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.”
Science
Video: NASA Announces Artemis III Crew
new video loaded: NASA Announces Artemis III Crew
transcript
transcript
NASA Announces Artemis III Crew
NASA announced the crew of Artemis III mission, which will fly to low-Earth orbit to test rendezvous and docking maneuvers with one or two lunar landers.
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“I am excited to welcome you as the next crew in the Artemis journey to successfully return to the moon — this time to stay.” “I’m honored by the role that I’ve been given. I’m also very humbled by the task in front of us. But first and foremost, I’m grateful.” “So with that, the Artemis II crew, comrade, hands you the baton. You got the controls.” “As you know, we had a significant anomaly at our Launch Complex 36A on May 28. We’ve redoubled our efforts and are moving forward.”
By Alisa Shodiyev Kaff
June 9, 2026
Science
Santa Monica Mountains’ last steelhead trout survived the Palisades fire — and even had babies
Scientists feared the Santa Monica Mountains’ last remaining steelhead trout were dead, smothered by debris flows unleashed by the Palisades fire.
But the endangered fish surprised them: A team of biologists recently spotted 30 of the rare trout — and 21 babies — in Topanga Creek.
“There was a lot of happy dancing in the creek,” said Rosi Dagit, principal conservation biologist for the Resource Conservation District of the Santa Monica Mountains, which works with public and private landowners to conserve natural resources.
That’s because the steelhead here are endangered, at both the state and federal levels. Once, they swam in most streams of the Santa Monicas, but their numbers plummeted amid overfishing and coastal development. Increasingly frequent wildfire has further stressed their habitat. Topanga Creek, a biodiversity hot spot, is home to their last known population in the mountains that stretch from the Hollywood Hills to Point Mugu in Ventura County.
The trout that were spotted, including this one, are part of a distinct Southern California population that’s listed as endangered at the state and federal levels.
(RCDSMM Stream Team)
The California Department of Fish and Wildlife spearheaded a complex mission to rescue trout threatened by the Palisades fire that sparked in January 2025.
Time was of the essence. The fire hadn’t yet been fully contained. But rain was on the way, which would sweep massive amounts of sediment from the denuded hillsides into the water. Fish are often killed this way.
Crews stunned the fish with electricity, scooped them up in buckets, trucked them to a hatchery and ultimately moved them to Arroyo Hondo Creek in Santa Barbara County.
Within days, Topanga Creek was choked with mud. Some assumed the fish left behind were goners.
But in March, the conservation district’s team found four. The following month, when water conditions were clearer, they saw more.
“These fish continue to amaze me,” said Kyle Evans, environmental program manager for the state Department of Fish and Wildlife, who had seen the damage to the creek. “I had seen populations get wiped out in similar situations. So when I heard, I was thrilled.”
Evans surmises the fish that survived were in an area of the creek where less charred material and sediment were swept in.
“These fish likely hunkered down, were hiding under some rocks or places to try to get away from the main concentration of flow,” he said. “And luckily they weren’t buried.”
The ones that were spotted were fairly small, around 6 to 14 inches. Rainbow trout and steelhead trout are the same species, but with different lifestyles. If the fish remain in freshwater, they’ll be considered rainbows. However, they can migrate to the ocean and become steelhead, where they typically grow larger before returning to their natal waters to spawn.
Topanga Creek hasn’t fully recovered from the damage it sustained, but scientists say it’s looking better. Surveys last year were “so depressing,” Dagit said, with very few animals, and stretches that were essentially transformed into flat roads from all the sediment buildup. Some of the riparian canopy burned right down to the creek.
Then came 32 inches of rain over the last nine months, scouring out and moving sediment, creating deeper pools. Dagit said they recently found newt egg masses for the first time in years, as well as a few adult newts and many frogs. Plants that provide cover are starting to recover.
She provided photos comparing certain pools last year and this year, some dramatically transformed. In September 2025, the Shrine Pool could have been an overgrown hiking trail. This April, it was filled with shallow water.
