A hiker walks off the path guiding to the biggest cedar tree in Vancouver’s Stanley Park during a tour of ancient trees.ETHAN CAIRNS/The Canadian Press
Over the past five years, more than 1.3 million Canadians have received a medical prescription for a dose of nature to alleviate health issues, though critics say the science is lacking.
The PaRx program was launched in Canada by the BC Parks Foundation in November, 2020, eventually expanding to other provinces. Crafted by health care professionals, the program recommends at least two hours per week of time in nature, in chunks of no less than 20 minutes at a time, and offers patients tips on how to achieve those goals.
The written prescriptions can be more effective in getting patients moving than verbal encouragement, but the medicine itself is ill-defined. There is no accepted definition of what constitutes nature, and science hasn’t yet explained how it works.
But hundreds of medical studies have found health benefits associated with being immersed in greenspaces. Experiencing nature can reduce blood pressure, cholesterol and the risk of preterm birth. Asthma, ADHD and coronary heart disease can be reduced. Cancer-related outcomes can be improved.
Some 18,000 Canadian medical practitioners are now writing nature prescriptions, aiming to counter a growing health issue: A majority of Canadians live in urban areas where access to the natural environment can be limited, and where sedentary lifestyles can lead to chronic disease.
Doctors all the way back to Hippocrates have advocated for the healing power of nature, and the first formal prescription program started in the United States a little more than a decade ago.
It is unclear, however, just what counts as greenspaces. Does sitting in a pocket park in the city offer the same benefits as hiking deep in the heart of an old growth forest?
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The PaRx program points to a broad review of the medical literature on the benefits of nature, published in the Environmental Research journal in 2018. The review found, based on more than 140 studies, that “green prescriptions involving greenspace use may have substantial benefits.”
The authors acknowledged that there is no universal definition of greenspaces, so they defined them as open, undeveloped land with natural vegetation, as well as urban parks and street greenery.
The other key limitation to the science is that the way in which nature helps people is not understood. The 2018 paper acknowledges that gap.
“Although this systematic review has uncovered a large body of research on the relationship between greenspace and health, there is a paucity of literature on the mechanisms underlying this relationship,” it says.
Ray Chipeniuk, an adjunct professor in the School of Planning and Sustainability at the University of Northern British Columbia, focuses on how the experience of nature relates to parks planning. His home is on 65 hectares of forested land near Smithers, regularly visited by grizzly bears.
“I have not the slightest doubt about the value of being out in natural places,” he said in an interview.
But Dr. Chipeniuk is critical of the PaRx program because medical science can’t define nature, much less measure out doses. In his paper published this year in the Parks Stewardship Forum, he argued that it’s important to distinguish between wild spaces and artificial park spaces that can trigger different responses in people.
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“It’s almost beyond hope that a halt would occur in the dispensing of these prescriptions, but there’s deep need for the parties endorsing the use of these PaRx prescriptions to look very carefully into the scientific basis for them,” he said in the interview.
“There really seems to be an uncritical acceptance of the idea that there is such a thing as nature which can be quantified and allocated, for particularly mental health problems. And I think we’re a long way from that.”
Dr. Ilona Hale is a family doctor and clinical researcher in Kimberly, B.C., who regularly dispenses PaRx prescriptions to her patients. The community, in the Purcell Mountains in the Kootenays, is surrounded by opportunities to connect with nature. The city boasts the largest municipal park in the province. But sometimes her patients need a nudge to get outside.
Dr. Hale is confident in the science that says exposure to nature is effective for many health conditions. She noted that most medications have side effects, so when she can, she’ll substitute a dose of nature instead.
“When I’m prescribing a pill, I’m very concerned to know that it works, and if it’s not working, then we’re going to stop it, because there are very real potential side effects to medication treatment,” she said in an interview.
“Whereas with this, I feel like if you’re going out in nature, and maybe you’re actually even being a bit physically active to get there, I don’t think there’s a lot of negative side effects.”
