On September 27, 1889, workers put the finishing touches to building the tower. It was an 11-story building and, thanks to its steel structure, is considered the first skyscraper in New York. The tower was long gone—a plum spot on Broadway was snapped in 1914—but its construction marked the beginning of a construction wave that hasn’t stopped until now.
More than 300 square miles (777 km2) of New York City is home to 762 million tons (£1.68 billion) of concrete, glass and steel, USGS researchers estimate. While this number includes some generalizations about shrinkage materials, this tonnage does not include fixtures, fittings, and furniture within that million buildings. Nor do they include the transportation infrastructure that connects them, nor the 8.5 million people who inhabit them.
All this weight has an extraordinary effect on the ground on which it is built. That foundation, according to a study published in May, is sinking 1 to 2 millimeters (0.04 to 0.08 in) per year due to pressure exerted by the city’s buildings above. And that’s something experts worry about – add land subsidence to sea level rise, and the relative rise in sea level is about 3 to 4 mm (0.12 to 0.16 in) per year. It may not seem like much, but after a few years, it adds up to the port city’s big problems.
New York has already suffered a downturn since the end of the last Ice Age. After easing the weight of the ice caps, some lands on the East Coast are expanding, while other parts of the coastal lands, including the part where New York City sits, seem to be doing just fine. “This relaxation causes the retreat,” says Tom Parsons, a research geophysicist at the University of California, Los Angeles. USGS Pacific and Marine Science Center in Moffett Field, California and one of the study’s four authors.
Parsons says the sheer weight of the city’s built environment exacerbates this degradation.
It is a global phenomenon. Parsons explains that New York City “can be seen as a proxy for other coastal cities in the United States and around the world that have growing numbers of immigrants, that have been associated with urbanization, and that are facing sea level rise.”
There are a wide range of reasons why coastal cities are collapsing, but the mass of human infrastructure pressing on the land plays a role. The scale of this infrastructure is enormous: in 2020, the mass of man-made objects has exceeded the mass of all living biomass. (Learn more about how concrete became the defining material of our time.)
Could anything be done to prevent these cities – home to hundreds of millions of people – from sinking into the sea?