is possible, Knaden is cautious about being too optimistic. “I don’t want the take-home message to be that pollution is not a problem,” he says. “Pollution is a problem.”
    This study focused on only one moth species, but Knaden’s team is now working on planning experiments with other pollinators that are easier to follow than tobacco hawkmoths. While he suspects honeybees might also be as adaptable as the moth was, that won’t be true of every pollinator. “The situation can become very bad for insects that are not as clever or cannot see that well.” More