Prioritize solutions that use the power of functioning ecosystems as infrastructure to provide natural services to benefit society and the environment; consider nature-based replacements for grey infrastructure.
🍏 Edible green infrastructures
Biodiversity is fundamental to maintain the variety of crops and livestock needed to support and preserve ecosystem services that sustain our food system and wellbeing. As cities densify and expand in size, they typically encroach on surrounding biodiverse areas, leading to the progressive degradation of ecosystem services. In turn, this pushes away urban food systems that are dependent on material inputs often sourced outside the urban region.
Edible green infrastructures are solutions that reimagine cities as productive sources of food, can boost local biodiversity as well as foster social cohesion. These infrastructures can take a variety of forms and are inspired by nature, for example, planting edible trees and plants throughout a city which are free to pick for residents.
Local governments can promote investments in edible green infrastructures (strategically planned multi-scale networks of different kinds of urban green and blue spaces) to create new biodiverse and productive spaces within the urban region, as well as rehabilitating polluted lands to improve soil health and productivity. Urban and spatial planning can also be used to permit these infrastructures, as well as enable residents to create their own. What is more, such solutions can be integrated within urban planning projects, for example, rain gardens and rain barrels, to reduce urban stormwater runoff and risk of floodings while redirecting and reusing urban rain and stormwater to supply urban farmers.
💧 Blue and green infrastructure for sustainable urban drainage
Cities worldwide are facing significant water-related challenges, including urban water runoffs, flooding, reduced water quality and severe water scarcity—exacerbated by rapid urbanisation and more frequent extreme weather events. On top of this, urban water runoff continues to be a major cause of water pollution in urban areas, carrying trash, bacteria, and other pollutants through gutters and stormwater systems into local waterways, typically without treatment.
City governments can pursue a “sponge city” approach by redesigning the urban fabric and integrating blue and green infrastructure (BGI) (e.g. rain gardens, permeable pavements, storage ponds, etc.) along traditional grey infrastructure (e.g. pipe networks, storage tanks, flood walls). This can help to absorb, store, filter and purify these water flows, in turn replenishing aquifers, reducing the need for expanding grey water management and minimising flood risk, while also reducing the heat island effect.
Cities can do so by, for example, integrating requirements for BGI into municipal urban planning rules for newly built up areas of city districts, industrial parks and development zones, and integrating sponge city building requirements into municipal urban planning rules. Then, local governments could also strengthen collaboration between all relevant stakeholders—from real estate developers to engineers, to water-utility organisations—to identify locally relevant opportunities for sponge cities.
🏢💧⚡ Nature-based solutions for the urban built environment
At the same time that global biodiversity loss has accelerated, humanity has become an urbanised species. And the trend towards urban living is set to continue: 80% of the world’s population will live in cities by 2050—by then, the equivalent to 9 billion people. Urban development has often progressed without regard to the ecosystems of which they are a part. Now the mass of human-made things, from pavements to apartments to phones, outweighs all natural biomass, such as our oceans, trees and animals.
Building with, as opposed to over, nature has long been perceived as more of a burden than an opportunity, but this is rapidly changing. Examples of Nature-Based Solutions (NBS) in cities span from simple concepts—permeable pavements to reduce flood risks or green roofs to improve biodiversity and energy efficiency—to practical actions, such a city manager installing trees and grass along steep slopes to prevent landslides, or an urban planner protecting or restoring a nearby forest or wetland that is crucial to the city’s water supply and quality. NBS can also be seen as an effective element to prevent the heat island effect and consequently reducing energy demand. NBS that follow the circularity concept, for example by recycling nutrients, are enablers of the circular transition and can be used as tools to build new resilient, circular urban ecosystems. Conversely, the circular economy creates favourable conditions to attract more investments for NBS scaling up.
Cities can promote these solutions by developing heat-deflecting green infrastructure on buildings and in public spaces, prioritising their development on top of existing or new grey infrastructure, such as a park on top of a parking garage, or an urban garden on top of a school. Cities can also subsidise projects and technologies at both a commercial and household level, including nature-based solutions in their climate and energy plans, as well as increasing awareness of the issue and the available solutions.