Migration this century will be to cities, and while social and economical sustainability is important, so too is environmental sustainability. We must make sure our cities are safe as the planet heats. And cities must also not make conditions worse: they currently consume two thirds of the global energy supply and generate three-quarters of the world’s greenhouse gas emissions. Some parts of some cities can be adapted for the new climate conditions; others will need to be abandoned or relocated; and new cities will need to be created to home billions of migrants.
Cities are particularly vulnerable to the impacts of climate change, experiencing the effects of heat, sea-level rise and extreme weather more acutely. Hard surfaces, such as concrete, absorb the sun’s heat, and tall buildings diminish air circulation, while concentrated human activity (including vehicle engines, heating and cooling units) all add to the so-called urban heat island effect, in which cities experience hotter temperatures than surrounding areas.
Urban temperatures are currently 1–2°C warmer than surrounding areas—and slum neighborhoods can be at least triple this. The same hard surfaces of concrete and asphalt prevent rainwater being absorbed, so storms can quickly lead to flooding. Cities, of course, also concentrate more people per area than rural places, meaning more people are affected by heatwaves, air pollution and the devastation of extreme weather.
Of the 100 cities worldwide that are most vulnerable to climate change, ninety-nine are in Asia and eighty are in India or China. More than 400 large cities with a total population of 1.5 billion are at “high” or “extreme” risk because of a mix of life-shortening pollution, dwindling water supplies, deadly heatwaves, natural disasters and the climate emergency, according to a 2021 report by global risks consultancy Maplecroft. As I’ve explained, the additional effects of humidity combined with temperatures just slightly higher than today will make equatorial latitudes intolerable.
Additionally, coastal cities that are home to around 60 per cent of the world’s population are experiencing sea-level rise at a rate four times faster than elsewhere, because the sheer weight of their buildings and infrastructure pushes the ground down relative to the water. Buildings and streets are sinking into the cavities created by construction work, causing flooding. Over the past sixty years, Shanghai (which means “above the sea”) has sunk by 2.6 meters, eastern Tokyo by 4.4 meters, Mexico City by almost 10 meters, and half of New Orleans, a city which is sinking at four times the rate at which the sea is rising, is already below sea level. These cities, which are currently absorbing migrants, will soon be generating them—and in large numbers.
Jakarta, the fastest-sinking city, is dropping at an alarming rate of 25 centimeters a year. The Indonesian government has decided on a mass migration as a solution. It will move its capital to a newly constructed city, to be named Nusantara, on higher ground on the forested island of Borneo. This multi-billion dollar project aims to save Jakarta’s citizens—who by 2050 will number 16 million—from the waves. However, the construction, which will take decades, will have huge environmental consequences for one of the most important planetary ecosystems, and still leave citizens vulnerable to extreme heat and fires.
Other cities are trying to hold back the waves with barriers and sea walls. Venice, built to accommodate the regular 45-centimeter rise and fall of tide in the Venetian lagoon, is now partially under water seventy-five times a year, with half of the major floods in its 150 years of record-keeping occurring since 2000. The government has constructed a barrier of submerged inflatable gates that can be raised during high tides to separate the lagoon from the sea. But the barrier has been designed to cope with no more than a 20-centimeter rise in sea level—something that could be exceeded as soon as 2050. Venice is already more of a museum than a living city—in the summer, around 60,000 tourists a day visit a city that’s home to just 52,000—as lack of investment and repeated inundations have led to a migratory exodus in recent decades. More than 120,000 residents have left Venice since the early 1950s, and over the last twenty years the pace has hastened. Soon it will be solely a museum. Other celebrated cities, or parts of them, will follow.
Cities have entrenched assets—there is enormous embedded wealth sunk into them, so there will always be financial imperative to shore them up even as residential areas submerge. Tokyo, Bangkok, even Dhaka and Lagos will not be completely abandoned. Instead they will become more engineered, with huge infrastructure investment. New York is planning the “Big U,” a vast sea wall to protect the financial district of lower Manhattan; but it would leave anyone living north of West 57th Street exposed to the waves. The city is already dealing with regular inundations, which in 2021 saw people swimming in flooded subway stations and geysers erupting out of the streets’ drainage covers.
