Natural infrastructure: A clear path towards urban resilience?

Robert McDonald
The Nature Conservancy, USA

There has been an explosion of interest in the idea of “urban resilience”. The Rockefeller Foundation was excited enough about the idea to create the 100 Resilient Cities network, and the World Bank has developed its own methodology to assess urban resilience, to name just two efforts. My own organization has created a global Resilient Cities program, consolidating our various natural infrastructure and biodiversity projects under one conceptual umbrella. The word “resilience” is amazingly flexible, being used for resilience to everything from coastal flooding to terrorism to economic downturns. Like “sustainable development”, “urban resilience” is useful to policymakers because it is so broad as to be all things good to all people.

While I am skeptical as a scientist about a term like “resilience,” I do see one positive thing about the explosion of interest in urban resilience: it focuses society’s attention on solutions. Environmentalists have spent a lot of the last few decades painting maps red, outlining the risks facing humanity and the world’s biodiversity. Thinking about ways to improve resilience inevitably forces us to paint maps green, outlining what solutions work where. For organizations like mine, the main solution we put forward is natural infrastructure, itself an umbrella term for all the different ways natural habitat or semi-natural features can help improve people’s lives: forest cover to prevent erosion from fouling drinking water sources, constructed wetlands to mitigate urban stormwater problems, parks to improve people’s physical and mental well-being, and much more.

I recently finished a book surveying the state of natural infrastructure planning and science for cities (Conservation for Cities: How to Plan & Build Natural Infrastructure). It was amazing to have time to research and catalogue the explosion of science around ecosystem service provision in cities. It’s gratifying to see that the tools are out there, to quantify or value almost any ecosystem service of importance to cities. While much work remains to make these tools usable for practical urban planning efforts, the fundamental science base is beginning to take shape.

The buzz around natural infrastructure and urban resilience has reached such a volume that I am beginning to worry that the idea is being oversold in some cases. Ecologists and engineers need to articulate clearly the limits of natural infrastructure. Just like grey infrastructure, natural infrastructure has a range of conditions in which it operates effectively, and outside of that range it will fail. A good example might be the use of coastal wetlands of other natural habitats to mitigate coastal flooding risk. Wetlands help a lot for everyday storms, attenuating wave energy and preventing erosion. But in big storms like hurricanes the storm surge overtops wetlands, and they play only a marginal role in attenuating wave energy.

Don’t get me wrong, I am a true believer in the power of natural infrastructure to help urban residents. Most of my professional life now is providing science support to the more than 30 cities where The Nature Conservancy has natural infrastructure programs. I just believe that for natural infrastructure to be taken seriously as a tool that can help cities achieve urban resilience, ecologists need to be able to honestly state what the tool can and cannot do.

(ALL RIGHTS, ALL USES) Robert McDonald, Ph.D.; Vanguard Scientist with The Nature Conservancy, based at the Conservancy's Worldwide Office in Arlington, Virginia. PHOTO CREDIT: Mark Godfrey © The Nature Conservancy
Dr. Robert McDonald is Senior Scientist for Urban Sustainability at The Nature Conservancy.

Header Image: High Line Park, New York, USA  Credit: Mark Watkins

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