Urban heat islands create thermal environments significantly hotter than surrounding rural areas, affecting the welfare of urban wildlife from insects to birds to mammals.
Urban heat islands create a welfare environment that wildlife adapted to local climate conditions did not evolve for. Species that colonised cities before heat island effects intensified now face thermal stressors outside their physiological comfort range. Urban birds breeding earlier may mismatch with food availability; urban mammals seeking shade during heat waves may venture into dangerous human spaces. The mitigation -- urban tree canopy, green roofs, permeable surfaces, light-coloured pavements -- reduces heat island intensity and provides direct welfare benefit to urban wildlife. These are also climate adaptation investments for human health that make the welfare case easier to integrate into planning decisions.