Beach sand replenishment at Fletcher Cove in 2018. Courtesy SANDAG

Only one-third of the sandy beaches between Santa Barbara and San Diego retain their full biodiversity because of efforts to groom them for beachgoers.

That was the conclusion of a study by researchers at UC Santa Barbara’s Marine Science Institute, who found that flattened dunes, destroyed native vegetation and groomed sand are anything but natural.

“After studying mainland beaches in Los Angeles and San Diego, one of the big a-ha moments for me occurred when I went out to the Channel Islands to study sandy beaches that have never had vehicles driving on them and have never been subjected to grooming, filling or bulldozers,” said coastal marine ecologist and study co-author Jenny Dugan.

On those beaches, she noted, coastal vegetation comes right down to the winter high-tide mark, sand collects in dunes of all sizes and shapes, and kelp washes onshore and accumulates in piles, providing food for an amazing variety and abundance of invertebrates, which, in turn, are food for shorebirds and fish.

The scientists concluded in the study published in the journal Ecological Indicators that the lack of biodiversity could have negative effects in terms of erosion, sea level rise and the health of the surrounding ocean and coastal ecosystems.

“We observed strong negative responses to these intense widespread practices on urban beaches in the biodiversity, structure and function across all the intertidal zones of beach ecosystems,” said Nicholas Schooler, a postdoctoral reseacher and the study’s lead author.

In comparisons between select urban beaches in Carpinteria, Malibu, Santa Monica, Redondo Beach, Huntington Beach and Carlsbad, and neighboring, minimally disturbed “reference” beaches within the same area, the scientists found that up to half of the natural inhabitants were missing on the urban beaches.

A major problems was found to be the differing grain size of sand brought in to replenish beaches. “Many beach species are very sensitive to sand grain size,” Dugan explained.

“This study will force us to make critical choices about whether we value well-groomed beaches or healthy natural ecosystems,” said David Garrison, a program director in the National Science Foundation’s Division of Ocean Sciences, which co-funded the research.

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