New Heat Maps Show Cities Where to Plant Trees for Cooling

Two new studies from UBC researchers give cities a block-by-block answer to one of the hardest questions in climate adaptation: where to plant trees so they actually cool people down. Tested in Kelowna, B.C., the pair of complementary tools sharpens satellite heat maps and then maps where new canopy can realistically go, moving city planting plans from broad citywide targets toward decisions at the scale of individual streets.

The first study, published in the journal Remote Sensing, takes on the blurry picture cities usually work from. Standard thermal pixels are 30 metre squares, big enough to blend rooftops, asphalt, lawns and existing canopy into a single averaged reading. Using an open-source machine-learning technique on Landsat and European Space Agency Sentinel satellite imagery, the research team refined the maps to 10 metre resolution, according to the University of British Columbia.

The sharper view revealed nearly five times as much temperature variation across the city. Hot spots showed up in patches as small as 700 square metres, roughly the footprint of a large residential lot, compared with broad 18,000 square metre blobs under conventional imagery, as reported by phys.org. Tree canopy and paved surfaces explained more than 65 per cent of the additional detail, a sign the method was detecting genuine landscape differences rather than digital noise. Knowing exactly where to plant trees starts with this kind of visibility: without it, a scorching parking lot can hide inside the same pixel as a shaded park.

Where to plant trees, and where they cannot go

Finding heat is only half the job. The second study, published in the journal Urban Forestry & Urban Greening, introduces CanopyFit, a modelling approach that answers where to plant trees and where the shade they cast will matter most. The team's lead researcher, Dr. Melissa McHale, puts the core problem plainly: a site can look empty on a map and still be impossible to plant, once buried pipes, overhead wires and other hidden barriers are accounted for.

The model screens out buildings, sports fields, underground utility corridors, wildfire buffer zones and environmentally sensitive ecosystems before it scores anything. Only then does it weigh remaining planting space against heat exposure and social and economic need. Cities have limited space and resources for planting, "so we need to be strategic," McHale said in the university's release. That discipline is what decides where to plant trees versus where to look for other fixes.

Applied across Kelowna, the model found room for 248 hectares of potential new mature canopy. But the opportunity is sharply uneven: just 20 per cent of the analysed land held 50.8 per cent of all the potential shade gains, the team reports. In other words, a relatively small slice of the city carries more than half of the cooling payoff, which is exactly the kind of finding that tells planners where to plant trees first.

The comparison between neighbourhoods shows how the answers differ street by street. Rutland emerged as a high-priority zone where heat, equity needs and planting space overlap, making it a strong candidate for new canopy. Midtown, by contrast, faces significant constraints despite high cooling needs, meaning trees matter there too but will need more resources, different species choices and long-term care. In places where the built environment leaves almost no room, the researchers point to alternatives such as removing asphalt, changing development rules or installing engineered shade, as reported by phys.org.

The payoff is measurable. Every ten per cent increase in tree canopy cuts mean radiant temperature, the heat people actually feel from their surroundings, by roughly one degree Celsius. That link between canopy and felt heat is the reason cities keep setting ambitious planting targets, and the reason aimless planting wastes them. Every budget goes further when planners already know where to plant trees before the first shovel hits the ground.

What this means for your city

The biggest practical news is that any city can use this. Both approaches run on widely available satellite data and open-source methods, so a planning department does not need a large budget to find its own hot blocks and its own realistic planting spots. The research was built on municipal timelines, tested against real planning decisions in a partnership dating back to 2022, and is already expanding to Vancouver, where an environmental consultancy has folded the model into its canopy forecasting tools. Any city could run the same playbook to decide where to plant trees, no research university required.

For renters and anyone who has endured a heat wave in a top-floor apartment, the shift from citywide targets to block-level decisions is a health story, not just a forestry one. A cooling strategy that finds the actual hot blocks, and confirms there is somewhere a tree can survive there, is the difference between a promise of future shade and shade that shows up on your street. City leaders deciding where to plant trees can now start with the people who feel heat the most.

The researchers are careful about one caveat. The maps track surface temperature, which is not the same as air temperature, so a hot-looking roof does not automatically mean the air around it is dangerous. The team also notes that some of the hottest, most built-up blocks simply have no plantable ground, and pretending otherwise just burns budgets. That honesty about limits is what makes the approach credible: it directs money where to plant trees and flags where trees were never the answer.

Urban planting is already getting scrappier worldwide, from parking lots turning into pocket forests to volunteer-run groves on dead land. The Kelowna research gives that energy a scientific backbone: find the real hot spots, rule out the impossible spots, and put limited trees where their shade helps most. For the full picture on how cities and plants are adapting together, see our Plants and Trees coverage.