Trees are an important urban asset providing many benefits: economic, environmental and social.
Restoring our natural systems is often more cost-effective than technological substitutes or building new infrastructure. Major economic benefits come through shading buildings in summer, reducing the need for air conditioning and, in turn, cutting energy costs.
Trees in streets enhance neighbourhood aesthetics and consequently are proven to increase property values. It is estimated that properties in tree-lined streets are valued around 30% higher than those in streets without trees.
Urban forests that provide significant canopy coverage improve the lifespan of certain assets, such as asphalt, by shading them from harmful rays and prolonging their lifespan.
Research suggests that a healthy green city helps alleviate the burden on national health systems. While it is difficult to create a direct link and quantify dollar savings, it is likely that urban forests reduce health costs associated with sedentary behaviour, obesity, and mental illness.
Research has shown that nature can boost the viability of businesses by drawing shoppers into business districts and encouraging them to spend more: US research found that customers prefer shopping in well-tended streets with large trees. The study also found they would pay 9–12% more for goods sold in central business districts with high quality tree canopy, and would travel further.
Established research confirms that the addition of trees and vegetation in the built environment is one of the most effective ways for mitigating the Urban Heat Island effect. Through the natural process of transpiration, trees help reduce day and night time temperatures in cities, especially during summer. Trees provide shade for streets and footpaths and their leaves reflect and absorb sunlight, minimising the heat absorbed by the built environment during the day.
Tree canopies and root systems reduce stormwater flows and nutrient loads that end up in our waterways. Broad tree canopies intercept and mitigate the impact of heavy rainfalls and healthy tree roots help reduce the nitrogen, phosphorus and heavy metal content in stormwater.
The role of urban vegetation is equally vital in ameliorating air pollution and greenhouse gases. Through the process of photosynthesis, trees take up carbon dioxide, nitrous oxides, sulphur dioxide, carbon monoxide and ozone from the atmosphere. They also provide habitat and enhance levels of biodiversity. Urban forests around the world have been shown to support a wide range of species, even endangered animals and other biological species of high conservation value.
During photosynthesis, trees convert carbon dioxide and water into sugar and oxygen and store carbon within their biomass. Consequently urban trees make an impact in absorbing carbon from the atmosphere.
A city's landscape helps define its character in much the same way as architecture or urban design because trees and other vegetation physically define a place. Landscapes are the setting for many everyday recreational opportunities such as organised sport, walking the dog or having a picnic and ultimately help forge a sense of connection to place.
Urban forests and green open space provide the place for major events, festivals and celebrations throughout the city. Events and spaces can bring diverse groups of people together through the provision of a public realm that is available for everyone to enjoy. Green spaces especially play an important role in the integration of minority groups and can assist in the adaptation process of immigrants into their host country.
Well-treed parks, gardens and streets encourage the use of open spaces, which have multiple
flow-on health benefits such as reduction in obesity and improvement in general physical and mental wellbeing. In an era where lifestyle-related illnesses are prevalent and 61% of Australian adults are overweight or obese, (obesity costs Australia's healthcare industry $58 billion in 2008) prevention methods are usually more effective than cures.
Studies have shown that green spaces provide therapy to children, allow creativity of mind, encourage exploration and adventure, promote physical activity, build resilience and enhance experiential learnings.
Skin cancer and other sun exposure illnesses highlight the importance of protection from sunlight's UV rays. Shade alone can reduce overall exposure to UV radiation by up to 75%. Our urban forest provides the best form of natural shade, with broad canopied street and park trees the most effective.
From a public health perspective, the shade provided by large canopied trees during hot summer days helps reduce localised daytime temperatures by up to two degrees Celsius. In major cities on days over 30 degrees Celsius, the risk of heat-related morbidity and mortality for people over 64 years of age and other vulnerable people (the young, and those with pre-existing illnesses) increases significantly. Evidence suggests that buildings with little or no surrounding vegetation are at higher risk of heat-related morbidity.
The availability of, access to, and even the ability to view green spaces and trees has positive effects on people's wellbeing. Many studies have explored the relationships between the amount of green in the landscape and associated levels of wellbeing or depression. In the Netherlands, disease rates, including mental disease, were shown to be of a lower prevalence in areas with higher percentages of green spaces within a 1km radius than those with lower percentages.