Trees for Life: The Benefits of Cooling Down

Having more trees in urban spaces is not only better to look at it also improves human mortality rates. As more extreme weather conditions are encountered due to the climate emergency, urban spaces, especially our cities, become hot micro climates in summer.


From June to August 2015, cities were on average 1.5oC warmer than the surrounding countryside. In total, 6,700 premature deaths could be attributed to hotter urban temperatures, which represents 4.3% of total mortality during the summer months and 1.8% of year-round mortality. 

The results of a study published in The Lancet has suggested that having more trees in our cities would have a cooling effect and thus reduce the numbers of deaths due to extreme heat.

An international team led by Mark Nieuwenhuijsen, director of the Urban Planning, Environment and Health Initiative at ISGlobal, estimated mortality rates of residents aged over 20 in 93 European cities (a total of 57 million inhabitants), between June and August 2015, and collected data on daily rural and urban temperatures for each city.

The analyses were performed at a high-resolution level (areas of 250m x 250m). First, they estimated the premature mortality by simulating a hypothetical scenario without urban heat island. Second, they estimated the temperature reduction that would be obtained by increasing tree cover to 30% and the associated mortality that could be avoided.

Key results Image credit ISGlobal

We’ve previously reported on studies which have shown the benefits of more green spaces for our well being Greening Our Urban Spaces . The Orkney News is also running a series on ‘The Lost Gardens of Orkney’.

ISGlobal researcher Tamara Iungman, explained:

 “Predictions based on current emissions reveal that heat-related illness and death will become a bigger burden to our health services over the next decades.”

Exposure to heat has been associated with premature mortality, cardiorespiratory disease and hospital admissions. This is particularly true for heat waves, but also occurs with moderately high temperatures in summer. Cities are especially vulnerable to higher temperatures. Less vegetation, higher population density, and impermeable surfaces for buildings and roads, including asphalt, lead to a temperature difference between the city and surrounding areas – a phenomenon called urban heat island. Given the ongoing global warming and urban growth, this effect is expected to worsen over the next decades.

Click on this link to access the report, Cooling cities for health through urban green infrastructure: a health impact assessment for European cities, published in The Lancet.

The report is the result of studying extreme heat which occurs in heavily built up cities but trees, shrubs, green spaces in our communities provide areas for wildlife to thrive. Wildflowers are essential for a wide variety of pollinators. The more we tarmac or pave over green areas, the more is lost for a host of living creatures, including the plants. Create a Pit Stop for Pollinators

Fiona Grahame

Leave a Reply