I am an environmental consultant in Arup’s...
Cities / Building with nature to create sustainable cities
Rapid urbanisation and migration continue to challenge the nature of our planet. In addition, pressures from climate change and flooding mean that cities need to find natural ways to adapt. I believe we need to understand and prioritise Green Infrastructure if we are to design sustainable, densely populated cities.
Green Infrastructure (GI) provides the ‘ingredients’ for solving urban and climatic challenges, by building with nature. GI is defined by the UK communities agency as a ‘network of multifunctional green space, urban and rural, which is capable of delivering a wide range of environmental and quality of life benefits for local communities’. GI is not just conventional open green space but encompasses parks, woodlands, street trees, allotments, private gardens, green roofs and green walls.
GI provides psychological, social and health advantages and a connection to nature, as well as a host of environmental benefits. Future cities will only prosper if they are understood as a complex adaptive system, where the relationship between humans and nature are entwined. However this complex relationship is often insufficiently considered during the design process, leading to negative environmental and social outcomes.
There are many connected GI and human elements to consider with any new built environment project. For example, we know that light regulates seasonal and daily cycles of many plants and animals, and that globally there is a 6% increase in artificial lighting per year. Scientists are now considering the possibility that the direction, brightness and wavelength of urban artificial lighting could lead to growth deformities in plants, with subsequent impacts to reliant animal species.
It has already been shown that climate change is disrupting flower pollination, causing bees to fly before flowers have bloomed and potentially affecting crop yields. It is clear that the dangers of unforeseen impacts on nature are real. Could a similar cycle of disruption resulting from other human influences affect the lifecycle of urban plants and animals?
Some cities are already grappling with these issues pragmatically. For example, two major rivers flow through Philadelphia, but in the last 100 years widespread urbanisation has concretised and restricted these rivers and sewers, increasing impervious surfaces and ultimately increasing stormwater flooding.
The city decided to use GI to restore the area’s natural capacity to capture water, using a multi-pronged strategy that included providing people with free rain barrels and replacing 30% of the city’s tarmac pavements and roads with porous ones. The Philadelphia Water Department also switched to a water metering system to monitor the volume of storm water that properties and businesses produce, subsequently incentivising them to retrofit their sites to include GI so that less water ends up in the sewer system.
However, implementing GI also brings many obstacles. Ownership, cost, maintenance, space and knowledge of the benefits prevent many local authorities from implementing GI. Furthermore, public safety and vandalism can prove to be challenging to overcome in some cases.
Designers and planners need to adopt a holistic way of thinking of these interdependent relationships when considering GI in city development. Additionally, relevant environmental impact data must be kept up to date. There also needs to be sufficient scientific understanding of the needs of various plant species to survive the ongoing impacts of a heavily human-modified landscape.
To improve the way GI is dealt with requires greater awareness of these issues, driven through continued research and public dialogue. Only then will our cities coexist successfully with Green Infrastructure.