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As cities have grown denser, urban foresters have argued that street trees are not merely decorative but function as low-cost infrastructure. A mature tree's canopy intercepts rainfall, reducing runoff that would otherwise overwhelm storm drains, while its shade can lower nearby pavement temperatures by several degrees, easing the urban heat island effect. Because young saplings take years to deliver these benefits, some cities have begun prioritizing species already known to tolerate compacted soil and road salt, rather than planting whichever tree is cheapest at a nursery. Critics counter that without adequate below-ground space and consistent watering during the first three years, even a hardy species will fail, meaning the upfront planting cost is only part of the investment required.