In recent years, various cities around the world have experienced a rapid growth in their rat populations, a phenomenon that raises concerns due to its health, environmental, and structural implications.
A study published in Science Advances analyzed data from 16 cities over more than a decade and revealed that in 11 of them rat activity significantly increased, with alarming peaks in cities like Washington D. C. (400%), San Francisco (300%), Toronto (180%), and New York (160%).
Factors explaining the rat expansion
Waste, urban infrastructure, and warmer climate create ideal conditions for their reproduction.
According to specialist Bobby Corrigan, the rat proliferation is due to multiple factors:
- Constant availability of food scraps, especially due to fast food consumption habits
- Irregular municipal garbage collection
- Construction works altering sewer systems, providing access to shelters
- Rising temperatures, allowing rats to remain active during milder winters
The urban heat island effect, where asphalt and buildings retain higher temperatures, exacerbates the issue. According to Climate Action Tracker, global warming could raise temperatures by 1.9°C to 2.7°C by the year 2100, further favoring the expansion of these rodents.
Preocupation over the increase in rodent population in homes and vehicles.
Public health risks
Rats can transmit serious diseases even in clean environments.
Experts cited by the BBC warn that rats, as they move through sewers and containers, can spread diseases such as:
- Leptospirosis: transmitted through contact with rat urine
- Hantavirus: contracted by inhaling particles of dried excrement
Moreover, their rapid reproduction worsens the problem: a single pair can produce over 1,000 offspring per year in dense and warm urban environments.
Limitations of traditional methods
Genetic resistance and neophobic behavior hinder control with poisons.
Researchers like Steven Belmain and Alan Buckle point out that rats exhibit neophobic behaviors, leading them to avoid new foods, including poisoned baits.
Furthermore, they have developed genetic mutations that make them resistant to anticoagulant drugs, raising ethical dilemmas due to the prolonged suffering they cause.
Preventive and educational strategies: the case of New York
Reducing outdoor waste and improving urban management are key to halting the expansion.
Given the ineffectiveness of chemical methods, cities like New York have opted for educational campaigns and preventive measures. According to Kathleen Corradi, former rat control manager, the following were implemented:
- Good citizen practices: minimizing waste and using rodent-proof containers
- Inspections and fines: to cut off the main food source for these animals
Urbanization and demographic projections
Population growth can exacerbate the problem if structural measures are not adopted.
The UK National Statistics Office projects that the population will grow from 67.6 million in 2022 to 72.5 million in 2032, which could favor the expansion of rats if urban infrastructure and waste management are not improved.
