Enlarge / Hummingbirds—like this golden-tailed sapphire from South America—draw the eye with their bright colors and busy, hovering flight. Biologists are drawn to understand the suite of adaptations they have evolved to survive extreme lifestyles. (credit: webguzs via Getty)

Everyone loves to watch hummingbirds—tiny, brightly colored blurs that dart about, hovering at flowers and pugnaciously defending their ownership of a feeder.

But to the scientists who study them, hummingbirds offer much more than an entertaining spectacle. Their small size and blazing metabolism mean they live life on a knife-edge, sometimes needing to shut down their bodies almost completely just to conserve enough energy to survive the night—or to migrate thousands of miles, at times across open ocean.

Their nectar-rich diet leads to blood-sugar levels that would put a person in a coma. And their zipping, zooming flight sometimes generates g-forces high enough to make a fighter pilot black out. The more researchers look, the more surprises lurk within those tiny bodies, the smallest in the avian world.

Scientists are uncovering various ways that air pollution can interfere with the ability of insects to pollinate plants. (credit: Utah.gov)

In the summers of 2018 and 2019, ecologist James Ryalls and his colleagues would go out to a field near Reading in southern England to stare at the insects buzzing around black mustard plants. Each time a bee, hoverfly, moth, butterfly, or other insect tried to get at the pollen or nectar in the small yellow flowers, they’d make a note.

It was part of an unusual experiment. Some patches of mustard plants were surrounded by pipes that released ozone and nitrogen oxides—polluting gases produced around power plants and conventional cars. Other plots had pipes releasing normal air.

The results startled the scientists. Plants smothered by pollutants were visited by up to 70 percent fewer insects overall, and their flowers received 90 percent fewer visits compared with those in unpolluted plots. The concentrations of pollutants were well below what US regulators consider safe. “We didn’t expect it to be quite as dramatic as that,” says study coauthor Robbie Girling, an entomologist at the University of Southern Queensland in Australia and a visiting professor at the University of Reading.

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An accountant who fills out spreadsheets at the beach, a dog groomer who always has time for one more client, a basketball player who shoots free throws to the point of exhaustion.

Every profession has its share of hard chargers and overachievers. But for some workers—perhaps more than ever in our always-on, always-connected world—the drive to send one more email, clip one more poodle, sink one more shot becomes all-consuming.

Workaholism is a common feature of the modern workplace. A recent review gauging its pervasiveness across occupational fields and cultures found that roughly 15 percent of workers qualify as workaholics. That adds up to millions of overextended employees around the world who don’t know when—or how, or why—to quit.

Enlarge / As female macaques age, the size of their social network shrinks. (credit: Jon G. Fuller/VW Pics/Universal Images Group via Getty Images)

Walnut was born on June 3, 1995, at the start of what would become an unusually hot summer, on an island called Rum (pronounced room), the largest of the Small Isles off the west coast of Scotland. We know this because since 1974, researchers have diligently recorded the births of red deer like her, and caught, weighed and marked every calf they could get their hands on—about 9 out of every 10.

Near the cottage in Kilmory on the northern side of the island where the researchers are based, there has been no hunting since the project began, which allowed the deer to relax and get used to human observers. Walnut was a regular there, grazing the invariably short-clipped grass in this popular spot. “She would always just be there in the group, with her sisters and their families,” says biologist Alison Morris, who has lived on Rum for more than 23 years and studies the deer year-round.

Walnut raised 14 offspring, the last one in 2013, when she was 18 years old. In her later years, Morris recalls, Walnut would spend most of her time away from the herd, usually with Vanity, another female (called a hind) of the same age who had never calved. “They were often seen affectionately grooming each other, and after Walnut died of old age in October 2016, at the age of 21—quite extraordinary for a hind—Vanity spent most of her time alone. She died two years later, at the grand age of 23.”

Enlarge (credit: Fernando Trabanco Fotografía via Getty Images)

Isaac Newton would never have discovered the laws of motion had he studied only cats.

Suppose you hold a cat, stomach up, and drop it from a second-story window. If a cat is simply a mechanical system that obeys Newton’s rules of matter in motion, it should land on its back. (OK, there are some technicalities—like this should be done in a vacuum, but ignore that for now.) Instead, most cats usually avoid injury by twisting themselves on the way down to land on their feet.

Most people are not mystified by this trick—everybody has seen videos attesting to cats’ acrobatic prowess. But for more than a century, scientists have wondered about the physics of how cats do it. Clearly, the mathematical theorem analyzing the falling cat as a mechanical system fails for live cats, as Nobel laureate Frank Wilczek points out in a recent paper.

Enlarge / Bioreactors that host algae would be one option for carbon sequestration—as long as the carbon is stored somehow. (credit: Getty Images)

More than 200 kilometers off Norway’s coast in the North Sea sits the world’s first offshore carbon capture and storage project. Built in 1996, the Sleipner project strips carbon dioxide from natural gas—largely made up of methane—to make it marketable. But instead of releasing the CO₂ into the atmosphere, the greenhouse gas is buried.

The effort stores around 1 million metric tons of CO₂ per year—and is praised by many as a pioneering success in global attempts to cut greenhouse gas emissions.

Last year, total global CO₂ emissions hit an all-time high of around 35.8 billion tons, or gigatons. At these levels, scientists estimate, we have roughly six years left before we emit so much CO₂ that global warming will consistently exceed 1.5° Celsius above average preindustrial temperatures, an internationally agreed-upon limit. (Notably, the global average temperature for the past 12 months has exceeded this threshold.)

