As more cities send vital roots underground, we create a world that is inadvertently preparing itself for a radiation emergency. The more we make the subsurface livable, the more likely it is that humans will survive to see the next several millennia.
In this description of underground cities, we’ve considered city designs that would make us comfortable living underground, and we’ve learned that our worst enemy underground will be seeping water. But we’ve danced around the real issue we’ll confront in our radiation-proof cities: food. As the atmospheric scientist Alan Robock of Rutgers University points out in one of his many papers on nuclear winter, the biggest issue we’ll face may not be radiation at all. It will be starvation in the wake of extensive burning:
Smoke—especially black, sooty smoke from cities and industrial plants—would block sunlight for weeks or months over most of the Northern Hemisphere. And, if a nuclear holocaust occurred in the Northern Hemisphere in summer, it would affect much of the Southern Hemisphere as well. The cool, dark conditions at the earth’s surface would eliminate at least one growing season, resulting in a global famine.
Famine will also be a problem if one of our planet’s many megavolcanoes goes off. Ash and soot from such an enormous eruption would be blasted into the stratosphere, cutting the planet off from life-giving sunlight. The atmosphere would likely be full of sulfides and dust as well, both of which we’d want to avoid. So we might be looking at generations who live much of their lives underground. Our underground cities will have to be farms as well as shelters. In the next chapter, we’ll explore in greater detail how such farms might work.
Just like underground cities, farm cities are being built already, for many of the same reasons. Farm cities, like the green cities the urban geographer Richard Walker described in his book on San Francisco, are far more energy efficient and environmentally sustainable than the industrial cities most of us inhabit today. They are also less likely to suffer famine. In the next chapter, we’ll speculate about what cities might look like in a century or two. It’s possible they’ll be nearly indistinguishable from the natural surface of the planet.
18. EVERY SURFACE A FARM
WE’VE EXPLORED HOW cities are not static objects to be feared or admired, but are instead a living process that residents are changing all the time. Given how much bigger and more common cities are likely to become in the next hundred years, we’ll need to change them even further. Using predictive models from the fields of engineering and public health, our future city designers will plan safer, healthier cities that could allow us to survive natural disasters, pandemics, and even a radiation calamity that drives us underground. But there is a yet more radical way we’ll transform our cities. Over the next two centuries, we’ll probably convert urban spaces into biological organisms. By doing this, we make ourselves ready to prevent two of the biggest threats to human existence: starvation and environmental destruction.
Eventually this biological transformation might result in cities unlike any that have existed before. But for now, the best way to understand how such a shift would begin is by paying a visit to a city park or garden. These are places that we’ve built in the middle of cities to closely resemble the natural world. Usually they are just as engineered and artificial as the buildings surrounding them, but they do a lot of things that buildings typically can’t do, such as sequester carbon, absorb runoff storm water, and provide a cool, shady environment without drawing any energy from the grid. Many city parks today are reclamations of previously blighted areas. In Vancouver, Canada, for example, residents of the Fairview neighborhood converted a stretch of abandoned railroad tracks into dozens of garden plots where locals grow vegetables, flowers, and grains around the still-visible iron rails. And in New York City, a group of enthusiasts lobbied the city to let them convert a historic elevated-train structure into a park, which is now called (appropriately enough) the High Line. This once abandoned viaduct now features trees and grasses that seem to sprout from its concrete columns. People in these cities and many others throughout the world are slowly blanketing their barren causeways in habitats where plants and animals can thrive.
If we want the populations of our cities to survive, however, we’re going to have to do a lot more than plant flowers in lower Manhattan. We’ll need to transform urban areas into regions that can, as much as possible, feed themselves. That means prairie cities can’t rely on distant countries for bananas, nor can people living in desert outposts expect to get grain from fertile basins hundreds of kilometers away. More pressingly, we need to build cities that draw energy from their local ecosystems. By growing biofuels, and using sunlight for power, we make it less likely that humanity’s home planet will one day no longer sustain our need for energy. The biological city could provide us with food and energy security for millennia to come.
Food on the Streets
When I visited Cuba in the early 2000s, the best places to buy fresh food in Havana were street markets where urban farmers sold whatever they’d cultivated on roofs or in window boxes, sidewalk gardens, and yards. I wandered around in one of these markets, located in a large, airy warehouse where a couple of dozen people had set out their goods in baskets and on blankets. One woman was selling four eggs, a few eggplants, and a cellophane bag of spices. Another sat back on her heels behind a blanket heaped with greens. Street markets occupied a precarious legal position under communism because they encouraged private enterprise. But instead of cracking down, the Cuban government was paying agricultural engineers to study the most productive methods of urban farming. The need to prevent starvation overrode ideological concerns.