One man described swimming out of a flooded station in Manhattan after a storm in 2005, while “next to me fleeing was a bunch of rats.” It could potentially get far, far worse, with New York City facing the possibility of being a meter under water by the end of the century. Rotterdam—already 2 meters below sea level—is planning another massive barrier system, along with floating houses. The densely populated atoll city Male, capital of the sinking Maldives, already has sea walls and other barriers. They protect the city—for now.
As King Canute demonstrated, the tide wins. The most vulnerable inhabitants of all these doomed cities are the poorest, including the migrant population—slum dwellers living in unsanitary housing and the rural people who join them, flocking to the city to seek safety when extreme weather hits. In other words, people today are migrating towards disaster. Cities have stronger infrastructure, more hospitals, and other essential services, so they are often seen as a refuge. Bangladesh’s capital, Dhaka, is one of the most densely populated cities—about 40 per cent of the city’s 14 million residents live in informal settlements, and 70 per cent of those were forced to leave their homes because of phenomena related to climate change, including cyclones and coastal and riverbank erosion.
But Dhaka is itself no safe haven. As I picked my way through a still-sodden slum there, residents showed me how high the waters reach—eye level—flooding their homes and destroying their few possessions. The entire neighborhood is forced to find refuge on the raised roads (which also flood since they lack drainage), sleeping exposed or in tents, during these inundations. And the lack of water and sanitation brings killer waterborne diseases.
When poor people migrate to cities they tend to get stuck there, having used all their resources in the move. While middle-class and wealthier people can afford to migrate to better locations, the poorest and most marginalized get trapped in the most vulnerable cities, unable to afford to move away. In 2018, the Migration Policy Institute conducted a comprehensive review of all the research evidence on climate and migration. It found that climate shocks are highly likely to reduce a community’s likelihood of moving (by hurting their ability to afford to migrate); when they do use migration as a survival strategy, it’s almost always within the local region.
The solution is to plan: safer cities for expected immigrants, relocation strategies for risky districts, and ways to facilitate international migrations. Governments can help by withdrawing their backing for property insurance and buying back land. However, in many cases compensation and buyouts for individual households look woefully inadequate. Moving communities can take decades of planning to ensure the best transition for livelihoods.
One place that’s taking it seriously is Kiribati, a state of low-lying coral atolls bisected by the equator, whose economy relies on fishing and coconut production. Over the past 5,000 years, these islands have been settled by waves of immigrants, from the early Austronesians to recent Europeans, who have built a rich culture. Now the entire population is preparing for mass emigration because of the dangerous sea-level rise. In 2014, President Anote Tong told me the country had reached “the point of no return.”
Kiribati is pioneering the steps that multiple other cities and nations will have to take as they face the reality of unlivable conditions. It has purchased territory in Fiji for its beleaguered population and is also helping its citizens find new livelihoods in other countries. Tong began his “migration with dignity” program a decade ago, beginning to move people gradually though employment abroad, such as sending nurses to New Zealand. His aim, he explained, is to avoid turning his citizens into refugees with a large humanitarian evacuation during an extreme weather disaster, as has befallen other islands, such as Puerto Rico.
Tong talked to me about his “duty and responsibility” to prepare citizens for the psychological—as well as practical—hurdle of leaving their ancestral land, graves and culture, including their familiar language, songs and stories. “I am determined to help our nation adapt to what is coming, which means addressing risks, and strengthening our resilience to our islands no longer sustaining human life,” he said. “We want our young people to be able to migrate voluntarily with dignity to other countries, so we’re investing in the education and skills to equip them.”
Planning is key not just for new cities, or foreign migrants, but also to encourage migrants from other unsafe places in the nation to move to safer cities. In Louisiana, for instance, government officials are spending $48.3 million to relocate households from the low-lying Isle de Jean Charles to higher ground forty miles away, as part of the first federally funded, climate change-induced community resettlement project in the US. New Zealand has a Managed Retreat and Climate Adaptation Act to help individuals and communities to relocate; the Canada-based Climate Migrants and Refugee Project is mapping dis placement within and into British Columbia. In Bangladesh, too, government agencies are looking into creating migrant-friendly towns outside major cities, to reduce the pressure on places like Dhaka.
