Skip to main content

Science Adviser, 3 February 2025

City rats are on the rise, and climate change and crowds are to blame

The warmer a city gets and the more people who move into it, the worse the rat infestations will likely become. That’s the conclusion of a first-ever global analysis of how and why rat numbers have changed over time.

Smart, cooperative, and resilient, rats have co-evolved with humans for millennia and have fine-tuned their ability to take advantage of garbage, debris piles, sewers, and small postage-stamp sized plots of soil along sidewalks for food and nesting. […] Cities that experienced greater rates of temperature increase and more people moving in were more likely to have bigger rat problems; climate change emerged as a driving factor behind urban rat swarms , the researchers report. Disappearing green space also seemed to benefit rat populations.

Read the article

Science Advances, 31 January 2025

Increasing rat numbers in cities are linked to climate warming, urbanization, and human population

Urban rats are commensal pests that thrive in cities by exploiting the resources accompanying large human populations. Identifying long-term trends in rat numbers and how they are shaped by environmental changes is critical for understanding their ecology, and projecting future vulnerabilities and mitigation needs. Here, we use public complaint and inspection data from 16 cities around the world to estimate trends in rat populations. Eleven of 16 cities (69%) had significant increasing trends in rat numbers, including Washington D.C., New York, and Amsterdam. Just three cities experienced declines. Cities experiencing greater temperature increases over time saw larger increases in rats. Cities with more dense human populations and more urbanization also saw larger increases in rats. Warming temperatures and more people living in cities may be expanding the seasonal activity periods and food availability for urban rats. Cities will have to integrate the biological impacts of these variables into future management strategies.

PDF Version