Science
Another unwelcome consequence of climate change: an explosion of urban rats
If scorching heat waves, destructive storms, prolonged droughts and rising seas aren’t enough to make some folks fear the consequences of climate change, perhaps this will do the trick: The warmer it gets, the faster rats multiply in cities that already struggle to contain them.
That is sure to be unwelcome news to Americans, who collectively endure well over $27 billion worth of property damage each year at the hands — and teeth — of rats. That doesn’t include the cost of the diseases the animals spread, such as hantavirus, murine typhus and bubonic plague, nor the mental health toll of living among them.
The new findings, reported Friday in the journal Science Advances, are based on records of rat sightings in 16 cities around the world. Unfortunately for humans, 11 of those cities saw their rat populations expand over the course of the study, while two cities held steady and only three achieved measurable declines.
That the rodents are thriving should come as little surprise. They’re perfectly suited to urban environments, where they make their homes in walls, basements and subway stations and feast on garbage, sewage, dog poop and abandoned pizza slices. The only continent they have yet to conquer is Antarctica.
A rat foraging in a dumpster in Richmond, Va.
(Jonathan Richardson)
“This species is really well-adapted to take food and convert that into new baby rats that are scampering around your neighborhood,” said Jonathan Richardson, a biologist at the University of Richmond who studies wildlife in cities and their impact on human health. “They do that really efficiently.”
One of the few things that slows rats down is cold weather. And with climate change, we have less of it.
Global warming causes average temperatures to rise, which reduces the number of wintry days. In cities, the trend is compounded by the fact that the built environment absorbs and retains more heat than the rural area around it, a phenomenon known as the urban heat island effect.
To investigate a possible link between rat populations and rising temperatures, Richardson and his colleagues searched for reliable data in the country’s 200 most populous cities. Conducting a thorough rat census was impractical — if not impossible — so they used municipal inspection logs and rat sightings reported to government agencies.
They found 13 cities that had kept consistent records for at least seven years. Then they widened their search and found three more cities overseas. The final group had rat data going back for an average of slightly more than 12 years.
Since the cities used different sources of data collected over different periods of time, the researchers came up with a standardized way to measure the change in rat sightings. They found that rat reports increased the most in Washington, D.C., followed by San Francisco, Toronto, New York City, Amsterdam, Oakland, Buffalo, Chicago, Boston, Kansas City and Cincinnati.
Three cities — New Orleans, Louisville and Tokyo — managed to reduce their rat populations during the study period. There were no significant changes in Dallas or St. Louis.
Los Angeles wasn’t included in the analysis because systematic rat records weren’t available. L.A. routinely ranks among the top three in pest control companies’ annual lists of America’s “rattiest cities,” but Richardson said the perennially large volume of rodent complaints had more to do with the city’s sprawling size than a uniquely rat-friendly environment.
Next, the researchers used statistical methods to see which factors might account for the differences in the cities’ rat control outcomes. About two-thirds of the variation could be explained by five things, including human population density and the amount of area covered by vegetation.
The most important factor was the change in a city’s average temperature — the more it rose, the more the rat population grew.
A rat crosses a subway platform in New York City’s Times Square.
(Richard Drew / Associated Press)
The change in a city’s minimum temperature had no bearing on rats. Richardson said the team initially was surprised by that, since cold weather extends the time it takes for female rats to become fertile and reduces the number of pups in a litter.
In more hospitable weather, a rat can become pregnant when she’s just two months old, and that pregnancy will last only three to five weeks. The researchers realized that if rising average temperatures caused winter conditions to arrive a week or two later and wrap up a week or two earlier, it could buy a rat enough time to squeeze in an extra reproductive cycle each year, Richardson said.
Santtu Pentikäinen, a researcher at the University of Helsinki who was not involved in the work, said the study authors made a convincing case that global warming is good for rats.
“The results just make sense,” said Pentikäinen, a member of the Helsinki Urban Rat Project.
Coauthor Maureen Murray, a wildlife disease ecologist at Chicago’s Lincoln Park Zoo and leader of the Chicago Rat Project, said she hoped the findings will “motivate people to care that climate change could exacerbate their rat problems.”
But Richardson said he wasn’t sure the prospect of “more rats scurrying around” will be any more galvanizing than pictures of “the sad polar bear floating on ice.”