While Dhaka, New Orleans and Venice will become increasingly unviable, with residents emigrating elsewhere, plenty of other cities will be able to cope with the coming changes, and benefit from a newly mobile workforce by offering them a new home. To be clear, all cities will need to adapt even if they face relatively minor impact from cli mate change, because of the transition to net zero greenhouse gas emissions. Well-located cities will draw many millions of people with complex needs, requiring safe, sustainable homes. These cities will need to be environmentally resilient, ensuring tight efficiencies in resource use, minimal waste and the elimination of dangerous pollution.All cities will need to adapt even if they face relatively minor impact from cli mate change, because of the transition to net zero greenhouse gas emissions.
The big risk for cities this century is extreme weather, and new developments must be appropriate to the risks. It makes no sense for migrants to escape drought in their homeland, only to move to a city that is vulnerable to flooding—it is simply trading one kind of climate risk for another.
High and low extremes in rainfall will become more frequent, and all cities will need to adapt so these events don’t become catastrophes. Rain gardens, which capture and channel stormwater into under ground cisterns or simple depressions in the ground, beneath planted rushes and other vegetation, have been installed in cities from New Orleans to London to cope with drought. The largest increases in heavy rainfall events are expected in high-latitude regions, including northern Europe and northern Asia.
China’s government has commit ted to 80 per cent of its cities having “sponge” capabilities by 2030, at a cost of some $20 million per square kilometer. Cities such as Wuhan now use green spaces, marsh zones and underground storage tanks to absorb rainfall and prevent floods. Others construct canals, widen sewerage, install fast-flow drainage and use permeable paving and surfaces. Barcelona is re-landscaping swathes of road surface to better absorb rainwater and mitigate heat.
Further north, Gothenburg in Sweden is embracing the increase in rain with new water-management infrastructure, as well as artificial waterfalls and a Regnlekplatsen, or “rain playground,” designed to be particularly fun when it’s wet, including a way for children to make pools, rivers and dams. Other cities are meeting the rising waters with innovative floating infrastructure, including houses, hospitals and agricultural beds, which can rise and fall with the water levels.
The Netherlands has several floating communities—the houses, often prefabricated, are fixed to the shore, often resting on steel poles, and are usually connected to the local sewer system and power grid. They are structurally similar to houses built on land, but instead of a basement, they have a concrete hull that acts as a counterweight, allowing them to remain stable in the water.
The Maldives is also planning a floating complex off Male, including affordable housing for 20,000 people, designed by Dutch firm Water studio. Artificial reefs under each house will help support marine life, while air-conditioning units will use pumped water from the deep sea for coolant. Flood-safe homes don’t have to be expensively engineered rarities—the Bangladeshi architect Marina Tabassum has designed award-winning, flat-packed, raised housing for refugees—made from bamboo, yet storm and flood-proof.
Heat is another serious problem that cities will have to solve, ideally using “passive” designs that enhance overall sustainability rather than adding carbon emissions. Demand for cooling will soar this century, becoming a key social justice issue, especially during heatwaves, when lack of access will prove deadly. Cooling already uses 20 per cent of global energy production, and this is expected to triple by 2050. Months of heatwave in the spring of 2022 across India and Pakistan meant hundreds of thousands of people were unable to work after 10 a.m., with load-shedding power outages leaving people without access to cooling or refrigeration.
Cooling is not just going to be a problem in the tropics, where there is already fast-rising demand, but in today’s temperate zones where vast populations will be headed. Insulation will help manage this burden, and strategic use of water—used for cooling by architects and planners for centuries—will also play a role. Many cities are planning new canals and water features. In Omonia Square, the central plaza in Athens, analysis has shown temperatures dropping by up to four degrees since a multi-jet fountain was installed in 2020. Rooftop and vertical gardens provide a holistic solution to heat, biodiversity loss and extreme weather, and although they’re most fecund in the tropics, using vegetation such as sedges works well in the far north.
In Chicago, rooftop vegetation proliferated after new laws and incentives were brought in in 2004. Half of the city hall is now covered with a roof garden and while summer temperatures on the uncovered area can reach 77°C, the gardened part stays closer to air temperature, about 32°C. Roof gardens can also capture rainfall, reducing stormwater runoff.
