A recent Guest Commentary asserts that the increasing numbers of sea lions and harbor seals (pinnipeds) around La Jolla have upset the delicate balance of the once-thriving La Jolla kelp bed ecosystem (“Declining kelp beds off La Jolla are one consequence of overpopulation of pinnipeds,” Kurt Hoffman, Jan. 23, La Jolla Light).
Among the asserted losses are a significant loss of giant kelp forest north of Point La Jolla and low numbers of yellowtail and white seabass. And, of course, there are the restrictions on human access to small portions of the bluffs and beach.
It seems that this idea was inspired by a 2023 La Jolla Light article featuring a Scripps Institution of Oceanography researcher who studies marine ecosystems and their management. That article discussed disappearing kelp forests — for unknown reasons — off La Jolla.
Research papers on kelp forests, including by SIO scientists and the California Marine Species Portal, describe kelp forests as extremely dynamic ecosystems. For example, records over a 50-year period show that within the La Jolla kelp forest, the northern section has much shorter periods of persistence — and reappearance — than the southern section. And as cited in a SIO-authored paper, the presence and extent of Southern California kelp forests are primarily forced by storms and nutrient stress associated with climatic cycles caused by El Niño/La Niña cycles and fluctuations in population size of sea urchins, which are important kelp grazers.
No one disputes that the bluff and beach closures to accommodate the presence and natural life activities of the pinniped constrain unlimited human presence. But from the pinnipeds’ perspective, there are few places where our coastal developments and recreation haven’t eliminated or constrained access to and use of “their” historical beaches and bluffs. The sea lion population has remained stable at around 300-350 since the city [of San Diego] commissioned a year-long study released in 2016 by Hanan & Associates.
For context regarding our local pinnipeds, it was only in the mid-1990s that harbor seals began moving from Seal Rock to the Children’s Pool and the early 2010s that significant numbers of sea lions began hauling out along the La Jolla bluffs. But seals were there much earlier, and an 1887 map of the area by the city engineer already referred to these areas now called Children’s Pool and South Casa Beach as Seal Rock and Seal Rock Point.
Whether the larger numbers of pinnipeds have much of an effect on our kelp forests may be worth studying. But because that ecosystem is very dynamic, any valid study would need to include multiple possible suspects. Let’s not be so quick to place that “blame” on the pinnipeds.
Bill Tippets is a La Jolla resident. ♦
