This B.C. Professor Is Tackling Climate Change One Tree At A Time

Caterina Valeo’s solution to the country’s extreme heat? Growing an urban forest.

By Ayesha Habib

Updated April 23, 2024

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(Photo: Courtesy of Caterina Valeo)

Ask anyone who spent the summer in British Columbia in 2021 and they’ll tell you a story of an oppressive heat that weighed on them like a fiery blanket. A heat dome killed 619 people that summer, exposing the ways urban infrastructure in the generally temperate province is not prepared for such extreme heat. Now, in the aftermath of the deadliest weather event on record in Canada, researchers and urban planners alike are searching for solutions.

Caterina Valeo, a mechanical engineering professor at the University of Victoria, is one of those researchers. And she’s turning to trees for an answer.

Studies have shown that green spaces in urban areas have cooling effects. But can we use trees to regulate the extreme heat caused by climate change? For the next three years, Valeo will try to pinpoint just how to do that.

Together with the City of Vancouver, Valeo and a team of researchers from the University of Victoria and the University of Calgary will work to design an urban forest that can mitigate the urban heat island effect, which is exacerbated by climate change. The research project will receive $180,000 over three years from the Pacific Institute for Climate Solutions. The goal: to implement these designs in Vancouver and then share them with other cities worldwide.

For Valeo, who specializes in urban hydrology, that begins with a storm. She plans on researching how to use what’s known as rainwater tree trenches (RTTs) to grow full-canopy mature trees in urban settings. RTTs are used to sop up stormwater—they’re planted in a trench, and an underground system connected to stormwater drains filters the excess water to reduce flooding. But Valeo intends to use RTTs to enhance cooling in an urban area—something that’s never been done before.

The trees in RTTs are grown in structural soil, which is loosely compacted and contains a large amount of stones. This allows the roots to grow more freely, creating faster-maturing trees with fuller, shade-creating canopies. RTTs are also planted in rows, which can create a wind-tunnel cooling effect, says Valeo.

While Valeo is confident about the promise of RTTs, there is still much to be done, like figuring out what type of tree will work best. “The project is about optimizing where you put RTTs, how many you plant and in what configuration in the city as it currently is, so that it’ll actually have a discernible impact,” she says.

Still in its early stages, the research project will monitor and model energy (from the sun’s radiation, for example) and water mass (rainfall and water vapour) in the city over time to determine the temperature at any given point. From there, they’ll be able to determine how the RTTs affect the temperature and where to put them.

Planting trees to offset extreme heat is a nature-based solution, which makes it more resilient, says Valeo. But planting a tree by itself isn’t enough. The challenge most urban planners face is how to optimally incorporate trees into a city’s landscape.

“Trees are often just viewed as an inconvenience—they get in the way of utility placements,” says Valeo. “We want to make these trees part of the utility that’s embedded within our urban infrastructure.”