Increasing the number of trees in cities could save thousands of lives each year as summer temperatures continue to rise, driven by climate change, a study has suggested.
Of 6,700 premature deaths linked to higher temperatures in European cities in 2015, almost one third — or 2,644 — could have been prevented by adding up to 30 per cent of urban tree cover, according to data published in The Lancet.
“Our results suggest large impacts on mortality due to hotter temperatures in cities, and that these impacts could be partially reduced by increasing the tree coverage to help cool urban environments,” said study co-author Mark Nieuwenhuijsen of the Barcelona Institute for Global Health.
A modelling study found that tree cover could reduce urban temperatures by an average of 0.4°C during the summer.
Policymakers need to adopt “integrating green infrastructure into urban planning” to promote sustainable and healthy city environments, the team said.
The other co-author Tamara Lungman, also of the Barcelona institute, said the situations was “becoming increasingly urgent, as Europe experiences more extreme temperature fluctuations caused by climate change; despite cold conditions currently causing more deaths in Europe, predictions based on current emissions reveal that heat-related illness and death will present a bigger burden to our health services over the next decade”.
“We already know that high temperatures in urban environments are associated with negative health outcomes, such as cardiorespiratory failure, hospital admission and premature death.
“This study is the largest of its kind, and the first to specifically look at premature mortality caused by higher temperatures in cities and the number of deaths that could be prevented by increasing tree cover.”
In the study, scientists estimated death rates of people over 20 years old in 93 European cities between June and August 2015.
There was a large variability in temperature-related mortality rates between cities, from no premature deaths attributable to hotter urban temperatures in Gothenburg, Sweden, up to 32 per 100,000 people in Cluj-Napoca, Romania.
Cities with the highest mortality rates linked to temperature were in Southern and Eastern Europe, where citizens would benefit most from an increase in tree coverage, the researchers said.
They said their findings supported the idea that urban trees provide substantial public health and environmental benefits.
However, they acknowledged that increasing tree coverage should be combined with other interventions to maximise urban temperature reduction — such as changing ground surface materials to reduce night-time temperatures — replacing asphalt with trees, for example.
Average tree cover in European cities stands at 14.9 per cent, so meeting the target of 30 per cent could prove challenging for some urban areas, they also noted.