Up to 90% of the global population living in cities in 2014 was exposed to particulate matter that exceeded air quality guidelines, according to the UN World Health Organization. Pollution can cause (or aggravate) some diseases related to respiratory and cardiovascular functions, especially in children, elderly and sick people. It also affects the environment with pollutants that can damage plants or lead to acid rain.
Trees can be part of the solution!
A study by The Nature Conservancy reports that the average reduction of particulate matter near a tree was between 7% and 24%. Leaves act as natural filters for both gases and particulate matter in urban environments. Trees also reduce air pollution by helping to cool urban areas and mitigate the urban heat island effect. Appropriate species selection and a thoughtful planting design can produce beneficial effects on air quality. A study from the National Recreation and Park Association showed that pollution removal by US urban park trees is on the order of 75,000 tons per year, equivalent to saving US$500 million per year.
Oscar Cusó, contributor for Cities4Forests and writer at National Geographic Spain.