The importance of nature
There is increasing recognition that creating a community that is resilient to the impacts of climate change cannot occur without a commitment to maintain, create and repair nature within our cities. This has been noted recently in a report on Why it’s vital to value nature:
Nature loss and climate change are two inter-related issues that compound each other, and they must be addressed together in tandem. To put it simply, we cannot reach net zero and achieve the UN Sustainable Development Goals without halting and reversing nature loss and measurably and visibly moving to a regeneration of the natural environment. Natural ecosystems can become one of our biggest allies in controlling the level of carbon dioxide in the atmosphere, and so limiting global warming (KPMG, 2022).
This is supported by the foundational principle of water sensitive urban design (WSUD) to enhance natural systems and integrate water and vegetation into our urban and built form. This is easily achieved through the creation of urban forests and urban greening in public and private spaces, as noted by Professor Peter Newman, in this video below.
Urban forests
Urban forests have many functions that mitigate and adapt to climate change. Urban forests assist with the management of stormwater and intense events. Leaves and branches intercept rainfall and the microbial activity in the root zone helps maintain soil permeability, which enhances infiltration and the ability to cope with intense rainfall.
Vegetation in the landscape provides cooling and reduces urban heat through evapotranspiration and shade. Trees can lower the Urban Thermal Climate Index by up to 10°C, reducing heat stress from “very strong” to “strong” in a heatwave (Coutts et al, 2013), potentially saving lives.
It is critical that our urban forests are planned to have access to a sustainable source of water, both while establishing but also over their lifetime. This is particularly vital in periods of high heat and low rainfall that occur during the Western Australian summer and autumn seasons. Facilitating passive watering of street trees through kerb breaks is an important WSUD strategy that also reduces local flooding while improving tree growth and long term health (Grey et al, 2019). Irrigation of trees, including passive infiltration with stormwater runoff, can increase canopy cover by up to 80% (Hitchmough,1994). This reduces tree watering and maintenance costs.
Investing in our urban forests also makes financial sense. For every dollar invested annually in tree planting and maintenance in five major cities, there was a return of $1.37-$3.09 based on the benefits of trees (i.e. energy savings, atmospheric CO2 reductions, stormwater runoff reductions, etc.) (McPherson and Muchnick, 2005).
Open space
Access to green space also increases community resilience through improving the physical and mental wellbeing of the community.
An investigation into the relationship between public open space attributes (i.e., quantity and quality) and better mental health (i.e., low risk of psychological distress) in residents of new housing developments in the Perth metropolitan area found that:
- residents of neighbourhoods with high quality public open space had higher odds of low psychosocial distress than residents of neighbourhoods with low quality public open space, irrespective of whether or not they used it. However, the quantity of neighbourhood public open space was not associated with low psychological distress.
- residents near medium or high-quality public open space have twice the odds of better mental health as those near low quality public open space.
- public open space quality appears to be more important for mental health than public open space quantity. Residents may not need to use public open space to benefit from it (Wood et al., 2012).
This demonstrates the importance of open space maintenance and supports investment in this type of community service.
References
Coutts, A.M., Nigel J.T., Beringer, J., Loughnan, M. and Demuzere M., 2013, “Watering our cities: the capacity for water sensitive urban design to support urban cooling and improve human thermal comfort in the Australian context”.
Grey V, Livesley SJ, Fletcher TD and Szota C., 2018. Establishing street trees in stormwater control measures can double tree growth when extended waterlogging is avoided. Landscape and Urban Planning, Vol. 178: 122-129.
Hitchmough J, 1994, Roof gardens and other landscapes involving finite volumes of artificial soils. Urban Landscape Management. Sydney, Inkata Press.
KPMG, 2022, Why it's vital to value Nature: Nature at the heart of decisions.
McPherson and Muchnick, 2005, Effects of street tree shade on asphalt and concrete. Journal of Arboriculture, 31(6): 303-310.
Wood, L., P. Hooper, S. Foster and F. Bull, 2017, "Public green spaces and positive mental health – investigating the relationship between access, quantity and types of parks and mental wellbeing." Health and Place 48: 63-71.