By 2030, 41 cities around the globe are projected to have a population of more than 10 million. Today’s 10 most populous cities—from Tokyo, with 38 million, to Sao Paulo, with 21—collectively house 257 million people.
It’s staggering to contemplate the massive flows of food, waste, vehicles, water and electricity necessary to support such concentrations of humanity. In such an urban world, which seems to consist of an interconnected mass of ducts, conduits, pipelines and byways, disaster can be just a leak away. And 55 percent of us now live in urban settings subject to such disruptions at one scale or another. Like reconfiguring an airplane while keeping it aloft, the problem of rebuilding urban infrastructures to meet population demands and avoid calamity is an overwhelming challenge.
With today’s global population of 7.6 billion growing to perhaps 8.6 billion by 2030, one analysis projects that urban areas will spread another 1,527,000 square kilometers (570,000 square miles) by then. That’s like converting the total land area of Mongolia or Alaska into one immense field of concrete, buildings and highways. This expansion will not take place in a vacuum, of course; it will have wide repercussions. As researchers say, “the conversion of Earth’s land surface to urban uses is one of the most irreversible human impacts on the global biosphere. It drives the loss of farmland, affects local climate, fragments habitats, and threatens biodiversity.”
Before our collective attention turns to schemes of geoengineering climate or colonizing other planets, we need to confront some ground-level issues. How will we engineer cities to safely sustain the billions of people who live today, and will live tomorrow, in our massive urban centers?
The kinds of problems we’re up against are well illustrated in the story of Mexico City. Can our experience there help us understand how to be more effective in engineering or geoengineering our world?
A Bowlful of Problems
Situated in a high-altitude bowl-shaped valley, Mexico City has a metropolitan population of more than 21 million, making it the largest Spanish-speaking city in the world. The region, traditionally called the Valley of Mexico, played an important role in Mesoamerican history. It has been continuously inhabited for thousands of years, with an estimated Aztec population of more than 200,000 in the early 1500s. By 2030 Greater Mexico City’s population is expected to reach 23.9 million.
It’s not surprising that, on its way to becoming a megacity, the area has undergone immense changes. What may be surprising is the nature of some of those changes. The valley, surrounded by mountains, was once a wetland under blue skies. Dominating the basin at 2,100 square miles (more than 5,400 square km) was Lake Texcoco, fed by natural springs and mountain runoff. Today the land is paved and farmed, the waters impounded and diverted, the lake gone. Access to fresh water is now among the once-vibrant Valley of Mexico’s most pressing problems.
“Mexico’s rainy season is intense and demonstrates that water is naturally meant to be a part of the landscape. Mexico City, the country’s capital, currently has one of the largest populations in the world, and its citizens are desperate for water.”
The geography of the valley not only contributed to water flow that created the lake; it directs air flow as well. Much like Los Angeles and central California’s San Joaquin Valley, which endure some of the highest levels of air pollution in the United States today, Mexico City is naturally plagued by restricted air flow that tends to trap pollutants at ground level. In 1992, the United Nations ranked the region’s air pollution the worst in the world.
Such factors all play an important role in a region’s future livability. We build cities that become “too big to fail” yet seem fated to do just that—sure to fail, because in our quest for space and dominance we’re either unaware of natural limits and hazards or, more likely, we choose to ignore them—or, most optimistically, we believe we can engineer around them.
In the case of Mexico City, all three have come into play. From the outset, it was a matter of building on a wrong foundation.
Water Over the Dam?
Since the time of the Aztecs, who built their capital in the middle of a lake in the Valley of Mexico, the area’s inhabitants have sought ways to control the water around them. When the Spanish conquered the Aztec Empire in the 16th century, they built Mexico City on the ruins of the island capital. But where the indigenous people had tried to carefully manage the region’s water, the colonists were more reckless. Over the course of 400 years, the city grew on the exposed bed of a shrinking Lake Texcoco.
