New Zealand Cities are slowly sinking

April 10, 2025

Share to Google Classroom

New satellite data shows that the coastlines of New Zealand’s major cities, including Christchurch, Wellington, Dunedin, and Auckland, are slowly sinking.

This land sinking, or subsidence, is making rising sea levels even more dangerous for these areas. The findings come from new research using advanced satellite technology released in 2025.

What’s Happening:
Globally, sea levels have risen by about 18cm since 1900 and are increasing more quickly now—about 4.4mm per year. But in New Zealand, the problem is even worse because parts of the land are sinking at the same time. In places like Christchurch, some coastal suburbs are sinking up to 8mm every year, which means sea levels are rising faster than they seem.

Why It Matters:
When land sinks and sea levels rise, it’s called relative sea-level rise. This can make storm damage worse and affect buildings, roads, and homes near the coast. For example, Christchurch is sinking by about 3.6mm each year, Wellington by 2.4mm, Dunedin by 1.6mm, and Auckland by 1.5mm. Combined with rising seas, this means some cities could see the water level rise by 70cm in 100 years.

How They Know:
Scientists used a special tool called InSAR, a radar system on satellites, to measure tiny changes in the Earth’s surface. It gives them a very detailed picture of how much the ground is moving—even within different parts of the same city.

Where It’s Worst:
Some of the fastest sinking spots are in Christchurch, especially areas affected by the 2011 earthquake. Other places, like Porirua Harbour, are also sinking quickly, especially where land was reclaimed from the sea during the last century.

LEARNING OPTIONS