As much as 25% to 70% of California’s beaches could completely erode by the end of the century due to rising sea levels and “cascading uncertainties in greenhouse gas emissions [and] global temperature projections,” according to a new study from the United States Geological Survey that collected two decades’ worth of satellite data from San Francisco’s Ocean Beach, The beach was used as a model to analyze the state’s entire 1,100-mile-long coastline.
The models used in the study, which has yet to be peer-reviewed and published, are based on sea level rise projections of 1.6 feet to 10 feet, a range that is expected to vary depending on the rate and reduction of carbon emissions over time. Ongoing climate trends and historically damaging storms also play a role in the acceleration of the shifting coastline, which could put several beaches at severe risk of erosion, including 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, leaving only rocky cliffs and coastal infrastructure behind.
The study follows up on a 2017 paper from the same researchers focused on Southern California, which predicted at the time that 31% to 67% of beaches in the region were susceptible to disappearing.
“Beaches are perhaps the most iconic feature of California, and the potential for losing this identity is real,” Sean Vitousek, the lead author on both studies, wrote at the time. “The effect of California losing its beaches is not just a matter of affecting the tourism economy. Losing the protecting swath of beach sand between us and the pounding surf exposes critical infrastructure, businesses and homes to damage.”
Last year, the National Oceanic and Atmospheric Administration predicted that sea levels would rise up to 8 inches in California and along the West Coast in the next 25 years. Meanwhile, the state government is reducing funds that would foster efforts to preserve beaches – in his budget this year, Gov. Gavin Newsom proposed a cut of more than $700 million from the “coastal resiliency” fund used to support the shoreline, the Washington Post reported.
The California Coastal Commission is warning cities against building seawalls or piling boulders to protect coastal homes from surging waves and storms, because they are no longer considered effective measures, simply redirecting rising seas to other areas and causing beaches to deteriorate faster. Instead, the commission is recommending natural alternatives like restoring sand dunes or managed retreat, which refers to the process of moving infrastructure inland and away from crumbling cliffs, the San Francisco Chronicle reported.
However, because the new study marks the first time that satellite shoreline models have been used for this type of research, Mark Merrifield, a coastal oceanographer at Scripps Institution of Oceanography in La Jolla, told the Guardian they should be taken with a degree of skepticism.
“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,” he told the outlet.
That being said, another 2009 study by the USGS revealed that about 40% of California’s beaches were already eroding over a long term period. Continuing to closely observe and manage them is key, Vitousek said.
“Beaches are natural resources, and it is likely that human-management efforts must increase in order to preserve them,” he said.
