Science·What on Earth?

Kids especially vulnerable to air pollution and effects of climate change, says influential medical journal

In this week's issue of our environment newsletter, we look at what a prestigious medical journal says about climate change and children's health and examine what a tree is worth.

Also: The Paris Accord as human rights treaty

(Sködt McNalty/CBC)

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This week:

  • Kids especially vulnerable to air pollution and effects of climate change, says influential medical journal
  • The Paris Accord as human rights treaty
  • What is the true value of a tree?

Kids especially vulnerable to air pollution and effects of climate change, says influential medical journal

A child is using an inhaler. A doctor watches.

An influential medical journal has joined the fight against global warming.

The New England Journal of Medicine (NEJM), one of the world's oldest medical journals, recently committed itself to increasing the public's knowledge of climate change because of its devastating effects on public health.

"We clearly recognize that climate change has become a health emergency," said Caren Solomon, deputy editor at NEJM. 

As part of these efforts, NEJM launched a series focusing on climate change and public health, with a key article, published June 16, focusing on the impact of fossil fuel emissions on children, including dermatologic, respiratory and cardiovascular diseases.

Kari Nadeau, who is the director of the Sean N. Parker Center for Allergy and Asthma Research at Stanford University in California, has seen the medical effects on children's health first-hand. 

"The children coming into my clinic have terrible asthma," said Nadeau, who co-authored the NEJM article in question. "They also have blood pressure changes. There are things going on, for example, in the way that their bodies are growing that are affected by wildfire smoke."

Nadeau says children are especially vulnerable because they metabolize their air intake much quicker while still in critical stages of development. Unfortunately, children of colour or those from low-income households are more at risk of the health effects of climate change and air pollution, due to poor health-care access and food insecurity.

The health impacts of climate change on children aren't just physical. 

"Air pollution is now associated with mental health problems in children in a number of studies in the U.S. and in Europe," said Frederica Perera, an environmental health sciences professor at Columbia University and the director of the Columbia Center for Children's Environmental Health in New York.

Perrera, who was the lead author of NEJM's article on fossil-fuel pollution and kids' health, noted there is also consistent anxiety and depression in children who are reconciling their future with the growing impacts of climate change. 

The NEJM's climate change series also features an opinion piece on how much power the Environmental Protection Agency (EPA) in the U.S. has in regulating greenhouse gas emissions, while another opinion piece focuses on the impact of climate change on health and care delivery.

Solomon said the Intergovernmental Panel on Climate Change (IPCC) report released in February on climate change impacts, adaptation and vulnerability reignited concerns about what global warming will reap if left unchecked. 

"At the same time, recognizing that there's been very little progress on the part of the U.S. government or many other governments to address this, we felt that it was important to redouble our efforts in this regard," Solomon said.

This commitment comes after NEJM editors — along with the editors of 200 other health journals worldwide — signed an editorial in September 2021 calling for global emergency action to limit global temperature increases, restore biodiversity and protect health.

The authors noted a number of interventions that can reduce the negative effects of climate change. Governments can enact comprehensive regulations around renewable energy sources and adaptation plans that include action steps for vulnerable populations. Meanwhile, communities can set up evacuation plans and centres for refuge. 

On a patient level, physicians can provide as much information and resources as possible. Nadeau recalls a time when a single mother came to her shortly after the wildfires in California started in August 2020. The mother didn't have the means to move her family out of the area, and her children had severe asthma, which was being exacerbated by the smoke.

"As doctors and with the community, we were able to get her free filters brought to her home," Nadeau said. Within a day of installing them, the kids' breathing difficulties decreased dramatically.

As a mother herself, Nadeau knows the importance of creating a safe and healthy environment for her children. That's why she wanted to contribute to the medical journal and help raise awareness of the broader effects of climate change.

"I absolutely feel compelled as a mom, as a pediatrician and as a researcher," Nadeau said. "I'm inspired more to make sure that we can do something now."

