Global Change Biology

Graphical Abstract Resource availability/reliability (blue) and quality (purple) differ between urban and non-urban areas and will interact with rising temperatures to influence the magnitude of biological impacts of climate change. Specifically, the urban environment could both buffer and exacerbate the biological impacts of rising temperatures. Greater water availability/reliability in cities buffers thermoregulatory costs, while poorer urban water quality exacerbates warming-related increases in disease risk and pollutants may reduce thermoregulatory capacity. Greater food availability and artificial light at night may buffer foraging-thermoregulation trade-offs in cities, while warming-related declines in food quality (e.g. carotenoids) are exacerbated in cities. Urban nest- and roost sites are poorly thermally buffered, hence of lower quality, than non-urban sites, while more shade is available in cities, especially in arid regions. Finally, the effects of rising temperatures are likely exacerbated by air pollution and vice versa, with impacts on the redox system and immune system. The UHI effect under climate change will likely continue to lead to relaxed thermoregulatory costs in temperate, continental and polar cities during winter, while exacerbating thermoregulatory costs in summer and in tropical cities compared with non-urban environments. Cities in arid zones often have a reversed heat island effect, buffering thermal costs.