California has lost 60% of its coastal dunes since the 1800s

The US Geological Survey announced Tuesday 10 November 2026 that California has lost 60% of its coastal dune area since the mid-1800s. A statewide assessment found that development, erosion and changes in land use reduced and fragmented the state’s coastal dunes.

According to the agency, coastal dunes currently extend along 352 km, or 22%, of California’s 1,625 km coastline. They cover almost 300 km2, representing a 60% decrease of 442 km2 since the mid-1800s.

Researchers from the University of California at Santa Barbara, the University of California at San Diego, the US Fish and Wildlife Service and USGS used historical maps, modern aerial imagery and LiDAR data. They also used a machine-learning tool to estimate the former extent of dunes and identify areas where they disappeared.

USGS Research Oceanographer and study co-author Dr. Sean Vitousek said most of the decrease in dune coverage was caused by people building structures on dune fields. He said much of San Francisco is developed over dunes that historically extended from Ocean Beach to what is now downtown.

The researchers found that the remaining dune ecosystems are more isolated and fragmented than historical stretches. This can make it harder for dune-dependent plants and animals to persist, move between coastal habitats and adapt to changing conditions. Southern and central California had significant declines.

The agency said dunes provide habitat for specialized species, support coastal communities and help reduce coastal flooding. The assessment identified where dunes were lost and where they remain, which the researchers said can help coastal managers prioritize restoration opportunities in suitable locations.