The Perfect Rat Storm; Rising Temps Power Population Spike; 390% Increase In DC In 10 Years; 300% In SF, 186% In NYC
Rat numbers are soaring in cities as global temperatures warm, research shows. Washington DC, San Francisco, Toronto, New York City and Amsterdam had the greatest increase in these rodents, according to the study, which looked at data from 16 cities globally. Eleven of the cities showed “significant increasing trends in rat numbers”, said the paper published in the journal Science Advances, and these trends were likely to continue.
Over the past decade, rats increased by 390% in Washington DC, 300% in San Francisco, 186% in Toronto and 162% in New York according to researchers, who analysed public sightings and infestation reports. Some big cities, such as London and Paris, were not included because they did not provide the necessary data – but researchers said the findings would apply to many similar cities around the world. “There’d be no reason to expect it to be different in other places,” said lead researcher Jonathan Richardson, from the University of Richmond in Virginia.
In Toronto, one of the worst-affected locations, a “perfect rat storm” has taken hold, with residents of Canada’s biggest city staring down a surging population. “When you walk the streets of Toronto, under your feet, deep in the sewage system, is a place teeming with rats,” said Alice Sinia, lead entomologist for Orkin, the country’s largest pest control company. “Increasingly we’re flushing them out into open spaces – either through construction or floods – and they have to go somewhere.”
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Rising temperatures correlated with rising rat numbers, researchers wrote in the paper. As small mammals, rats struggle during winter, but in higher temperatures they can breed for more of the year and forage for longer. In Toronto, cold winters had long acted as “mother nature’s pest control”, said Sinia, killing off swaths of the population. But mild temperatures had helped rodents of all kinds in the city to keep breeding. The fact that rat numbers increased fastest in cities that were warming fastest was “the gloomiest outcome of the study”, said Richardson. Last year was the hottest on record, with average temperatures 1.6C above preindustrial levels.
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https://www.theguardian.com/environment/2025/jan/31/rat-numbers-cities-climate-temperatures-rodents
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