Field Notes
Why do urban trees grow faster?
Despite (or maybe because of) all the stresses of the built environment, city trees are starting to grow faster than their rural siblings — by up to 20% potentially.
Until recently it was always thought to be the other way round; with rural growth quicker in the more suitable and harmonious surroundings.
But as our urban temperatures increase with the trapped heat island effect, nature as alway seems to adapt with trees and forests reacting to their immediate surroundings and creating beneficial effects. This happens in several ways: firstly increased photosynthesis that leads to greater growth and cooling transpiration.
Secondly, the increase in the growing season allows for a percentage of additional growth.
Thirdly, the increase in that same alchemic photosynthesis that allows trees to exudate more carbohydrates out through their roots to build symbiotic relationships that allow for greater take up of minerals and water.
The more rapid formation of the canopy allows shade but also greater transpiration for the trees and forest floor to keep cool, as well as greater pollution processing and Co2 capture. Trees and ideally dense pockets of forest are still by far the best way to cool the urban environment and counteract the heat island effects we are seeing.
