Global Warming and Urbanization Exacerbate Rat Infestations; Experts: Key to Prevention Lies in Living Environment
Public health expert Professor Chan Chang-Chuan points out that rat populations are increasing in most cities worldwide due to global warming and accelerating urbanization. He emphasizes that the goal of urban rat control is not eradication, but to make cities unsuitable for rats to survive.
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- 📰 Published: May 7, 2026 at 13:16
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Central News Agency
(Central News Agency reporter Tseng Yi-Ning, Taipei, 7th) The issue of rat infestations is drawing attention. Public health expert Chan Chang-Chuan points out that rat populations are increasing in most cities worldwide, a phenomenon linked to global warming and accelerating urbanization. He emphasizes that the goal of urban rat control is not eradication, but to make cities unsuitable for rats to survive.
Professor Chan Chang-Chuan, a distinguished professor at the Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, recently posted on Facebook, citing a multinational study published last year in "Science Advances." The study indicates that rat populations are continuously rising in most cities globally.
Chan Chang-Chuan explained that this study involved research teams from multiple countries, including the United States, Japan, the Netherlands, and Brazil, jointly analyzing data from 16 cities worldwide. The study period spanned approximately 7 to 17 years, tracking rat trends using citizen reports and government inspection records. The results showed a significant increase in rat populations in 11 out of the 16 cities during the study period.
Among the cities studied, Washington D.C., San Francisco, Toronto, New York City, and Amsterdam showed the most significant growth trends in rat populations, followed by Oakland, Buffalo, Chicago, Boston, Kansas City, and Cincinnati. The magnitude of rat population growth trends varied greatly among cities; for example, the rat population growth trend in Washington D.C. was three times that of Boston and 1.5 times that of New York City.
In contrast, Tokyo, Louisville, and New Orleans showed declining rat populations, with New Orleans experiencing the largest decrease. Dallas and St. Louis did not show significant changes in rat population trends.
Chan Chang-Chuan stated that the study indicates the increase in rat populations is not accidental but influenced by three major environmental factors. First, climate warming: as global temperatures rise, winters become less severe, reducing rat mortality and extending their activity and breeding periods. In other words, rats that would have struggled to survive harsh winters can now successfully endure the winter and even continue to breed.
Second, accelerating urbanization: the research team pointed out that the increase in urban buildings and infrastructure provides more habitats for rats, such as underground pipelines and building crevices. At the same time, the reduction of green spaces concentrates rats more in human activity areas. Third, rising population density: more people generate more garbage and food waste, providing a stable and abundant food source for rats.
The study suggests that cities should change their strategies from traditional poisoning and trapping to more comprehensive environmental management, including improving waste management to reduce food sources; strengthening building design to reduce habitats; establishing long-term monitoring systems; and promoting integrated prevention strategies. Chan Chang-Chuan points out that the goal of urban rat control is not to "eliminate rats" but to make cities "unsuitable for rats to survive."
The few cities in the study that showed declining rat infestations also offer experience and lessons for rat control. Chan Chang-Chuan cited New Orleans, where the department responsible for rat control actively monitors rat activity and strengthens cooperation with other municipal departments and residents to jointly conduct rat control education. Tokyo has high hygiene cultural standards, promoting improved sanitation.
Chan Chang-Chuan notes that this study reminds us that the rat problem is not merely a simple hygiene issue, but a result of the combined effects of climate change, urbanization, and human behavior. In future urban development, how to reduce these environmental risks through effective governance and policy design will become an important issue, because while cities become more suitable for human life, they may inadvertently be creating a more ideal living environment for rats. (Editor: Li Heng-Shan) 1150507
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(Central News Agency reporter Tseng Yi-Ning, Taipei, 7th) The issue of rat infestations is drawing attention. Public health expert Chan Chang-Chuan points out that rat populations are increasing in most cities worldwide, a phenomenon linked to global warming and accelerating urbanization. He emphasizes that the goal of urban rat control is not eradication, but to make cities unsuitable for rats to survive.
Professor Chan Chang-Chuan, a distinguished professor at the Institute of Environmental and Occupational Health Sciences, College of Public Health, National Taiwan University, recently posted on Facebook, citing a multinational study published last year in "Science Advances." The study indicates that rat populations are continuously rising in most cities globally.
Chan Chang-Chuan explained that this study involved research teams from multiple countries, including the United States, Japan, the Netherlands, and Brazil, jointly analyzing data from 16 cities worldwide. The study period spanned approximately 7 to 17 years, tracking rat trends using citizen reports and government inspection records. The results showed a significant increase in rat populations in 11 out of the 16 cities during the study period.
Among the cities studied, Washington D.C., San Francisco, Toronto, New York City, and Amsterdam showed the most significant growth trends in rat populations, followed by Oakland, Buffalo, Chicago, Boston, Kansas City, and Cincinnati. The magnitude of rat population growth trends varied greatly among cities; for example, the rat population growth trend in Washington D.C. was three times that of Boston and 1.5 times that of New York City.
In contrast, Tokyo, Louisville, and New Orleans showed declining rat populations, with New Orleans experiencing the largest decrease. Dallas and St. Louis did not show significant changes in rat population trends.
Chan Chang-Chuan stated that the study indicates the increase in rat populations is not accidental but influenced by three major environmental factors. First, climate warming: as global temperatures rise, winters become less severe, reducing rat mortality and extending their activity and breeding periods. In other words, rats that would have struggled to survive harsh winters can now successfully endure the winter and even continue to breed.
Second, accelerating urbanization: the research team pointed out that the increase in urban buildings and infrastructure provides more habitats for rats, such as underground pipelines and building crevices. At the same time, the reduction of green spaces concentrates rats more in human activity areas. Third, rising population density: more people generate more garbage and food waste, providing a stable and abundant food source for rats.
The study suggests that cities should change their strategies from traditional poisoning and trapping to more comprehensive environmental management, including improving waste management to reduce food sources; strengthening building design to reduce habitats; establishing long-term monitoring systems; and promoting integrated prevention strategies. Chan Chang-Chuan points out that the goal of urban rat control is not to "eliminate rats" but to make cities "unsuitable for rats to survive."
The few cities in the study that showed declining rat infestations also offer experience and lessons for rat control. Chan Chang-Chuan cited New Orleans, where the department responsible for rat control actively monitors rat activity and strengthens cooperation with other municipal departments and residents to jointly conduct rat control education. Tokyo has high hygiene cultural standards, promoting improved sanitation.
Chan Chang-Chuan notes that this study reminds us that the rat problem is not merely a simple hygiene issue, but a result of the combined effects of climate change, urbanization, and human behavior. In future urban development, how to reduce these environmental risks through effective governance and policy design will become an important issue, because while cities become more suitable for human life, they may inadvertently be creating a more ideal living environment for rats. (Editor: Li Heng-Shan) 1150507
Choose to stand with facts, every sponsorship you make is a force to protect press freedom.
Download the Central News Agency "First-hand News" APP to stay updated with the latest news.
The text, images, and audio-visual content of this website may not be reproduced, publicly broadcast, or publicly transmitted and used without authorization.