As cities worldwide experience rising temperatures, a new study reveals that warmer weather is attracting increasing rodent populations, leading to a surge in rat complaints and disease transmission risks.
Cities with higher temperatures and dwindling green space also have more rats. The relationship between rising temperatures and increased rat complaints is clear: as cities get hotter, people report seeing more rodents.
Urban areas experience higher temperatures due to the urban heat island effect, where built-up surfaces absorb and retain heat.
This phenomenon is caused by a combination of factors, including pavement, 'buildings' , and vehicle emissions.
According to the EPA, cities can be up to 1-3°C warmer than surrounding rural areas.
Increased temperatures can lead to heat-related illnesses, energy consumption, and air pollution.
Strategies to mitigate this effect include green roofs, urban forestry, and cool pavements.
A new study analyzed data from 16 cities around the world and found that those with the biggest temperature increases over time had more rat complaints over the same period. Urbanization was another factor linked to higher rat populations. The researchers suggest that warmer weather may make it harder to control rat numbers and reduce the spread of diseases carried by these rodents.
Rats are a significant problem in cities, causing damage estimated at $27 billion per year in the United States alone. They contaminate food, spread diseases like ‘leptospirosis‘ and ‘murine typhus‘, and chew through car wiring and crops. The world spends around $500 million annually trying to combat rat infestations.
Rats are highly intelligent rodents known for their agility, curiosity, and adaptability.
They are primarily nocturnal, spending most of their time at night foraging for food.
Rats are social animals, often living in colonies with a dominant male and female.
Their diet consists mainly of seeds, fruits, and insects, although they can also thrive on human-provided food.
In the wild, rats can live up to 2-3 years, while domesticated rats can live up to 4 years or more with proper care.
Climate Change Fuels Rat Populations
Jonathan Richardson, an urban ecologist at the University of Richmond in Virginia, notes that his colleagues had predicted a rise in rat populations due to climate change. However, this study provides the first data to support their hypothesis. By analyzing records of rat complaints and pest inspection reports from 13 U.S. cities, as well as Toronto, Tokyo, and Amsterdam, the researchers found that around 70% of the cities studied experienced an increase in rat numbers.
Climate change refers to the long-term warming of the planet, primarily caused by human activities that release greenhouse gases, such as carbon dioxide and methane, into the atmosphere.
The burning of fossil fuels for energy is a significant contributor to climate change.
Rising temperatures lead to melting glaciers, sea-level rise, and extreme weather events like hurricanes and droughts.
According to NASA, the average global temperature has risen by about 1°C since the late 1800s.
The cities with the largest rodent rises were San Francisco, Toronto, New York City, Amsterdam, and Washington, D.C. The study’s findings suggest that warmer temperatures are a major driver of increased rat populations. Richardson explains that unseasonably warm winters may give rats more time to forage outdoors, allowing them to breed more frequently.
Disease Risks on the Rise
Niamh Quinn, a human-wildlife interactions advisor at the University of California Division of Agriculture and Natural Resources, warns that when humans and rats share space, there’s a risk of disease transmission. ‘Leptospirosis‘ , for example, can be deadly to humans and unvaccinated pets.
Bobby Corrigan, a rodentologist and rat consultant on the study, notes that warming weather also means fewer opportunities to control population numbers. In the past, pest managers knew when to prepare for rats moving indoors in winter and take advantage of lower birth rates during this season. However, with temperatures rising year-round, managing rat populations has become increasingly challenging.
The study’s findings highlight the need for effective strategies to mitigate the impact of climate change on urban ecosystems and reduce the spread of diseases carried by rodents.
- sciencenews.org | Hotter cities? Here come the rats
