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Trees along highways combat motor vehicle pollution, study finds

A new study has found that trees and bushes, when planted near highways, significantly reduce the air pollution from motor vehicles.

By Ground Report Desk 23 Mar 2024

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Trees along highways combat motor vehicle pollution, study finds

A new study has found that trees and bushes, when planted near highways, significantly reduce the air pollution from motor vehicles. This type of pollution has links to various illnesses.

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Researchers sampled air quality at five sites along metro Atlanta interstates and highways over two three-month periods. The researchers found a 37% reduction in soot and a 7% reduction in ultrafine particles at sites with natural or ornamental vegetation when they compared these sites to similar ones without vegetation.

Roadside trees, bushes cutting Air Pollution

"They provide benefits that go beyond aesthetics," Roby Greenwald, an associate professor of public health at Georgia State University in Atlanta, said in a university news release.

"But," he added, "I don't want to give anyone the impression that we can solve all of the problems associated with motor vehicle emissions simply by planting trees."

Greenwald, the lead author of a new study, sampled air quality along five Atlanta-area highways and interstates. PLoS One, the journal, recently published the findings.

publive-image — _{The road and highway network in Chhattisgarh early 2000s. Many new highway projects are under construction. Photo Credit: Wikimedia Commons}

Evidence is increasingly linking motor vehicle pollution to conditions such as asthma, chronic bronchitis, lung cancer and heart attacks. Greenwald and his colleagues urgently call for solutions to the problem of high pollution levels near roadways, noting that 45 million people in the United States who live, work or attend school are within 300 feet of a major highway.

The vegetation on the roadside reduces air pollution through several mechanisms, including creating a large surface area for small particles to stick to. The new study extends previous research into the part that vegetation can take in reducing air pollution. It does this by sampling at various sites over a long period and using a model that lets the researchers consider factors like wind direction, traffic volume, and the distance to the highway.

Vegetation reduces air pollution levels

When air at sites with natural or ornamental vegetation was compared with that from similar sites without vegetation, the results were clear: Soot levels were 37% lower and ultrafine particles, 7% lower.

"Trees and bushes near roadways don't solve the problem of air pollution caused by motor vehicles, but they can help reduce the severity of the problem," he said.

Motor vehicle exhaust has been linked to asthma, chronic bronchitis, lung cancer and heart attacks, and remedies are urgently needed, researchers said.

They pointed out that 45 million people live, work, or go to school within 300 feet of a major highway in the U.S. The roadside vegetation pulls pollutants from the air in several ways. For instance, it provides a large surface area where small airborne particles can land.

Previous research investigated the role that roadside vegetation can play in cleaning the air over time. The researchers accounted for factors such as wind direction, traffic volume, and proximity to the highway using a model.

Greenwald said that local governments should make it safe, convenient and agreeable for people to reach their destinations without a motor vehicle to have a bigger impact on air quality. This might involve increasing the availability of public transportation, or developing and improving bike and pedestrian paths, for example.

Trees curb roadside air pollution

The study highlights the significant impact that roadside vegetation can have on reducing air pollution from motor vehicles. This is particularly relevant for India, where rapid urbanization and infrastructure development often lead to increased vehicular emissions and subsequent air pollution.

In India, tree-cutting for road widening and other infrastructure projects has been a concern. For instance, the National Highway Authority of India (NHAI) has undertaken initiatives to transplant trees uprooted due to road widening. The Supreme Court of India has also observed the need for a protocol for projects requiring tree cutting to minimize environmental damage. This indicates a growing awareness and effort to balance development with environmental conservation.

Benefits of roadside vegetation

Air Quality Improvement: As the study suggests, vegetation can trap particulate matter, reducing pollutants like soot and ultrafine particles.
Climate Regulation: Trees and plants absorb carbon dioxide, helping to mitigate climate change effects.
Noise Reduction: Vegetation can act as a sound barrier, reducing noise pollution from highways.
Biodiversity: Roadside greenery can provide habitats for various species, promoting biodiversity.
Aesthetic Value: Green spaces enhance the visual appeal of urban areas.

For India, adopting roadside vegetation strategies could address several urban challenges:

Health Benefits: With high levels of air pollution in cities like Delhi, vegetation can help improve air quality and public health.
Urban Heat Island Mitigation: Trees provide shade and cool the air, countering the heat island effect common in densely populated areas.
Water Management: Properly planned vegetation can aid in water retention and reduce runoff during monsoons.

Given these benefits, urban planners in India must integrate green spaces into city landscapes. This includes not only preserving existing trees but also strategically planting new vegetation as part of road and infrastructure projects. By doing so, India can work towards sustainable urban development that prioritizes both the environment and public well-being.