Tree planting may reduce premature deaths in European cities

    WORLD  03 February 2023 - 03:05

    The Conversation academic journal has published an article arguing that planting trees in urban areas can reduce the impacts of urban heat islands on human health. Caliber.Az reprints the article.

    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 per cent and 3 per cent. 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 2–3 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 per cent in every urban neighbourhood.

    A graphic showing why urban areas are hotter than nearby rural areas.

    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 per cent increase in neighbourhood tree cover has been associated with a 19 per cent 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 per cent better working memory development in children at schools with the highest levels of greenness compared to those at the least-green schools.

    More trees means less heat

    We found substantial variation in UHI death rates across European cities. In 2015, Gothenburg in Sweden recorded no premature UHI deaths, while urban heat was responsible for 32 premature deaths per 100,000 people in the Romanian city Cluj-Napoca.

    The cities with the highest UHI death rates were in southern and eastern Europe. Most of these cities generally had low tree coverage and recorded the highest UHI effect.

    Just 3.3 per cent of Thessaloniki in Greece is covered by trees, resulting in urban temperatures 2.8℃ higher than the surrounding area. By contrast, 27 per cent of Gothenburg is covered by trees, delivering an UHI effect of just 0.4℃.

    Overall, southern European cities will benefit most from increasing their tree cover. Our model estimates that Barcelona could reduce its UHI death rate by 60 per cent by meeting the 30 per cent tree coverage target.

    A street view of Gothenburg with trees lining the road and colourful buildings in the background.

    The way forward

    But the intensity of the UHI effect depends on multiple factors and is specific to each city. While vegetation cover influences urban temperatures during the day, nighttime temperatures are driven by the height of the urban canyon.

    The cooling capacity of a tree canopy also varies. This depends on the type and size of trees, which are themselves contingent on the city’s natural climate and the degree to which trees are maintained.

    Drier climates, like Thessaloniki, favour smaller trees that have fewer leaves. By contrast, Gothenburg’s cooler and wetter climate favours larger and leafier trees that provide better protection from daytime heat.

    Due to this variation, we built a tool called the Cooling Efforts Index. The index assesses how much cooling can be achieved in each city for every 1 per cent increase in tree cover. We also generated high-resolution maps for each city to identify the areas where tree coverage is needed most urgently.

    In some cities, the majority of urban forests will grow on private land. Tree planting programmes must therefore encourage residents to plant trees.

    In Victoria, a city on Canada’s western coast, neighbourhoods are offered a CAD$1,000 (£610) grant to plant residential trees. So far, over 78 trees have been planted on private property across the city.

    Space can also be a major constraint in compact urban areas. So increasing tree cover to 30 per cent may be challenging for some European cities.

    But each city can adapt this target to its local context. For example, a lower tree canopy target can be combined with alternative measures like green roofs in compact urban areas.

    Terrace roofs account for 67 per cent of Barcelona’s roof surface area. As the city’s urban population continues to rise, the city council has launched a guide to transform roofs into areas with partial or total plant cover. The guide sets out the social and environmental benefits of green roofs and offers advice for choosing the right kind of terrace roof for the building.

    View from the rooftop terrace overlooking Barcelona's skyline.

    Incorporating urban green infrastructure into cities should make them more resilient to climate change. But planting trees may not be enough. Tree growth is a long processes and around half of newly-planted trees die within two years. Preserving existing trees and complementing tree planting schemes with other measures that reduce the intensity of UHIs, such as reducing car use, are similarly important.

    Urban trees provide substantial public health and environmental benefits. Our study suggests that by increasing tree coverage, premature UHI deaths in European cities can be reduced. But for the resilience of cities to increase, it remains important to combine greater tree coverage with other urban green infrastructure.


