Rats are on the rise across urban landscapes, with new research confirming their populations are climbing as temperatures increase due to climate change. A study published recently in the journal Science Advances highlights alarming trends, showcasing data from 16 cities, where rising temperatures correlated strongly with surging rat numbers.
Urban ecologist Jonathan Richardson, leading the research from the University of Richmond, emphasizes the connection: “Rats are really well-adapted to take advantage of food resources and convert it to new baby rats, which you’ll see more frequently as temperatures rise.” According to the study, urban areas with the fastest warming saw the largest increases in rat populations.
Among the cities analyzed, Washington D.C. reported the highest increase, experiencing a stunning 390 percent surge over the past decade. Close behind were San Francisco with 300 percent and Toronto with increases reaching 186 percent, presenting what some local authorities have termed the “perfect rat storm.”
When evaluating how climate impacts these rodent populations, the study drew data from public complaint records spanning from 2007 to 2024. Cities like Toronto are grappling with concerning rat numbers; over 1,600 rat-related calls were made to the municipality’s helpline last year, up from 940 just four years prior. “It’s really significant quality-of-life problem when people are suddenly confronted with rats entering their homes or workplaces,” stated Toronto City Councillor Alejandra Bravo.
Interestingly, the surge relates to climate conditions facilitating rat reproduction. Warmer winters historically acted as “mother nature’s pest control,” limiting rat populations. Now, with milder winter seasons, breeding can occur for longer periods, contributing to population surges. “Last year was the hottest on record, with temperatures 1.6C above preindustrial levels, impacting cities heavily,” said Richardson.
Certain cities managed to buck the trend, with New Orleans, Louisville, and Tokyo observing declining rat numbers. New Orleans is often lauded for its proactive measures, which include public education campaigns on rat-proofing properties. Tokyo benefits from high expectations of cleanliness and quick reporting mechanisms for sightings, contributing to lower population figures. Bobby Corrigan, rodentologist from New York City, stresses, “The big takeaway is this is not going to get any easier as climate change creates favourable environments for urban wildlife.”
Cities across the globe are now urged to adopt integrated pest management strategies to curb rising rat populations. Cleaning up trash effectively, monitoring sanitation, and investing resources for long-term management strategies can create adverse conditions for rats. “We need to start collecting reliable and systematic data,” Kaylee Byers, public health researcher at Simon Fraser University, noted, stressing the gap present when addressing the urban rodent challenge.
With the downtown areas of cities increasingly becoming hotbeds for rats and urbanization continuing, the call for efficient municipal strategies grows louder. “For Toronto, this is especially pressing,” added Richardson, underscoring the glaring absence of dedicated pest management resources for such a sizable city.
Rat populations’ growth signifies broader environmental issues tied to climate change, challenging urban infrastructures, public health, and mental well-being. The implication remains clear: as cities face rising temperatures, the intersecting dynamics of urban life and rodent populations will demand careful, systematic approaches to manage the present and avert future challenges.