Climate change is helping rats increase their populations

February 8, 2025

Scientists have already linked climate change to more severe weather, rising sea levels, and melting polar ice caps. And now, a new study offers more bad news.

Urban rat populations are booming around the world due in large part to rising average temperatures.

Rats already cost the United States approximately $27 billion each year in damage to infrastructure, crops, and contaminated food supplies. At the same time, media reports tend to suggest that rat populations are skyrocketing.

In the first study of its kind, scientists found a correlation between climate change and a rise in urban rat populations.

Rising temperatures seem to be helping rat populations grow faster, according to a new study in the journal Science Advances. Researchers found cities that have seen the most warming had more sightings of rats, an indication that the population has grown.

They found that denser urban environments and higher human populations helped boost the number of rats. Warmer temperatures seemed to be the biggest influence. Cities with the biggest growth rates were Washington D.C., San Francisco, Toronto, New York City and Amsterdam.

Richardson, author on the study, says climate change could pose an additional challenge for cities trying to manage rats, many of which have programs that are already under-resourced and understaffed. Rats are known to spread pathogens, as well as damage infrastructure. They can also cause a mental health burden for people living with rat infestations.

About 40 percent of the overall increase in rat sightings is linked to rising temperatures in cities, according to the analysis.
Over the past decade, rat sightings in D.C. jumped by more than 300 percent, while in New York they went up by 162 percent, according to Richardson. “We live in an infinite sea of rats,” said Niamh Quinn, a human-wildlife interactions adviser.

Of course, it’s more than just rising temperatures allowing rats to proliferate. Urban rodents thrive in areas with poor trash management, where broken garbage bags and open dumpsters offer rats a daily feast.

Kaylee Byers, assistant professor of health sciences at Simon Fraser University in Canada says "The key for controlling rats is controlling ourselves, by better managing food waste and restricting access to trash ("garbage in = rats out"). "We're often focused on this 'see a rat, kill a rat' mentality and — spoiler — that's not working," she says.

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