This might be why her team got contrasting results in their analysis: The more individual microplastics in the gut, the greater the microbial diversity, but the higher mass of microplastics, the lower the diversity. The more particles a bird eats, the greater the chance that those hitchhiking microbes take hold in its gut. But if the bird has just eaten a higher mass of microplastics—fewer, but heavier pieces—it may have consumed fewer microbes from the outside world.
Meanwhile, particularly jagged microplastics might be scraping up the birds’ digestive systems, causing trauma that affects the microbiome. Indeed, the authors of the plasticosis paper found extensive trauma in the guts of wild flesh-footed shearwaters, birds that live along the coasts of Australia and New Zealand, that had eaten microplastics and macroplastics. (They also looked at plastic particles as small as 1 millimeter.) “When you ingest plastics, even small amounts of plastics, it alters the structure of the stomach, often very, very significantly,” says study coauthor Jennifer Lavers, a pollution ecologist at Adrift Lab, which researches the effects of plastic on sea life.
Specifically, they found catastrophic damage to the birds’ tubular glands, which produce mucus to provide a protective barrier for the inside of the stomach, as well as hydrochloric acid, which digests food. Without these key secretions, Lavers says, birds “also can’t digest and absorb proteins and other nutrients that keep you healthy and fit. So you’re really prone and susceptible to exposure to other bacteria, viruses, and pathogens.”
Scientists call this a “sublethal effect.” Even if the ingested pieces of plastic don’t immediately kill a bird, they can severely harm it. Lavers refers to it as the “one-two punch of plastics” because eating the material harms the birds outright, then potentially makes them more vulnerable to the pathogens they carry.
A major caveat to today’s paper—and the vast majority of microplastics research—is that most scientists haven’t been analyzing the smallest of plastic particles. But researchers using special equipment have recently been able to detect and quantify nanoplastics, on the scale of millionths of a meter. These are much, much more numerous in the environment. (This is also why the finding that there are 11 billion pounds of plastic floating on the ocean’s surface was probably a major underestimate, as that team was only considering particles down to a third of a millimeter.) But the process of observing nanoplastics remains difficult and expensive, so Fackelmann’s group can’t say how many might have been in the seabirds’ digestive systems, and how they too might influence the microbiome.
It’s not likely to be good news. Nanoplastics are so small that they can penetrate and harm individual cells. Experiments on fish show that if you feed them nanoplastics, the particles end up in their brains, causing damage. Other animal studies have also found that nanoplastics can pass through the gut barrier and migrate to other organs. Indeed, another paper Lavers published in January found even microplastics in the flesh-footed shearwaters’ kidneys and spleens, where they had caused significant damage. “The harm that we demonstrated in the plasticosis paper is likely conservative because we didn’t deal with particles in the nanoplastic spectrum,” says Lavers. “I personally think that’s quite terrifying because the harm in the plasticosis paper is quite overwhelming.”
Now scientists are racing to figure out whether ingested plastics can endanger not only individual animals, but whole populations. “Is this harm at the individual level—all of these different sublethal effects, exposure to chemicals, exposure to microbiome changes, plasticosis—is it sufficient to drive population decline?” asks Lavers.
The jury is still out on that, as scientists don’t have enough evidence to form a consensus. But Lavers believes in the precautionary principle. “A lot of the evidence that we have now is deeply concerning,” she says. “I think we need to let logic prevail and make a fairly safe, conservative assumption that plastics are currently driving population decline in some species.”
As people’s incomes rise, they tend to switch from “starchy staples” like grains, potatoes, and roots to meat and dairy products. “You’d think there would be big cultural differences across human populations in these patterns,” says Thomas Tomich, a food systems economist at the University of California, Davis, who wasn’t involved in the new paper. “There are some, but it is surprising how almost universal this shift is: how increasing income, especially going from poor to middle class, really affects people’s consumption of livestock products.”
Yet cattle and milk products are especially critical to the climate conversation because they are such massive sources of methane emissions. Ivanovich’s modeling shows that by 2030, ruminant meat alone could be responsible for a third of the warming associated with food consumption. Dairy would make up another 19 percent, and rice a further 23 percent. Together, these three groups would be responsible for three-quarters of warming from the global food system.
There’s a silver lining, though: The team thinks we can avoid half of this warming by improving our food system and diets. That starts with eating fewer cows and other ruminants—the fewer fermenting stomachs out there, the better. New food technologies can certainly help, such as plant-based meat imitations like the Impossible Burger or meats grown from cells cultured in labs, also known as cellular agriculture. Researchers are also experimenting with feed additives for cows that reduce the methane in their burps.
