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Another unwelcome consequence of climate change: an explosion of urban rats

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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.

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(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.

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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.

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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.

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.

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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.”

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Contributor: Those cuts to 'overhead' costs in research? They do real damage

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Contributor: Those cuts to 'overhead' costs in research? They do real damage

As a professor at UC Santa Barbara, I research the effects of and solutions to ocean pollution, including oil seeps, spills and offshore DDT. I began my career by investigating the interaction of bacteria and hydrocarbon gases in the ocean, looking at the unusual propensity of microbes to consume gases that bubbled in from beneath the ocean floor. Needed funding came from the greatest basic scientific enterprise in the world, the National Science Foundation.

My research was esoteric, or so my in-laws (and everyone else) thought, until 2010, when the Deepwater Horizon offshore drilling rig exploded and an uncontrolled flow of hydrocarbon liquid and gas jetted into the deep ocean offshore from Louisiana. It was an unmitigated disaster in the Gulf, and suddenly my esoteric work was in demand. Additional support from the National Science Foundation allowed me to go offshore to help figure out what was happening to that petroleum in the deep ocean. I was able to help explain, contextualize and predict what would happen next for anxious residents of the Gulf states — all made possible by the foresight of Vannevar Bush, the original architect of the National Science Foundation.

Now the great scientific enterprise that has enabled my research and so much more is on the brink of its own disaster, thanks to actions and proposals from the Trump administration. Setting aside the targeted cuts to centers of discovery such as Harvard and Columbia, and rumors that California’s public universities are next, the most obvious threats to research are the draconian budget reductions proposed across virtually all areas of science and medicine, coupled with moves to prevent foreign scientists from conducting research-based study in the U.S. The president’s latest budget calls for around a 55% cut to the National Science Foundation overall, with a 75% reduction to research support in my area. A reduction so severe and sudden will reverberate for years and decimate ocean discovery and study, and much more.

But a more subtle and equally dire cut is already underway — to funding for the indirect costs that enable universities and other institutions to host research. It seems hard to rally for indirect costs, which are sometimes called “overhead” or “facilities and administration.” But at their core, these funds facilitate science.

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For instance, indirect costs don’t pay my salary, but they do pay for small-ticket items like my lab coat and goggles and bigger-ticket items like use of my laboratory space. They don’t pay for the chromatograph I use in my experiments, but they do pay for the electricity to run it. They don’t pay for the sample tubes that feed into my chromatograph, but they do support the purchasing and receiving staff who helped me procure them. They don’t pay for the chemical reagents I put in those sample tubes, but they do support the safe disposal of the used reagents as well as the health and safety staff that facilitates my safe chemical use.

They don’t pay salary for my research assistants, but they do support the human resources unit through which I hire them. They don’t pay for international travel to present my research abroad, but they do cover a federally mandated compliance process to make sure I am not unduly influenced by a foreign entity.

In other words, indirect costs support the deep bench of supporting characters and services that enable me, the scientist, to focus on discovery. Without those services, my research enterprise crumbles, and new discoveries with it.

My indirect cost rate is negotiated every few years between my institution and the federal government. The negotiation is based on hard data showing the actual and acceptable research-related costs incurred by the institution, along with cost projections, often tied to federal mandates. Through this rigorous and iterative mechanism, the overhead rate at my institution — as a percentage of direct research costs — was recently adjusted to 56.5%. I wish it were less, but that is the actual cost of running a research project.

The present model for calculating indirect costs does have flaws and could be improved. But the reduction to 15% — as required by the Trump administration — will be devastating for scientists and institutions. All the functions I rely on to conduct science and train the future workforce will see staggering cuts. Three-quarters of my local research support infrastructure will crumble. The costs are indirect, but the effects will be immediate and direct.

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More concerning is that we will all suffer in the long term because of the discoveries, breakthroughs and life-changing advances that we fail to make.

The scientific greatness of the United States is fragile. Before the inception of the National Science Foundation, my grandfather was required to learn German for his biochemistry PhD at Penn State because Germany was then the world’s scientific leader. Should the president’s efforts to cut direct and indirect costs come to pass, it may be China tomorrow. That’s why today we need to remind our elected officials that the U.S. scientific enterprise pays exceptional dividends and that chaotic and punitive cuts risk irreparable harm to it.

David L. Valentine is a professor of marine microbiology and geochemistry at UC Santa Barbara.

Insights

L.A. Times Insights delivers AI-generated analysis on Voices content to offer all points of view. Insights does not appear on any news articles.