Our universe might be chock-full of cosmic wonder, but you can observe only a fraction of astronomical phenomena with the naked eye. Meteor showers, natural fireworks that streak brightly across the night sky, are one of them.
The latest observable meteor shower will be the Lyrids, which has been active since April 14 and is forecast to continue through April 30. The shower reaches its peak April 21 to 22, or Tuesday night into Wednesday morning.
According to NASA, the Lyrids are one of the oldest known meteor showers, and have been enjoyed by stargazers for nearly 3,000 years. Their bright, speedy streaks are caused by the dusty debris from a comet named Thatcher. They appear to spring from the constellation Lyra, which right now can be seen in the eastern sky at night in the Northern Hemisphere.
The moon will be about 27 percent full tonight, appearing as a thick crescent in the sky, according to the American Meteor Society.
To get a hint at when to best watch for the Lyrids, you can use this tool, which relies on data from the Global Meteor Network. It shows fireball activity levels in real time.
And while you gaze at the heavens, keep an eye out for other stray meteors streaking across the night sky. Skywatchers are reporting that the amount of fireballs is double what is usually seen by this point in the year.
Where meteor showers come from
There is a chance you might see a meteor on any given night, but you are most likely to catch one during a shower. Meteor showers are caused by Earth passing through the rubble trailing a comet or asteroid as it swings around the sun. This debris, which can be as small as a grain of sand, leaves behind a glowing stream of light as it burns up in Earth’s atmosphere.
Meteor showers occur around the same time every year and can last for days or weeks. But there is only a small window when each shower is at its peak, which happens when Earth reaches the densest part of the cosmic debris. The peak is the best time to look for a shower. From our point of view on Earth, the meteors will appear to come from the same point in the sky.
The Perseid meteor shower, for example, peaks in mid-August from the constellation Perseus. The Geminids, which occur every December, radiate from the constellation Gemini.
How to watch a meteor shower
Michelle Nichols, the director of public observing at the Adler Planetarium in Chicago, recommends forgoing the use of telescopes or binoculars while watching a meteor shower.
“You just need your eyes and, ideally, a dark sky,” she said.
That’s because meteors can shoot across large swaths of the sky, so observing equipment can limit your field of view.
Some showers are strong enough to produce up to 100 streaks an hour, according to the American Meteor Society, though you probably won’t see that many.
“Almost everybody is under a light-polluted sky,” Ms. Nichols said. “You may think you’re under a dark sky, but in reality, even in a small town, you can have bright lights nearby.”
Planetariums, local astronomy clubs or even maps like this one can help you figure out where to go to escape excessive light. The best conditions for catching a meteor shower are a clear sky with no moon or cloud cover, sometime between midnight and sunrise. (Moonlight affects visibility in the same way as light pollution, washing out fainter sources of light in the sky.) Make sure to give your eyes at least 30 minutes to adjust to seeing in the dark.
Ms. Nichols also recommends wearing layers, even during the summer. “You’re going to be sitting there for quite a while, watching,” she said. “It’s going to get chilly, even in August.”
Bring a cup of cocoa or tea for even more warmth. Then lie back, scan the sky and enjoy the show.
Where weather is least likely to affect your view
Storm systems sweep across the country in early spring, and some will be obscuring skies tonight. But there will still be plenty of areas with clear skies, particularly in parts of the central United States.
“The best spot is going to be in the Upper Midwest,” said Rich Bann, a meteorologist with the Weather Prediction Center.
Minnesota, Wisconsin and Iowa will offer especially good sky-viewing weather and a beach on the Great Lakes could be a nice spot to look up at the stars.
But don’t expect to view the show from Chicago, as Illinois could see some thunderstorms. The weather will be better in the Northern and Central Plains, particularly the eastern Dakotas.
High, wispy clouds are expected over the Ohio and Tennessee Valleys and into parts of the Mid-Atlantic. But, Mr. Bann said, “you may be able to see some shooting stars through thin clouds.”
Clouds will be draped across much of the Southeast and the Northeast, though there could be some clearing in Florida, Georgia, the Carolinas and Virginia. Remember, the meteors could be visible all night long. If you look outside and see clouds, try again later.
Catching the spectacle will be challenging across much of the West, particularly from Washington into Northern California, where a storm system is bringing rain and snow. That system will move east overnight.
There are likely to be some pockets of clear skies at times across southern Nevada, northwest Arizona and southwest Utah, Mr. Bann said.
