New York City is Sinking Under its Own Weight

What's the story?

• A new study in the Earth's Future journal found that New York City is sinking under the weight of its buildings, with climate change and sea level rise contributing to the process.

What's happening?

• The study found that the mass of the 1,084,954 buildings across NYC's five boroughs is 1.68 trillion pounds. This is equivalent to approximately 1.9 million fully loaded Boeing 747-400s.
• Geological and satellite data aided the researchers in their key discovery, leading to the belief that the city is sinking at a rate of about 1 to 2 millimeters a year. More developed areas, like lower Manhattan, Brooklyn, and Queens, are sinking at a rate of 4½ millimeters a year.
• The sinking can be attributed to various causes, not merely the weight of the buildings. Tom Parsons of the U.S. Geological Survey, and one of the lead authors of the study, said:

"We could see some correspondence where there's construction on very soft soils and artificial fill. And there's a lot of different causes of it, such as post glacial relaxation that happened after the last ice age, or groundwater pumping."

• Geophysicist Sophie Coulson said:

"This research takes a look at an important human factor that has only recently come into focus — the effect of urban building loads on coastal land subsidence."

A global problem

• As of 2020, scientists estimated that all the things humans have ever made weigh more than every living thing on Earth. 
• A 2022 study found that 44 of the 48 most populous coastal cities around the world contain areas that are sinking faster than sea levels are rising.
• Parsons said, "it's a global issue," and pointed to research that shows 99 cities around the world being impacted, such as Venice, Mexico City, and Jakarta. Jakarta is sinking so quickly that the government is considering relocating the capital.

The climate change connection

• Worldwide, the projected sea level rise is between 200–600 millimeters by 2050. Sea level rise in NYC is occurring twice as fast as the global rate, and scientists have projected that it could rise between eight and 30 inches by 2050.
• New York City is ranked third in the world regarding exposure to flooding damage, and 90% of the 67,400 structures in the flood-risk areas were not built to floodplain standards.
• Climate change will also lead to more frequent and extreme rainfall and flooding events in the region. More specifically, the paper states that greenhouse gas appears to be reducing the natural wind barrier along the east coast, creating higher-intensity hurricanes.
• Parsons said:

"We're a ways off from the ocean simply moving in. But we've had a couple of major hurricane events with Sandy and Ida in New York where heavy rainfall caused inundation in the city, and some of the effects of urbanization have allowed water to come in."

• The paper ultimately points to the complex web of factors at play:

"[E]very additional high-rise building constructed at coastal, river, or lakefront settings could contribute to future flood risk."

Are you worried about sinking cities?

—Emma Kansiz