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.
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.”
Shortages persist because of complex structural problems. Take, for instance, one that the pandemic briefly made visible: the reality that many American medications are manufactured somewhere else, at the end of long supply chains. In some cases, the raw materials, known as active pharmaceutical ingredients, or API, come from offshore, primarily India and China. In others, the entire drug—raw materials mixed with other ingredients into a finished product—is made abroad by a contract manufacturing organization. “It’s possible that, even though there are three products on the market with three labels, it’s all coming from the same facility,” says Michael Ganio, a clinical pharmacist and ASHP’s senior director of pharmacy practice and quality. “There also could be three manufacturers that are all sourcing from the same API manufacturer. The transparency is not there.”
Transparency could begin to solve the problem. More information is a necessary first step for forecasting shortages and building a resilient system that can blunt their impact. It’s especially important because most shortages don’t occur among new blockbuster drugs, but among older ones that sell on thin profit margins. The supply of those drugs is most likely to be disrupted by contamination, mechanical breakdowns, or other production problems—because while the FDA requires manufacturers to keep production lines safe, it doesn’t require them to reinvest in equipment on any particular schedule to keep those lines running. The business case for investing in a legacy product is a lot less compelling than for a high-earning breakthrough one.
Advance warning that a production line is coming down, due to materials supply or manufacturing problems, could help regulators balance the market. But that kind of disclosure would require companies to divulge proprietary information. “It’s hard to legislate the free market, and most of the problems that need to be solved have some element of the free market,” says Erin Fox, who is senior director of drug information at University of Utah Health Care and leads a research team that supplies information on shortages to ASHP.
Fox is also part of a committee at the National Academies of Science, Engineering and Medicine that proposed reforms in a report last year. It lays out a series of prompts for federal actions, such as enlarging the National Strategic Stockpile, which currently holds bioterror-defense drugs, and carving out international trade compacts to preserve an uninterrupted flow of ingredients. It also proposes developing a federal rating system that scores companies on resiliency planning and disclosure. (A quality-rating system has been endorsed by an FDA report as well.)
For companies, the National Academies report recommends carrots rather than sticks, acknowledging that firms can’t be compelled to release private information and recommending incentives to persuade them to be more forthcoming. Those federal ratings, for instance, could be used by health care organizations to justify paying slightly higher prices for drugs’ as a reward for transparency.
Adoption would be challenging. “We’re constantly battling increasing drug costs,” Ganio says. “So it’s not easy to go to a hospital CFO or director of pharmacy and say, ‘Hey, we’re going to buy a product that’s costs a little bit more, but we think it’s a good investment.‘”
But, he points out, shortages already force health care organizations to pay more, directly in labor costs and indirectly in hits to patient safety. A 2019 study by the consulting firm Vizient estimated that US hospitals spend an additional $359 million per year on staff time and overtime to cope with shortages. That same year, Australian researchers identified 38 studies that found that shortages harm patients through longer waits for treatment, longer hospitalizations, bad reactions to substitute drugs, surgical complications, and in some cases preventable deaths.
Health care personnel think tackling the challenge would be worth it, to avoid the chaos that grips their systems whenever shortages arrive. “Every time, we have to come up with a protocol for what we’re going to use instead,” says Melissa Johnson, a professor of medicine at Duke University and president of the Society of Infectious Diseases Pharmacists. “What don’t we have this week? Can we identify alternate sources? Do we have to compound our own?”
Maintaining the status quo means failing to address the problem, and letting the burden of drug shortages fall on frazzled pharmacists—and sick children and panicked parents who can do nothing but wait.
Memory and perception seem like entirely distinct experiences, and neuroscientists used to be confident that the brain produced them differently, too. But in the 1990s, neuroimaging studies revealed that parts of the brain that were thought to be active only during sensory perception are also active during the recall of memories.
“It started to raise the question of whether a memory representation is actually different from a perceptual representation at all,” said Sam Ling, an associate professor of neuroscience and director of the Visual Neuroscience Lab at Boston University. Could our memory of a beautiful forest glade, for example, be just a re-creation of the neural activity that previously enabled us to see it?
“The argument has swung from being this debate over whether there’s even any involvement of sensory cortices to saying ‘Oh, wait a minute, is there any difference?’” said Christopher Baker, an investigator at the National Institute of Mental Health who runs the learning and plasticity unit. “The pendulum has swung from one side to the other, but it’s swung too far.”
Even if there is a very strong neurological similarity between memories and experiences, we know that they can’t be exactly the same. “People don’t get confused between them,” said Serra Favila, a postdoctoral scientist at Columbia University and the lead author of a recent Nature Communications study. Her team’s work has identified at least one of the ways in which memories and perceptions of images are assembled differently at the neurological level.
When we look at the world, visual information about it streams through the photoreceptors of the retina and into the visual cortex, where it is processed sequentially in different groups of neurons. Each group adds new levels of complexity to the image: Simple dots of light turn into lines and edges, then contours, then shapes, then complete scenes that embody what we’re seeing.
In the new study, the researchers focused on a feature of vision processing that’s very important in the early groups of neurons: where things are located in space. The pixels and contours making up an image need to be in the correct places or else the brain will create a shuffled, unrecognizable distortion of what we’re seeing.
The researchers trained participants to memorize the positions of four different patterns on a backdrop that resembled a dartboard. Each pattern was placed in a very specific location on the board and associated with a color at the center of the board. Each participant was tested to make sure that they had memorized this information correctly—that if they saw a green dot, for example, they knew the star shape was at the far left position. Then, as the participants perceived and remembered the locations of the patterns, the researchers recorded their brain activity.
The brain scans allowed the researchers to map out how neurons recorded where something was, as well as how they later remembered it. Each neuron attends to one space, or “receptive field,” in the expanse of your vision, such as the lower left corner. A neuron is “only going to fire when you put something in that little spot,” Favila said. Neurons that are tuned to a certain spot in space tend to cluster together, making their activity easy to detect in brain scans.
Previous studies of visual perception established that neurons in the early, lower levels of processing have small receptive fields, and neurons in later, higher levels have larger ones. This makes sense because the higher-tier neurons are compiling signals from many lower-tier neurons, drawing in information across a wider patch of the visual field. But the bigger receptive field also means lower spatial precision, producing an effect like putting a large blob of ink over North America on a map to indicate New Jersey. In effect, visual processing during perception is a matter of small crisp dots evolving into larger, blurrier, but more meaningful blobs.