The Eden Project in Cornwall is an experiment with environmentally sustainable architecture; each dome contains its own ecosystem. In the future, cities might grow food or energy sources in such domes, or they might serve as water- and air-filtration devices for eco-buildings. (illustration credit ill.15)
In this example of eco-architecture, a hotel’s living walls are fed by a rooftop water source. The photograph was taken by Robinson Esparza, in the Huilo Huilo preservation area in Chile. (illustration credit ill.16)
Though that ad-hoc urban farmer’s market in Havana felt like a medieval oasis in the middle of a bustling, cosmopolitan city, it was actually a good demonstration of how people might grow and buy their food in the cities of tomorrow. They’ll do it by slowly converting cities into farms. At the time I was in Cuba, Raquel Pinderhughes, an urban planning professor at San Francisco State, wrote that there were over 8,000 farms in Havana, covering about 30 percent of the region’s available land. If you rode into the countryside on a bus that picked you up on Havana’s busy Malecón, a promenade along the seawall, you’d find that the high-density city quickly shaded into suburban residential areas peppered with farmland. Land planners sometimes call this system periurban agriculture. It transforms suburban consumer sprawl into a rich source of food production.
In the hot, dry valleys of Pomona, California, a nonprofit group called Uncommon Good has helped set up an urban farm where unemployed immigrants with farming experience grow organic food to sell in local markets. This Pomona farm, like many others, uses the “small-plot intensive farming” (SPIN) model, designed by urban farmers in Canada to maximize crop yields in areas of less than an acre. The idea behind SPIN is both agricultural and economic. Farmers vary their crops and use sustainable fertilizers to keep their small plots of soil fecund, and they sell by direct marketing in their local areas. This maximizes food production and minimizes the resources that the farmers need to transport that food to buyers. It’s easy to imagine many cities transformed by a SPIN model over the next 50 years, where people grow their own food to eat and sell to neighbors—who in turn sell different food, so that local diets can remain varied.
But will cities transform farming as much as urban farmers hope their methods will transform cities? In his book The Vertical Farm: Feeding the World in the 21st Century, Columbia University environmental-health
professor Dickson Despommier argues that cities of the future might feed themselves by creating farms inside enormous, glass-walled skyscrapers where every floor is a solar-powered greenhouse. All water in these skyscraper farms would be recycled, and the structures themselves would be designed to be carbon neutral. While critics question whether it would be possible to heat, power, light, and tend skyscraper farms without wasting a lot of energy, Despommier’s thought experiment is a good one. We are going to need ways to produce enormous amounts of food in cities, often indoors, and trying to figure out how we’d do that in a skyscraper—or an underground cavern, for that matter—is a step in the right direction.
Our future buildings may be sprouting gardens on the outside, too. A popular way to transform cities in Germany is by building green roofs, which are basically special systems designed to convert rooftops into gardens. This isn’t just a matter of heaping some dirt up and throwing seeds on it. Green roofs are a complex system of layers designed to protect the roof, absorb water, and hold soil in place. Though they are unlikely to be useful for farming, some studies have shown that green roofs help cut energy costs by keeping buildings cooler in the summer months. They also reduce storm-water runoff, which is a huge issue in cities. Because most cities are covered in nonporous, nonabsorbent surfaces, all the grime, toxins, and trash in the city are washed out by rainwater during storms—and carried into nearby waterways, farms, and oceans. Having a roof that can absorb rainwater does a tremendous amount of good for the local environment and cuts costs related to water purification and treatment.
Bringing natural environments into cities isn’t just about feeding ourselves. It’s also about figuring out how to manage our energy consumption using tricks borrowed from nature. Growing shade plants on our roofs can help cut energy costs in summer, just as designing photosynthetic antennae like the ones mentioned in chapter 11 can help us power computers without burning coal. Natural ecosystems conserve energy remarkably well. As we learn to imitate that, our cities might become highly advanced technological entities that look strangely like the postapocalyptic jungle version of New York City in The World Without Us.
Managing the Land
MIT’s environmental-policy professor Judith Layzer offered me a vivid picture of what life might be like in such a city. She believes that, ideally, most future human communities would be based in cities, leaving enormous stretches of land free for farms and wildlife. “We need to re-regionalize,” she told me. “A global economy doesn’t make sense environmentally. So your ecosystem would become your bioregion.” She described a world where communities would be organized around bioregions like the dense forests and rocky coasts of the mid-Atlantic states or the prairie grasslands of North America’s Great Basin. “Most of your food should come from your region,” she said, and farm labor would be done by people rather than machines. But, she asserted, “nobody would be working as hard as they are now” because life would have a much slower pace. “You’d have goats mowing lawns,” she said, her face quirking into a grin. “It would be less efficient in the contemporary sense. Long-distance travel would be more of a hassle. You’d bike everywhere.” In her ideal city, where food was local and energy carbon neutral, “you’d do everything with natural systems.” And the population of a city would never rise above a few million.
