Putting shade where it counts: A classification approach for prioritizing tree planting locations using heat equity and shade modelling

Source abstract

Climate change and urbanization are increasing heat-related risks in cities; these risks are distributed unevenly. Decision makers aim to improve equity and outdoor thermal comfort by increasing tree cover, but outcomes depend strongly on local-scale factors such as planting constraints and shade overlap. There remains a need for municipal decision-support workflows that combine site-specific planting feasibility, equity, and high-resolution shade modelling to identify effective and equitable interventions. We developed an ArcGIS Pro-based workflow to evaluate the relative cooling and equity impacts of feasible new tree plantings using solar radiation-based shade modelling and a tree equity index in Kelowna, Canada. We segmented the city into 400 m x 400 m areas for comparison and classified each area by planting priority. Tree shading potential was unevenly distributed across the city, with the top 20% of planting areas by new canopy area accounting for 50.8% of total modelled shade gain. While some areas with high equity priority also exhibited high shading potential, others showed limited capacity for shade provision under current biophysical and regulatory constraints, highlighting practical limits to improving heat equity through tree planting alone. To support planning and implementation, we integrated total shade gain, shading efficiency, and equity values into a screening-level classification of tree planting priority. This approach provides a replicable and transferable decision-support tool that helps municipalities identify where tree planting is both feasible and impactful, improving the alignment between heat mitigation goals, equity objectives, and on-the-ground constraints.