The future of cities

 Can green infrastructure lead the way?

By Michael Casey

As cities continue to grow, so do the challenges of managing urban heat, record-breaking floods, and extreme weather events that are pushing some urban areas toward uninhabitable locations. Addressing these challenges requires a diverse urban toolkit, one that embraces high-tech, low-tech, and even no-tech solutions.

Among these tools, nature-based solutions such as urban green infrastructure stand out as a vital strategy for creating resilient, people-centred cities. Could integrating nature into our urban landscapes be one of the most essential tools for safeguarding our future?

Recently I wrote about the effects of fire on our communities and where green infrastructure solutions such as green roofs and walls may work towards mitigating fire and climatic issues, but now we see more and more evidence highlighting how other forms of nature-based solutions are also helping communities throughout the world.

One of the most significant benefits of Urban Green Infrastructure (UGI) is its ability to reduce the Urban Heat Island (UHI) effect. Cities absorb and retain heat due to concrete, asphalt, and other man-made surfaces. This leads to increased temperatures, making urban areas significantly warmer than surrounding rural areas. UGI helps counteract this by increasing tree canopy cover, which provides shade and lowers surface temperatures. Green roofs and walls also contribute by insulating buildings and reducing heat absorption, while permeable surfaces help in reducing overall heat retention in urban spaces.

Extreme rainfall events are becoming more frequent due to climate change, leading to urban flooding. UGI enhances stormwater management by improving water infiltration through rain gardens, bioswales, and permeable pavements. Vegetation helps reduce runoff, while restored natural waterways and urban wetlands increase the capacity to store and filter excess rainwater, mitigating the risk of floods.

Another critical role of UGI is in improving air quality and supporting carbon sequestration. UGI helps absorb carbon dioxide, thereby reducing greenhouse gas concentrations in the atmosphere. Trees and vegetation also act as natural filters, trapping airborne pollutants such as particulate matter and nitrogen oxides. This contributes to cleaner air and offers significant health benefits for urban populations.

Urbanisation often leads to habitat loss, which endangers local flora and fauna. UGI supports biodiversity by creating green corridors that connect fragmented ecosystems and provide safe habitats for pollinators, birds, and small mammals. This helps maintain ecological balance and enhances soil health, ensuring that urban environments continue to support diverse life forms.

Beyond its environmental advantages, UGI provides substantial economic benefits. Investing in these solutions can lead to economic growth by increasing property values in areas with abundant green spaces. It also attracts businesses and tourism, creating aesthetically appealing environments that enhance the desirability of urban areas. Additionally, it reduces energy costs by offering natural cooling mechanisms, which, in turn, lower the demand for artificial air conditioning and heating. This has a flow-on effect to other benefits.

Access to green spaces improves public health by promoting outdoor activity, reducing stress, and enhancing well-being. Urban greenery also lowers noise pollution, making cities more liveable. Community involvement is key to sustaining urban green infrastructure. Public education, tree planting, and programs like Adopt-a-Park foster ownership and environmental responsibility, ensuring long-term success.

To make this a reality, urban planners, policy makers, communities all need to work together to integrate UGI into city development and to also value the asset. To ensure widespread adoption, cities must implement zoning regulations that mandate the inclusion of green spaces in new developments. Governments should also provide financial incentives for green infrastructure projects, making it easier for private developers to incorporate sustainable solutions into their designs. Public-private partnerships can further accelerate urban greening initiatives, allowing businesses and communities to contribute to the transformation of urban landscapes.

Some of the following examples around the world are proven projects that work towards integrating UGI into our cities with maximum outcomes.

