Ratimageddon: How rising temperatures and city life are fueling rat infestations

Rats are surging in cities around the world as warming temperatures, busy urban waste cycles, and dense living conditions create welcoming environments for rodents, researchers and pest-control professionals say.

In the United Kingdom, residents report more frequent infestations, with Cleankill, a pest-control company operating across the south of England, noting a 20% rise in calls over the past two years. The British Pest Control Association (BPCA) says more than half of its member companies have seen higher rat callouts in the last five years. Separately, Freedom of Information requests compiled by a drainage repair firm show councils logged more than half a million rat infestations between 2023 and mid-2024. Those numbers underscore a trend that appears nationwide and beyond.

International patterns mirror the UK. A study published in Science Advances examined 16 cities and found that 11 recorded significant increases in rat activity over seven to 17 years. In Washington, DC, the rise approached 400%; San Francisco 300%; Toronto 180%; and New York City 160%. Only three cities showed declines, including Tokyo and New Orleans. The researchers found that cities experiencing greater temperature increases over time tended to see larger rat increases, with some locations approaching a 2C rise during the study period. Global temperatures are projected to rise between about 1.9C and 2.1C by 2100, according to Climate Action Tracker, a consortium of climate researchers.

Rats do not hibernate, so milder winters can extend breeding seasons and expand populations. A female rat typically has around six litters a year, each with up to 12 pups, and young can begin breeding after about nine weeks. That combination means two rats can potentially produce more than 1,000 offspring in a single year, a reality that becomes more pronounced in cities where heat traps from asphalt and buildings create warmer microclimates. Researchers point to several contributing factors beyond temperature: the growing urban footprint, with more buildings, pipes and drains that provide shelter, and a persistent supply of fast food and other discarded calories that sustain populations during the year.

Climate projections add a long-term dimension to the challenge. While wet and cold winters historically kept rat numbers in check, warming trends are expected to persist. As temperatures rise, winters become milder, and the survival and reproduction of urban rat populations are likely to continue increasing in many regions. In that context, urban planners and public health officials are reexamining how cities manage waste, water systems, and housing to reduce opportunities for rats to thrive.

Dr Bobby Corrigan, an urban rodentologist, helped connect rising city rat activity to temperature changes in a study that looked at 16 North American cities. He notes that the warmer climate widens the window during which rats are actively breeding and feeding, while urban density concentrates food sources. “Cities experiencing greater temperature increases over time saw larger increases in rats,” the study concluded, with some cities recording sharp growth even as some others declined due to local conditions. The work buttresses the view that climate change is shaping pest dynamics just as much as city management practices.

At the same time, rat-control science has not stood still. Traditional poisons, mainly anticoagulants, require a week to act and can be less effective when rats learn to avoid baits. Some strains have shown genetic mutations that confer partial immunity, complicating control efforts. Researchers are exploring humane alternatives, including the potential use of oral contraceptives, though such approaches are still under study and not yet deployed at scale.

In New York City, the scale of the challenge prompted the creation of a program led by Kathleen Corradi, who was appointed by the mayor in 2023 as the city’s Rat Tsar. Corradi has described a three-year effort to curb rat numbers through public outreach, behavior change, and better waste practices. Her “rat academy” trains residents to recognize rat activity and to report it, while inspectors investigate reports and impose fines when households fail to address problems. A key component of the program is a shift toward rat-proof waste containers rather than plastic bags left on the street, a move aimed at cutting off the rodents’ food sources. Corradi says the approach has shown some progress, but that sustained reductions depend on residents adjusting habits and authorities maintaining robust waste-management practices.

Closer to home in Croydon, a London suburb, a story from a single estate illustrates how quickly a city environment can become favorable to rats. John Gladwin, who lives there with five children, discovered shredded soil bags beneath the kitchen sink and a pungent, musty odor that pointed to an infestation. Rodents moved through bins and into living spaces, prompting the family to remove toxins and implement deterrents. Cleankill’s Alex Donnovan shows how bins overflow and food waste becomes a magnet for rats, and how even extensive baiting and control efforts can struggle to keep populations in check when waste-management practices fail. Donnovan stresses that cutting off access to food sources is essential for long-term success, and that once food scraps are plentiful, even strong rodenticides lose their bite.

Rising temperatures, overflowing bins, changing diet patterns and the expansion of urban areas all combine to create a major public-health and urban-management challenge. The Office for National Statistics projects the UK population will grow from about 67.6 million in 2022 to roughly 72.5 million by 2032, with a larger share living in cities. In such a landscape, the emphasis on high-quality waste handling, improved drainage and targeted, humane pest-control strategies grows with urgency. For many experts, the lesson is clear: if cities address the food sources and shelter that support rat populations, they can slow, and perhaps reverse, the trend of rat overruns.

Dr Corrigan argues that the key to sustained reduction lies in changing human behavior and city systems rather than relying solely on poison. “If we take care of our city environment, then we won’t have to be so inhumane to them,” he says, emphasizing the role of waste management, housing improvements and public cooperation in reducing rat food sources. “By not giving them access to the food and scraps, then we don’t have to poison them and kill them and torture them and all the crazy things we do to them.”

The challenge now is implementing solutions at scale and at speed. As populations continue to grow in urban areas and as climate change progresses, the conditions that favor rats may become more widespread, underscoring the importance of integrated urban design and proactive pest-management strategies that reduce the opportunities for rats to thrive.

In the long run, the convergence of climate trends and city life suggests that the fight against rat overruns will require a combination of science, policy, and daily citizen participation. As researchers and public health officials continue to study rat behavior and population dynamics, city leaders are urged to invest in drainage infrastructure, waste collection systems, and housing improvements that reduce the environments in which rats thrive. The human and economic costs of inaction—ranging from disease transmission to degraded quality of life—underscore the need for practical, humane and scalable solutions that can adapt to changing climates and growing urban populations.

As cities look to meet these challenges, the Croydon experience and New York’s Rat Tsar program offer real-world lessons about what works when waste management and community engagement are aligned with scientific insights. The path forward is likely to combine smarter urban design with behavior change, backed by sustained investment in infrastructure and a careful, humane approach to pest management.