This kind of regionalism might be good for our ecosystems, but it probably couldn’t be as “natural” as Layzer imagines. Obviously, if people are depending on their bioregion for food, they’ll be more vulnerable to the vicissitudes of climate and seasonal drought. We’ll need cutting-edge technology to help these bioregional cities weather periods when the local ecosystem can’t support the population.
One possible way we’ll do this is by looking to outer space. At UC Santa Barbara, an international group of climate scientists, geographers, and geologists use satellite data to predict where drought will strike next. They call themselves the Climate Hazards Group, and their success at predicting drought is almost uncanny. Currently, they focus most of their efforts on Africa. Amy McNally, a geography researcher with the group, said she and her colleagues helped predict the summer 2011 drought in Somalia by correlating data drawn from satellite images of rainfall in the region with rain gauges on the ground. “They predicted the drought and the resulting famine a year in advance,” she said. Unfortunately, “even with that much forewarning, response didn’t make it in time for it to not get to a famine-level crisis.” But the group had gained more evidence about what signs indicated droughts to come.
One of the key indicators comes from satellite observations of greenery on the ground. Just as green roofs keep buildings cooler, a green ground cover keeps the soil cooler, wetter, and more likely to yield a good crop. When plants die back too much, drought may be on its way in the next season. McNally said the satellite she uses measures the wavelengths of light reflected back from the West African region she studies. Plants reflect green light back into space, where the satellites measure percentages of green light versus other wavelengths. As a result, McNally can get an extremely precise picture of how much green is required on the ground to guarantee a good growing season. The big issue in Africa is that most regions don’t use extensive irrigation, so farmers are dependent on rainfall for a successful crop. A dry season can mean death. But it doesn’t have to.
Knowing we’ve got an impending drought might mean shoring up water supplies for irrigation that could keep a valuable plant cover protecting the soil. As our cities become more closely tied to their bioregions, science teams like the Climate Hazards Group could become crucial to urban planning. With the technology and data we have now, McNally said, “we can make predictions like ‘In the next twenty years, you’ll have five droughts, which is two more than usual.’ ” This kind of information could prove invaluable to farmers planning their water usage, or governments trying to set up trade arrangements with areas that won’t be affected by the drought. As we gather more data on how droughts happen, we may be able to make more accurate predictions about when famine is likely to strike—and stop it before it starts.
Satellite imagery and technology are not a panacea for food-security problems. In fact, as we discussed earlier, famine is usually caused by political and social upheaval. Fixing that will require more than good science. You could say the same thing about our energy problems. But it’s possible that our political priorities will change along with our changing urban environments.
The Biological City
As we move further into the future, our cities won’t just be swaddled in gardens and farms. They might also become biological entities, walls hung with curtains of algae that glow at night while sequestering carbon, and floors made from tweaked cellular material that strengthens like bones as we walk on it. New York architect David Benjamin is part of a new generation of urban designers who collaborate with biologists to create building materials of the future. I met him in Studio-X, a branch of Columbia University’s school of architecture located in a bare-bones whitewashed work space south of Greenwich Village. Students focused on monitors full of three-dimensional renderings of buildings, or sketched at drafting tables between concrete columns. It looked like the kind of place that could, in 50 years, be sprouting a layer of grass from its walls—or something much stranger than that.
Benjamin described the shift to biological cities using quick, precise gestures that reminded me of someone penciling lines on a blueprint. “It might look the way it looks now,” he said. “The city could be made with bioplastics instead of petroleum plastics, but it would look very similar. A machine for making genetically modified organisms (GMOs) would exist in factories the way they do today for making medicine and biofuels.” So the plastic fittings around windows would be manufactured from modified bacteria rather than fossil fuels, but as a city dweller you’d notice little difference. Benjamin and a group of other architects and biologists have worked with Autodesk, the company that makes the popular AutoCAD software many archit
ects use to design buildings, to create a mock-up of AutoCAD for biological designs, called BioCAD. Pulling out his laptop, Benjamin showed me a demonstration of the biological-design-software interface. The designer can choose between biological materials with different properties, like flexibility or strength. Having chosen those, the designer directs the program to create structures that look like marble cake, a multicolored swirl of substances combined into a single structure that gives in the right places and holds steady in others.
Over time, these living cities would start to look different. They’d be transformed by synthetic biology, a young field of engineering that crafts building materials from DNA and cells rather than more traditional biological materials like trees. Benjamin described a recently created synthetic-biology product called BacillaFilla, designed by a group of college students in England. The students engineered a common strain of bacteria to extrude a combination of glue and calcium when put into contact with concrete. They applied the bacterial goo to cracks in concrete, and over time it filled the cracks completely and then died, leaving behind a strong, fibrous substance that has the same strength as concrete. The students described BacillaFilla as the first step toward “self-healing concrete,” and their efforts are just one among many designed to create biological substances that could heal ship hulls, metal girders, and more.
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