New tools pinpoint where urban trees could provide the most relief from heat
Cities trying to cool sweltering streets often set broad tree canopy targets. But those targets can overlook the reality that not all shade is equally useful, and not every neighborhood has room for more trees.
Two new studies from researchers at the University of British Columbia (UBC) offer cities a more precise approach to planting trees to combat urban heat. The tools pinpoint the hottest blocks and neighborhoods, identifying where new trees could provide the greatest relief. Dr. Melissa McHale, senior author of the studies, explained that while cities know they need more tree canopy, they still have to decide where planting is feasible and where shade will make the biggest difference.
Conventional satellite imagery, which typically uses 30-meter pixels, blends together the temperatures of different surfaces like asphalt, lawns, and tree canopy into a single average. The new machine-learning technique used in the studies sharpens these images to a 10-meter resolution, revealing temperature variations that were previously undetected. This allowed the researchers to identify small hot spots down to just 700 square meters - roughly the size of a large residential lot.
The second study took this a step further, using a modeling tool called CanopyFit to map where new trees could realistically be planted. This tool excludes areas like buildings, sports fields, and environmentally sensitive zones, then assesses shade potential alongside heat exposure and social/economic need. The model found that 248 hectares (610 acres) of mature canopy could be added in Kelowna, but that 20% of the area held over half of the potential shade gains.
This means that some neighborhoods have ample planting space, while others face high heat and need for trees but lack room for new trees.
The researchers suggest that in neighborhoods with high heat and limited planting space, alternative approaches like removing asphalt, changing development rules, or installing engineered shade may be needed. By combining these high-resolution mapping techniques with local information, cities can develop more strategic and targeted tree planting plans to reduce urban heat.
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