Climate Change Raising Rat Populations in Cities Worldwide

By Abbas Nazil
A recent study has revealed that urban rat populations are growing significantly in cities worldwide, with climate change playing a major role in the surge.
The research, published in Science Advances, analyzed data from 16 cities, including Washington, DC, San Francisco, Toronto, New York City, and Amsterdam—places experiencing the most dramatic increases.
The study linked the boom in rat populations primarily to rising temperatures, which allow the rodents to forage and reproduce for longer periods each year.
The presence of rats in urban environments has long been a concern due to their impact on infrastructure, public health, and city management.
Rats damage buildings, contaminate food supplies, and even pose fire hazards by gnawing through electrical wires.
The financial toll in the United States alone is estimated to be around $27 billion annually. Additionally, rats carry more than 50 pathogens that can be harmful to humans, including leptospirosis, a disease that can cause severe kidney and liver damage or even death if left untreated.
Beyond the physical and economic threats, researchers note that rat infestations contribute to increased stress and anxiety among urban residents.
Washington, DC, stands out as one of the worst-affected cities, with its rat population growing 1.5 times faster than in New York City.
Experts attribute the situation to the city’s record-high temperatures in recent years, which have extended the breeding season for rats.
Officials have attempted various control measures, including public awareness campaigns and experimental birth control programs, but results have been inconclusive.
DC authorities rely heavily on public reports of rat sightings to track infestations, though experts caution that such data can be flawed, as people tend to report only when they notice something unusual rather than consistently monitoring rat populations.
The study found that while factors such as population density and low urban vegetation contribute to rat infestations, climate change remains the dominant force.
Warmer winters enable rats to survive in greater numbers, while extended growing seasons provide them with more food sources and shelter.
Urban field ecologist Michael Parsons, who was not involved in the study, explained that warmer temperatures allow food odors to travel farther, making garbage and waste even more attractive to rats.
Despite the rising numbers in most cities, three cities—New Orleans, Louisville, and Tokyo—have successfully reduced their rat populations.
Researchers credit these cities’ success to proactive public education campaigns and citywide efforts to minimize food waste and debris that attract rodents. Study co-author Jonathan Richardson, a biology professor at the University of Richmond, emphasized that focusing solely on lethal extermination is not a sustainable solution.
Instead, he advocates for measures that remove the factors sustaining rat populations, such as food waste management and improved urban sanitation.
Experts warn that as climate change continues to push global temperatures higher, the rat problem will only worsen unless cities adopt long-term, strategic control methods. While completely eradicating urban rats is unrealistic, officials like DC’s rodent control program leader Gerard Brown remain hopeful that cities can reduce rat populations to a manageable level.
As climate patterns shift, urban centers must adapt their strategies to keep rats in check before the issue spirals further out of control.