Observed Impacts of Heatwaves

This chapter provides an overview of the observed impacts of heatwaves, focusing on human populations, the economy, society, infrastructure, domesticated animals, terrestrial wildlife, and marine environments. For human populations heat-related mortality is a major concern, with heatwaves causing more deaths than any other natural hazard in some countries. Vulnerable groups, such as the elderly and children, are disproportionately affected, with significant increases in mortality rates during heatwave events. The health impacts of heatwaves can be exacerbated by chronic diseases, pregnancy, and behavioural changes. Economically, heatwaves impose substantial costs on infrastructure, labour productivity, and healthcare systems. The agricultural sector is also affected, with heatwaves causing significant reductions in crop yields and livestock productivity. Increased aggression, mental health issues, and changes in social behaviour as social impacts arising from heatwaves are also touched upon. Because infrastructure systems, especially energy and transport, are highly vulnerable to heatwaves, impacts often manifest in the form increased cooling demand during heatwaves leading to grid failures and brownouts and blackouts and damage to rail and road networks via road heave and rail buckling, resulting in delays and increased maintenance costs. Domesticated animals and wildlife are not spared from the impacts of heatwaves. High mortality rates among cattle, poultry, and other farm animals are common during heatwave events. Wildlife, including some iconic species, also suffer significant mortality due to heatwave related heat stress. Marine environments are equally affected, with marine heatwaves causing widespread mortality among some marine species, disrupting food webs, and altering ecosystem structures. The chapter underscores the urgent need for systematic data collection on heatwave impacts to develop effective risk management strategies. It calls for integrated global systems to accurately record heatwave-related deaths and economic losses. The chapter concludes by emphasizing the importance of understanding the full scale of heatwave impacts to inform policy and adaptation and mitigation measures.