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Inequitable impacts of urban noise pollution harm people and wildlife

In a new study from Colorado State University, researchers have uncovered the pervasive and inequitable impact of urban noise pollution, revealing a disturbing link to historical practices of racial discrimination. 

The study represents a significant advancement in our understanding of how systemic injustices, particularly redlining, continue to shape our urban ecosystems.

Racial discrimination

Redlining, a discriminatory practice initiated in 1933 by the Home Owners’ Loan Corporation, involved grading neighborhoods based on race and wealth. 

Wealthier and predominantly white neighborhoods received favorable grades, while diverse, lower-income communities were encircled in red, marking them as undesirable for investment. Though outlawed in 1968, the repercussions of this practice are still evident today, particularly in the distribution and intensity of urban noise pollution.

Sara Bombaci is an assistant professor at CSU’s Department of Fish, Wildlife, and Conservation Biology and the lead author of the study. She emphasized the importance of considering these systemic injustices when examining ecological and evolutionary impacts. 

Heightened noise levels

The study revealed that neighborhoods which were historically redlined experience significantly higher levels of noise pollution today. Specifically, grade D neighborhoods endure maximum noise levels 17% higher than their grade A counterparts. 

For humans, prolonged exposure to high levels of noise can lead to a range of health issues. These include hearing impairment, stress-related illnesses, sleep disturbances, cardiovascular problems, and a diminished quality of life. Children, older adults, and those with pre-existing health conditions are particularly vulnerable to these effects.

Noise pollution also disturbs wildlife, affecting communication, reproduction, and survival strategies. For instance, birds may alter their song frequencies to compete with urban noise, which can impact mating calls and territory defense. Other animals might avoid noisy areas altogether, leading to habitat fragmentation and reduced biodiversity.

Urban noise distribution

The research team analyzed urban noise distribution across historical racial divisions in 83 U.S. cities, alongside a comprehensive review of hundreds of studies on the impacts of noise on wildlife. 

The study is the first of its kind to explicitly link noise pollution with redlining, offering a clear example of how environmental issues intersect with social injustices. 

The findings are alarming: Not only are communities in redlined areas suffering from higher levels of noise, but this noise is also above the levels known to cause significant health issues.

Addressing the problem 

Addressing this injustice is not simply a matter of reducing noise levels. Bombaci argues for a holistic approach to urban planning that integrates noise mitigation into the development of green spaces and parks.

Cities like Denver are working toward equitable planning to improve access to parks and green space in underserved communities. Bombaci said noise should be considered in those plans.  

“If we’re adding green space without mitigating impacts of noise, we might not be fully recognizing the benefits of these green spaces,” she said. 

According to Bombaci, wildlife might not bounce back in urban green space if noise pollution remains a problem, but noise mitigation can help. Conservation funding and urban planning can benefit both people and wildlife.  

Urban noise pollution

Urban noise pollution is an increasingly recognized environmental concern, characterized by unwanted or harmful outdoor sound created by human activities, including traffic, construction, industrial, and recreational noises. 

This type of pollution is prevalent in urban environments, where the density of population and development leads to a greater concentration of noise sources.


The sources of urban noise are varied. Traffic noise is a significant contributor, especially near roads and highways. Industrial activities, such as manufacturing and construction, also play a role, often contributing not just to the volume of noise but also to its persistent nature. 

Recreational noise from public events, music venues, and nightlife can further exacerbate the situation, particularly in densely populated urban centers.

Mitigation strategies 

Addressing urban noise pollution requires a multifaceted approach. Urban planning and design play crucial roles, including the creation of noise barriers, strategic placement of green spaces, and zoning regulations that separate residential areas from major noise sources. 

The adoption of quieter technologies in transportation and industry, along with enforcing strict noise control regulations, is essential. Public awareness and education about the impacts of noise pollution may also help to mitigate this issue.

The study is published in the journal Nature Ecology & Evolution.

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