Leafy trees are essentially the only cost-effective solution for addressing both deteriorating air quality and rising urban temperatures, a major new report by the Nature Conservancy, published in October 2016, has stated.
In their article The Big Green Payoff From Bigger Urban Forests, CityLab shares the report’s findings, explaining that residents of the ultra-dense, ultra-populated, and ultra-polluted cities of Southeast Asia would experience an especially high return on investment (ROI) on trees, with the benefits far outweighing the expense.
According to City Lab, levels of PM2.5 – particles emitted from car and factory pollution that stay in the air and can be easily inhaled – often exceed 600 micrograms per cubic metre in multiple locations around Beijing, when the safe daily average, according to the World Health Organization, should be just 25.
Fortunately, leafy trees have been proven to absorb from 7 to 24 percent of these particles, which are known to cause an estimated 3.2 million deaths per year globally.
The Nature Conservancy report estimates the potential impact increase investment in trees would have on Beijing’s air quality and urban temperatures.
“The new study estimates that for an annual additional investment of $2.9 million in street trees, 2.2 million Beijing residents could see a reduction in PM2.5 greater than 1 microgram per cubic meter per 24-hour period,” the City Lab article states.
“Most people would see a far greater reduction, exceeding 10 micrograms per cubic meter. And more than 2 million people would also feel a reduction of 1.5° C (2.7° F) in summertime air temperatures.”
The report’s lead author, Rob McDonald, said while these reductions demonstrate the potential for trees to reduce mortality rates connected to heat waves and particle pollution, they shouldn’t be mistaken for the complete answer.
Instead, he suggests trees should be thought of as surprisingly powerful tools for cities dealing with climate-related health concerns.
“Cities often think about tree planting budgets totally separately from their health budgets,” he said. “We want cities to see the link between the two.”
Hames Sharley’s Adelaide Studio Director, Darren Bilsborough, delved into the economic and health benefits of investing in trees in an article published in Architecture Australia in 2013, by asking the question “How does government maintain current spending levels while dealing with the consequences of an eroded tax base?”
Popular commentary on this subject contends that governments should run a balanced budget or that there should be a return to a budget surplus.
Notwithstanding the complexities associated with any discussion around economic policy, Darren suggests that perhaps a more constructive conversation would be one which focused on wellbeing.
One way of doing this, Darren suggests, would be to explore the concept of “biophilic urbanism” as a way of increasing the quality of life without the need for increased tax.
“The concept of biophilic urbanism (biophilia being a term used to recognize our basic human desire to connect with nature) may well provide us with the means to access this opportunity without increasing tax rates, instead achieving savings through improved efficiencies in the delivery of essential services and even increasing the revenue base through associated increases in productivity,” he said.
“In October 2012 the Australian Bureau of Statistics updated Measures of Australia’s Progress (MAP), a collection of key indicators that help to answer the question ‘Is life in Australia getting better?’
“The figures showed that although Australians have a higher income, an increased life expectancy and are better educated compared with a decade ago, the number of threatened plants and animals increased over the last ten years, as did total net greenhouse gas emissions.”
Investing in more trees and parks is a solution that is not only environmentally friendly and economically and politically practical it will also allow our cities to adapt to future climate change.
“The physical greening of our cities and precincts will also have the important role of combating the “urban heat island effect,” which makes cities hotter than surrounding rural areas,” Darren said.
“By cutting the amount of heat-absorbing surfaces and providing cool shade, greening helps cool cities. That pays off in terms of lower demand for air conditioning, less energy use and fewer infrastructure requirements.
Darren also argues that contact with nature has been found to enhance healing and improve general wellbeing.
“People living near open spaces report fewer health and social problems, whether they live in a rural or urban residence, and regardless of their level of education and income,” he said.
“Even the presence of limited amounts of vegetation, such as grass and a few trees, has been correlated with enhanced coping and adaptive behaviour.
“Biophilic urbanism promotes the physical greening of our cities and as a result of an inevitable move away from car dependence.
“The biophilic city absorbs more carbon than it emits and is a place that literally breathes life into its surroundings, positively influencing its local climate and contributing to the total well-being of its inhabitants.”