Expanding citywide green cover could also lead to an increase in zoonotic diseases: study

As exhilarating as urban life may seem, it comes with evident and inescapable drawbacks. While it offers opportunities to meet diverse people and engage in varied experiences, the accompanying high living costs, congested traffic, and polluted air often prompt city dwellers to yearn for retirement in rural villages elsewhere.

Another significant issue is the prevalence of rodents. Rats and other disease-carrying rodents thrive in cities, particularly in bustling ones. Researchers suggest that the conditions in cities were so favourable for rats that thousands, if not millions, of them may have perished due to food shortages during the COVID-19 lockdown. Additionally, as governments worldwide strive to increase urban greenery, these creatures could benefit greatly from such environmental changes, potentially creating a haven for diseases transmitted by animals.

The concept of urban greening has gained momentum as a means to mitigate the adverse effects of urbanisation on the environment and human health. However, recent studies have revealed a potential unintended consequence: an increased risk of diseases transmitted by rodents.

Zoonotic diseases, which are infectious diseases transmitted from animals to humans (such as the coronavirus), present significant public health challenges globally. Wild rodents, in particular, act as reservoirs for various zoonotic pathogens. When these rodents inhabit urban environments, especially those undergoing greening initiatives, the risk of pathogen transmission to humans rises.

Although urban greening offers numerous benefits, such as improved air quality and biodiversity, it may inadvertently amplify the risk of zoonotic disease transmission, as explained in the study.

The research focused on major Dutch cities like Amsterdam, Rotterdam, and Eindhoven, revealing that areas with higher levels of urban greenery tended to harbour more wild rodents. Furthermore, these green spaces create favourable conditions for the proliferation of vectors like ticks and fleas, which are essential for transmitting vector-borne zoonotic pathogens.

In natural settings, higher predators could help control rodent populations. However, humans, as the primary apex predators in cities, view rats as unclean and refrain from hunting them for food, allowing city rodent populations to proliferate unchecked.

The study's author, Marieke de Cock, notes that both the extent of urban greenery and food-related factors are positively correlated with the abundance of wild rats. Moreover, the absence of predators is more critical than the degree of greenery for the abundance of small mammals, including rats and mice.

As the number of city rodents increases, so does the prevalence of disease-causing pathogens among them. More infected rodents, ticks, and fleas heighten the risk of such diseases spreading to humans. Although greener spaces facilitate rat proliferation, further research is needed to understand the impact of human-rat exposure on disease risk.

As cities continue to embrace urban greening initiatives, it is essential to adopt a holistic approach that considers both the ecological benefits and potential health risks. By comprehending the complex interplay between environmental factors, rodent populations, and disease transmission dynamics, public health authorities can develop targeted interventions to protect human health.

The research findings have been published by Wageningen University.