Some of Southern California’s Most Iconic and Popular Beaches Have Lost Nearly All of Their Biodiversity

by on July 31, 2019 · 7 comments

in California, Environment, Ocean Beach, San Diego

by Sonia Fernandez, University of California – Santa Barbara / Phys-Org / July 31, 2019

To most people, a beach is a beach. You could likely take an image of almost any urban beach in Southern California—the flat, mostly featureless expanse of sand against blue-green water and blue skies—swap it with one of nearly any other urban beach in Southern California, and chances are that only a trained eye would notice the difference. Some of these differences lie just beneath the surface, however, and are actually quite important ecologically.

Dig just few inches into the sand on many beaches in Southern California—home to some of the most biologically diverse sandy beaches in the world—and you’ll find it teeming with life such as sand crabs, clams and beach hoppers. But for about a third of the sandy beaches extending from Santa Barbara to San Diego, only a small subset of these highly specialized beach animals remain, and in reduced numbers at that.

This lack of biodiversity, say researchers at UC Santa Barbara’s Marine Science Institute (MSI), is an unintended consequence of the quest to maintain the Instagram-ready, tourist-accommodating, iconic look of Southern California’s urban beaches. Cities up and down the coast have flattened dunes, destroyed native vegetation and groomed the sand with heavy equipment such that what many of us have come to call “natural beauty” is in fact about as natural as a sand parking lot.

All of this, the scientists write in a paper in the journal Ecological Indicators, has massive impacts on the larger beach ecosystem. Further, it could already be having negative effects in terms of erosion, sea level rise and the health of the surrounding ocean and coastal ecosystems.

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.

This well-tuned ecosystem has been disrupted on Southern California’s urban beaches, say Dugan and her co-researchers. Heavy machinery is often employed to rake trash and debris out of the sand—and large quantities of sand from elsewhere are brought in to replenish sand washed away by storm and wave action. Some beaches are groomed daily, often twice. The frequency of disturbance to many beaches by these widespread activities is greater than any known farming or land management practice. [ed: our emphasis.]

“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 researcher within MSI and the study’s lead author, He conducted the research when he was a Sea Grant trainee.

Some of these results came as no surprise to the researchers. In previous studies, the team found disturbance from beach grooming caused strong negative impacts to upper intertidal biodiversity on Southern California beaches and in one study those impacts persisted for more than three decades. The current study, funded by Sea Grant and the National Science Foundation, took a much wider and deeper look at the diversity of beach ecosystems affected by these management practices, revealing the scale of impacts across the entire intertidal zone as well as the region.

“We explored how disturbance from these management practices affected ecological communities on different spatial scales,” Schooler said, “including that of littoral cells, which are basically compartments of the coast that contain a sand source, usually rivers, alongshore transport of sand by waves and currents, and a sink where sand exits the system, such as a submarine canyon.”

The results are sobering. 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 littoral cells, the scientists found that up to half of the natural inhabitants were missing on the urban beaches. The ones that remained tended to be the same few species across all littoral cells.

“Beaches within a littoral cell can often support very similar intertidal communities, but those communities vary distinctly from cell to cell,” Schooler explained. However, the disturbance to the sand caused by grooming and filling on urban beaches has homogenized the intertidal communities of those beaches across littoral cells in Southern California, he added.

One reason for the impacts, according to Dugan, is that in addition to the habitat destruction and disturbance by the heavy machinery used for grooming, beaches are often nourished or filled with the “wrong” sand.

“Many beach species are very sensitive to sand grain-size,” she explained. Beach clams, for instance, require fine-grained sand in order to flourish. But the sand brought in by the dump truck to fill urban beaches comes from harbor dredging or quarries miles away and is coarser than the long-lived, slow-growing beach clams can handle. An increase in sand grain-size from beach filling can exclude a great variety of species of beach animals from living on an urban beach.

The severe drop in intertidal species diversity documented in this study is a cause for concern—and not only because of the loss of unique intertidal species. It also renders the urban beach ecosystem more susceptible to collapse, the scientists said. Fewer species occupying important roles in the food web means that the system is more likely to be thrown out of balance should one species disappear. Reduced diversity and abundance of invertebrates in the sand could also mean less food for the fish and shorebirds that depend on beaches.

Although sandy beach ecosystems are generally thought of as highly resilient given their conditions of constantly moving sand and water, the study results show how sensitive these ecosystems are to human disturbance. This was particularly apparent for wrack-associated species—the small invertebrates that inhabit the upper intertidal zone and rely on stranded kelp wrack for food and shelter. This group typically represents around 40% of the biodiversity on Southern California beaches.

“For one of our urban study beaches, wrack-associated species were completely undetectable in our surveys, representing a major loss in both diversity and ecosystem function,” explained Schooler. The extreme vulnerability of wrack-associated species follows a theme in their continued research on sandy beach ecosystems.

“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. “Shorebirds and other marine life we value are critically dependent on resources provided by thriving ecosystems.”

“We started out doing ecology for ecology’s sake, asking basic questions on the diversity and functioning of sandy beach ecosystems,” study co-author David Hubbard, of MSI, said of this study. “The more we worked in Southern California, the more we realized how altered many of the beach ecosystems were.”

With this new information, however, they hope to turn some of that around. Managers of urban beaches, such as those in the Beach Ecology Coalition, have been receptive, the researchers said. It will take more education, they noted, but if the managers better understand, for instance, that native dune plants can prevent beach erosion and buffer against sea level rise, or that a healthy beach invertebrate population could take care of kelp wrack without help from heavy grooming equipment, some unique species richness and ecosystem resilience could be restored to sandy beaches.

