By Annie Bauer-Civiello, Reef Check Director, Restoration Program
Big Sur is known for its lush canopies of kelp forests made up of giant kelp and bull kelp. It has substantial ecological and cultural significance to California and is rated among the top tourist destinations for outdoor activities. However, like other sites in California, recent Reef Check survey results show signs of kelp decline.
Since 2015, Reef Check has monitored eight sites across the Big Sur coast. When surveys began, purple urchin densities averaged less than one urchins per square meter. However, recent surveys conducted in 2022 show that urchin densities have increased to an average of about seven urchins per square meter. In the last two years, multiple of our long-term sites have reported over 20 urchins per square meter across transects. Urchin densities have been found to be highly variable and patchy. In addition, the overall average of giant kelp densities has shown a decline since 2015. This increase in urchin populations and decline of kelp has raised concern. It suggests the urgency of protecting some of the most pristine habitats on the California coast.
When a local community member of Big Sur indicated their concern for kelp forests, particularly at Big Sur Reef, a barren approximately 2.5 acres in size, Reef Check began surveying this site. Initial results identified urchin densities to average 22 urchins per square meter, with a complete loss of canopy kelp within the barren. What is unique about this site is that it is surrounded by relatively healthy kelp forest on all sides. We believe that this will assist with a faster recovery of the kelp forest.
In October, Reef Check partnered with commercial urchin divers to reduce urchin loads at the site. In 12 days, divers removed 6,000 lbs of urchins, averaging 3.7 cm (1.45 inches) in size. Divers have reduced urchin densities in the barren to less than a quarter of their densities before the intervention.
In the new year, Reef Check plans to use various restoration tools combined with ecosystem monitoring to understand how early intervention can improve restoration efficiency. We are looking forward to returning to this site in early spring to see the effects of the urchin removals. The learnings from this project will improve our understanding of how early intervention may be scaled for restoration along the West Coast.