This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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 by University of British Columbia researchers offer a more targeted approach. Tested in Kelowna, B.C., the complementary tools can identify urban hot spots down to individual blocks and determine where new trees could deliver the greatest benefits. "Cities often know they need more tree canopy, but they still have to decide exactly where planting is possible and where shade will make the greatest difference," said Dr.
Melissa McHale, a professor in UBC's Faculty of Forestry and Environmental Stewardship and senior author of both studies. "Together, these approaches move us from broad citywide targets toward decisions at the scale of the streets and neighborhoods where people actually experience heat." Satellite thermal maps give cities a bird's-eye view of surface temperatures, but often lack the detail needed for block-by-block planning. Standard 30-meter pixels can blend the temperatures of rooftops, asphalt, lawns and tree canopy into a single average.
In the first study, published in Remote Sensing, UBC researchers tested an open-source machine-learning technique that sharpens imagery from Landsat and Sentinel-2 satellites to 10-meter resolution. The higher-resolution maps revealed nearly five times as much temperature variation across Kelowna. With conventional 30-meter imagery, hot spots appeared in broad areas averaging 18,000 square meters (4.4 acres), roughly two and a half Canadian football fields.
The 10-meter approach detected much smaller hot spots, as small as 700 square meters (7,500 square feet), about the footprint of a large residential lot. Landscape features like tree canopy and paved surfaces explained more than 65% of the additional temperature detail, indicating the method was detecting real landscape differences rather than digital noise. While surface temperature is not the same as air temperature, the freely available approach could help cities identify small hot spots that conventional mapping misses.
Finding heat is only part of the challenge; cities also need to know where trees can realistically be planted and provide useful shade. In the second study, published in Urban Forestry & Urban Greening, the team used CanopyFit, a modeling approach conceived and spearheaded by McHale and developed with the Urban Ecology and Sustainability Lab and her municipal partners, to map practical planting potential. It excludes areas unsuitable for planting, such as buildings, sports fields, underground utilities, wildfire buffer zones and environmentally sensitive ecosystems, then assesses shade potential alongside heat exposure and social and economic need.
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