Chasing Carbon

On a chilly November day with snow flurries gently falling around me, I found myself lounging in brief moments of sunshine on a pebble beach alongside the Don River. With one eye, I was watching a group of students who were practising water sampling techniques, making sure they could carry out these procedures in my absence. At the same time, I was following a propeller plane flying low above us, as it made its descent to the airport on the Toronto Islands. I was also noting signs of industry, such as a tall smokestack and the growl of a transport truck on Commissioner Street. It occurred to me that one could easily mistake the signs of nature immediately around us—the still river lined with senescing plants and a flock of ducks—as a forgotten in-between landscape, lost in the rush of urbanization, like a meadow below a freeway overpass or a patch of wetlands that one might notice looking out of an airplane window, right before the tarmac begins. 

Nothing could be further from the truth. 

We were sitting in the heart of Biidaasige Park, which opened in June 2025. Biidaasige means “sunlight shining toward us” in Anishinaabemowin. Rather than being a space that the city forgot about, it is the epicentre of what some of my colleagues have described as possibly the largest urban climate adaptation project on the planet. My peaceful moment by the riverside was the consequence of 1.25 billion dollars from municipal, provincial, and federal funds, as part of the broader ongoing Port Lands Flood Protection Project. Led by Waterfront Toronto, this project has transformed the mouth of the Don River from a site of intensive industry and pollution to a desirable neighbourhood for humans and wildlife.

I was lucky enough to visit this same spot in spring 2022, when, donning a hard hat and steel-toed boots, I was guided through what they called the “grand canyon,” which was the newly excavated course for the Don. The excavated soil, piled high on either side of us, could have apparently filled the SkyDome (or Rogers Centre, as it is now called). Following decades of exposure to industrial pollutants, the soils first were categorized according to what hazardous contaminants they held and then heaped into hills. To keep local sparrows from nesting in them prior to treatment, the area was patrolled by a live falcon.

One worker mentioned to me that he was doing this so that his grandkids could play there some day. Walking through that moonscape in early 2022, I could hardly have believed that, in just a few short years, my own toddlers would be playing there on Biidaasige’s opening weekend.

On that chilly day in November, rather than playing in the dirt, my students and I were there to study the water and what it contained. After all, it’s not every day that a city creates a new aquatic landscape from scratch, including a river mouth, ponds, and wetlands that flood when the river rises. Healthy wetlands offer countless benefits, and the waters of Biidaasige will doubtless be an invaluable refuge for human and non-human Torontonians alike during future heat waves. Aquatic landscapes, however, have a complex role when it comes to their relationship to the climate.

Inland waters around the world tend to be a natural source of the greenhouse gases carbon dioxide and methane, making them an important part of our planet’s carbon cycle, keeping our climate stable over time. Our actions (for instance, increasing nutrients or pollutants) can directly and indirectly impact waters, resulting in major changes to their greenhouse gas fluxes. So when we create a new aquatic environment on what was previously an industrial site, we alter our relationship not only with the land and water but with the air as well.

My students and I are not the only people interested in understanding what’s happening with the flow of carbon in Biidaasige; our ROM-funded research is in collaboration with scientists at Toronto Metropolitan University and uses data shared with us by the Toronto and Region Conservation Authority. Conversations with interested scientists further afield, including with Environment and Climate Change Canada, are also underway. Collectively, this work will help us understand how these new aquatic ecosystems are functioning, potentially guiding future management and stewardship decisions, while keeping us mindful of our society’s relationship with the atmosphere.

This type of work is not uniquely relevant to Toronto. Cities around the world are dramatically changing the way they are interacting with their local waters. Some highlights include Cheonggyecheon (a stream in Seoul that replaced an elevated highway in the early 2000s), dramatic improvements being made to water quality of and urban integration with rivers in cities across Europe (for instance, the improved condition of the Seine River in Paris, which now allows public swimming after a century-long ban), and the Chinese “sponge city” urban planning initiative, which embraces a nature-based approach to making cities more sustainable and resilient to floods. Scaling out to such a global perspective, we can see that Toronto’s work at the mouth of the Don is part of a broad shift in the ways that cities globally are embracing their natural environments.

Whether due to ideology or necessity, prior generations often treated urban waterways as little more than convenient channels for exporting refuse or exchanging goods for commerce. This continued until waterways became so polluted that they became a threat to public health, at which point it was frequently considered best to bury or drain them, rather than attempt any sort of remediation. Today, cities are increasingly recognizing that the waters that occupy our communities can serve a much more meaningful purpose, becoming the very features that make urban living enjoyable, sweetening the air and softening the blow of daily stresses. It should be no surprise that in some places, such as England, doctors can now offer patients “blue prescriptions,” advising increased time along waterfronts to help with anxiety, depression, and high blood pressure, following peer-reviewed research demonstrating the effectiveness of time spent near water.

Ultimately, my students and I are tracking the carbon in Biidaasige, dipping beneath the water’s surface to get a sense of how the carbon is interacting with the atmosphere along with any other potential urban effects that now flow through this site, such as the high salt concentrations each winter from road salt applications across the city. In one sense, we’re improving our understanding of the city’s “carbon footprint”—whether new urban aquatic environments such as Biidaasige result in a net increase or decrease to greenhouse gases in the atmosphere. More broadly, though, I like to think we’re taking the pulse of the city. Doing this work, we are able to measure, at a very fundamental level, how our actions play out in the complex interacting relationships between the land, waters, air, humans, and non-humans.

In the case of Biidaasige, this site is reputed to have been the largest wetlands complex of the entire Great Lakes system prior to being drained and channelized into the Keating Channel in the late 1800s. Just as the flow of carbon examined through our research doesn’t tell us what the system was like 150 years ago, the renaturalization work carried out by Waterfront Toronto does not reproduce, in any meaningful way, what was lost. Instead, it is a new step for the city as we approach and address a litany of social and environmental challenges ahead of us. Overall, this work is a step toward mindfulness, bringing broad conversations together to help shape the path we are walking as a society.

Soren Brothers is the Allan and Helaine Shiff Senior Curator of Climate Change at ROM.