Seeing green

Last year saw people across the globe begin regular park walks or picnics in green spaces for safe socialisation and exercise. Roads & Infrastructure investigates the role greenery can play in future infrastructure planning and delivery for social, health and environmental benefit.

A 2019 study, published in Frontiers in Psychology, monitored the levels of the stress hormone – cortisol – from samples taken before and after people spent time in nature.

It found that by spending 20 to 30 minutes in nature, people’s cortisol levels dropped therefore reducing stress.

While this study and others have proved vegetation has benefits for mental well-being, bringing nature into cities may have significant benefits for infrastructure too.

The Greening Australia organisation states trees and other green infrastructure help to reduce the amount of heat being absorbed and released by absorbing sunlight and shading hard surfaces.

It says trees, shrubs and grasses are also natural coolers, they draw soil moisture into their leaves which then evaporates and cools the air.

As a practical example of the benefits of greenery in infrastructure, the Greater Sydney Commission records urban heat as a key performance indicator for wellbeing.

Using NSW Department of Planning, Industry and Environment data it compared the percentage of residents found to have exposure to high urban heat in 2016, in each of Sydney’s six districts, with the percentage of urban tree canopy cover in these areas.

The North District, which had the highest urban tree canopy cover of 40 per cent, had the least number of residents with exposure to high urban heat – at just two per cent of the population.

The next smallest percentage of heat exposure was the South District with 17 per cent of people exposed to high urban heat. The South District also recorded the second highest tree coverage percentage, at 24 per cent.

With train and bus stations, carparks and tramways a key part of infrastructure in many of Australia’s urban and city areas, turning this infrastructure green could have significant benefits for liveability.

Green roof gains

These benefits and possibilities are beginning to be recognised by asset managers and owners in Australia. In October 2020, the Victorian Government announced its first park and ride facility at Bulleen. The bus terminal will feature a green roof, which will include walking and cycling paths, trees and other plants.

Sydney’s One Central Park, a residential building, was recently constructed with greenery covering around 50 per cent of the building’s façade. It also features a motorised heliostat which captures and directs sunlight into its adjacent park in the space where sunlight is blocked by the tower.

With this progression of green building gaining momentum, we spoke to registered landscape architect and Lecturer at UNSW Sydney, Dr. Sara Padgett Kjaersgaard about the benefits that could be realised if public transport infrastructure embraces greenery.

“We know green spaces reduce the urban heat island effect created by asphalt and buildings, so trees are an essential component of reducing heat in our cities,” she says.

“Green spaces can also improve mental health, they give us an opportunity for respite and recreation and they provide multiple opportunities for local biodiversity.”

In 2016, the Australian Bureau of Statistics found 71 per cent of Australians live in major cities, many of these spaces are often covered with hard surfaces such as concrete or asphalt.

“Another major benefit of increasing green infrastructure in our cities is to mitigate damage caused by flooding. Where we have hotter environments or increased storm activity, green spaces and trees help to filter water into the ground and mitigate the impacts of those high storm events,” Padgett Kjaersgaard says.

Green spaces are natural assets and are an important role in the culture of Indigenous Australians, in terms of how they read and connect to Country.

Concept image from the North East Link Project

“Trees and green places are a big part of the repositories of lore and stories about place and the way that place, or the landscape of cities are read and understood in Indigenous culture,” she says.

Many of the missed opportunities to increase green spaces and coverage in our cities and towns are in the delivery of public infrastructure, for example; train stations, footpaths, cycle ways, bus stations and alongside roads.

There are now examples of the inclusion of green infrastructure in policy from around the world. In Copenhagen Denmark, vegetation and soil is a mandatory obligation on roofs with a pitch less than 300. Incentives are also available for refurbishments of older rooftops.

France mandates the inclusion of green roofs for all new commercial buildings. Whilst Toronto Canada, has passed a by-law requiring green roofs on new commercial, institutional and residential developments on buildings that have a gross floor area of 2000 square metres or more.

“These changes are really bold steps forward to reduce heat emittance off those roof surfaces, to effect the microclimate, increase pollinator biodiversity, and to create a more carbon-neutral city,” Padgett Kjaersgaard says.

Putting down the roots in policy

As a Fellow and previous Director of the Board of the Australian Institute of Landscape Architects, Padgett Kjaersgaard and her colleagues penned a submission to Infrastructure Australia in 2015, regarding green infrastructure.

Titled ‘15 year infrastructure plan for Australia’, the submission outlined project and policy recommendations for a National Green Infrastructure Strategy, which advocated for Green Infrastructure to become an national asset class.

It also called for the use of the Sustainable Sites Initiative (SITES) rating system to be applied to all federally funded infrastructure projects.

“If green infrastructure were to become an asset class in its own right, it would be budgeted for, but also then maintained which would filter right down to council level, including the parks and streets,” Padgett Kjaersgaard says.

“This way green structures would have an economic value as any other equipment that needs to be maintained and replaced.”

Implementing green spaces within infrastructure can also provide value for developers, as it now adds to sustainability goals and targets on projects.

“What a national policy might help us do is get green spaces incentivised, so that they become normalised. Then the public will ask, ‘why doesn’t that building have a green roof?’. If it means it captures water, increases pollinator biodiversity or even if it’s a green wall that cools the station while people wait for the train, these ideas all benefit people,” she says.

In regional towns for instance, green spaces can help to provide active transport connections in the form of walking or cycling and can encourage people to visit certain places.

Larger green linkages would also help towards preserving Australia’s 85 eco-regions, of which only 46 were found to meet the International Convention on Biological Diversity (CBD) protection mandate, which Australia has attempted to implement.

In the Journal of Landscape Architecture, landscape architect Simon Kilbane argues, most forms of infrastructure are networks for example power grids, roads, drainage and telecommunications. Yet the idea of large-scale interconnected habitat is not something the public may typically appreciate as ‘essential infra-structure’.

Padgett Kjaersgaard says the Woolgoolga to Ballina Pacific Highway, for which landscape architecture practice Corkery Consulting together with architects Studio Colin Polwarth were commissioned as specialist consultants to coordinate the landscape and urban design for the whole project, is a good example of green infrastructure.

The works have created a section of road infrastructure which has been improved to include green outcomes. The project also collaborated with the traditional custodians of the land to further improve the infrastructure.

Aboriginal participation targets were exceeded with over one million hours worked on the project by Aboriginal employees and 20 nations were represented in the works.

The project also installed 3600 biodiversity offsets and 300 kilometres of fauna fencing. Teams planted 130 hectares of koala food trees and hydromulched 1250 hectares of land, to protect loose soil in the event of floods and ensure the soil encourages plant growth.

“There are great exemplars of green infrastructure across Australia but what we need is a coordinated approach at a national level that would allow big projects to be funded for this asset class,” Padgett Kjaersgaard says.

“It would be great if some of the key green linkages in cities and towns were identified as national priorities in Infrastructure Australia’s ‘Infrastructure Priority List’ and adequately funded. Green spaces – green cycleways, connected green parks and green streets that support the active movement of people and species are fundamental to Australia’s continued prosperity and the health and wellbeing of the community.”

She says after all when you are getting social and environmental outcomes from a project you are going to have a better serving public asset.