Scientists modeled the effects of increasing the number of trees by up to 30% in 93 European cities and found it can decrease urban temperatures by an average of 0.4 degrees Celsius (0.7 degrees Fahrenheit) and prevent deaths linked to heatwaves, as per the press release via EurekAlert! Currently, the average coverage of city trees in Europe is only 14.9%.
The authors of the study, titled "Cooling Cities Through Urban Green Infrastructure: A Health Impact Assessment of European Cities," published in The Lancet, emphasized the need of incorporating more sustainable and climate-resilient measures into municipal policy choices to promote climate change adaptation and enhance population health.
Urban Heat Island Effect
A 2022 global study by the Joint Research Center, which focuses on the difference between surface temperatures of urban areas and their neighboring rural areas in summer, found that cities often suffer from the 'heat island' effect. It is the phenomenon of temperatures being higher in cities compared to their rural zones or surroundings.
As the European Union (EU) reports, the urban heat island effect only amplifies the effect of heatwaves in cities and increases the risk to human health.
The team from the Joint Research Center examined the difference in land surface temperatures of urban areas with a population of 50,000 people and rural areas during the summer season between 2003 and 2020.
Using satellite data, scientists discovered that surface temperatures in cities were up to 10-15°C higher than in rural areas. According to the report, the temperature in severe heat islands in cities throughout the world has increased up to 1°C on average since 2003.
The study's worldwide scope and high-resolution geographical analysis allow it to compare cities in different climatic zones and even different regions of megacities.
The excess heat is mostly produced by a lack of greenery, exhaust from air conditioning systems, as well as dark-colored asphalt and building materials that absorb and trap heat.
Sadly, 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 of Increasing Tree Cover in Cities
Heatwaves are reaching new highs and lasting longer in recent decades all around the planet, as per Science Alert. The Lancet study lead author Tamara Iungman, a researcher at the Barcelona Institute for Global Health (ISGlobal), said that heatwaves are getting more critical as Europe faces more dramatic temperature changes due to climate change.
The team calculated death rates for people aged 20 and above between June and August 2015. They created two modeling scenarios in which data was compared to daily average city temperatures.
The first model compared temperature without the heat island in cities, while the second model simulates the temperature reduction if tree cover is increased by at least 30%.
During the summer of 2015, the temperature in cities was 1.5 degrees Celsius higher than in the surrounding countryside. Cluj-Napoca, Romania, had the greatest temperature differential by around 4.1 degrees Celsius. Across all cities, 75% of the total population resided in places that were at least one degree warmer, while 20% lived in locations that were at least two degrees warmer.
Cities in southern and eastern Europe have the greatest rates of temperature-related death. But they found that urban tree planting on the right scale and places, as well as under certain conditions will likely lead to a modest and real reduction of heat-related deaths in urban areas.
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