Want a healthier, more just city? Plant trees

At the gym recently, a locker mate querulously remarked how a squirrel had gnawed through a screen in his window. “What d’ya do?” another fellow asked. “I cut down all my trees,” was his draconian reply. Aside from the scorched-earth finality of such a resolution, by clear-cutting his yard, my change room neighbour may well have undone most of the health benefits he had derived through years of gym membership.

In a new Toronto-based study, researchers have found that city trees, especially those lining our streets, are linked to “significant, independent, and reliable increase in health benefits,” and that even small increments of street trees could lead to marked health improvements.

The multi-authored study, “Neighbourhood Greenspace and Health in a Large Urban Centre,” using highresolution satellite imagery and questionnaire-sourced health perception research, found that adding more trees on your street, in terms of health perception, was like getting a hefty salary boost.

The study, published earlier this month in the journal Scientific Reports, noted that having even 10 more trees on your block was tantamount, in terms of health perception, to a $10,000 deposit in your bank account, being seven years younger, or moving up the real estate snack bracket to a tonier neighbourhood, one with a $10,000 higher median income.

While other studies have chronicled general effects of green spaces on health, this research is distinctive in detailing the positive effects of individual trees, and their placement in a city, upon human health.

City trees clearly increase property values, reduce heating and energy use, and improve air quality. A 2014 report by TD economists confirmed that Toronto’s 10.3 million trees represent $80 million in environmental services and infrastructure cost benefits.

But this latest study indicates that people who live in treed neighbourhoods are healthier and report significantly fewer cardio-metabolic conditions (after accounting for socio-economic and demographic factors).

Using data gleaned from 30,000 individuals and encompassing 530,000 trees, the researchers examined not only individual self-perceptions of health, but also heart conditions, prevalence of cancer, mental health problems and diabetes. Headed by University of Chicago psychologist Marc Bergman, the research team notes that while self-perception of health is admittedly subjective, it does strongly correlate with objective health measures.

For Faisal Moola, a director of the David Suzuki Foundation and co-author of the study, these findings have far-reaching social and environmental justice implications. For him, the study reveals that while trees are “the great equalizers” in terms of health outcomes, there is “great inequality” in terms of nature access in the city. Poorer neighbourhoods, he observes, are impoverished not only economically, but also ecologically. They often lack green space and tree canopy, leading to diminished health and quality of life for their residents.

According to Moola, who also teaches in the forestry program at the University of Toronto, more investment in trees in disadvantaged neighbourhoods must go hand in hand with poverty-elimination policies, such as a guaranteed living wage.

This marriage of social and environmental justice, recently heralded by Pope Francis in his potentially game-changing encyclical, Laudato Si, was embodied by the thousands who joined Naomi Klein, Jane Fonda, and environmentalist Bill McKibben on Toronto’s streets earlier this month in the Jobs, Justice and Climate rally.

This new tree study helps illustrate that, within cities, urban tree lines often follow the fault lines of social, economic, political and ecological disparity. Just as we experience racial and economic inequality, we also experience “unequal ecologies,” places where people experience both economic and ecological marginalization.

This tree study underscores how city policies around tree planting can help address such imbalances.

Yet it is also part of a growing crescendo of researchers, activists, religious leaders, and engaged persons around the globe who realize, along with the late “geologian” Thomas Berry, that “you can’t have healthy people on a sick planet.” Health, prosperity, justice, happiness, ecological integrity and tree-lined neighbourhoods — all are part of an “ecosystem” of a flourishing of life, human and non-human.

The idea of preserving and increasing our urban forest is not a squirrelly idea, but represents sound science, wise urban planning, and a far-sighted investment in public health, as well as a potentially powerful tool in addressing ecological disparity.

And it is good for squirrels too.

The latest study says people who live in treed neighbourhoods are healthier and report significantly fewer cardio-metabolic conditions