Climate change and the city: analysis of the urban heat island effect on mortality in Valencia, Spain

Abstract

Abstract Background Heatwaves are increasing due to climate change and they are responsible for more fatalities than any other extreme meteorological phenomenon. An excess of mortality can occur during heatwaves, and it is usually higher in cities than in rural areas. This can be partly explained by the urban heat island effect, a human-induced modification of the local temperatures. This study assessed the effects of the July 2017 heatwave -one of the highest in recent years according to Heat Index available data- in Valencia (Spain). Methods Analytic, observational, and retrospective study on the effects of the 27-31 July 2017 heatwave in the city and province of Valencia on population mortality. Observed and expected number of deaths in our population were compared, using the same period of 2013 as a reference, and Standardized Mortality Ratio (SMR) was calculated for the capital city (urban area) and the province (suburban and rural areas) of the Valencian Region (Spain). Results The analysis showed a significant excess of mortality in the city of Valencia (787,808 pop) during the July 2017 heatwave, with an SMR of 1.634 (95% CI 1.356-1.952). In that period 116 deaths occurred, mean age 79.7 years, 50,7% women. By age groups, the population above 65 years was identified as the most vulnerable, with an SMR of 1.607 (95% CI 1.311-1.949). The mortality excess was 8% higher among men compared to women, although the difference was not significant. No significant increase in mortality was found in the province of Valencia (1,752,899 pop). Conclusions The July 2017 heatwave in the Region of Valencia brought an excess of mortality in its capital city, which did not take place in rural areas. Elderly are especially vulnerable to these extreme temperature events. Our findings raise awareness on the importance of climate change mitigation and adaptation measures, especially as regards its effects in urban areas. The regional heatwave protocol for nursing homes was enhanced. Key messages Adverse climate events are increasing due to global warming. The July 2017 heatwave in the Region of Valencia brought an excess of mortality in its capital city, especially among elderly. This study raises awareness on the need for climate change mitigation and adaptation measures, especially as regards the urban heat island effect.