As the surface water disappeared, water engineers in the era of Mexican president Porfirio Díaz (1876–1911) turned to aquifers, digging hundreds of wells. But with no flow from above to refill the underground reservoirs, they drained faster than they could naturally recharge. Although authorities recognized the problem in the 1940s, a substantial underground-water dependence persists today.
Yet the aquifers aren’t enough to sustain the region. In spite of heavy seasonal rainfall and flooding, Mexico City still faces shortages and now depends on inter-basin delivery of one quarter of its water from what is called the Cutzamala System, by which water is transferred to the Valley of Mexico from as far as 150 km (90 miles) away. It’s a remarkable feat of hydro-engineering, employing a network of dams and reservoirs in the Cutzamala basin, six main pumping stations, and 322 km (200 miles) of tunnels and open canals. Just as Los Angeles receives much of its vital water supply via pipelines over the mountains from Northern to Southern California, so the Mexican system thrusts water 3,600 feet (1,100 meters) from the lowlands up to the Valley of Mexico.
Since this is a hugely energy-intensive operation, the city’s imported water is “probably the most expensive on the planet,” Manuel Reyes, head of supply at the Mexico City Water Department, told The Guardian in a 2015 report.
The report also describes the friction the inter-basin water transfer is causing. Just as the Los Angeles Aqueduct stirred resentment when it dehydrated California’s lush Owens Valley in the early 1900s, so pulling water away from the growing population of the Cutzamala basin is generating controversy and discord. The rural communities rely on subsistence farming to eke out a livelihood, yet their lack of political power may condemn them to simply surrendering their source of irrigation, following in the footsteps of Owens Valley farmers to the north.
Now, reports journalist Carly Schwartz, “water is diverted backwards and sideways and against its natural flow, in the process contaminating it with pollution and draining some communities dry while saturating others in waste and filth.”
“There is a vicious cycle of contamination. The city sends us pollution and we send it back in the food. It’s a big health problem.”
Sink and Shake
The whole Valley of Mexico has suffered the unforeseen, unintended, generations-long consequences of this engineered water crisis. As historian Barbara Mundy notes, “Mexico City suffers from both chronic flooding and a shortage of freshwater; the problems once solved by the great engineers of the ancient Aztecs are at hand again.”
Even with the importation of water, about two thirds of the supply is drawn from the aquifers. A natural consequence of this groundwater extraction is land subsidence. Mexico City is sinking—in some places up to 10 meters, more than 30 feet, over the past century, and elsewhere in the valley as much as 12 meters.
As the rate is not uniform, dozens of cracks and sinkholes have appeared, leading to further consequences for roads and underlying infrastructure. For example, damage to the city’s water pipes from subsidence, age and lack of maintenance has meant the loss of as much as 40 percent of available fresh water.
One more insult to the region’s sustainability looms. Sitting at the edge of a number of tectonic plates, Mexico’s unique geology makes it vulnerable to seismic catastrophe. But according to some theories of ground motion, the overextraction of groundwater may contribute to increased seismic activity, leading to further subsidence.
If that isn’t disturbing enough, lakebed sediments are also less stable during an earthquake, a fact that does not bode well for the region’s ability to ride out a major event. “Two very dangerous effects [are] coming together,” explains Yann Klinger of the Global Physics Institute in Paris: “The seismic waves are trapped in the basin and amplified. And furthermore, the unconsolidated sediments (clay, sand) lose their coherence in the shaking and become like liquid, a little like quicksand.”
“The Valley of Mexico is particularly vulnerable to seismic activity due to the prevailing geological and topographical conditions, including a closed basin with soft soils and extensive urbanization on drained lakebeds.”
The Megacity as Microcosm
Mexico City is a microcosm of what we’ve done Earth-wide. Attempting to construct our world beyond natural limitations, we have tended to move forward with a kind of willful blindness to the future consequences of our actions. By constructing dams, levees, canals, dikes and pipelines; draining wetlands; diverting rivers and redesigning water systems; cutting down forests and concentrating populations in urban centers, we have mostly ignored the immediate effect on biodiversity, on other humans, and on future generations that will inhabit these areas.