Dannielle Piper

Reader feedback

Maude Page wrote:

"I recently read your article titled 'As Europe experiences extreme heat and drought, EU votes for power plan critics call "greenwashing.' While I appreciate the coverage on environmental and climate issues, I often see articles that perpetuate the myth that the climate crisis can be solved if we move to renewables. This article seems to be no exception.

"The reality is that our energy and electricity needs are deep and varied, and that we simply cannot transition to only renewables — at least not in the foreseeable future. Renewables work only when complemented by baseload capacity, which only hydro, nuclear and fossil fuels can provide. Anything else would mean temporary blackouts every time the sun isn't shining or the wind isn't blowing. If we want to move away from CO2 emissions, we need at least hydro or nuclear as electricity sources. Furthermore, gas is used a lot as a heating source, which would require significant investments in infrastructure (big and small) to transition away from. Not to say that it can't be done, but it certainly can't be done quickly.

"These facts and complexities are actually not well understood in society in general, and the myth of renewables as our saviours is often exacerbated by environmentalists, media and the general public on social media.

"I wish your articles would make it more clear that while there can be misgivings about gas or nuclear, the realities are complex and renewables alone cannot sustain us into the future. We have to make choices and we need a variety of options to get us there. It should be your responsibility to educate the public on these issues."

Fran Bazos:

"It is heartbreaking to see the EU, just like Canada, talk one way and make decisions about energy sources that fly in the face of global climate reality. Here, the Trudeau government says we need to reduce dependence on fossil fuels, while pushing, in spite of ballooning costs, the building of pipelines to transport oil, not today, but in the years ahead, because pipelines are not built in a day, but over many years with billions upon billions of taxpayer dollars.

"The reality is that the fossil fuel industry is still in the driver's seat, and we have all become numbed by the totally false narrative spewed by governments worldwide. I wonder what these leaders will be thinking as they watch this planet that sustains us all, including those very politicians, go up in flames and environmental collapse?"

Write us at

Old issues of What on Earth? are right here.

CBC News recently launched a dedicated climate page, which can be found here.

Also, check out our radio show and podcast. Do you know your carbon footprint? Now, do you know who told us to think about our personal carbon footprint? An oil company, in aid of distracting from its own role in global warming. Host Laura Lynch explores this issue, as well as the climate magic of the mighty caribou, in this week's encore edition of What On Earth What On Earth now airs on Sundays at 11 a.m. ET, 11:30 a.m. in Newfoundland and Labrador. Subscribe on your favourite podcast app or hear it on demand at CBC Listen.

The Big Picture: The Paris Accord as human rights treaty

When nearly 200 nations agreed to the Paris Accord in 2015, there was jubilation among dealmakers — and even a few tears. They resolved to keep the rise in global temperatures below 2 C from preindustrial times by aiming for 1.5 C — and the way to do that was to dramatically reduce carbon emissions. The fact that there was near-unanimous agreement on the need to reduce emissions was, indeed, new.

But the euphoria quickly faded. While the nations were in agreement with the larger aim (avoiding catastrophic warming), skeptics pointed out that leaving each country to work out its own emissions-reduction strategy jeopardized the collective goal. As it turns out, a lot of countries aren't even meeting their own targets (Canada included). The Climate Action Tracker, which measures how countries are faring in sticking to their Paris promises, shows that not a single nation has a 1.5 C-compatible plan. Countries like Costa Rica, Ethiopia and the United Kingdom are deemed "Almost Sufficient," while Canada is in the "Highly Insufficient" category. 

The broader takeaway is that while it was a milestone of climate action, the Paris Accord was not an ironclad contract, and has given nations room to backslide. But a recent interpretation by Brazil's Supreme Court offers a bold twist — it suggests that the Paris Agreement supersedes national law. In a ruling ordering the Brazilian government to reactivate a climate fund, the country's highest court said the Paris Accord was "a type of human rights treaty" and as such, "there is … no legally valid option to simply omit to combat climate change."

