“The planet’s health depends on how cities evolve.” This is a core message of this in-press article by Pincetl on cities in the age of the Anthropocene. Urbanization plays a somewhat paradoxical role in the planetary transformations that we’ve come to (nearly) embrace as encompassing the Anthropocene, because whereas cities are focal points for these processes, they also offer the potential to mitigate anthropogenic environmental change. How will this contradiction play out?Industrialization—powered by fossil fuels—greatly accelerated urbanization. Fossils fuels enabled enormous shifts in agricultural practices, and thus mass migrations to cities, creating a positive feedback in the process. The resultant “urban metabolism” exacts an enormous environmental [and social] toll that permeates well beyond the land area encompassing any given city. Pincetl points out that, whereas cities take up only 2% of Earth’s land surface, they consume 75% of Earth’s resources. And the two critical resources enabling urban development and growth are water— the most basic ingredient to sustaining life in any known form, and oil (or gas or coal)—the fossil fuel(s) that unlocked an energy density previously unknown. In this sense, the megacities of today emerged out of the miscibility of oil and water.

But these ingredients, as well as so many of the other resources that enable cities to grow, must be extracted from their hinterlands, and stories abound of the impacts that urban metabolisms impose on far-flung regions.

Consider the example of Los Angeles—the improbable locus of the largest metropolitan area in the US. Improbable because it is a certifiable desert, and really does not possess water sufficient to sustain its enormous population. LA’s path to becoming the population and finance hub of the West Coast, and one of the globe’s megacities links to the career of William Mulholland, the civil engineer who spearheaded the infrastructural plan that brought water to LA from distant mountains. The LA aqueduct, completed over a century ago, ferries water that originates in the Eastern Sierra and flows into the Owens Valley, and channels it downhill nearly 240 miles to the LA metro. This massive transfer of resources ultimately transformed the Owens Valley and Owens Lake into a desert, fueling the bitterness of the early 20th-century California Water Wars. This was memorably, if not completely accurately depicted in the film Chinatown; it is recounted more soberly in the National Geographic documentary, Water & Power: A California Heist.

Photo by author

Pincetl cites an analogous example occurring in China—the South-to-North water transfer megaproject that brings water from the Yangtze River in the humid south to the more arid north, with Beijing as a primary recipient, and for the hinterlands, vast uncertainty regarding their long-term sustainability. Contrast this model with that of groundwater mining for the Chinese city of Xi’an, and analogous cities sited where surface water remains insufficient. The famous terra cotta army hails from Xi’an, discovered by a farmer digging a water well. Today, Xi’an is gaining infamy as the site of major land subsidence and earth fissuring (Peng et al., 2016)—urban hazards that embody the externalities resulting from intense over-exploitation of groundwater driven by rapid economic development. In this case, the city of Xi’an itself bears the burden of its own gluttonous metabolism.

Although water forms our most fundamental need, cheap, transportable, and high-density energy enabled development of the megacities of the late 19th, and the 20th and 21st centuries, and that energy derived predominantly from fossil fuels. Prior to the age of petroleum, coal formed the fossil fuel of choice, and entire mountains of the hinterlands were consumed in the processes of industrialization and urbanization. With the addition of petroleum, the exploitation of fossil fuels has now imposed an externality that extends well beyond the hinterlands— to the very atmosphere enveloping the planet. So, unsurprisingly, urban metabolism plays a significant role in climate change.

Haze over Los Angeles; photo by author

Most city governments recognize this, and have taken steps toward programs intended to curb emissions or move toward greater sustainability. But Pincetl argues that such programs will fail where neoliberalism prevails. As income inequality grows, the poor will continue to bear a disproportionate brunt of negative climate outcomes. Thus she calls for greater efforts to quantify urban metabolism, to enable adequate policy responses for mitigating the voracious and unsustainable appetites of cities by better revealing how the human system links to the Earth system.

The current scale of disruption of Earth systems imposed by cities’ unfettered metabolism, largely enabled by fossil fuel, cannot continue apace. Pincetl argues for a major evolution in our approach—away from growth and GDP as models, because systems predicated on consumption will ultimately disrupt the planetary systems on which we depend. That evolution might involve relying on the recycling of “embedded” materials already mined from the hinterlands; reimagining the economic and social models of what it means to live well in harmony with the Earth system; a new ethics of what constitutes enough; and ultimately, a true accounting of urban metabolism and the feedbacks between human and Earth systems.

Preparing for any journey requires realistic estimates of the materials needed to sustain the metabolism for the journey’s duration. Pincetl’s argument centers on a simple recognition: of the unsustainability—and social inequality—of continuing to mine these materials from the finite hinterland of Earth. She urges quantification of this recognition in order to guide our journey towards a future where cities can “be organized for human well-being.”