California is known for golden sands and endless waves, but much of the state’s famous shoreline could vanish in the future. That’s according to a new study, which found that between 25% and 70% of California beaches might be washed away by the end of the century, leaving only cliffs or coastal infrastructure in their wake.
The study used satellite data collected over the past two decades to examine California’s 1,100-mile-long coast. Researchers from the US Geological Survey (USGS) used those satellite images, combined with models of climate crisis-driven sea level rise ranging from 1.6 to 10ft, to estimate the shape and position of the state’s coastline by 2100. The amount of sea level rise will depend on how much carbon is pumped into the atmosphere now and in the future.
The paper, which is in the process of being peer-reviewed for publication, follows on from a 2017 study conducted by the same researchers focused on the rate of coastal erosion in southern California. That study found a similar fraction of southern California beaches – between 31 and 67% – were susceptible to vanishing.
“Beaches are perhaps the most iconic feature of California, and the potential for losing this identity is real,” wrote Sean Vitousek, the researcher who led both the 2017 study and the current one. “Losing the protecting swath of beach sand between us and the pounding surf exposes critical infrastructure, businesses and homes to damage. Beaches are natural resources, and it is likely that human-management efforts must increase in order to preserve them.”
The California Coastal Commission is already encouraging cities to harden their coastline by building seawalls or depositing large rocks that can help protect them from pounding waves (though sea walls can cause sand to erode faster from adjacent beaches). Restoring natural sand dunes can also help protect beaches. The study points to several areas at particular risk of severe erosion: Point Arena and Humboldt Bay in northern California, Pismo Beach and Morro Bay in central California, and Newport Beach and San Clemente in southern California.
Losing beaches can have ripple effects on the communities that live inland. A study published in January showed that with 3ft of sea level rise, San Diego county would lose a quarter of picnic areas, half of its lifeguard towers, and 15% of restrooms at coastal access sites. That affects lower-income, historically marginalized populations the most – coastal dwellers tend to be whiter, older and wealthier than the average California resident. Without lifeguards, parking and other amenities, it becomes more difficult for people living far from the coast to enjoy the benefits of remaining beaches.
The new study is the first time that satellite-derived shorelines have been used for this type of analysis, says Mark Merrifield, a coastal oceanographer at Scripps Institution of Oceanography in La Jolla, who was not involved in the research. But he warns that the predictions have a wide amount of uncertainty, so they should be taken with some skepticism, he says. “Beach morphology models in general have limited skill in predicting contemporary change, there are few datasets available for validation of the methodology, and projections of future wave and water level conditions introduce another level of uncertainty.”
The beaches that have made California famous are already changing, with a 2009 USGS study finding that about 40% of beaches were already experiencing long-term erosion. Looking forward, the shape and size of the beaches is not yet clear, like a wave in the distant view. More research will be needed to bring the future into sharper relief. “It’s a complicated topic,” says Merrifield.
Regardless, the study’s authors conclude that “substantial management efforts”, such as dune restoration, will be needed to maintain the beaches as they exist today. “It’s pretty sobering,” Vitousek recently told the San Francisco Chronicle. “This is a slow process when we’re talking about 2100, but it’s not that slow.”