What if our cities were more like forests?

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Imagine walking through an ancient broadleaf forest. Did you ever think of it as a system? Above your head, trees reach for the sun, harnessing solar energy. Beneath your feet, the ground teems with unseen fungal networks, breaking down forest floor debris. Everything is interconnected. Nothing is wasted.

What if our future cities could mimic these natural structures and systems? Would they be better, more resilient places?

The grand twin challenge; rapid urbanisation and climate change

Cities across the world face two key challenges; rising populations and climate change.

The UN estimates that 55% of the global population already lives in urban areas and that figure is projected to rise to 68% by 2050. At the same time, cities are experiencing more frequent and extreme weather events, including flooding, and heat waves. Coastal cities at the sharp end of these effects and yet the urban extent in low lying coastal areas is increasing faster than in other regions.

Furthermore, the coronavirus pandemic has demonstrated cities’ vulnerability to epidemics, while heightening awareness of our need to connect with nature in urban spaces for the sake of our mental and physical health.

Forests: the ultimate blueprint for city planning?

In contrast to cities, forests have evolved slowly, over many thousands, even millions, of years, to become highly resilient ecosystems. These systems have developed efficient processes for heating, cooling, and managing resources from waste to food. Each layer of the forest offers valuable insights into how a largely vertical environment creates a thriving ecosystem.

The forest ground: Soil. The foundation of the forest’s ecosystem, soil filters water, and provides and stores essential nutrients for a myriad of life forms. It helps regulate surface temperatures, as well as capturing carbon dioxide.

Imagine what our cities would be like if we could ground them in soil? Permeable, soil-based ground in our cities could reduce stormwater pollution, mitigate flooding, and reduce the urban heat island effect. De-paving also increases the amount of land available for habitat restoration, and urban farming, providing us with beauty and greater connections to the natural world.

Exemplar projects like Copenhagen’s Courtyard of the Future, where WSP acted as consultant engineer, show how sustainable drainage systems (SuDS), such as swales and rain gardens, can enhance our urban environment as well as boosting city resilience.

Forest ground: Mycelial networks. Mycelium are the tiny thread-like hyphae or ‘roots’ of larger fungal organisms that wrap around tree roots. These threads create a vast mycorrhizal network, which connects individual plants together and is able to transfer water, nitrogen, carbon and other minerals.

Understanding how these relatively simple organisms have created such an effective, highly adaptive transport network could inform the design of our communication, transport and energy networks of the future.

Trees. Supporting a variety of plants, from lichens to epiphytes, trees provide shelter and habitat not only in life but death; a vivid illustration of the regenerative qualities of the forest. In a woodland, a fallen tree is an opportunity for new ground cover plants to grow and new habitats.

Like trees, buildings are vertical structures and likewise provide shelter, but beyond this point the comparison falters. But what if buildings were designed to be ‘alive’? Imagine a building, enmeshed in its landscape, that harvested the energy of the sun, sequesters carbon and makes oxygen.

Imagine too if cities could mimic the life cycle of a tree, providing opportunities in ‘death’. A vacant site has the potential for ‘meanwhile’ uses, while its materials too have value, for example, as construction materials for new developments elsewhere.

Forest canopy. As the highest layer of the forest, the canopy includes most of the interface between leaf and light making it the area of greatest energy input into the forest ecosystem. ‘Green’ roofs are the canopies of our cities.

In Sweden, WSP is exploring the full potential of unutilised urban roofs for economic, ecological and social gains by using the GIS-based tool Solkartan (the Sun Map). The multi-dimensional data that this powerful tool produces can help assess a roof’s potential as a green space.

Given that the vast majority of the buildings we will use in 2050 already exist, or are in planning, the scope for green roofs to help decarbonise our stock as a retrofitted measure is immense.

Resilient cities: The future

Nature based solutions should be an important part of our cities’ future and offer a multitude of benefits, not least improving health outcomes for urban communities. We are used to thinking of a city as the antithesis of a natural environment like a forest. But we are a part of nature and can only benefit from cities that are more in step with natural systems.

Imagine if a walk through your home city was more like a walk through a forest; where you experienced cleaner air and a greater diversity of life; where everything was connected and nothing was wasted. Wouldn’t delivering this reality make for a better future for us all, and our planet?

Ludo Pittie is a Director and Head of Landscape & Urban Design at WSP UK 

Feature Image Source: WSP UK

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