The Shrine Pool in September 2025, left, and the same location in April 2026, right, with RCDSMM’s Isaac Yelchin donning a wetsuit.
(RCDSMM Stream Team)
Topanga Creek is home to another endangered fish, the small but hardy northern tidewater goby, often described as cute. Not long before the trout operation, Dagit led a rescue of hundreds of these fish too. Many were repatriated to the lagoon at the mouth of the creek in a moving ceremony last June.
There’s still the matter of what to do with the trout that were moved to Santa Barbara County last year. Evans would like to bring them home to the Santa Monicas at some point, but isn’t sure if it will happen. On one hand, they could bolster the small, genetically isolated surviving population. On the other, they might inadvertently bring in a disease or bacteria. There is some time to decide. Evans estimates the creek still needs to recover for two to three more years.
For now, the fish are functioning fine in their adopted creek. Experts worried the trauma wrought by the move would disrupt their spawning process, but they had babies that spring. This year, they spawned again.
Science
Pacifica pier cracks, another coastal casualty as seas continue to rise
The Pacifica Municipal Pier was shut down and taped off Thursday after city workers noticed cracks running through the landmark structure and concrete chunks falling into the ocean.
It’s just one of many coastal California structures that have recently crumbled under pressure from a rising and relentless ocean.
Officials from the small, beach city south of San Francisco said the pier was closed due to “cracking, separation, and displacement of the concrete walkway and structural elements.”
It will stay closed while structural engineers asses its safety.
Photos taken by city employees show a wide crack that runs from top to bottom and across the structure as well. Other photos show a large horizontal crack under the foundation of a small restaurant on the pier, the Chit Chat Cafe.
The cafe was also shut down.
This is not the first time the 53-year-old pier has shown signs of stress. In 2021, part of it was shut down after handrails along the edge collapsed. And in 2023, after a series of storms pummeled the Central California coast, damaging parts of the pier, the structure was partially closed for more than year.
Those same storms caused extensive damage in Aptos and Capitola, 70 miles south, where piers and waterfront infrastructure were swept away or damaged.
In 2024, a 150- to 180- foot section of the Santa Cruz wharf was ripped off by powerful waves.
At least 10 of the state’s dozens of coastal public piers were closed for part or all of 2024 due to structural damage sustained in winter storms since 2022. At least five others have longer-term upgrades planned to address structural issues.
“These things are costly to maintain,” said Zach Plopper, senior environmental director at Surfrider. “They are a part of our California coastal culture in many ways, but we’re going to need to reckon with, one, the state that they’re in, and two, the continuous and worsening threats they’re going to experience,”
He said most of the piers were constructed in the early 1900s, and they weren’t built to withstand decades of rough seas, storms and rising sea level.
“With this incoming El Niño, which is forecasted to be significant, and this marine heat wave we’re in the midst of, we’re kind of in uncharted waters as far as what this winter could bring in terms of storms and swells to the California coast, and we’re likely going to see a lot more damage,” he said. “Not just piers, but roads and other coastal infrastructure up and down the state.”
There was no storm in Pacifica earlier this week, so no single event could be blamed for the destruction.
However, a 2025 report from an outside engineering firm, GHD, found that several sections of the pier were in “poor” or “serious” condition, and they recommended closure before anticipated storms or events that could “subject the piles to high winds, swells and large waves.”
The firm found several areas of the pier where concrete was missing and rebar was exposed and corroding.
“The pier has continued to experience high winds and large waves in a harsh marine environment,” the engineers wrote in the report, noting that continuous exposure to seawater or marine spray was “detrimental” to the structure.
A 2023 city report estimated it would cost $19 million to repair.
That same year, a state law was enacted to require local governments along the California coast to plan for sea level rise in the coming decades.
Sea level has risen some 8 inches, on average, along the coast in the past 150 years, Plopper said, and researchers anticipate another foot in the next 25 years.
“We’re going to see profound shifts on our coastline, none that we have ever experienced before, and building static structures on the coast just doesn’t work all that well,” he said. “We’re going to have to make some really hard decisions.”
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