    Subscribe to our Telegram channel

Read also

AUKUS plans on nuclear submarines can trigger another arms race, says Beijing

30 March 2023 - 15:44

ICJ to rule Iran's claim on assets frozen by US

30 March 2023 - 14:42

US Senate favors ending COVID-19 national emergency

30 March 2023 - 15:24

Pakistan militants kill four police officers

30 March 2023 - 13:31

New artillery round shoots farther than some missiles, can hit moving targets

30 March 2023 - 13:55

China willing to work with Russian military on several fronts - defence ministry

30 March 2023 - 13:35
Latest news

    Kazakhtsan's PM renews tenure upon president's appointment

    30 March 2023 - 15:51

    AUKUS plans on nuclear submarines can trigger another arms race, says Beijing

    30 March 2023 - 15:44

    Number of travellers from Azerbaijan to foreign countries increases

    30 March 2023 - 15:31

    US Senate favors ending COVID-19 national emergency

    30 March 2023 - 15:24

    Iranian aggression continues unabated

    Azerbaijan-Israel-Türkiye bloc might make Iran think twice before attacks

    30 March 2023 - 15:17

    Azerbaijani MFA accuses Armenian PM of manipulative remarks


    30 March 2023 - 15:10

    Azerbaijani FM meets with his Palestinian colleague

    30 March 2023 - 15:02

    Spanish embassy may open in Azerbaijan

    30 March 2023 - 14:55

    ICJ to rule Iran's claim on assets frozen by US

    30 March 2023 - 14:42

    Pashinyan calls European Council's Michel to discuss regional peace

    30 March 2023 - 14:36

    Azerbaijani FM informs Israeli president on Armenia's continuous non-peaceful actions

    30 March 2023 - 14:30

    "Israel has no coalition against Iran, acting alone is madness"

    Interview with Israeli journalist

    30 March 2023 - 14:30

    Israeli president congratulates Azerbaijani FM on embassy's opening in Tel Aviv

    30 March 2023 - 14:23

    Azerbaijani, Japanese top officials discuss post-conflict situation in South Caucasus

    30 March 2023 - 14:16

    General Milley: US won't be able to stop Chinese nuclear development

    30 March 2023 - 14:10

    Top US general says Russians facing heavy losses in Bakhmut

    30 March 2023 - 14:02

    New artillery round shoots farther than some missiles, can hit moving targets

    30 March 2023 - 13:55

    Russia detains WSJ journalist on spying allegations

    30 March 2023 - 13:47

    Armenia refrains from supporting clause on Ukraine in "Summit for Democracy" declaration

    30 March 2023 - 13:41

    China willing to work with Russian military on several fronts - defence ministry

    30 March 2023 - 13:35

    Pakistan militants kill four police officers

    30 March 2023 - 13:31

    China, Brazil sign deal to use own currencies for trade instead of dollar

    30 March 2023 - 13:17

    Armenia, Czech Republic to boost military-technical cooperation

    30 March 2023 - 13:11

    Ukraine strikes Russian-held city as talk of counterattack grows

    30 March 2023 - 12:58

    Resettled Azerbaijanis in liberated Talysh village involved in employment programmes

    30 March 2023 - 12:51

    ISW: Russia relying on Iran for military, technological support in Ukraine

    30 March 2023 - 12:45

    Azerbaijan Central Bank tries to extinguish flames of inflation

    Review by Caliber.Az

    30 March 2023 - 12:43

    Russian military base in Armenia holds training with MiG-29 jets

    30 March 2023 - 12:39

    US to allocate $9.5 billion for deomocracy support globally by 2024

    30 March 2023 - 12:32

    Azerbaijan, major Hungarian company sign investment deal

    30 March 2023 - 12:31

    Azerbaijani notaries to accept foreign official documents without legalization

    30 March 2023 - 12:20

    Pope's deteriorated health condition cancels his appointments

    30 March 2023 - 12:19

    What's behind India's strategic neutrality on Russia's invasion of Ukraine

    30 March 2023 - 12:13

    US Senate supports annulment of outdated Iraq war authorisations

    30 March 2023 - 12:07

    Azerbaijan initiates criminal case into deportation of Azerbaijanis from modern-day Armenia

    30 March 2023 - 12:00

    Azerbaijani Air Force conduct complex aerobatics, combat maneuvering


    30 March 2023 - 11:52

    Japan allocates $470 million aid package to Ukraine

    30 March 2023 - 11:52

    Why Saudi Arabia is following Iran to join China and Russia's security bloc

    Analysis by Newsweek

    30 March 2023 - 11:45

    Ukraine confirms "partial success" of Russian troops in Bakhmut

    30 March 2023 - 11:40

    UK intelligence: Kremlin preparing to mobilize 400,000 soldiers under guise of “volunteers”

    30 March 2023 - 11:33

    Russian peacekeeping vehicles face no obstacle on Lachin road

    30 March 2023 - 11:26

    Orthodox monks in Kyiv refuse eviction

    30 March 2023 - 11:19

    Western Azerbaijan Community accuses EU's Armenia mission's head of slander

    30 March 2023 - 11:14

    Taiwan’s president lands in US amid threats from China

    30 March 2023 - 11:07

    VP Kamala Harris holds back tears during visit to African slave fort

    30 March 2023 - 11:02

All news