In 93 major European cities such as London and Barcelona, more than 6,700 people died prematurely from heat in 2015, and more than 2,600 of these could have been prevented.
Researchers at the Barcelona Institute for Global Health suggest planting trees as a possible solution. As a result, the annual number of deaths from heat stress could fall by 40 percent, they say.
Rising global temperatures are also increasing the number of deaths from heat-related causes in densely built-up urban areasieden. Extreme heat is becoming more common, leading to so-called heat islands in urban areas.
The researchers assessed the mortality rates of people over the age of 20 living in 93 European cities (57 million inhabitants in total), between June and August 2015. In doing so, they also collected data on daily temperatures in the countryside and in each city.
Temperatures in urban areas can be significantly higher than in rural areas because building materials such as asphalt and concrete retain heat. In small forests in the city it can easily be twenty degrees cooler than on a nearby sidewalk. Green space can significantly reduce the temperature in cities, according to the study.
Currently, about 15 percent of the area in the major cities is shaded by trees. Planting more trees significantly reduces heat stress. Many city centers are already too hot, the researchers say.
In general, the cities with the highest heat death rates are in southern and eastern Europe. These are also the cities that would benefit most from more trees. The authors do acknowledge that planting more trees can be difficult in some cities because of the existing spatial layout.