Planting Trees in Cities Could Reduce Deaths from Extreme Heat
Sourced from Truthdig
Urban development leads to fewer shaded areas and more heat-absorbing paved surfaces. Cities tend to be warmer than their rural surroundings as a result, a phenomenon known as the urban heat island (UHI) effect. During the summer daytime, cities can be up to 12℃ hotter than rural areas.
UHIs are a major environmental hazard for urban dwellers. Research suggests that for each 1℃ rise in temperature, the risk of death increases by between 1% and 3%. Heat exposure also increases the risk of suffering cardiovascular and respiratory illnesses.
Our research calculated the death rates of urban inhabitants across 93 European cities (57 million people in total) between June and August 2015. We found that 6,700 premature deaths during this period were linked to UHIs.
But the pace of global warming is accelerating and 2 billion to 3 billion people are expected to live in cities by 2050. The health impacts of UHIs will likely worsen in the coming years.
Several strategies exist to protect urban residents from the impacts of heat. These include covering roofs and facades in vegetation (green roofs), decorating them in lighter colours, and replacing paved surfaces with areas of vegetation. Our modelling revealed that one-third (2,644) of UHI deaths in Europe could be prevented by increasing tree canopy cover to 30% in every urban neighbourhood.
Urban tree guidelines
This target was established last year by a study published in the Journal of Forestry Research. Since then it has been adopted by several cities worldwide, including Barcelona (Spain), Bristol (UK), Philadelphia (US), Canberra (Australia) and Seattle (US).
Urban forests regulate a city’s microclimates effectively. Research found that urban forests cooled the average temperature of 601 European cities by 1.1°C and by as much as 2.9°C.
Leafy neighbourhoods are also linked to improved mental and physical health. In California, a 10% increase in neighbourhood tree cover has been associated with a 19% reduction in rates of obesity and type 2 diabetes.
Surrounding greenness, particularly greenness at schools, can be important in the cognitive development of children. Cognitive testing of schoolchildren in Barcelona revealed a 6% better working memory development in children at schools with the highest levels of greenness compared to those at the least-green schools.
From the Living Architecture Monitor
