In parts of northern Java, the ground is literally giving way faster than many people realize. And that changes the math for flooding—sometimes dramatically.
A study published today in Science Advances reports that land subsidence, or the sinking of the ground, is outpacing ocean-driven sea-level rise along nearly the entire northern coastline of Java Island, Indonesia. Java is home to more than 150 million people—about 2% of the global population—so the stakes aren’t abstract. They show up in daily life: in crowded coastal areas where water can creep in, linger, and then come back again.
Misryoum newsroom reported on the research, which takes an unusually wide and detailed look at how the hazard is spreading. Using satellite radar data and advanced machine learning techniques, the research team mapped land subsidence across Java in unprecedented detail. The picture they produced spans both urban and rural areas, and it’s not static—ground sinking is widespread and rapidly evolving. In some places, rates reach up to 1.5 meters per decade, exceeding the rate of global sea-level rise affecting Jakarta, Cirebon, Semarang, Surabaya and other major coastal cities in Indonesia.
The authors describe this as a fundamental shift in coastal risk. “This study reveals a fundamental shift in how we understand coastal risk,” lead author Leonard Ohenhen said. “In many parts of Java, the land itself is sinking so rapidly that it is overwhelming the effects of ocean-driven sea-level rise. That means the hazard is not just coming from the ocean; it is being driven from below the ground.” Ohenhen, now an assistant professor at UC Irvine, conducted the work while he was a Lamont Postdoctoral Fellow.
What makes the findings especially worrying is how large the contribution from sinking land could be. By integrating satellite observations with sea level projections, the researchers found that land subsidence could account for up to 85% of relative sea-level rise along much of Java’s coastline by 2050. They also project that more than 75% of the coastline will be dominated by subsidence-driven flooding risk over the next 25 years. Coastal communities are already experiencing relative sea-level rise rates far exceeding global averages—so for many residents, it’s not a future problem waiting politely in the margins.
A big part of the reason this is happening is, at least in many locations, local human activity—especially groundwater extraction. Misryoum editorial desk noted the study identified key drivers of subsidence, including intensive groundwater withdrawal in urban areas, agricultural water use, industrial extraction and natural sediment compaction in delta regions. The work also tackles an obstacle that often slows coastal science: a lack of ground-based monitoring. To get around it, the team developed a novel approach using satellite data to create “virtual tide gauges” every five kilometers along the coastline. That allowed them to reconstruct past and future sea level changes with unprecedented spatial detail, revealing risk patterns that vary sharply across short distances.
“This kind of high-resolution assessment is needed in coastal regions around the world,” co-author Folarin Kolawole, a structural geologist at LDEO and an assistant professor in Columbia’s Department of Earth and Environmental Sciences, said. Co-author James Davis, a geodesist at LDEO, added: “What matters most for coastal communities is not just global sea level, but how the land and sea are changing in that specific place.”
Even though the study is focused on Java, the researchers argue the lesson could travel. Misryoum analysis indicates that many coastal regions worldwide may be dealing with similar, often unseen dynamics. The team emphasizes that adaptation has to go beyond managing ocean rise; it should include active monitoring and mitigation of land subsidence. “Subsidence is one of the most actionable components of coastal risk,” Virginia Tech geoscientist Manoochehr Shirzaei, a co-author, said. Unlike global sea level rise, which demands global solutions, subsidence can often be managed locally through policy, infrastructure and sustainable resource use.
And the sensory part—what it might mean on the ground—isn’t hard to imagine. You can picture a low street that smells faintly of damp concrete after a storm, water not quite leaving, and then the next tide doing the same thing again. Except in this case, the tide isn’t the only culprit. The land is settling too—quietly, relentlessly, and fast.
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