A researcher has reported on the North Coast’s shocking degree of deforestation – not on land, but underwater, as 93 percent of the region’s ocean kelp forests have been decimated in a “perfect storm” of adverse conditions.
The loss of most the North Coast’s bull kelp forests was reported during a July 18 webinar lecture by California Department of Fish and Wildlife (CDFW) Senior Environmental Scientist Dr. Laura Rogers-Bennett.
“Multiple stressors” converged to effect it. An ocean water warming trend – dubbed “the blob,” which described its broad and amorphous geographical range -- began in 2014 and persisted for two years. A third year of warm water conditions ensued during a so-called “Godzilla” El Niño pattern.
The “press of warm water stress” contributed to what Rogers-Bennett described as a “big switch” in kelp productivity from a healthy “stable state” to an “alternative stable state” of barrenness.
Rogers-Bennett said an initial impact was actually seen in the year prior to the water warming, with the outbreak of sea star wasting disease whose scale was unprecedented.
Sunflower starfish, once “very common in our region,” are now ‘locally extinct in our area,” she continued. That allows the population of their prey, purple sea urchins, to mushroom uncontrollably.
“We saw that the purple sea urchin recruitment event was huge and we got tons and tons of purple sea urchins – 60 times more than we’d seen in previous surveys,” said Rogers-Bennett.
Masses of them swarmed on the kelp forests, devouring them until only bare “urchin barrens” remained.
She displayed a 2012 photograph of a nearshore area in Sonoma County with kelp visible above the water surface, thick enough to make swimming through it difficult. A current photograph of the same area shows open water.
Kelp is an important food source for red abalone, a species whose population has crashed. The economically vibrant red abalone fishery was closed in 2018.
That year, “We started to see worsening of conditions under the water,” said Rogers-Bennett, with urchins swarming over barren rock, resorting to eating calcified algal rock cover and each other.
Most of the North Coast’s bull kelp forests are (or were) in Mendocino and Sonoma counties but the ecological impact affects the entire region. Rogers-Bennett said abalone surveys in 2016 and 2017 included the two counties as well as Humboldt County.
Of 6,000 abalone inspected, 25 percent of them were “shrunken” – a phenomenon that “we’ve never seen before,” she continued. The percentage is usually less than .5 percent.
Rogers-Bennett said that from 2017 to 2018, abalone in the region experienced a 72 percent population decline. Now, the abalone population is reduced to “just being shells that are counted – we’ve been counting huge numbers of shells during our surveys when typically we only count a couple.”
Other affected species include rockfish, which find prey in kelp forests and use them as cover when young.
“We’re going to be seeing, potentially, more impact to some of our important obligate (kelp-dependent) species,” said Rogers-Bennett.
The response to the region’s ecological crisis includes uniting a “huge suite” of stakeholders, scientists and government agencies. The partnership has drafted a “kelp recovery action plan” and launched a “Help the Kelp” campaign.
The recovery plan focuses on restoration, research, monitoring and educational outreach.
An urchin harvesting business, Urchinomics, is interested in culling the purple urchins and “ranching” them, said Rogers-Bennett, cultivating their roe by feeding them an algae-based food it has developed.
An “urchin airlift” – essentially an underwater vacuum cleaner – has been deployed at three restoration sites, with 41 metric tons of sea urchins removed.
Water conditions have moderated but the marine ecosystem remains altered and in a state of transition with destination unknown.
“We don’t know what the system will change into,” said Rogers-Bennett. “We’re in uncharted waters here, this isn’t a phenomenon that we’ve seen in the past on the North Coast so we don’t have a good sense of what’s coming next which makes our continued observations and science very important.”
But funding is limited and Rogers-Bennett said a grant application to monitor kelp recovery “just got turned down.” But she added that new patches of kelp are being observed in atypical places, including Humboldt County.