Urban trees and parks are a key part of the urban grid and landscape, but few are aware of the impact they can have on a city’s air quality.
Green areas, usually called urban forests, can lower air pollution, improve air temperatures, facilitate stormwater management, absorb greenhouse gas (carbon dioxide) emissions. The benefits derived depend on the relative sizes of the green area and the grey area.
Air temperatures in parks and green areas are lower than in surrounding areas, sometimes as much as 7°C cooler than in surrounding urban areas. This decrease in temperature is crucial in countering the effects of global climate change caused by urbanisation.
By reducing air temperature, energy use and the air pollution generated by cooling systems in buildings are also reduced. Trees and vegetation also absorb pollutants, reducing the amount of carbon dioxide gas in the air.
Trees on streets and in parks are not only capable of reducing air temperature and pollution, but their leaves can also absorb 95 per cent of UV radiation, which helps human health.
Though Australian cities are well known for their large parks and public gardens, the same cannot be said about urban trees as their future seems uncertain. Most of the tree population in urban centres is aged and represents a potential danger for pedestrians, vehicles and buildings. Pressure from insurers and high removal and replacement costs are combining to make street trees all but extinct.
Government assistance is essential to embracing the concept of urban forests to secure the future of street trees and promote sustainable living in Australian cities.
In February, the City of Sydney adopted a new Urban Forest Strategy, launched by Lord Mayor Clover Moore. The strategy’s goal is to provide a healthy and diverse landscape in streets and public areas, improving the environment and lifestyle of each citizen.
Sydney has committed to maintaining and protecting its existing trees and to increase the actual average total canopy cover over the land from 15.5 per cent to 23.25 per cent by 2030 through tree planting and maintenance programs along streets, in public parks and on private properties.