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The greening of cities: Integrating nature into urban design

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By 2050, 68% of the world’s population will live in urban areas. That’s according to a United Nations report released in 2018. The population of our cities will have grown by 2.5 billion, the report predicts, and the majority of countries will have more than 50% of their population city-based. Barring the no-longer-entirely-inconceivable scenario of some cataclysmic event triggering a planetary-scale back-to-the-land movement in the interim, this is the future for which policymakers should be preparing.

Conversations about livable cities often revolve around issues like optimizing buildings for energy efficiency, enhancing public transit, creating walkable neighborhoods and de-clogging our streets of fossil fuel-powered vehicles. And we absolutely should be talking about all of those things. But the prospect of urbanization on the scale the UN predicts means that these advances must be embedded in a more fundamental recalibration of how we think about the relationship between the built environment and the natural one.

Recent decades have given us a taste of the kind of blowback we can expect if we continue to replace nature with concrete at our current pace. From biodiversity loss to the spread of pandemics, the consequences of our misguided belief that human beings are somehow above and separate from the natural world are excruciatingly plain to see. To ensure that an urbanized future is a livable one, instead of trying to dominate and detach ourselves from nature we are going to need to start designing the places we live with nature as their central feature.

The natural features already in our cities do more for us than most of us probably appreciate. Take street trees, for example. In the Colorado city of Boulder, 650,000 urban trees sequester 18,709 tons of carbon; absorb 139 tons of air pollutants, including carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide and particulate matter; and reduce stormwater runoff volume by approximately 422 million gallons. Tree shade reduces annual average cooling costs by 22% per household, equating to a citywide annual savings of $1.65 million. Nationwide, one study estimates that urban trees provide heat-reduction services, in the form of reduced health impacts and energy consumption, worth between $5.3 billion and $12.1 billion every year. A 2017 report from the Texas Trees Foundation found that planting trees in the hottest areas with high-density residential buildings reduced heat-related deaths by more than 20%.

Another example is so-called “green stormwater infrastructure” (GSI) – of which urban trees are a key component. An increasingly common feature in American cities, GSI uses plants, soil and natural drainage to capture and cleanse rain where it falls. Rain gardens, green roofs and permeable pavement, for example, can remove pollutants from rainwater and allow the water to soak into the soil, evaporate into the air, or be held temporarily to reduce flooding.

But the importance of nature to the cities of the future extends way beyond its functional utility. A fundamental need to connect with the natural world is something hardwired into us as human beings, and a growing body of science shows that experiences of nature benefit our health and wellbeing in numerous ways. Time spent in natural environments is now known to boost our mental and physical health; improve cognitive performance, attention, memory and creativity; reduce depression; improve sleep; lower stress and generally enhance our overall happiness and wellbeing. There’s even evidence that living close to green spaces can help us live longer.

To put it another way, when we are deprived of nature, our health – both mental and physical – suffers. Which is why, as we march towards a future of concrete and asphalt, the task of forging the right relationship between nature and cities is essential to ensure the wellbeing of these cities’ inhabitants.

Often the way policymakers and developers have responded to urban population growth is by replacing green space with high-density development. Density done right is certainly necessary – we’re all going to have to live closer together and closer to the things we need, especially since radically reducing our reliance on cars to get around is an urgent climate imperative. But doing it right means using land in ways that reduce our encroachments on the natural world, especially on the urban periphery, and preserving plentiful green spaces. Often this hasn’t happened, and indeed much of the green space lost to development to accommodate urban population growth has been lost to the roads and parking lots we’ve built to serve the influx of cars that comes with the influx of people.

Ensuring that increased density doesn’t come at the expense of green space is also going to necessitate a wider effort to incorporate nature into urban design. Cities across the world have already done so in a wide variety of ways, from parks and connected networks of urban greenspace to green roofs, green walls and roadside gardens. The growing movement of architects and designers in the emerging field of biophilic urban design have shown us what our cities could look like if we were to take this to scale.

This can only happen, however, when policymakers start treating nature as the essential infrastructure it is – and invest accordingly. This shouldn’t be such a tall order: after all, natural infrastructure often makes good economic sense, augmenting or replacing artificial infrastructure in cost-effective and environmentally beneficial ways that deliver lasting returns. But we have a long way to go to clear away the financial, institutional and attitudinal barriers that keep us from taking advantage of it. To build sustainable and happy cities, we can’t afford to wait.

Image via Piqsels