Urban forests save lives, analysis finds

29 03 2015

Green space is essential to our health, according to David Suzuki Foundation report

Urban forests save lives, analysis finds

The City of Vancouver aims to plant 150,000 more trees by 2020.

Photograph by: Gerry Kahrmann , Vancouver Sun

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 today 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 — including tens of thousands in Canada — and the risk of heat-related deaths goes up between one and three per cent with every increase of 1 C, the researchers note.

The most profound benefits of improved air quality accrue when the density of the green canopy approaches 50 per cent, well above the 18-per-cent canopy covering the City of Vancouver. The City’s Greenest City Action plan calls for another 150,000 trees to be planted by 2020, including 15,000 on city-owned land and parks.

The density of the urban forest across Metro Vancouver exceeds 40 per cent.

“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.”





One response

30 03 2015
Alan Smith

The amount of pollution absorbed by trees is quite a small percentage and in the Winter when wood burning starts, trees either have no leaves or are dormant and do not absorb pollution when they are most needed. Smoke from a neighbour’s fire pit or when a cold day in the Summer encourages lighting a fireplace, the smoke will pour into neighbours’ homes without encountering trees. Hopefully the David Suzuki Foundation will use their prestige to support ending wood burning in urban areas.

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