Marine heatwaves are becoming more frequent and intense, causing mass mortality events and welfare suffering for marine animals including fish, invertebrates, and marine mammals.
Marine heatwave welfare is a mass casualty event that illustrates how climate change creates welfare harm at population and ecosystem scales that dwarf individual-level interventions. Mass die-offs of seabirds, sea lions, salmon, and invertebrates involve suffering on an enormous scale, and these events are becoming more frequent. The welfare response at individual level - rescue of stranded or distressed animals - is important but cannot scale to address mass events. The welfare response at systemic level is climate mitigation: reducing the warming that makes these events more frequent and severe. Marine heatwave welfare is therefore a direct argument for urgent climate action as an animal welfare priority alongside its human welfare implications.