Drone view of the Morro Bay sand spit and dune system, with Morro Rock at left, illustrating one of California's remaining coastal dune landscapes. Photo Credit: Kyle Emery
A new statewide assessment by researchers at the University of California, Santa Barbara and collaborating institutions has found that California has lost approximately 60% of its coastal sand dune systems since 1850. The study, published in the journal Earth's Future, is the first comprehensive inventory of dune change along the California coastline and documents widespread habitat loss driven primarily by urban development, land-use change, and erosion.
The researchers estimate that California's coastal dunes once covered roughly 739 square kilometers (285 square miles). Today, only about 300 square kilometers (116 square miles) remain. While natural processes such as erosion at estuaries and river mouths accounted for a relatively small amount of dune loss, the overwhelming majority resulted from human activities, including road construction, agriculture, urban expansion, and the introduction of invasive plants.
Comparison of the Humboldt Bay coastal dune system in 1854 (left), 1948 (center), and 2016 (right), illustrating changes in dune extent over more than 160 years. Courtesy Image
Lead author Tim Baxter, a postdoctoral researcher and physical geographer who conducted the research in the laboratory of Ian Walker, professor of geography and principal investigator at the UC Santa Barbara Marine Science Institute (MSI), emphasized the broader impacts of this decline.
“There are major implications of this loss for the California coast, including reduced habitats for plants, insects and other invertebrates, birds and small mammals,” Baxter said. “Importantly, we also lose coastal protections against storms and sea level rise.”
The study identified the largest losses in California's most densely developed coastal regions. More than 95% of the original dune systems in the San Francisco and Los Angeles areas have disappeared as land was converted for housing, transportation infrastructure, commercial development, and other uses.
“The thing that surprised me most was the scale of loss in San Francisco and Los Angeles,” said Kyle Emery, principal investigator at the UC Santa Barbara Marine Science Institute (MSI) and co-author of the study.
Central California also experienced substantial change, losing approximately 60% of its historic coastal dunes over the past 165 years. Researchers found that roughly half of the remaining dune systems have become isolated from the natural coastal processes that sustain them because of roads and other infrastructure. The study also documented localized dune growth in parts of Southern California where restoration efforts are underway.
To complete the statewide assessment, the research team combined historical maps, aerial photographs, LiDAR data, machine-learning techniques, and field observations to reconstruct changes in California's dune landscapes over time. The authors note that this approach could be applied to coastlines elsewhere in the world to help identify restoration opportunities and strengthen resilience to climate change.
Although dune restoration can provide important ecological and coastal protection benefits, the researchers emphasize that it is not appropriate for every shoreline. Local conditions, available space, costs, and community priorities all influence whether dune restoration is a practical solution.
The research was supported by the UC Office of the President Climate Action Research Initiative.
Research in this paper was also conducted by Ian J. Walker (PI), Jenifer E. Dugan (PI), David M. Hubbard, Karina K. Johnston, Sarah Smith, Dakota R. Fee, and Dan Willett at UC Santa Barbara; Laura Engeman and Jenna Wisniewski at UC San Diego; Sean Vitousek at the U.S. Geological Survey Pacific Coastal and Marine Science Center; and Andrea J. Pickart at the U.S. Fish and Wildlife Service.
Adapted from reporting by Sonia Fernandez, “California has lost more than half of its coastal sand dunes, first-ever comprehensive assessment reveals,” The Current, UC Santa Barbara, 2026.
Ten Mile Beach, MacKerricher State Marine Conservation Area, Mendocino County. Photo Credit: Kyle Emery