Amy Graff contributed reporting.
WASHINGTON — Amid growing national security concerns, the FBI said Tuesday that it has launched a broad investigation in the deaths or disappearances of at least 10 scientists and staff connected to highly sensitive research, including four from the Los Angeles area.
“The FBI is spearheading the effort to look for connections into the missing and deceased scientists. We are working with the Department of Energy, Department of War, and with our state and state and local law enforcement partners to find answers,” the agency said in a statement.
The FBI’s announcement comes after the House Oversight Committee announced that it would investigate reports of the disappearance and deaths of the scientists, sending letters seeking information from the agencies involved in the federal inquiry as well as NASA, which owns the Jet Propulsion Laboratory in La Cañada Flintridge, where three of the missing or dead scientists worked.
“If the reports are accurate, these deaths and disappearances may represent a grave threat to U.S. national security and to U.S. personnel with access to scientific secrets,” Reps. James Comer (R-Ky.), chairman of the committee, and Eric Burlison (R-Mo.) wrote in the letters.
President Trump told reporters last week that he had been briefed on the missing and dead scientists, which he described as “pretty serious stuff.” He said at the time that he expected answers on whether the deaths were connected “in the next week and a half.”
Michael David Hicks, who studied comets and asteroids at JPL, was the first of the scientists who disappeared or died. He died on July 30, 2023, at the age of 59. No cause of death was disclosed.
A year later, JPL physicist Frank Maiwald died at 61, with no cause of death disclosed.
Two other Los Angeles scientists are part of the string of deaths and disappearances.
On June 22, 2025, Monica Jacinto Reza, a materials scientist at JPL, disappeared while on a hike near Mt. Waterman in the San Gabriel Mountains.
On Feb. 16, Caltech astrophysicist Carl Grillmair was fatally shot on the porch of his Llano home. The Los Angeles County Sheriff’s department arrested Freddy Snyder, 29, in connection with the shooting. Snyder had been arrested in December on suspicion of trespassing on Grillmair’s property.
Snyder has been charged with murder.
There is no evidence at this point that the deaths and disappearances, which occurred over a span of four years, are connected.
A spokesperson for NASA, which owns JPL, said in a statement on X that the agency is “coordinating and cooperating with the relevant agencies in relation to the missing scientists.
“At this time, nothing related to NASA indicates a national security threat,” agency spokesperson Bethany Stevens wrote. “The agency is committed to transparency and will provide more information as able.”
Representatives from Caltech, which manages JPL, did not immediately respond to a request for comment.
The sun had barely risen over the Pacific Ocean when a small motorboat carrying a team of Indigenous artisans and Mexican biologists dropped anchor in a rocky cove near Bahías de Huatulco.
Mauro Habacuc Avendaño Luis, one of the craftsmen, was the first to wade to shore. With an agility belying his age, he struck out over the boulders exposed by low tide. Crouching on a slippery ledge pounded by surf, he reached inside a crevice between two rocks. There, lodged among the urchins, was a snail with a knobby gray shell the size of a walnut. The sight might not dazzle tourists who travel here to see humpback whales, but for Mr. Avendaño, 85, these drab little mollusks represent a way of life.
Marine snails in the genus Plicopurpura are sacred to the Mixtec people of Pinotepa de Don Luis, a small town in southwestern Oaxaca. Men like Mr. Avendaño have been sustainably “milking” them for radiant purple dye for at least 1,500 years. The color suffuses Mixtec textiles and spiritual beliefs. Called tixinda, it symbolizes fertility and death, as well as mythic ties between lunar cycles, women and the sea.
The future of these traditions — and the fate of the snails — are uncertain. The mollusks are subject to intense poaching pressure despite federal protections intended to protect them. Fishermen break them (and the other mollusks they eat) open and sell the meat to local restaurants. Tourists who comb the beaches pluck snails off the rocks and toss them aside.
A severe earthquake in 2020 thrust formerly submerged parts of their habitat above sea level, fatally tossing other mollusks in the snail’s food web to the air, and making once inaccessible places more available to poachers.
Decades ago, dense clusters of snails the size of doorknobs were easy to find, according to Mr. Avendaño. “Full of snails,” he said, sweeping a calloused, violet-stained hand across the coves. Now, most of the snails he finds are small, just over an inch, and yield only a few milliliters of dye.
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