Lawns, shrubs and trees cool and clean the air in urban environments, absorbing air pollutants and particulate matter and improving human health, according to an analysis released by the David Suzuki Foundation.
Urban forest is a particularly potent filter for airborne particulates, which is an aggravating factor in lung disease and asthma. Scientists estimated that urban forest in London, U.K., with a density of 20 per cent, removes between 852 and 2,121 tonnes of coarse particulates each year.
Urban forests — all the trees, shrubs, lawns and pervious soils in an urban setting — also absorb ground-level ozone, nitrous oxide and carbon monoxide, all associated with increased illness, hospitalizations and death, according to the report.
Researchers reviewed 102 peer-reviewed studies published during the past five years for their analysis, which concludes that trees, green roofs and walls and natural greenspaces provide significant health benefits for urban dwellers by reducing temperatures and pollutants.
Poor air quality is responsible for millions of deaths each year worldwide — and the risk of heat-related deaths goes up between one and three per cent with every increase of 1 C, researchers note.
“This report demonstrates the immense value in bringing nature to the city at all scales and the potential payoff for city agencies and designers that connect the dots between green spaces, creating green urban corridors,” said spokeswoman Aryne Sheppard in a statement.
The report is a shopping list of known health impacts associated with air pollution that could be mitigated by increasing the density of urban forests.
Ozone exposure appears to be associated with low birth weights and poor neurodevelopment, while fine particulate matter leads to increased lung cancer rates.
“This report confirms that abundant urban green spaces are essential for our health,” said lead author Tara Zupancic. “Protection from extreme temperatures and air pollution can reduce illness and even save lives.”
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