How trees reduce noise pollution in urban areas

Urban areas are notoriously noisy. The sounds of traffic, construction, industry and densely populated areas dominate the soundscape of cities around the world. While noise pollution may seem an inevitable side effect of urban life, it need not be so. The careful application of greenery, especially trees, in urban planning can drastically reduce noise levels and improve the quality of life for city dwellers.

At Van den Berk Nurseries, we are passionate about the power of trees to transform urban environments. For more than 85 years, we have provided landscape architects, urban planners and private landowners with quality trees to beautify properties and public spaces. And one of the most impactful benefits trees offer is their ability to dampen urban noise pollution.

The problem of noise pollution

Noise pollution refers to sounds in the environment that disrupt daily activities and cause annoyance, stress and even hearing loss. The World Health Organisation has identified noise pollution as the second biggest environmental health risk in Europe, after air pollution. Excessive noise exposure is associated with negative effects on cardiovascular health, cognitive performance, sleep patterns and mental health. With more than half the world's population living in cities, reducing noise pollution is an urgent issue worldwide.

In urban environments, the main sources of noise come from transport, industry and human activity. Road, rail and air traffic produce noise levels as high as 85-90 decibels, well above the EPA's recommended limit of 70 dB. Construction sites, manufacturing, ventilation systems and other mechanical processes also contribute to urban noise. Even noise from commercial establishments and dense populations talking, moving and living in close proximity to each other can create a constant background noise of 60-70 dB.

Prolonged exposure to noise at these levels can increase stress hormones, raise blood pressure and interfere with concentration and learning ability. As urbanisation increases worldwide, excessive noise poses an increasing threat to public health. It is necessary to find creative solutions to keep urban noise at acceptable levels.

How trees help

Trees may seem an unlikely solution to such an immense problem. But in fact, greenery is very effective in absorbing and blocking noise. Leaves, branches and trunks help to disperse, deflect and absorb sound vibrations instead of reflecting them. This is especially true of broad-leaved deciduous trees, whose large, abundant leaves best disrupt sound waves.

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Strategically planted trees and landscape buffers can reduce traffic noise by 5-10 decibels. A reduction of just three decibels halves the perceived loudness, while a five-decibel reduction is equivalent to a 70% reduction in loudness. Trees also filter more high-frequency sounds, which are most disturbing to human ears. Other vegetation layers such as shrubs, grass and mulch further dampen reverberation and sound reflection.

Trees along busy roads create natural sound barriers that minimise traffic noise. Green roofs and vertical greenery systems also insulate buildings from outside noise. City parks and open spaces with an abundance of trees provide a quieter respite from urban noise, promoting concentration and well-being.

Optimal species and placement

Certain tree species are better at reducing noise than others. Evergreens such as pines and spruces with dense foliage have excellent sound absorption. Broad-leaved deciduous trees such as Platanus, Acer, Quercus and Tilia with large leaves also work well. Species that thrive in the local soil and climate are best suited to an area's conditions. A mix of both evergreen and deciduous trees provides sound attenuation in all seasons.

A quick way to reap the benefits of sound-damping trees is to plant mature trees. Here at Van den Berk Nurseries, we recommend choosing trees with a stem circumference of at least 30-35 cm for optimal immediate impact. These established trees with sturdy trunks and developed crowns provide immediate noise insulation, visual screening and shade. By placing mature buffers of this size along busy roads or near industrial areas now, you won't have to wait years for small plantings to nature. Although it is an initial investment, mature trees of this calibre will quickly begin to reduce decibel levels and improve liveability. Other benefits such as improved air quality can also be realised faster by planting larger trees. Contact us at Van den Berk to add substantial, awe-inspiring trees that make an immediate difference.

The placement of trees is also important. Trees planted in groups or staggered rows are ideal for blocking noise. Tree rings and multiple rows disperse sound in all directions. Trees should be planted as close as possible to the noise source for maximum effect.

Here at Van den Berk Nurseries, our expert tree consultants can recommend the ideal tree species and design ideas to reduce noise in specific environments, whether along highways, around industrial areas or within mixed-use city blocks. We grow hardy, healthy trees suitable for urban planting that grow into effective noise barriers.

Additional benefits of urban trees

Besides absorbing noise, expanding urban trees also offers many other benefits. Trees remove air pollution by absorbing carbon dioxide and particulate matter, releasing oxygen, and promote infiltration of rainfall into the soil. They reduce the heat island effect through shade and evapotranspiration. Trees also increase biodiversity and provide habitats and food sources for birds and beneficial pollinators.

Trees also have mental health benefits: they reduce stress, anxiety and aggression. Property values increase in neighbourhoods with trees; shopping areas see more business when there is shade from trees. With careful selection and placement, trees can reduce glare, provide privacy and creatively screen unwanted views.

On top of all these functional benefits, trees also offer immense aesthetic value. They beautify neighbourhoods, parks, business districts and any other urban space. Thoughtful tree planting creates inviting spaces for recreation, connection and improved quality of life.

Achieving green, peaceful cities

Urban trees are a simple, cost-effective solution with far-reaching noise reduction and livability benefits. To soften the volume in our cities, urban park initiatives should be prioritized. Here are some steps city planners, landscape architects and other green space advocates can take:

• Conduct studies to identify noise hotspots and opportunities for targeted tree planting.
• Develop comprehensive master plans for urban parks that make trees a major infrastructure investment.
• Adjust zoning plans and building codes to mandate noise-reducing tree buffers around major noise sources.
• Convert unused plots and degraded spaces into parks and green infrastructure.
• Maximise the number of trees along all streets, medians, car parks and other pavements.
• Involve communities in tree planting.
• Provide appropriate underground soil volumes/improvement and above-ground space for healthy tree growth.

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With concerted efforts and strong tree-planting initiatives, our city parks can become lush green sanctuaries that make city life more peaceful. A green canopy in the city can refresh our bodies, uplift our spirits and protect our ears from the noise of the city. The future of cities lies in embracing trees for what they can achieve.