Higher Temperatures Mean More Rats in the World’s Cities

Climate change means good news for rats

Rat in a drain
A close up portrait of a rat as it emerges from a drain pipe.
Getty Images

If you live in a large U.S. city, you may well have rats on your mind — or just be seeing rats on a regular basis. In New York City, for instance, there’s a rat czar — someone whose governmental purview is trying to get the city’s rat population down. As a recent New York Times article explained, that’s easier said than done, with new regulations on trash bins one of the latest permutations in this conflict.

Overall, however, the rats may have the advantage. Why is that? Well, it has to do with rising temperatures all over the world — which is a very good thing if you’re a rat looking to reproduce. The title of a paper published this week in the journal Science Advances gives a good overview of the issues at hand: “Increasing rat numbers in cities are linked to climate warming, urbanization, and human population.”

“Warming temperatures and more people living in cities may be expanding the seasonal activity periods and food availability for urban rats,” the study’s authors wrote. What that translates into is a win-win for rats: more people living in cities means more food for rats to eat, and warmer temperatures means that rats have more time to both search for food and engage in the act of, well, making more rats.

According to the study, only three cities — Tokyo, Louisville and New Orleans — showed a decline in their rat population. As for increases in the rat population, the top five cities globally were Washington, D.C., San Francisco, Toronto, New York City and Amsterdam.

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The study’s lead author, Jonathan Richardson, explained that even short changes to seasonal boundaries can have a big effect on rat populations. “[T]hat’s one, two, maybe even three or four weeks across the entire year where those rats can be above ground foraging, acquiring more food and maybe squeezing out one or two more reproductive cycles,” he told the Associated Press. It’s one more alarming trend to chalk up to climate change.

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