Out in the fields, rice growers can significantly reduce methane emissions by switching between wetting and drying paddies, instead of leaving the plants flooded. Researchers are also developing crops that fix their own nitrogen, in a bid to reduce nitrous oxide emissions. (Legumes do this automatically, thanks to symbiotic bacteria living in their roots.) One team has made rice plants that grow a biofilm to act as a home for nitrogen-fixing microbes, thus reducing the need for synthetic fertilizers. Making such fertilizers is extremely energy-intensive, so reducing reliance on them will further reduce emissions.
But Ivanovich stresses that rich nations certainly can’t force methane-conscious diets on economically developing ones. In some parts of the world, a cow is simply food and milk, but to a subsistence farmer, it may be a working animal, or currency. “It’s really essential that no changes to dietary composition are made without being culturally relevant, and supportive of local production practices and how they contribute to economic livelihoods,” she says.
Ivanovich’s 1-degree figure is an estimate, not a prophecy. For one thing, she can’t intricately model how new food and farming technologies might reduce emissions in the decades ahead. And environmental scientist Adrian Leip, a lead author of last year’s IPCC report on climate mitigation, points out that while these technologies are promising, it’s not clear when—or how rapidly—people will adopt them. “At a certain point in time, one of those technologies—I don’t know whether it will be cellular agriculture or whether it will be plant-based analogs—will be so cheap. It will be so tasty and nutritious that people will start thinking: Why on Earth did I ever eat an animal?” says Leip, who wasn’t involved in the new paper. “I believe it must happen, because I really don’t see good reasons not to happen. And so if the social norms start to shift, it can go really quick.”
Further complicating matters is an additional feedback loop: As the food system raises global temperatures, crops will have to endure more heat stress and ever fiercer droughts. “This is really a dynamic interplay of two-directional change,” says Ivanovich, “where our agriculture that we produce affects our changing climate, and our changing climate really affects how well we’re able to produce crops and support our global population.”
But she does offer a note of hope: Methane abates rapidly once people stop producing it. It disappears from the atmosphere after a decade, whereas CO2 lasts for centuries. “If we reduce emissions now, we experience those reductions in future warming quite quickly,” she says.
Scientists have good estimates of where the retreating grounding line is, thanks to satellites watching for tiny changes in the ice’s elevation. But they haven’t had a good picture of what the glacier’s belly looks like at the grounding line, because it’s under thousands of feet of ice. “These data are really exciting because we’re getting a look into a hidden system,” says University of Waterloo glaciologist Christine Dow, who studies Antarctic glaciers but wasn’t involved in the research.
Video: ITGC/Schmidt/Washam
With Icefin, the researchers could remotely pilot a camera while measuring the salinity, temperature, and oxygen content of the water. “We saw that the ice base itself was very complex in its topography, so there’s lots of staircases, terraces, rifts, and crevasses,” says British Antarctic Survey physical oceanographer Peter Davis, the lead author of one of the papers and coauthor on the other. “The rate of melting on different surfaces was very different.”
Where the glacier’s underside (or basal ice, in the scientific parlance) is smoother, melting is definitely happening, but at a much slower rate than where the topography is jagged. That’s because a layer of cold water rests where the ice is flat, insulating it from warmer ocean water like a liquid blanket. But where the topography is sloped and irregular, there are more vertical surfaces where warm water can attack the ice, including making incursions from the side. This melting creates a peculiar “scalloped” look, like the surface of a golf ball.
These complex, expanding basal features could then influence the rest of the ice. “If you open up features underneath the ice, you also get similar reflections of them on the surface, because of the way that the ice is floating,” says Davis. “So there’s a fear that if you’re widening these rifts and crevices under the ice, you can destabilize the ice shelf, which could lead to greater disintegration over time.”
This story originally appeared in The Guardian and is part of theClimate Deskcollaboration.
They are gray and rectangular, and if you laid all 2 billion of them together they would cover an area roughly the size Connecticut, about 5,500 square miles. Parking lots have a monotonous ubiquity in US life, but a growing band of cities and states are now refusing to force more on people, arguing that they harm communities and inflame the climate crisis.
For many years, local governments have required the construction of parking lots as part of any development. These measures, along with expansive highways that cut through largely minority neighborhoods and endless suburban sprawl, have cemented cars as the default transportation option for most Americans.
Starting in January, though, California will become the first US state to enact a ban on parking minimums, halting their use in areas with public transport in a move that Governor Gavin Newsom called a “win-win” for reducing planet-heating emissions from cars, as well as helping alleviate the lack of affordable housing in a state that has lagged in building new dwellings.
