Kelp Forest Restoration Project

The kelp forests off the southern California coast are known to be some of the most diverse and productive ecosystems in the world. They provide habitat and food for over 700 species of algae, invertebrates, and fish. Many of these kelp forests support large sport and commercial fisheries as well as a vibrant recreational diving industry.

Over the past 100 years, the Palos Verdes Peninsula has lost approximately 80% of its giant kelp canopy cover. During this time, sedimentation, development, urban runoff, and storms have limited kelp growth. Concurrently, overfishing in kelp forests has contributed to the loss of key sea urchin predators and competitors. This has allowed purple sea urchins, a dominant kelp herbivore, to overrun the reef and devour the remaining kelp.

The purpose of the kelp forest restoration project is to convert these desolate monoculture sea urchin barrens into diverse and resilient ecosystems. Without intervention and direct restoration, kelp forests may take decades to return. To speed up the recovery process of this vital ecosystem, The Bay Foundation has initiated, and currently leads, a partnership of researchers, fishermen, and conservationists in the removal of the overly abundant purple sea urchins.

Before Restoration -> After Restoration

Sea urchins that inhabit barrens have little to no food access due to the lack of macroalgae in their surroundings. Consequently, urchin barrens are generally comprised of small, malnourished, and even disease-ridden sea urchins. Conversely, sea urchins living in diverse kelp forests are healthier and larger. They also have larger gonads, or ‘uni’, the edible part of the sea urchin common in sushi and important to the fishery. By lowering the density of purple sea urchins in the barren areas, we observe an immediate positive response in urchin health and gonad growth.


urchins 5-12-11-16

Differences in urchin gonad between a healthy kelp forest and urchin barren


Progress to Date

  • 56.88 acres of restored kelp forests off the Palos Verdes Peninsula.
  • 5 commercial urchin fishermen employed throughout project.
  • Over 10,000 hours underwater restoring kelp.
  • Purple urchin reduced from an average of 30/m2 to ~2/m2.
  • Red urchins increase in gonad (uni) weight by 168% in restoration sites off the PV Peninsula.
  • Increases in kelp, invertebrate, and overall fish diversity and biomass observed.
  • Recreationally targeted finfish increases in density and biomass



Learn More

Urchin Paper

Project Report – July 2017 to June 2018

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