PAIR 3 — SCIENCE AND URBAN TREE POLICY Passage A Cities seeking relief from extreme heat should expand tree canopy in neighborhoods that have the least shade. Satellite studies repeatedly associate greater canopy with lower summer surface temperatures, while tree-lined streets also offer pedestrians protection from direct sunlight. Because historically underserved neighborhoods often have fewer mature trees, canopy investment can address both climate adaptation and unequal exposure. Programs should set measurable neighborhood targets and fund planting on public land as well as voluntary planting on private property. Trees require maintenance, but that is an argument for stable budgets, not for delay. No single intervention will eliminate urban heat, yet a broad planting program is one of the few measures capable of improving comfort, air quality, and streetscapes at the same time. Passage B Canopy percentage is an attractive policy target because it is easy to map, but treating all new canopy as interchangeable can waste resources. A tree that dies after two summers contributes little cooling, and a species poorly matched to local water conditions may demand unsustainable irrigation. Placement also matters: trees shading sidewalks and west-facing walls can reduce human heat exposure more effectively than the same canopy added beside an unoccupied lot. Cities should therefore begin with block-level heat measurements, pedestrian patterns, soil conditions, and long-term survival estimates. Tree planting may remain part of the response, but it should be combined with shade structures, reflective surfaces, and building improvements where those measures perform better. Success should be measured by reduced exposure, not simply by the number of trees planted or the percentage of land viewed from above. QUESTION 9: The passages differ primarily in that Passage A emphasizes

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