Several cities across the country are now rushing doing the same, with Anchorage, Alaska; Cambridge, Massachusetts; and Nashville, Tennessee, all recently loosening or scrapping requirements for developers to build new parking lots. “These parking minimums have helped kill cities,” said Gernot Wagner, a climate economist at Columbia Business School who accused political leaders of making downtowns “look like bombs hit them” by filling them with parking lots.
“Getting rid of parking minimums is an amazing step. It’s a piece in the puzzle of climate policy,” said Wagner, who pointed out that transportation is the largest source of planet-heating emissions in the US. “There’s a major rethink going on now, which is good for cities and for families.”
Climate campaigners and public transportation advocates have seized upon the previously esoteric issue of parking minimums, posting aerial pictures on social media demonstrating the vast swathes of prime urban land given over to parking lots and pushing city councils to foster denser communities with more opportunities to walk, cycle, or catch buses and trains rather than simply drive.
Cities such as Buffalo, New York; and Fayetteville, Arkansas, scaled back parking minimums a few years ago and have reported a surge in activity to transform previously derelict buildings into shops, apartments, and restaurants. Developers previously saw such work as unviable due to the requirement to build plots for car parking, in many cases several times larger than the building itself.
Nashville is among a new wave of cities hoping to do the same. “It’s about the climate, it’s about walkability, it’s reducing traffic and the need for everyone to have a car,” said Angie Henderson, a member of the Nashville Metropolitan Council, who proposed the parking change for the city’s core area.
Henderson said she was struck by how a dental practice in her district was forced to construct a parking lot for 45 cars, requiring the clearing of trees from a nearby hillside, despite only having space for a handful of patients.
Berlin, Nevada, is a treasure chest for paleontologists. Just down the road from now-abandoned gold and silver mines, a rockbound collection of bones hints at an even richer past. The Berlin-Ichthyosaur State Park is teeming with dozens of fossils of ancient marine reptiles. That bone bed is so abundant and weird that researchers have been scratching their heads over it for decades.
“There are sites with way more dense occurrences of ichthyosaur skeletons, including places in Chile and Germany,” says Nick Pyenson, curator of fossil marine mammals at the Smithsonian National Museum of Natural History. “But this place, Berlin-Ichthyosaur in eastern Nevada, has really escaped explanation for a long time.” In one particular quarry, at least seven individuals from the genus Shonisaurus—a bloated, bus-sized dolphin with four limb-like flippers—lay essentially stacked atop one another.
Previous hypotheses largely focused on physical or environmental reasons for the cluster of fossils. One suggested that the animals had gotten stranded in shallow water and died as a group some 230 million years ago. Or maybe a volcanic eruption did them in. Pyenson had another hunch, one that his team tested using 3D visualizations of the site, as well as fossils and other clues in the geological record.
Writing in the journal Current Biology, today Pyenson’s team presents evidence that the shonisaurs came there to reproduce. The team concludes that the animals migrated long distances to give birth, like some whales do today. The discovery not only represents an example of “convergent evolution,” in which the same traits independently evolve in different species, but also the oldest example of migration in groups to a designated calving ground.
“They’re making quite a convincing case,” says Lene Liebe Delsett, a vertebrate paleontologist at the University of Oslo, Norway, who was not involved in the study. “Ichthyosaurs were the first large marine tetrapods. And throughout the Triassic, they varied quite a lot, so there was a large diversity. It’s just a very interesting period of time to know more about.”
The origin story of the shonisaurs begins with death—a lot of it.
Some 251 million years ago, between the Permian and Triassic periods, Earth’s biggest extinction event annihilated about 95 percent of all marine species. This so-called “Great Dying” mowed down the diverse landscape of creatures in the ocean.Some of the animals that grew back in their place turned out to be weirder and larger than ever before.
The ensuing Triassic started an evolutionary arms race. Prey evolved harder shells and better mobility, predators crunched through ammonite shells and hunted fish better than ever, and so on. Ichthyosaurs, which evolved from terrestrial reptiles into new species of various sizes, partly drove this pressure and quickly dominated the ocean. The Shonisaurus genus, in particular, grew to be some of the largest marine predators around. “They achieved whale sizes before anything else,” says Pyenson.
Pyenson is normally more of a whale guy; he specializes in mammals, which split from reptiles about 325 million years ago. But ancient marine reptiles like those under the order Ichthyosaur bear many similarities to existing marine mammals. Their ancestors came from land, they birthed live young, they had similar flippers, and they are tetrapods, meaning four-limbed. And Pyenson is well versed in this type of mystery. About a decade ago in Atacama, Chile, he and his South American collaborators used 3D mapping and chemical analyses to show that a tight cluster of at least 40 fossilized whales must have died from a toxic algal bloom 7 to 9 million years ago.
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