A new study finds that land subsidence, a phenomenon where land sinks due to groundwater depletion, may threaten more than a billion people by 2040. The climate crisis and exploitation of our water resources may further exacerbate an issue already forcing leaders to move entire cities and rethink agricultural practices.
Across California’s Central Valley, the land is sinking. In some places, by as much as 28 feet. In fact, this phenomenon—known as subsidence, which occurs when too much groundwater is extracted from vulnerable rock formations—is global. Indonesia is moving its capital city of Jakarta because of it; Venice suffers floods all too regularly now due to subsidence, too.
This gradual sinkage damages buildings, affects drinking water access, and creates nightmare flooding scenarios. With seas rising due to climate change, people don’t need their homes dropping any lower. Unfortunately, a new study published in Science Dec. 31 has found that land subsidence may threaten a whopping 1.6 billion people around the world by 2040. Some 635 million of these individuals may be at increased risk of flooding, in particular.
Welcome to The Frontline, where you can count on science to prove just how unjust the warming of the world is. I’m Yessenia Funes, climate editor of Atmos. This week won’t feature any themes; I’ll be focusing more on daily news for the new year. You might’ve missed this study last week, which is the first (according to the authors) to look at land subsidence at a global level. If we don’t reduce greenhouse gas emissions fast—and even if we do—hundreds of millions of lives will potentially be at risk.
In a world where the population keeps steadily rising and businesses keep emitting carbon dioxide, land subsidence may threaten eight percent of the global land surface. All the damage that may result from such geological changes could expose more than $8 trillion of our global GDP. Subsidence is projected to affect major populations in India, China, Egypt, and the Netherlands. In terms of dollars, however, the U.S. is top of the list.
Here’s the thing, though: Property and infrastructure damage can be repaired. As for human lives? Once they’re lost, they’re lost forever.
“Global communities are definitely at risk,” says co-author Michelle Sneed, a land subsidence specialist with the U.S. Geological Survey’s California Water Science Center. “In the Central Valley of California, we don’t have sea level rise to worry about. We have a lot of infrastructure that gets damaged, but it’s fixable.”
In the U.S., the Central Valley is among the regions most at-risk of subsidence. However, so are parts of the East Coast and Midwest. In Asia, where most of the global population is projected to be exposed, the Chinese coast is especially vulnerable. The climate crisis will exacerbate this phenomenon, per the study. So despite contributing very little to the warming of our world, many communities in the Global South may suffer yet another hit from it.
“The richer populations will build seawalls or move to safer locations as land level drop and sea levels rise due to climate change, leaving the poor to suffer the most.”
The team of researchers—which represent all corners of the world where this phenomenon occurs—pioneered a new model using an already established statistical method to predict where subsidence may occur in the future. They reviewed hundreds of papers and looked at irrigation patterns, groundwater demand, and population data to make their conclusions. The team lacked some data on pumping rates and geological information for different regions, but that’s expected when taking a first-of-its-kind global look. The methodology didn’t raise any eyebrows for Thomas Farr, a recently retired scientist with NASA’s Jet Propulsion Laboratory who has worked with several of these authors on other research.
As the paper makes clear, its findings are based on a business-as-usual climate scenario where we fail to respond to the climate crisis. That means in a world where we do take on this task, the numbers may not be as bad. Leaders can also prepare for these potential outcomes now and adapt to prevent such a vast impact on people.
“As we understand the causes of subsidence on a case-by-case basis, we can better minimize it,” Farr said in an email. “Subsurface geology makes some areas, like the southern part of the San Joaquin Valley, more susceptible than others, so those areas need to be pumped less. In some areas, we can increase the amount of recharge of the aquifers artificially or at least protect the recharge zones of threatened aquifers.”
That was the goal of this research, Sneed says: to raise awareness. Officials are rarely proactive about subsidence; their response is usually reactive. That needs to change. This study can help by giving officials an idea of where to look.
“Subsidence really doesn’t get a lot of attention,” Sneed says. “It’s a slow moving disaster, so it just doesn’t have that punch that a hurricane would have.”
However, the impacts are very real for the people living through this disaster—and the impacts are set to grow much worse if our leaders don’t prepare or take action. After all, subsidence is a result of overexploitation of water, a resource that’s becoming increasingly more valuable in a drier climate. When giant farms extract too much water, they don’t leave enough behind for smaller farms or communities that rely on well water for their household needs, says Peter Gleick, a water expert and President-emeritus of the Pacific Institute, a California-based organization that advocates for sustainable water usage. That’s why Gleick says this is “absolutely an environmental justice issue.”
“Around the world, especially in coastal communities where land is subsiding due to groundwater overdraft, the richer populations will build seawalls or move to safer locations as land levels drop and sea levels rise due to climate change, leaving the poor to suffer the most,” he told me via email.
Water is life. Communities need sustained access to safe, affordable water. They also need to be kept out of harm’s way when the waters start rising and the land starts sinking. Some of these environmental changes are already baked in, but the potential harm to people’s lives is not. That’s entirely preventable.