We’ve had some very knowledgeable people as Vancouver City Arborists. Any tree planted on city boulevards, city owned parks and public spaces is under the care taking of the Park Board and their arborists. Paul Montpellier educated a generation of city staffers on trees species, and was also a well-known author and illustrator of children’s books. Arborist Bill Stephen would quickly tell you that as lungs of a city a tree over fifty years exhales 6,000 pounds of oxygen in its lifetime, contributing 120 pounds of oxygen a year. He also taught the International Society of Arboriculture course for Arborist licensing.
In 2008 I visited Sadhu Johnston when he was working in the City of Chicago as Chief Environmental Officer. He told me about the 2007 tragic Chicago marathon race where 185 people got ill and one person died as temperatures soared way beyond 26 degrees celsius. In response, marathon organizers sponsored the planting of myriads of street trees to counter the urban heat sinks of pavements, and to ameliorate spiking temperatures.
These folks have known for a long time what The Nature Conservancy is now publishing- “Trees can soak up fine particle pollution from cars, power plants, and factories — an important job, given that particulates wreak havoc on human lungs and kill some 3.2 million people worldwide each year. The precise effect varies from city to city, but generally trees do improve air quality. Urban trees can also cool down neighborhoods anywhere from 0.5 degrees Celsius to 2 degrees Celsius on the hottest summer days, which is vital during deadly heat waves. (Studies have found that every additional 1 degree Celsius in a heat wave leads to a 3 percent or more increase in mortality.)”
It just makes sense to support policies of tree replacement and augmentation and to think of adding shade trees in parks, schools and on private property. There is a lot of environmental value in the financial cost of a tree.