Study: more trees in cities could save lives during heatwaves

Some natural coolants in Geneva. © Keystone / Martial Trezzini

A study of 93 European cities, including Geneva, Basel, and Zurich, reckons that upping the level of urban tree coverage could save thousands of lives.

The modelling study published on Tuesday in The Lancet journal estimated that raising the urban tree coverage to 30% – from the current average of 14.9% – could help to reduce temperatures by o.4°C during summer heatwaves.

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As such, one-third of the 6,700 heat-related deaths in the 93 cities in 2015 could have been avoided, according to the researchers.

“We already know that high temperatures in urban environments are associated with negative health outcomes, such as cardiorespiratory failure, increased hospital admissions and premature deaths,” lead researcher Tamara Iungman said in a press release.

“Our goal is to inform local policies and decision makers about the benefits of strategically integrating green infrastructure into urban planning to promote more sustainable, resilient and healthy urban environments.”

Swiss trio

In Zurich in 2015, 10 deaths could have been prevented, in Geneva five, and in Basel three, the authors calculated. The Swiss cities have vegetation cover rates of 12%, 14% and 24% respectively.

Temperatures in urban areas are also markedly higher than in the rural zones around them: 1.5°C on average across Europe. In Zurich, this value in 2015 was 2.5°C, but this could be lowered by o.5°C by doubling the amount of trees and vegetation.

The study found that the southern and eastern regions of Europe are most affected by these problems. Cluj-Napoca in Romania recorded the highest difference between urban and rural temperatures, at 4.1°C.