As 18th-century demographer and economist Thomas Malthus noted, we regulate our population by the resources we can draw on. Thus, he said, as our food supply grew, so would our population. How well this hypothesis seems to apply to our cities: we will fill and overfill right up to the limit. And so we are forever on the edge of catastrophe. It’s a problem of failing to do today what will be best for tomorrow.
“Mexico City’s situation is chaotic and absurd. We could have natural pure water, but for hundreds of years we have been draining it away so we have created an artificial scarcity,” Marco Alfredo, president of the Mexican Association of Hydro-engineers, told The Guardian. “This is not an engineering problem: we have the expertise and the experience. It is also not a problem of economics: we have the financial resources to do what needs to be done. It’s a problem of governance.”
It’s an unfortunate reality that we tend to realize our mistakes after the fact, after the damage is done, or when the problem becomes overwhelming. And so those saddled with keeping Mexico City (and its water) running tomorrow seem mired in forever retrofitting what was poorly conceived yesterday.
A Plan for Renewal?
Some do see reasons for optimism. The World Design Organization (WDO) is an international group that promotes the thoughtful redesign of cities. Operating with the mission to “advocate, promote, and share knowledge of industrial design driven innovation that has the power to create a better world,” WDO seeks ways to achieve the United Nations Sustainable Development Goals.
WDO named Mexico City its “World Design Capital 2018” for its “commitment to use design as an effective tool for economic, social, and cultural development.” Mugendi M’Rithaa, WDO president at the time of the announcement, expressed high hopes: “Mexico City will serve as a model for other megacities around the world grappling with the challenges of urbanization and using design thinking to ensure a safer, more liveable city.”
Will the proposal offered by Mexico City designers in their bid to win this recognition accomplish what the city needs? According to the WDO website, “the exhibitions, conferences, urban interventions and educational projects will be guided by six transversal sub-themes relating to urban challenges of the 21st Century: people, mobility, city identity, environment, public space and creative economy.”
When we look at these broad themes, it appears that the design initiatives focus entirely on above-ground issues. And the proposed solutions seem largely cosmetic: “Design Week Mexico, a non-profit organisation that promotes design as an engine of social change, . . . plans to focus on the borough of Miguel Hidalgo, introducing new health, communications and security programmes, a bike sharing programme, urban gardens, parks and playgrounds.”
“Mexico City is a dynamic space constantly generating creative projects. We have created a local agenda of expositions, independent events and initiatives in the cultural scene of the city following the topic of socially responsible design.”
Multiple millions concentrated in megacities across the globe depend on the success of endeavors such as these. An effective redesign of urban spaces, however, will need to be much more than cosmetic; bike-sharing and playgrounds may be good, but they won’t solve Mexico City’s most pressing issues.
As is so often the case in seemingly intractable matters, one must be willing to go below the surface to identify and deal with the underlying causes of a problem. In the case of Mexico City, this has a quite literal application. A centuries-long lack of foresight and planning—counting the cost of decisions and actions affecting the city’s ongoing relationship with and need for water—and failing to recognize the need to build on a suitable foundation in the first place, has led to many of today’s infrastructure problems. True renewal will require leadership decisions ensuring that these issues are addressed and solved for the benefit of all, including the poorest and least advantaged.
Counting the cost. Building on a solid foundation. Looking out for the welfare of others. These are well-known biblical principles that each of us can live by as individuals. Unfortunately, they aren’t traits for which most politicians are known, yet it’s to the politicians that the world looks for sound decisions and meaningful change in today’s growing megacities.
From the penthouses to the homeless shelters and out onto the streets themselves, grappling with the challenges of urbanization to create truly livable cities that meet the most basic water, food and housing needs of all a city’s inhabitants will test the most creative designers and leaders. When we add our changing climate into the mix, we have the makings of some of the most demanding environmental problems—problems of extraordinarily complex dimensions—that humanity has ever faced. The potential impacts of our collective decisions have never been greater.