Green Infrastructure
As urban development spreads, natural land surfaces are replaced with structures like roads, buildings, and footpaths for the new communities. Unlike natural landscapes that absorb rainfall and evapo-transpirative cooling occurs, surfaces in urban areas absorb more heat and encourage rainfall to run off these surfaces, leaving less moisture in the ground.
Urban areas also trap this absorbed heat due to nonporous and non-reflective surfaces, meaning at night temperatures do not drop significantly, providing limited respite from the daytime heat. In addition to this, urban environments contain other sources of heat, like waste air from air conditioners and vehicle engines. These are then combined with the trapped absorbed heat, making urban areas significantly hotter than less urbanised areas.
This is known as ‘Urban Heat Island effect; the phenomenon that causes cities to become ‘islands of heat’. It intensifies heat waves in cities, increasing air conditioner use, in turn creating a cycle of heat!
Enter Green Infrastructure.
Green Infrastructure is the designed and natural vegetation found in cities and towns such as parks, reserves, wetlands and riparian corridors, gardens, orchards, street trees and newer ‘greening technologies’ like green roofs and walls. Implementing GI into the urban landscape has the potential to cool the urban microclimate by providing shade and evapo-transpirative cooling whilst also reducing heat retention.
By simply increasing tree canopy cover in neighbourhoods, we can achieve healthier communities for both people and wildlife through lower temperatures. NSW Premier Gladys Berejiklian said the government would spend $38.7 million over the next four years on its "Five Million Trees" initiative, as part of its plan to boost Sydney's existing tree canopy from 16% to 40% by 2030, with the first million trees to be plated by 2022.
"That means reduction in temperatures in peak times around five degrees Celsius because we know trees are greater air conditioners. They will cool your home in summer and the deciduous trees keep it warm in winter."
This proposed green infrastructure will not only effectively reduce heat but provide numerous additional health co-benefits such as:
Assist with flood alleviation and management
Improve stormwater quality
Have positive impact on people’s health and wellbeing
Provide habitat and biodiversity benefits
Provide attractive public spaces
Provide opportunities for recreation and leisure
Encourage economic growth and investment
Provide opportunities for urban agriculture or food gardening
Improve mental and physical wellbeing.
Statistically, a 10% increase in tree cover can reduce land surfaces by more than 1˚C and some research from the states found that for every dollar invested in planting trees, cities will see an average of $2.25 return on that investment each year.
What can we do? A great way to be involved is planting and registering trees. We can make our homes and local area a greener, cooler and more beautiful place to live. Just 1 or more small trees will make your home cooler and more private, with improved air quality. Recognise your efforts by registering your tree online.