Environmental activists are gathered. One holds a sign saying 'Proteger la planete' (protect the planet, in French).
(Christophe Simon/AFP/Getty Images)

Hot and bothered: Provocative ideas from around the web

What is the true value of a tree? Experts say cities should consider climate-related benefits

A cyclist rides down a tree-lined street.
(Justine Boulin/CBC)

Along a street in Edmonton, mature trees sit protected by a green fence, near the construction of a new light-rail transit line. Signs show the value of the foliage: A rosybloom crabapple tree is worth $1,389, while a spruce is pegged at $2,185.

The price tags are a somewhat common practice in Canada, where an assessment formula is used to determine the monetary value of a tree in case it's damaged or killed.

But forestry and biology experts say those dollar amounts don't fully capture the environmental value of trees in an urban landscape — especially as they play an increasingly important role in helping deal with climate change.

"I think the monetary assessments are an important tool that we have, but we need to take them with a grain of salt in terms of what they may be capturing and what they may be missing," said Carly Ziter, an assistant professor of biology at Concordia University in Montreal.

Some tree benefits that are often unaccounted for, particularly in cities, include their cooling effect, ability to capture carbon and role in maintaining biodiversity. 

Such aspects need to be assessed to determine a tree's true value, experts say, so as to encourage the preservation of the current tree population — and to better protect the next generation of growth.

Municipalities and property owners typically turn to arborists or other experts for plant appraisal, and the value is determined based on several factors, including height, species, health and location.

Those factors are then used as part of a formula to determine a monetary amount in the event of an asset loss, as is done in Edmonton. But the formula that Edmonton and many other municipalities use — The Guide for Plant Appraisal — doesn't yet include an environmental benefit element, said Jacqueline Butler, an arborist and project leader in the city's forestry department.

One of the reasons Canadian municipalities use the guide's formula (and similar appraisal methods) is because those values are defensible in court, when there may be property disputes or other legal challenges, said Michael Petryk, director of operations with Tree Canada, a non-profit organization dedicated to planting and nurturing trees in rural and urban environments.

"The [courts] would view that tree as a piece of the property," Petryk said.

Cecil Konijnendijk, a professor of urban forestry at the University of British Columbia in Vancouver, said it's time more municipalities look beyond the dollar amount and more widely assess why trees are important.

Some cities in Canada and elsewhere have already assessed the environmental value of their urban forests.

For example, the structural value of Toronto's urban forest is assessed at about $7 billion, with carbon storage alone valued at $25 million. That's on top of the $28.2 million in ecological services — things like air pollution removal, energy savings and carbon sequestration — that the urban forest provides annually, according to the city's 2021-2022 strategic forest management plan.

One way municipalities assess that broader environmental value is by using i-Tree, a popular, peer-reviewed software suite from the USDA Forest Service. It helps organizations and city leaders understand how much carbon dioxide and air pollution is removed by a single tree or an urban forest, how trees can help with stormwater run-off and other benefits.

But Konijnendijk said the i-Tree formula only captures part of the picture.

"We also have things like public health. We have things like biodiversity. Esthetics. And those aspects are often much more difficult to quantify."

The cooling effect that tree canopies can provide is extremely important and valuable, said Alison Munson, a professor in forest ecology at Laval University in Quebec City and a member of CRAUM, a research partnership into the city's urban forests.

In some cases, mature trees can cool down residential areas by several degrees, compared to streets without a similar tree canopy. 

There are other benefits, too, said Munson, particularly in urban settings: carbon sequestration as a tree grows, filtering out pollution and particulates in the air — and even buffering against noise. 

Munson, Konijnendijk and Ziter all say ongoing monitoring of trees and long-term planning around our urban forests is critical.

"It's not about tree planting as much as it's about keeping the trees alive. The average urban tree doesn't often get much older than 30, 40 years. So if you could double that lifespan, you would get a lot of ecosystem services," said Konijnendijk.

"That's where it starts: The good stewardship of the existing tree population and protecting the trees as best as we can in urban situations."

Stephanie Dubois

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Editor: Andre Mayer | Logo design: Sködt McNalty

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