Scientists say New York City is sinking by up to four millimetres a year under the weight of all its skyscrapers. A team of geophysicists from the United States Geological Survey calculated that there are 1,084,954 buildings in the city, weighing around 764 billion kilograms. This weight does not include fixtures and fittings in buildings, the transport infrastructure, or the weight of the city's 8.5 million inhabitants. Lead researcher Dr Tom Parsons said the gradual subsidence, coupled with rising sea levels, could make New York prone to natural disasters. He warned that "every additional high-rise building could contribute to future flood risk," especially along coastal and riverfront areas.

The researchers compared what is happening to New York to the problems Venice and Jakarta are having. Venice is experiencing more floods despite the construction of a $5.3 billion system of sea walls. Indonesia is building a new capital city from scratch because Jakarta is sinking. The United Nations has forecast that 70 per cent of the world's population will inhabit cities by 2050. Parsons said: "When you build a city and it gets full of people, you end up with subsidence." He warned that New York City was "emblematic of a place that people migrate to and that obviously has a high concentration of construction." Increasing urbanisation will exacerbate problems for cities.