Urban bushland has health benefits beyond being a great place to go for a walk. It filters our air and water, helps cities avoid extremes in temperatures, and is linked to lower rates of chronic disease.
But these and other health benefits are virtually never accounted for in local and state land development processes.
Urban planners need to consider these health benefits when making decisions about the future of our cities.
What do we mean by urban bushland?
Urban bushland ranges from a bush park of native trees, to wetlands – in fact any native vegetation characteristic of the local region. With its undisturbed soils and associated wildlife, urban bushland is more diverse than other types of green spaces in our cities, like parks. So it adds significantly to neighbourhood biodiversity.
The more unfragmented the landscape, or unaltered the bushland, the more likely it will be to retain its biodiversity. Hills, watercourses and gullies, or a mixed forest, have greater biodiversity than flat land or a plantation of trees. Landscapes that change by the season add to that diversity.
The health benefits of green spaces (and urban bushland) partly comes from this biodiversity.
In cities, health benefits work at two levels. Not only do local residents receive health benefits when they use urban green spaces, the wider urban population also feels the health effects.
The closer residents live to green space, particularly if it is accessible or usable, the better they report their health.
For an individual, access to green spaces contributes in multiple ways: it reduces stress, it helps us recover from illness or injury, and our thinking abilities improve when we are more contemplative and mindful of our green surroundings.
The quality of green spaces plays a role in the health benefits for locals. For example, views of diverse vegetation more effectively lowers stress compared with less-diverse vegetation.
Exposure to biodiversity from the air, water, soils, vegetation, wildlife and landscape, and all the microbes associated with them (the sort retained in uncleared bushland and wetlands) enhances our immunity. This is thought to be the key to the health benefits of nature.
Wealth and health
The relationship between health benefits and living close to urban green spaces, including urban bushland, might be interpreted as being an effect of wealth. We know wealthier people tend to live in greener suburbs and wealthier people tend to be healthier.
But many studies take wealth into account, with the weight of evidence suggesting a direct health benefit from exposure to biodiversity.
So if the health benefits are due to the urban green spaces itself (and not related to wealth), they should be spread more evenly across the population.
Perhaps the health of poorer city dwellers will improve by living near to diverse green spaces, like bushland. Failing to provide access to nature entrenches health inequalities.
Urban bushland provides health benefits not just for local residents but for the whole city.
Forests and woodlands clean our urban air by removing particles and absorbing carbon dioxide. This reduces premature death, acute respiratory symptoms and asthma exacerbation across the city.
A recent review highlights the host of physical health problems that are reduced in urban areas with more nature, including less heart disease, obesity and diabetes. Mental health is also improved in urban areas where people are living with more green space.Author provided
Urban bushland improves city water. Wetlands and the vegetation around them clean our water by filtering, reducing exposure to pollutants carried in groundwater or surface water run-off.
Vegetation also moderates extremes of temperature providing shade when it is hot and less exposure when it’s cold and so reduces heat- or cold-related illnesses.
Shrinking urban bushland
Where new suburbs are developed on the outskirts of cities, the end result is usually near-complete clearing. Urban bushland is replaced with smaller, fragmented, more sanitised, open and neat spaces.
These are designed for a narrower (but still important) set of usable attributes, like a bike path, lawns and a playground. But the original values of the bushland are lost. This pattern is repeated in the expanding suburbs of cities across Australia.
If some urban bushland, wetlands or other landscape assets have been retained, the pressure on them from development is relentless, as seen recently in Western Australia where a highway is due to be extended through the Beeliar Wetlands.
Planning for better planning
Planning processes need to use ways to assess what we might lose and what we might gain from clearing bushland.
This could involve asking what types of services existing bushland provide for local residents and the city in general. These will include their role in providing clean air and water, controlling floods, cycling nutrients, as well as their recreational or spiritual services.
These could be compared with services the proposed development offers. The comparison should make decision makers, and more importantly the public, better able to judge the true worth or cost of a development.
Such cost-benefit analyses are usually used somewhere in planning processes but rarely, if ever, are the values of biodiversity and ecosystem services considered, or the cost savings from health benefits of bushland.
These sorts of cost-benefit analyses can also be used to account for the health effects associated with local bushland. Such health assessments (or health impact assessments) need to be more widely used. And where land subdivision, road building and suburban housing developments are planned, health assessments may need to be compulsory to better account for the contribution of urban bushland to health.
See also tomorrow’s article on green spaces in our cities
Pierre Horwitz holds (uncompensated) positions with the journals EcoHealth and BioScience. He is a member of The Beeliar Group, Professors for Environmental Responsibility.
Carmen Lawrence is president of the Conservation Council of Western Australia.
Alison Reid does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.
Authors: Pierre Horwitz, Professor, School of Science, Edith Cowan University