Barangaroo Reserve is one of Sydney’s most iconic urban forests (Credit: Leigh Staas)
Authors: Samiya Tabassum and Michelle Leishman, 23 Sept 2021
When we think of the words ‘urban forest’, most people immediately think of trees. However, this is not entirely true. Urban forests not only include the trees found in urban landscapes, but also shrubs, groundcovers and the soils that support them. Together, these components make up living ecosystems, much like a natural forest, which in cities can look like urban parks and gardens, streetscapes, and residential gardens.
It is important to have diverse and resilient urban forests because they provide a variety of useful co-benefits. The main types of co-benefits provided by urban forests include, but are not limited to:
Free thermoregulators: Urban forests can decrease the energy needed for heating and cooling by providing shade and cooling in summer and insulation and wind-chill protection in winter. Scientists have found that shading by street trees can reduce daytime temperatures by 5-20°C, combating the urban heat island effect which causes higher temperatures in built up areas (read more details in the ‘Urban Heat Islands… or Archipelagos?‘ blog). In addition to shade, urban forests also provide cooling benefits through a process known as evapotranspiration. This is when the sun’s rays hit a tree’s canopy, causing water to evaporate from the leaves (read more details in the ‘Not all urban green is equally ‘cool’!’ blog). This cools the leaves down – much like how a wet towel on your face cools you down on a hot day – and reduces the surrounding air temperature. The importance of urban forests is becoming increasingly apparent as more and more people living in urban areas succumb to heat related illnesses each summer.
Resources for wildlife: Urban forests can provide habitat, food and landscape connectivity for fauna, with some fauna species actually being more abundant in urban areas than natural vegetation. When natural disasters such as bushfires occur, urban forests can provide much needed refuges for wildlife until they can return to their homes (read more details in the ‘Why is biodiversity important for cities?’ blog).
Reducing carbon pollution: Urban forests remove carbon dioxide from the atmosphere through photosynthesis. This carbon is then used by plants to grow and is essentially locked away, a process known as carbon sequestration. Since carbon dioxide is one of the main gases contributing to climate change, it is vital that we plant and maintain as much area of urban forest as possible.
Providing a breath of fresh air: Urban forests capture and trap harmful airborne pollutants such as dust, ozone, nitrogen oxides, sulphur dioxide and carbon monoxide, making cities a healthier environment for people.
Reducing stormwater runoff: Urban forests reduce the amount of stormwater runoff because leaves and branches physically intercept and ‘store’ water before it gradually evaporates from plant surfaces or percolates through the soil. Urban forests provide permeable surfaces into which water can infiltrate and plants absorb this water through their roots and allow it to return to the atmosphere through evapotranspiration. Urban forests help to lower the amount of pollutants and runoff that enter our creeks and waterways, and reduce the chances of flooding.
Sound proofing: Urban forests can significantly reduce noise from road traffic by acting as a sound buffer between homes and roads.
Social and economic benefits: Urban forests can increase community congeniality, reduce stress, promote physical activity and generally improve wellbeing. In fact, Japanese people regularly partake in a practice known as shinrin-yoku or ‘forest bathing’ in which they mindfully experience forests using all their senses. Studies have even shown that communities with a high level of vegetation have reduced levels of crime. House prices have also been shown to be higher for properties with nearby street trees in several major cities around the world.