Trees could reduce urban heatwave mortality by one-third

• Increasing tree cover to 30% would save 0.4 degrees Celsius.
• Foliage covers somewhat less than 15% of urban areas in Europe on average.
• This increased heat is mostly produced by a lack of greenery.

PARIS: Researchers suggested Wednesday that planting more trees in metropolitan areas to reduce summertime temperatures could reduce mortality directly attributable to hot weather and heatwaves by one-third.

According to their findings in The Lancet, increasing tree cover to 30% would save 0.4 degrees Celsius (0.7 degrees Fahrenheit) locally on average during the hot summer months.

According to the data, one-third of the 6,700 premature deaths caused by higher temperatures in 93 European towns in 2015 may have been avoided.

Currently, foliage covers somewhat less than 15% of urban areas in Europe on average.

According to lead author Tamar Iungman, a researcher at the Barcelona Institute for Global Health, the study is the first to forecast the number of early deaths caused by higher temperatures in cities that could be avoided with more tree cover.

“We already know that high temperatures in urban environments are associated with negative health outcomes, such as cardiorespiratory failure, hospital admission, and premature death,” he said in a statement.

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

The so-called urban heat island effect causes cities to have greater temperatures than surrounding suburbs or countryside.

This increased heat is mostly produced by a lack of greenery, air conditioning system exhaust, and dark-colored asphalt and building materials that absorb and trap heat.
Climate change has already exacerbated the situation. Last year was Europe’s hottest summer on record, and the second warmest year on record.

Health benefits

Heatwaves are reaching new highs and lasting longer in recent decades all around the planet.

Cold weather still kills more people in Europe than hot weather. However, climate models predict that heat-related disease and death will place a greater load on healthcare systems within a decade.

“This is getting more critical as Europe faces more dramatic temperature changes as a result of climate change,” Iungman added.

Between June and August 2015, the researchers calculated mortality rates for persons over the age of 20, accounting for 57 million people in total.

In two modeling scenarios, this data was analyzed in relation to daily average city temperatures.

The first contrasted the temperature of the city with and without urban heat islands. The second simulation simulated a 30% increase in tree cover, resulting in a temperature decrease.

During the summer of 2015, cities were 1.5 degrees Celsius warmer than the surrounding countryside. Cluj-Napoca, Romania, had the greatest temperature differential (4.1 degrees Celsius).

Across all cities, 75% of the total population lived in places that were at least one degree warmer, while 20% lived in locations that were at least two degrees warmer.

Overall, cities in southern and eastern Europe had the greatest temperature-related mortality rates.

“This is an important piece of research,” commented Laurence Wainwright, a lecturer at the University of Oxford’s Smith School of Enterprise and the Environment.

“Urban tree planting — on the right scale, in the right places, and under certain other conditions — likely leads to a modest-yet-real reduction in heat-related deaths in many urban areas.”

Previous research has shown that green areas can improve cognitive functioning in youngsters and the elderly, as well as reduce cardiovascular disease, dementia, and poor mental health.

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