Urban Heat Islands

Cities often register temperatures several degrees higher than the surrounding countryside, creating what ecologists call urban heat islands. Dark roofs and paved roads absorb sunlight during the day and release it slowly at night, so cities rarely cool down fully. This steady warmth reshapes local food webs. Insects emerge earlier in spring, and the birds that feed on them must adjust their breeding schedules or go hungry. Warmer winters also favour invasive trees such as Ailanthus altissima, which leaf out earlier than native oaks and seize sunlight before slower species wake. Planners now fight these effects with reflective paint, rooftop gardens, and shade trees, all of which lower surface temperatures and soften the heat that radiates back into the streets after dark.