Rat populations are rising dramatically in cities worldwide, and new research suggests that global warming, urbanization, and increasing human density are the driving forces behind this troubling trend.
A study published in Science Advances analyzed data from 16 major cities, including New York, Washington, and Amsterdam, and found that 11 of them experienced a increase in rats over time.
According to NHI, only three cities saw a decline.
Why Are Rats Thriving in Cities?
Two species—Rattus norvegicus (brown rats) and Rattus rattus (black rats)—now inhabit every continent except Antarctica.
These resilient rodents have adapted to human environments for millennia, learning to exploit garbage, sewage, and even tiny patches of soil along sidewalks for food and shelter.
Cities with rising temperatures and higher population densities saw the largest increases in rat numbers, according to the study. Warmer weather extends their breeding seasons, while larger human populations provide a steady supply of food waste.
"The warmer a city gets and the more people move into it, the worse rat infestations are likely to become," the researchers conclude.
The Hidden Costs of Urban Rat Infestations
Rats are more than just a nuisance—they pose a serious threat to public health and infrastructure. They are known carriers of over 50 zoonotic diseases, including:
Leptospirosis (which can cause liver and kidney damage)
Hantavirus pulmonary syndrome (a potentially fatal respiratory disease)
Murine typhus (a bacterial infection spread by fleas)
Bubonic plague (the disease behind the infamous Black Death)
Beyond health concerns, rats cause an estimated $27 billion in damage annually in the United States alone, by chewing through electrical wiring, damaging buildings, and contaminating food supplies.
Living in close proximity to rats doesn’t just create sanitation issues—it can also impact mental health.
Studies show that persistent rat infestations contribute to stress and anxiety, particularly in low-income urban communities, where infestations are often the worst.
What Can Be Done?
With rat populations on the rise, cities will need to adapt their pest control strategies.
Experts suggest that improving waste management, sealing off nesting areas, and addressing climate-related factors will be key in curbing rat infestations before they spiral further out of control.