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This article generally aligns with a Center Left point of view. Learn more about this AI-generated analysis
Perspectives

The following AI-generated content is powered by Perplexity. The Los Angeles Times editorial staff does not create or edit the content.

Ideas expressed in the piece

  • The article contends that indirect costs (overhead) are essential for research infrastructure, covering critical expenses like laboratory maintenance, equipment operation, safety compliance, administrative support, and regulatory processes, without which scientific discovery cannot function[1].
  • It argues that the Trump administration’s policy capping indirect cost reimbursement at 15% would inflict “staggering cuts” to research support systems, collapsing three-quarters of existing infrastructure and crippling scientific progress[2][3].
  • The piece warns that broader proposed NSF budget cuts—57% agency-wide and 75% in ocean research—threaten to “decimate” U.S. scientific leadership, risking a shift in global innovation dominance to nations like China[3].
  • It emphasizes that these cuts ignore the actual negotiated costs of research (e.g., UC Santa Barbara’s 56.5% rate) and would undermine “discoveries, breakthroughs, and life-changing advances”[1].

Different views on the topic

  • The Trump administration frames indirect costs as excessive “overhead” unrelated to core research, justifying the 15% cap as a cost-saving measure to redirect funds toward prioritized fields like AI and biotechnology[1][2].
  • Officials assert that budget cuts focus resources on “national priorities” such as quantum computing, nuclear energy, and semiconductors, arguing that funding “all areas of science” is unsustainable under fiscal constraints[1][3].
  • The administration defends its stance against funding research on “misinformation” or “disinformation,” citing constitutional free speech protections and rejecting studies that could “advance a preferred narrative” on public issues[1].
  • Policymakers contend that reductions compel universities to streamline operations, though federal judges have blocked similar caps at other agencies (e.g., NIH, Energy Department) as “arbitrary and capricious”[2].
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How Bees, Beer Cans and Data Solve the Same Packing Problem

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How Bees, Beer Cans and Data Solve the Same Packing Problem

Animation of the same plastic spheres disappearing one at a time.

A holy grail in pure mathematics is sphere packing in higher dimensions. Almost nothing has been rigorously proven about it, except in dimensions 1, 2 and 3.

That’s why it was such a breakthrough when, in 2016, a young Ukrainian mathematician named Maryna Viazovska solved the sphere-packing problem in eight dimensions, and later, with collaborators, in 24 dimensions.

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Union presses California’s key bird flu testing lab for records

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Union presses California’s key bird flu testing lab for records

The union representing workers at a UC Davis lab that tests and tracks bird flu infections in livestock has sued the university, demanding that records showing staffing levels and other information about the lab’s operations be released to the public.

Workers in the lab’s small biotechnology department had raised concerns late last year about short staffing and potentially bungled testing procedures as cases of avian flu spread through millions of birds in turkey farms and chicken and egg-laying facilities, as well as through the state’s cattle herds.

The University Professional and Technical Employees-CWA Local 9119 said that it requested records in December 2024 in an attempt to understand whether the lab was able to properly service the state’s agribusiness.

But UC Davis has refused to release records, in violation of California’s public records laws, the union alleged in a lawsuit recently filed in Alameda County Superior Court.

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UC Davis spokesperson Bill Kisliuk declined to comment on the lawsuit’s specific allegations.

“The university looks forward to filing our response in court. We are grateful for the outstanding work of the CAHFS lab staff, including UPTE-represented workers, during the 2024 surge in avian flu testing,” Kisliuk said in an email.

UC Davis has previously denied that workplace issues have left the lab ill-equipped to handle bird flu testing. Kisliuk had said the facility “maintained the supervision, staffing and resources necessary to provide timely and vital health and safety information to those asking us to perform tests.”

According to copies of email correspondence cited in the lawsuit, UC Davis in January denied the union’s request for records regarding short staffing or testing errors, calling the request “unduly burdensome.” It also denied its request for information about farms and other businesses that had samples tested at the lab, citing an exemption to protect from an “invasion of personal privacy.”

Workers at the lab had previously told The Times that they observed lapses in quality assurance procedures, as well as other mistakes in the testing process.

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Amy Fletcher, a UC Davis employee and president of the union’s Davis chapter, said the records would provide a necessary window into how staffing levels could be hurting farms and other businesses that rely on the lab for testing. Fletcher said workers have become afraid to speak about problems at the lab, having been warned by management that the some information related to testing is confidential.

The Davis lab is the only entity in the state with the authority to confirm bird flu cases.

The union, known as UPTE, represents about 20,000 researchers and other technical workers across the University of California system’s 10 campuses.

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