50 million Chinese live in cities that will sink below sea level by 2120

The third of Urban areas in China Sinking at an alarming rate, it is estimated that 100 years A quarter of coastal areas will be Below sea level.

Specifically, an analysis of the country's major cities shows this 45% They are drowning 3 mm every yearAnd another 16% And even more so, at a rateOne centimeter per year at least.

The main reasons areDepletion of groundwater aquifers That's below, too Weight of buildingsgetting bigger and bigger, which will take Measures to reverse this.

These are the main conclusions of a study that used data from Synthetic aperture interferometry radaror InSAR, from Sentinel-1 satellite The European Space Agency, ESA, has been operating ever since 2015.

50 million Chinese live in cities that will sink

The study was published a few days ago in the magazine SciencesThis was done by researchers from Peking University led by Jingyun Fang.

In the conclusions they highlight the areas where they live now 50 million Chinese He will stay Flooded By the sea 2120due to the cumulative effect of collapse and High water levels For greenhouse:

“We found a high risk of coastal flooding unless appropriate protection measures are implemented and maintained.”

They also point out that currently nearly half of the cities suffer from “UN”. Moderate to severe collapse“And note that this is due to”Human activity“:

The planetary scale problem

And An analytical article accompanying the research He points out that among the most affected areas are Beijing I TianjinIt is among the 16% that sink one centimeter per year.

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This article mentions that ShanghaiThe largest city in China collapsed 3 meters In the last 100 years, And the Sentinel-1 InSAR data found that Keep doing it

authors, Robert Nicholsfrom University of East AngliaAl-Rijani Unit, ed Manouchehr Sherzaithe follower Virginia Tech University, In the United States, experts in the use of this data warn against this The planetary scale problem:

“The ground is collapsing almost everywhere. If we do not take this into account now in our adaptation and resilience plans, we could face widespread destruction of infrastructure in the coming decades.”

They claim it is a problem affecting e.gto 20% of the world's populationAnd stopping the extraction of water from groundwater aquifers and refilling it is an order The most urgent action To slow it down. They gave an example of what happened there Tokyo I osaka, In Japan in the 1970s.

A natural phenomenon in which humans accelerate

Collapse of ground surfaces, or drop, It is a natural phenomenon that depends on Geological structure of the Earth's interior This is usually the case I lent I fixedBut this human action is accelerating in many places.

In this sense, they note that this occurs mainly in… Alluvial plainsespecially To the coastAnd the collapse is faster The more human presence and activity.

Researchers say it was a relatively rare phenomenon until now He studied a littlethat the searches performed were Fragmented and unsystematic This has changed with InSAR.

This radar emits pulses that make it possible to measure the extent of its change Satellite distance to each point of the Earth's surface, and to do this it is combined with measurements Global Positioning System American

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Both works published by Science confirm this thanks Tremendous accuracy From this radar for the first time it was possible Systematic and comprehensive follow-up of urban collapse.

Nearly 1 billion Chinese in 82 major cities

The research has now been conducted using data collected by InSAR between 2015 and 2022 from 82 cities in China with more than two million people. 74% of the country's urban population lives there.

here they are 920 million peoplehalf in 10 large urban agglomerations, in one of the largest, fastest and most extensive urban expansions in human history. In fact, it may be the largest of all.

The authors found this The largest buildings They sink less Of the smaller, and they believe that this is because The foundations are much deeper Previously, this protected them.

Also, the weight of infrastructure, such as Highways, roads and railways Contributing to the collapse, but also Vibrations Which are created by vehicular traffic.

Another big contributor is Water extraction From groundwater aquifers, which make Check the ground's porosity and compactionwhich also happens in Oil exploitation.

Determine the effects of each cause

This is an amazing number and 5% Of the areas of 82 cities, they are sinking at a rate 2.2 cm per yearThis is a fact considered by the authors Very disturbing

They warn about that, too Different causes act simultaneouslyIn order for us to be able to separate the effects of one from the other, it is necessary to conduct more research that allows this Building models to work on.

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They end up pointing In the dam system Which China is building to prevent the sea from expanding on the coasts, which they describe as “huge“And I tell them They're drowning too.

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