If scorching heat waves, destructive storms, prolonged droughts and rising seas aren’t enough to make some folks fear the consequences of climate change, perhaps this will do the trick: The warmer it gets, the faster rats multiply in cities that already struggle to contain them.That is sure to be unwelcome news to Americans, who collectively endure well over $27 billion worth of property damage each year at the hands — and teeth — of rats. That doesn’t include the cost of the diseases the animals spread, such as hantavirus, murine typhus and bubonic plague, nor the mental health toll of living among them.The new findings, reported Friday in the journal Science Advances, are based on records of rat sightings in 16 cities around the world. Unfortunately for humans, 11 of those cities saw their rat populations expand over the course of the study, while two cities held steady and only three achieved measurable declines.That the rodents are thriving should come as little surprise. They’re perfectly suited to urban environments, where they make their homes in walls, basements and subway stations and feast on garbage, sewage, dog poop and abandoned pizza slices. The only continent they have yet to conquer is Antarctica.A rat foraging in a dumpster in Richmond, Va.(Jonathan Richardson) “This species is really well-adapted to take food and convert that into new baby rats that are scampering around your neighborhood,” said Jonathan Richardson, a biologist at the University of Richmond who studies wildlife in cities and their impact on human health. “They do that really efficiently.”One of the few things that slows rats down is cold weather. And with climate change, we have less of it.Global warming causes average temperatures to rise, which reduces the number of wintry days. In cities, the trend is compounded by the fact that the built environment absorbs and retains more heat than the rural area around it, a phenomenon known as the urban heat island effect.To investigate a possible link between rat populations and rising temperatures, Richardson and his colleagues searched for reliable data in the country’s 200 most populous cities. Conducting a thorough rat census was impractical — if not impossible — so they used municipal inspection logs and rat sightings reported to government agencies. They found 13 cities that had kept consistent records for at least seven years. Then they widened their search and found three more cities overseas. The final group had rat data going back for an average of slightly more than 12 years.Since the cities used different sources of data collected over different periods of time, the researchers came up with a standardized way to measure the change in rat sightings. They found that rat reports increased the most in Washington, D.C., followed by San Francisco, Toronto, New York City, Amsterdam, Oakland, Buffalo, Chicago, Boston, Kansas City and Cincinnati.Three cities — New Orleans, Louisville and T
Sab. Feb 1st, 2025