Jakarta, the capital city of Indonesia, is sinking with subsidence rates observed at 25cm a year. This is all due to extracting water from the aquifers that exist under the city, coupled with a very soft soil structure has resulted in the weight of the built city literally sinking into the ground. Imagine a balloon deflating – well this is how the aquifers are responding to the water extraction. And the worst part for the residents of the city is that they are also facing rising sea levels; they now currently sit well under sea level which has made some parts uninhabitable. Blue infrastructure, the network of natural and engineered water-related systems that help manage water resources, enhance climate resilience, and support biodiversity in urban environments, has provided solutions such as artificial reefs to hold back ocean storm surges, but this is such a small contribution. The city is making some great progress with other projects such as the Tebet Eco Park in Jakarta which has successfully revitalised a disused urban green space into a sustainable biodiverse, and community-friendly open space. It features wetlands, pedestrian bridges, recreational areas, and eco-friendly initiatives for public well-being and environmental conservation. It also works at slowing down the river, while allowing for better management of storm water events and recharging the depleted aquifers. The reduced water run off through the existing concrete channel has helped reduce flood waters reaching the main city of Jakarta.

North American cities have been integrating sanitary and stormwater sewage systems for years as aging infrastructure has made it more practical to transport and manage these combined wastewater flows together. The problem with this approach is when heavy rainfalls occur; they often overwhelm the sewage system with flows of untreated sewage reaching beaches and rivers. One way to combat this is through the use of green roofs and Water Sensitive Urban Desing (WSUD) such as rain gardens and bioswales which are all forms of UGI and WSUD solutions that work at capturing and slowing the rain fall before it moves to the storm water infrastructure. Extensive green roofs for instance (which have substrates typically shallower than 180mm) have been proven to reduce total runoff by 60% and detain up to 85% of the first flush in a rain fall event. This water can typically be held for hours before it’s released into the storm water system and by then the main floods may have started to subside. Add in plant materials to your green roof and they then become another measure in retaining rain water in their leaves and stems. These green roof initiatives have reduced polluted water reaching natural waterways and continues to work towards healthy and greener cities.

The Punggol project in Singapore showcases sustainable water management through a network of waterways, reservoirs, and eco-friendly drainage systems. A new design of this suburb meant the existing concrete channels had to be updated to deal with the vast amounts of storm water, all while creating a vibrant greenspace that residents could start to use. The project incorporates rainwater harvesting, wetland filtration, and bioengineering techniques to enhance flood resilience and water quality. Features like Punggol Waterway Park and Sengkang Floating Wetland support biodiversity while naturally filtering and managing stormwater run-off. This has now become a very popular space for Singaporeans to use and has increased property values while creating new jobs in the area.

The City of Joondalup in Western Australia has adopted a proactive Climate Change Strategy focusing on sustainable infrastructure, urban greening, and community resilience. Through its Leafy City Program, nearly 6,300 trees were planted across 12 suburbs, while an additional 10,000 trees were introduced through the Winter Tree Planting Program. These efforts have increased the city’s canopy cover from 9% in 2014 to 12% in 2020, mitigating urban heat and enhancing biodiversity. Other initiatives include water-sensitive urban design, climate-adaptive policies, and community engagement in conservation. By integrating green infrastructure, Joondalup is fostering a climate-resilient, liveable city, setting a benchmark for sustainable urban development in Australia. Positive environmental effects of the initiatives include reduced ambient air temperature and cleaner air through absorption of polluting gases, reduced cooling energy consumption costs and water savings through reduced evaporation rates, increased habitat for wildlife, street appeal, community amenities including safer walking environments and shading, and improved community health and wellbeing.

Urban Green Infrastructure is a powerful tool for mitigating climate change, enhancing biodiversity, and improving urban resilience. By integrating green solutions into city planning, policymakers, urban planners, and communities can create healthier, more sustainable, and climate-resilient cities. The time to act is now, and through collaborative efforts, cities can transform into greener, more liveable environments for future generations.

Michael Casey

Director of Evergreen Infrastructure,

Company Director at the Australasian

Green Infrastructure Network

Advisor, Technical Panel for the

AIPH World Green Cities Awards

E: michael@evergreeninfrastructure.com.au