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As the world races to decarbonize everything from the electricity grid to industry, it faces particular problems with transportation—which alone is responsible for about a quarter of our planet’s energy-related greenhouse gas emissions. The fuels for transport need to be not just green, cheap, and powerful, but also lightweight and safe enough to be carried around.

Fossil fuels—mainly gasoline and diesel—have been extraordinarily effective at powering a diverse range of mobile machines. Since the Industrial Revolution, humanity has perfected the art of dredging these up, refining them, distributing them and combusting them in engines, creating a vast and hard-to-budge industry. Now we have to step away from fossil fuels, and the world is finding no one-size-fits-all replacement.

Each type of transportation has its own peculiarities—which is one reason we have different formulations of hydrocarbons today, from gasoline to diesel, bunker fuel to jet fuel. Cars need a convenient, lightweight power source; container ships need enough oomph to last months; planes absolutely need to be reliable and to work at subzero temperatures. As the fossil fuels are phased out, the transport fuel landscape is “getting more diverse,” says Timothy Lipman, co-director of the Transportation Sustainability Research Center at the University of California, Berkeley.

Enlarge / This aerial picture taken on December 8, 2023, shows the US-Mexico border wall in Sasabe, Arizona. (credit: VALERIE MACON/AFP via Getty Images)

In a vast stretch of the Sonoran Desert, between the towns of San Luis Río Colorado and Sonoyta in northern Mexico, sits a modest building of cement, galvanized sheet metal, and wood—the only stop along 125 miles of inhospitable landscape dominated by thorny ocotillo shrubs and towering saguaro cactuses up to 50 feet high. It’s a fonda—a small restaurant—called La Liebre del Desierto (The Desert Hare), and for more than 20 years, owner Elsa Ortiz Ramos has welcomed and nourished weary travelers taking a break from the adjacent highway that runs through the arid Pinacate and Grand Desierto de Altar Biosphere Reserve.

But the dedication and care of this petite woman go beyond her simple menu. Every two weeks, she pays out of pocket for a 5,000-gallon tank of water to distribute to a network of water troughs strategically placed in the area. By doing so, she relieves the thirst of bighorn sheep, ocelots, pronghorn, coyotes, deer, and even bats that have been deprived of access to their natural water sources.

“The crows come to the house and scream to warn us that there is no more water ... it’s our alarm,” says Ortiz Ramos in her distinct northern Mexico accent. Her words sound straight from an Aesop’s fable, but they take on stark realism in this spot. Covering large parts of Arizona, California, and the Mexican states of Baja California and Sonora, the Sonoran Desert—along with the Lut Desert in Iran—was cataloged in 2023 as having the hottest surface temperature on the planet, at 80.8° Celsius (177° Fahrenheit).

Enlarge / Pharma interest and investment in radiotherapy drugs is heating up. (credit: Knowable Magazine)

On a Wednesday morning in late January 1896 at a small light bulb factory in Chicago, a middle-aged woman named Rose Lee found herself at the heart of a groundbreaking medical endeavor. With an X-ray tube positioned above the tumor in her left breast, Lee was treated with a torrent of high-energy particles that penetrated into the malignant mass.

“And so,” as her treating clinician later wrote, “without the blaring of trumpets or the beating of drums, X-ray therapy was born.”

Radiation therapy has come a long way since those early beginnings. The discovery of radium and other radioactive metals opened the doors to administering higher doses of radiation to target cancers located deeper within the body. The introduction of proton therapy later made it possible to precisely guide radiation beams to tumors, thus reducing damage to surrounding healthy tissues—a degree of accuracy that was further refined through improvements in medical physics, computer technologies and state-of-the-art imaging techniques.

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In the urgent quest for a more sustainable global food system, livestock are a mixed blessing. On the one hand, by converting fibrous plants that people can’t eat into protein-rich meat and milk, grazing animals like cows and sheep are an important source of human food. And for many of the world’s poorest, raising a cow or two—or a few sheep or goats—can be a key source of wealth.

But those benefits come with an immense environmental cost. A study in 2013 showed that globally, livestock account for about 14.5 percent of greenhouse gas emissions, more than all the world’s cars and trucks combined. And about 40 percent of livestock’s global warming potential comes in the form of methane, a potent greenhouse gas formed as they digest their fibrous diet.

That dilemma is driving an intense research effort to reduce methane emissions from grazers. Existing approaches, including improved animal husbandry practices and recently developed feed additives, can help, but not at the scale needed to make a significant global impact. So scientists are investigating other potential solutions, such as breeding low-methane livestock and tinkering with the microbes that produce the methane in grazing animals’ stomachs. While much more research is needed before those approaches come to fruition, they could be relatively easy to implement widely and could eventually have a considerable impact.

Enlarge (credit: RamonCarretero/Getty)

A hammerhead shark less than one meter long swims frantically in a plastic container aboard a boat in the Sanquianga National Natural Park, off Colombia’s Pacific coast. It is a delicate female Sphyrna corona, the world’s smallest hammerhead species, and goes by the local name cornuda amarilla—yellow hammerhead—because of the color of its fins and the edges of its splendid curved head, which is full of sensors to perceive the movement of its prey.

Marine biologist Diego Cardeñosa of Florida International University, along with local fishermen, has just captured the shark and implanted it with an acoustic marker before quickly returning it to the murky waters. A series of receivers will help to track its movements for a year, to map the coordinates of its habitat—valuable information for its protection.

That hammerhead is far from the only shark species that keeps the Colombian biologist busy. Cardeñosa’s mission is to build scientific knowledge to support shark conservation, either by locating the areas where the creatures live or by identifying, with genetic tests, the species that are traded in the world’s main shark markets.