Urban heat islands — areas of cities significantly warmer than surrounding rural land — create thermal stress for urban wildlife, affecting behavior, reproduction, and survival.
Urban heat islands are a welfare modifier for every animal living in a city. Species that evolved in temperate climates experience temperatures in urban centers that may approach or exceed their thermal comfort limits on hot days. Wildlife in cities lack the behavioral options that rural animals have — shade trees are sparse, cool water bodies are rare, and the concrete-heavy built environment retains and radiates heat. Urban greening — tree canopy expansion, green roofs, water features — benefits wildlife welfare as directly as it benefits human urban comfort.