New research highlights that rising seas are not the only threat to coastal communities: the land itself can sink, making “relative sea-level rise” faster than ocean measurements alone. The findings indicate that densely populated coastal regions can experience an average relative sea-level rise of about 6 millimeters per year, nearly three times the global coastal average. This acceleration occurs when subsidence lowers the ground relative to sea level, increasing the impact of storm surges, flooding, and high tides.
Across sources, the causes of sinking include groundwater pumping and resource extraction such as oil and gas development. Urban development can also contribute through processes like sediment compaction. In addition to human activities, natural geological processes play a role in how quickly different areas subside. As a result, some coastal cities see faster land subsidence and greater flooding risk than would be expected from sea level rise alone.
Improving groundwater management is identified as a potential way to slow sinking in vulnerable areas, though the problem is described as driven by multiple interacting factors.