{ 7 comments… read them below or add one }

Frank Gormlie July 31, 2019 at 12:17 pm

Okay, all you scientists who are so opposed to saving Mauna Kea better read this one carefully.


Peter from South O July 31, 2019 at 1:16 pm

And the lesson here (as relates to the research being done on Mauna Kea) is?


retired botanist July 31, 2019 at 3:56 pm

I think the lesson is, without necessarily putting words in Frank’s mouth, that conventional beach management has prioritized the human species’ desire for raked, wrack-free, trash-free, manicured ground. The tie-in to Mauna Kea is also the prioritization of human desire vs undisturbed land (whether that priority is science based, hygiene based, or aesthetics based).
With the Mauna Kea controversy, the issues are biodiversity, tradition and cultural preservation, and the need for further scientific exploration. With shoreline management, the issues are human health (and believe me, you probably don’t want to know what’s actually living in the sand that doesn’t belong there), aesthetics, and tourist revenue (no sand, no people). So in the latter case, we continually import and create an artificial beach shoreline (one that’s cleaned of rotting seaweeds (and styrofoam trash, and doesn’t disappear every winter) and in the former case, we cast aside preservation of biodiversity and a minority’s claim to cultural space in the interest of future scientific endeavor.
In both scenarios, we’re tampering with ecosystems and just can’t seem to leave them alone, and we have decided (god help us) on what we think is in humans’ best interest!
Another good example of this sort of tinkering is the La Jolla Children’s Pool: it’s still a controversy, though it flares up and dies down depending on City Hall. The issue? Whose pool is it? The seal’s, the people’s, the tourist’s? Ropes up, ropes down. Stink up? Power-wash stink down, there goes the guano, but save the nearby condos from the smell…
The moral of these stories, and it doesn’t take a lot of high-falutin’ science to understand it, is that if we insist on pushing nature around and try to mold it to our idea of how it should be configured, or used, we run the risk of irreversibly altering it in such a way that no species, including ourselves, gets any benefit.


Peter from South O July 31, 2019 at 4:52 pm

Fer cryin’ out loud. Try a Google Earth satellite view of Mauna Kea. Zoom out so you can see the whole island, then zoom in to the summit. Plenty of surface photos there, too.
Biodiversity is an issue here? No. No it is not.


retired botanist August 1, 2019 at 7:41 am

Aah, Google Earth! That’s a postcard far below the scope of the Mauna Kea project. ALL projects requiring environmental review, and SoCal has plenty of them- in beach, desert, alpine, or riverine habitats- start out as one story and, once approved, usually evolve into something quite different when executed.
The EIS for the Mauna Kea project follows the usual flawed, prescribed pattern of the review process. That is, what the project sets out to do is very different from what the project ends up doing, with respect to the environment. One can argue “the law” and “the process” to Kingdom come, but these projects are NEVER just what they say they are.
Take, e.g., desert solar projects. Most present with a single, long linear road to the “product”, a couple of alternatives, and always the promise to “minimize and avoid” environmental impact where “feasible”. In practice, not so much. Due to one thing or another, they never end up that way. Maybe the access roads weren’t sufficiently analyzed, so then a “variance” [variance= additional, after the fact, impact that gets approved] is needed. Maybe due to slope or arroyo constraints an unanticipated additional staging area needs to be added. Add another variance. Oops, a necessary borrow area, not considered in the original proposal, needs to be tacked on. Another variance. The telescope project would likely manifest very similar “tweaks”.
What starts out as an environmentally iffy project can eventually mushroom into a disastrous one. Here’s a small sample of what would be impacted by the Hawaiian telescope project (taken from the EIS):
1) “In Hawaiian culture, natural and cultural resources are one and the same. Historical documents reveal that most shrines are located on the summit plateau.”
2) “At least 10 confirmed, indigenous Hawaiian species of resident fauna occur in the Alpine Stone Desert ecosystem” [not to mention plants]
3) “263 historic properties [have been identified], most of them shrines, but also burials.”
4) The project “will include a 0.6-mile road and utility improvements from existing facilities to the TMT Observatory” [utility improvements=soft phrase for further impact]
5) “The Access Way will follow existing roads to the extent possible” [extent possible= we don’t really know yet]
6) The endangered Mauna Kea silversword is known to occur at lower elevations within the MKSR.
7) “…From a cumulative perspective, the impact of past and present actions on cultural, archaeological, and historic resources is substantial, significant, and adverse; these impacts would continue to be substantial, significant, and adverse with the consideration of the Project and other reasonably foreseeable future actions. The cumulative impact of past and present actions to geologic resources in the astronomy precinct has been substantial, significant, and adverse, primarily due to the reshaping of the summit cinder cones…These impacts would continue to be substantial, significant, and adverse with the consideration of the Project and other reasonably foreseeable future actions. The MAGNITUDE [my emphasis] or significance of cumulative impact to the alpine stone desert ecosystem … is not yet fully determined…”
A Google Earth aerial is not going to show you this.


Peter from South O August 1, 2019 at 11:05 am

I fully agree with your last sentence. What Google Earth will show anyone is that the summit is already the observatory, criss-crossed with access roads and the multitude of telescope facilities, the denuded landscape, etc. In other words, get a feel for what is being discussed. Hard to put a visual on “reshaping the cinder cones” without such an aid.
And I take back my entire rant about lichens.


retired botanist August 1, 2019 at 1:54 pm

Hahaha, Whew, I was gettin’ worried about you not lichen the lichens! :-)


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