California’s sand dunes are vanishing and their disappearance could mean more floods and damage from storms in Santa Barbara.
Coastal sand dunes — mounds of sand along beaches formed by wind-blown sediment — play a crucial role in shielding beachside communities like Santa Barbara from coastal flooding.
Eroded sand dunes partially led to the massive floods that pummeled Santa Barbara in February 2024, said geographer Timothy Baxter. The floods caused the county and state to declare a local emergency and forced downtown residents to evacuate.
Baxter was the lead author of a UC Santa Barbara study which found that California has lost 60% of its sand dunes since its Gold Rush years — when the first statewide assessment of coastal sand dune loss was taken.
“For coastal communities, apart from losing these critical habitats, one of the main implications of this loss is a reduction in shoreline protection from coastal erosion and rising sea levels, which is only going to get worse in the future,” Baxter said.
Though sand dune ecosystems in Santa Barbara County are most evident in Rancho Guadalupe and Vandenberg Space Force Base, smaller fields can be found in Carpinteria and Santa Barbara, areas which Baxter estimates have lost 40% of their sand dunes.
But smaller than average sand dune loss doesn’t mean less significant.
“Those larger systems are really important,” Baxter said. “But it’s actually the smaller, narrower systems which are sometimes more important for coastal protection because communities are often built behind those narrower dune systems.”
As climate change makes coastal communities more vulnerable to rising sea levels, both cities have begun restoration efforts to boost sand dune systems and mitigate climate change impacts.
In 2022, the city of Santa Barbara removed the invasive ice plants along 1.1 acres of East Beach’s coastal sand dunes, replacing them with 3,200 plants native to the Central Coast.
Native dune species planted on the site include red sand verbena, pink sand verbena, silver bur ragweed, seashore false bindweed, beach suncup, and seacliff buckwheat.
“The site was specifically selected due to its heavy ice plant infestation and its location near a high-use multiuse path, making it a highly visible and impactful area for restoration,” said Lauren Bennett, spokesperson for the city’s public works department.
The city is also considering dune restoration measures to address coastal flooding and erosion for the next 30 years as part of its Waterfront Adaptation Plan.
“These measures have the potential to help reduce coastal hazards while supporting the Plan’s goal of saving the sandy beach and enhancing habitat,” said climate adaptation analyst Timmy Bolton, who works with the city to prepare the community for sea level rise.
Over in Carpinteria, the city recently began seeking community input to restore its historic dune system along Carpinteria City Beach as part of a long-term project to mitigate the impact of flooding and sea-level rise. Some current solutions also include removing invasive species.
Invasive species like ice plant, found commonly throughout California’s Central Coast, trap too much sediment, preventing it from shifting to nourish the dune system further inland. This kind of over-vegetation disrupts the natural development of the dune systems.
“They can, in some cases, enhance erosion because they grow so widely that if there’s a storm event, big chunks of the dune will fall off,” Baxter said.
Native dune species, on the other hand, are adapted to appropriately trap sand, helping build sand dunes into protective mounds.
“By planting native dune species, you’re encouraging the development of the sand dunes which have those protective effects,” Baxter said.
Santa Barbara County has only lost roughly 10% of its dunes overall, but this is because the county encompasses some of the state’s largest sand dune systems.
“It doesn’t sound like a lot but that’s because the Vandenberg dunes are so big,” said Baxter.
Vandenberg Space Force Base includes 9,100 acres of sand dunes.
The countywide loss is also lower than average because there hasn’t been the development of a big city on local dune fields, unlike Los Angeles and San Francisco. In those cities, 95% of native sand dunes have been lost.
According to the study, development of large cities, agricultural growth and erosion have led to the disappearance of sand dunes over time. Additionally, nearly half of remaining sand dunes are isolated from the coast, which prevents beach sand from feeding into the sand dunes.
“All along the coast, especially in southern and central California, you have seen pretty much everywhere the loss or degradation of dunes,” Baxter said. “The area of dunes might not have been lost as much, but in nearly all cases, you’ve seen the degradation of dune fields.”
Other than planting native species, allowing rivers to run naturally so that they can feed sand and sediment into the coastal area helps build sand dunes. Removing large breakwaters or jetties, like the one at Santa Barbara Harbor which traps sediment, also aids in maintaining sand dunes.
“There’s been some kind of restoration efforts within Santa Barbara County,” Baxter said. “But a wider implementation of those efforts have been hindered by a lack of knowledge of where sand dunes are and how they’ve changed over time.”
