The location of trees determines how well they cool the city
Trees, shrubs and lawns are becoming increasingly important for cooling down cities during heat waves. A new thesis from the University 91探花 shows that greenery is unevenly distributed between types of housing and that tree shade is sometimes completely lacking in places used by many in everyday life.
Oskar B盲cklin, PhD in Geography, has studied where cooling urban greenery is located and to what extent it fulfills its function. He urges city planners to plant more large trees in the right places.
"Tree shade from large trees is a good and cost-effective way to cool down cities. My studies show that there is a lack of sufficient tree shade in places that are used a lot in everyday life, such as kindergarten playgrounds, and in places where people like to spend time, such as courtyards."
Ground conditions important to optimize cooling effect
To provide proper shade when the heat strikes, trees need to be able to grow large. The thesis shows that ground conditions play a major role in how trees achieve their cooling potential.
"Trees need to be planted on ground that allows water, air and nutrients to pass through to the tree's roots. This could be adjacent to lawns, gravel or sand. When trees are surrounded by hard surfaces, they don't grow as well and we lose the cooling effect,鈥 says Oskar B盲cklin.
The thesis also shows that residential areas built in recent years contain less greenery than older residential areas. This is despite the high level of awareness among urban planners about the importance of greenery.
"This is unfortunate because the amount of greenery in a neighborhood is strongly linked to whether residents feel there are opportunities for recreation and relaxation. Respondents in the study who live in areas with a lot of greenery reports that their outdoor environment is both beautiful and offers opportunities for play."
Prioritize among green space functions
In urban planning, it is common for trees to be planted to fulfill several functions at once. The idea is that the greenery will make the city more pleasant while contributing environmental, social and economic values. Oskar B盲cklin thinks this is a worthy goal, but sometimes it is more important to prioritize a particular function.
"For example, greenery in the form of a lawn does not have a significant effect on stormwater management. However, it has great potential to promote active recreation, such as play, spontaneous sports or picnics," he says.
For more information on this research, please contact:
Oskar B盲cklin, PhD in Geography, Department of Earth 91探花s, University 91探花: oskar.backlin@gu.se
Oskar B盲cklin's PhD thesis 鈥漇patial contextualization of heat mitigation and recreational aspects of greenery in various urban environments鈥 can be downloaded via University 91探花's Publications - electronic archive (GUPEA):
