This Centuries-Old Pest is Thriving Like Never Before

Rats have plagued humans for centuries, but as cities expand and temperatures rise, these resilient creatures are thriving like never before. Local governments are struggling to control that swell, and there’s an essential first step they need to undertake: a rat census.

My research team and I analyzed more than a decade of data, and the evidence points to a clear uptick around the world. Nearly all of the 16 cities we examined recorded significant growth in their rat numbers during that period, despite millions of dollars spent annually on mostly chemical-based rodent control. Municipal “wars on rats” have been a losing battle. Our study identified some important reasons for that lack of success.

In part, this is because urban environments provide ideal conditions with abundant food waste and the safety of our built infrastructure. But most alarmingly, broader environmental and demographic trends are working against our efforts.