While the subject of sea-level rise has rightfully gotten much attention, its lesser known twin – land subsidence – has also been emerging as an urgent challenge for many coastal cities.

A new study led by Ms Cheryl Tay, a PhD student under the National Sea Level Programme at the Earth Observatory of Singapore and the Asian School of the Environment, sheds light about the scale of the challenge. 

The study found that 42 out of 48 of the world’s most populous coastal cities are sinking, and they do so at median rates of up to 16.1 millimetres (mm). It also found that at its peak, subsidence can occur as quickly as 43 mm per year, which is 10 times more than the current global mean sea-level rise of 3.7 mm per year.

Local land subsidence mostly happens in rapidly expanding megacities, where an increased demand for groundwater and rapid urban development cause soil compaction.

Below is a short clip explaining the key findings of the paper, which can be found here.

This research contributes to the Singapore National Sea Level Programme supported by the National Research Foundation, Singapore and Singapore’s National Environment Agency.