The Living Air Purifiers Cities Need More Of

Sourced from UN Environment

In our all-too-hectic urban lives, a city park is a great place to unwind. Trees and green spaces have mental health and well-being benefits, on top of being great for relaxation and recreation.

Trees also help reduce air pollution. According to the study Tree and forest effects on air quality and human health in the United States, particulate matter, which is particularly damaging to lungs, is retained on tree surfaces, while leaves act as filters, absorbing polluting gases.

But the study also warns that while trees can mitigate the effect of air pollution, deposits of air pollutants on leaves can also affect photosynthesis “and therefore potentially affect pollution removal by trees”. As with everything, balance is key.

The cooling effect of trees

Trees can also significantly cool temperatures in cities. In hot climates, tree cover can reduce energy expenditure on air conditioning, while driving down the consumption of air polluting fossil fuels that power these cooling systems. Experimental investigations and modelling studies in the United States have shown that shade from trees can reduce the air conditioning costs of detached houses by 20–30 per cent.

“Trees could reduce temperatures in cities up to 8°C, lowering use of air conditioning and related emissions by up to 40 per cent,” says Simone Borelli, an Agroforestry and Urban/Periurban Forestry Officer with the Food and Agriculture Organization of the United Nations.

“When part of a wider landscape mosaic, large green patches within and around cities would also reduce emissions through avoided sprawl and excess mobility requirements,” he adds.

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