When it comes to discussions about climate change, people are mostly familiar with the very real issue of rising sea levels.

But a recent study came out this year that touches upon a rather alarming and relatively under-discussed issue that’s also connected to climate change: subsidence.

What’s subsidence? Well, subsidence is the sudden sinking or gradual collapsing of the ground beneath us.

If you didn’t know this before, you should now: the ground is literally sinking beneath our feet, and it could be a problem 10x bigger than sea level rising.

20% of the world’s population will be affected by ground sinkage by 2040

A new global analysis study found that almost 20% of the world’s population will be affected by subsidence by 2040. This amounts to approximately 635 million people.

But what does that mean? What are the causes of subsidence?

Subsidence is caused by human activities (such as the removal of groundwater) as well as natural phenomena. Groundwater depletion is a particularly common practice in hotter places with less access to consistent water supplies, like in California.

Subsidence can cause earth fissures (cracks formed on the ground), damage buildings and civil infrastructure, increase the risk of floods and, importantly, reduce the storage capacity for aquifer systems.

Aquifer systems are important for a lot of places around the world. Many cities are only able to get their water from an aquifer. Subsidence could lead to immense water shortages for the people who live in these cities.

Subsidence might be 10x a bigger problem than rising sea levels

This is partly due to the fact that the areas at risk for subsidence tend to be closer to densely urban and irrigated areas (areas that are supplied with water from pipes, sprinklers, ditches, or streams) that have high demands for groundwater.

Because subsidence is likely to occur near densely populated areas, more people will be affected by it.

Agricultural areas and areas affected by droughts are also more likely to experience subsidence.

This means not only could subsidence limit cities’ abilities to store water, it could affect farming and food production too.

22% of the world’s major cities are in potential subsidence areas

According to the study, 1596 major cities around the world are in potential subsidence areas.

Countries that are already affected by this problem include the United States, the Netherlands, Italy, Japan, Indonesia, the Philippines, China, Mexico, Vietnam, Egypt, Iran, and other mediterranean countries.

Major coastal cities with high flood risk globally are even more likely to experience subsidence.

Unfortunately, it’s difficult to assess the true impact subsidence could have largely due to the fact that there isn’t enough information available.

But if cities around the world develop effective land-subsidence policies which include monitoring exposed areas, evaluating potential damages and figuring out how much it will cost to implement  these policies, the effects of subsidence could be decreased.

Relevant data stories

Sources