Painting roofs and other surfaces white also reduces heat. One study found that a clean white roof that reflects 80 per cent of sun light will stay about 31°C cooler on a summer afternoon, and reduce indoor temperatures by up to 7°C. A cool roof can save as much as 40 per cent of air-conditioning costs, the researchers calculated. Even in India, where most roofs are made from metal, asbestos and concrete, and temperatures can reach 50°C, lime-washing roofs managed to keep indoor temperatures up to 5°C lower. This low-cost tool could produce a cooling effect comparable to offsetting 24 giga-tonnes of carbon dioxide—the equivalent of taking 300 million cars off the road for twenty years—if roofs were whitened worldwide.
White roofs will also play a key role in more northern cities as the world heats, and scientists are continuing to develop more reflective paints. The best so far reflects more than 98 per cent of sunlight. This is significant because every 1 per cent of reflectance on a roof works out as 10 watts per square meter less heat from the sun. So using ultra-white paint to cover a roof area of about 93 square meters, could produce a cooling power of 10 kilowatts, which is more powerful than the central air-conditioners used by most houses.
These twenty-first century refuge cities will need not just to battle extreme conditions, but to do so while mitigating climate change. Buildings alone account for more than half a city’s carbon emissions on average, and 70 per cent in major cities such as Paris, London and Los Angeles. By 2050, the goal is for all buildings to use only as much energy as they generate; and the mayors of nineteen cities, including London, have agreed to get there by 2030. It starts with insulation to avoid heat leaking through walls, floors and ceilings, as well as windows that reduce heat intake, and reflective roofs.
For existing buildings, this can be time-consuming. The Dutch Energiesprong whole-house refurbishment is not cheap but wraps homes in insulated panels that snap on easily like Lego. Thermal wallpaper, which can be decorated over, is another option. Fully decarbonizing means replacing (and electrifying) inefficient heating and cooling systems, which are, in turn, responsible for more than half of a building’s energy use, in addition to hot water and lighting. Heat pumps can be placed under parks, public squares, roads, rivers and canals in every city to heat and cool buildings. The city of Ithaca in New York has raised
$100 million through an innovative investment program to decarbonize all of its buildings while creating new jobs by 2030—something more cities could try.
Zero-carbon new-builds are easier to design efficiently, and the rapid expansion of cities this century is an opportunity to innovate.
Melbourne’s Pixel Building, which opened in 2011, has panels to control the amount of light coming into the building, and “smart” windows allow heat to escape on summer nights while filtering in fresh air. Solar panels and wind turbines sit on the rooftop, generating renew able power. Canada’s first carbon-neutral building, in Waterloo, Ontario, also has solar walls and a three-story green wall to offset carbon emissions. Smart heat and light-responsive materials and fit tings will become standard in buildings, from outer skins that shade them during the hottest parts of the day and allow the sun in during cooler times, to floors that generate electricity from footfall, and rain water systems that help minimize water loss.
New housing for expanding migrant cities is likely to be prefabricated and modular for ultimate ease of construction and flexibility of use and reuse, as the city’s demography changes, especially if formerly uninhabitable cities become livable again towards the end of the century. These prefabs can be made from organic materials, such as bamboo or fast-growing softwoods that are specially engineered to give them the strength and durability of harder materials. Building from wood actively locks in carbon, in contrast to concrete and steel, which are together responsible for 13 per cent of global emissions.
One study found that using wood to construct a 120 meter sky scraper could reduce the building’s carbon emissions by 75 per cent. Wood is also lighter, faster and versatile—wooden skyscrapers, or “plyscrapers,” are under construction across the globe from Norway to New Zealand, made from cross-laminated timber (CLT) stuck together with fire-resistant glue, which is as strong as structural steel and better at withstanding fires (steel can buckle and even melt). Most of our new housing could be kits of light, five or six-story blocks built from CLT, enabling rows of street housing to go up in days. The French government has ruled that all new public buildings must be made from at least 50 per cent timber. The Swedish town of Skellefteå has wooden schools, bridges, a skyscraper and hotels, even car parks.
Several companies already make prefabricated wooden housing complexes that can be delivered by lorry and rapidly assembled, such as IKEA spinoff BoKlok, which arrives with solar panels and other self-sustaining features. The beauty of trucked-in housing is that it can be trucked out again and redeployed where it’s needed. In the dynamic housing landscape of mass migration, this could be very useful.
Excerpted from Nomad Century: How Climate Migration Will Reshape Our World by Gaia Vince. Copyright © 2022. Available from Flatiron Books, an imprint of Macmillan, Inc.