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The photography in this story was supported by the Pulitzer Center.

When Alex MacLean wants to see how buildings and open spaces in a city relate to each other, he rents a small plane, taxis down a local airport’s runway, and cruises low—at somewhere between 150 and several thousand meters. As the elements line up the way he wants, MacLean swings open the hinged window in his door and trains his camera on the ground. For several seconds, the plane—sometimes while spiraling downward—flies itself, as MacLean methodically frames his shots.

Since long before drones democratized aerial photography, MacLean, who trained as an architect, has taken pictures from the sky, helping urban planners and other architects visualize ideas and document projects; but he also pays keen attention to how his aerial perspective can draw attention to what he sees as the creeping environmental degradation of the Earth. Recently, he took a multi-flight solo tour of the US East Coast from Maine to Florida over the course of a year, seeking perspective on the expected impacts of sea level rise.

He had known, of course, that rising waters pose serious risks to coastal states, but he was unsettled by the scale of vulnerability he discovered everywhere he flew: “There’s going to be a huge economic burden coping with all the problems that come with sea level rise.”

The US Global Change Research Program indicates that global sea level has risen between 16 and 21 centimeters since 1900. It’s virtually certain the seas will keep on rising, and at an accelerating rate. The complexity of predicting how quickly polar ice sheets will shed mass into the oceans makes it hard to forecast with precision how quickly the water will go up. But the latest US National Climate Assessment concluded that, at its extreme, global sea level could rise by as much as 2.4 meters by the end of the century.

Sea level rise varies from place to place due to many factors, including changes in currents, such as an apparent slowdown underway in the Gulf Stream, and vertical movement of the Earth’s crust. North America is still adjusting to the retreat of glaciers 12,000 years ago. Northern New England, for instance, has been rebounding since it was freed from the weight of glaciers after the last ice age, counteracting sea level rise.

In North America, the Atlantic coast is at greatest risk from higher seas. A substantial fraction of the shoreline slopes gently to the ocean with relatively few protective bluffs. And the region has hundreds of kilometers of low-lying sandbar-like barrier islands, some densely developed. Both the US East and Gulf Coasts endure storm surges from perennial hurricanes.

During his flights between Maine and Florida, MacLean noticed something he hadn’t given much thought to before: thousands of industrial sites and vast amounts of critical infrastructure perched perilously close to the water’s edge, not far above the current high water level.

He flew by nuclear power plants, electric power lines, and airports. Many kilometers of track along a popular rail route between Boston, Massachusetts, and Washington, DC, closely hug the shore. A flood could cause a major disruption. He couldn’t see it, but MacLean also flew over kilometers of buried fiber optic cable carrying high-speed internet signals, also at high risk of flooding. A recent study found that in the next 15 years, sea level rise will put more than 6,500 kilometers of communications lines never meant to be underwater for long periods of time at risk of disabling floods.

Wherever he went, he saw sewage treatment plants. They’re important amenities for protecting public and environmental health, and they’re often located right along the coast, where they discharge treated effluent. But wastewater plants can’t work if they’re underwater. A study published last year found that with an increase in sea level of about 90 centimeters—a rise likely to occur well before the end of the century—162 such plants currently serving 10 million people in coastal states will no longer be operable. Michelle Hummel, an engineering professor at the University of Texas at Arlington and the lead author of the paper, says people often fixate on flooding of their homes, but from a national perspective, five times as many people will lose service when sewage plants fail than will experience direct flooding. “We need to be thinking more broadly about who is going to be impacted by sea level rise and how it will affect their communities,” she says.

During his project, MacLean’s winged shadow regularly slipped across oil industry infrastructure, including myriad tank farms and sprawling refineries built for convenient access to tankers. ExxonMobil’s petroleum terminal in Everett, Massachusetts, just a 15-minute flight from his own home in a Boston suburb, is an example. The site has been the subject of a drawn-out lawsuit over the possibility that a storm made more dangerous by higher sea level could wash toxic chemicals into nearby Boston Harbor. The Conservation Law Foundation, the public interest firm behind the suit, argues that ExxonMobil’s plans for preventing a chemical spill must take into account the effects of sea level rise and other environmental conditions. Otherwise, attorney Christopher Kilian asserts, the company is in violation of federal acts, such as the Clean Water Act. ExxonMobil counters that chemical safety rules don’t include any such requirements.

The case is expected to stretch on for at least another year, and could set a far-reaching precedent. If the judge overseeing the case ultimately decides against the company, thousands of industrial plants near the coast could be held responsible for safeguarding their operations against the impacts of climate change.

Whatever the outcome of the court case, much of the public and private infrastructure MacLean surveyed will either have to be armored against flooding or shuttered, cleaned up, and moved in the coming decades. The National Climate Assessment concludes that unless significant progress is made cutting back on planet-warming gases by the end of the century, losses to the US economy could reach hundreds of billions of dollars each year. The monumental task of responding to sea level rise will be just one part of global warming’s incalculable price tag.