Giant Kelp Returns to Palos Verdes Restoration Sites

An urchin barren before removal of urchins. (Photo Credit: David Witting, NOAA)

Kelp forests are rebounding one year after NOAA’s Montrose Settlements Restoration Program and partners remove problem urchins from former kelp forest areas. The Bay Foundation, the lead organization for the Palos Verdes Kelp Forest Restoration Project, recently published post-restoration monitoring results that show a significant return of kelp, other algae, and fish.

Since July 2013, scientific divers, commercial urchin divers, and volunteers have been removing an overpopulation of urchins from “urchin barrens,” areas where kelp forests have disappeared and do not have a chance to grow. These urchins are undernourishedand will eat any kelp plant or alga that settles on the seafloor. In some areas, biologists were finding 300 urchins per square meter. The goal is to reduce these numbers to less than two urchins per square meter (see maps). So far divers have removed almost two million urchins from 12.5 acres!

Already, giant kelp as tall as 25 feet is extending towards the surface of the ocean in areas that have been cleared of urchins. Here are some more results from the first year report:

  • Giant Kelp increased 1-2 fold in restored sites and is >25ft. long in some areas
  • Fish species richness (number of species) doubled in restored sites
  • Fish biomass increased in restored sites
  • Urchin gonads (measure of ecosystem health and value to fishery) are 361% higher in restored areas

These dramatic results are a testament to how simple it can be to restore a kelp forest if ecosystem balance is achieved.

A restoration site after urchin removal. Look at the giant kelp growing! (Photo Credit: David Witting, NOAA)

Kelp forest restoration will benefit many important invertebrate and fish species. One marine species in particular, abalone, have critically low numbers because of overharvesting, disease, and a lack of quality habitat. This project will provide one of the necessary stepping stones for the recovery of abalone species. The presence of abalone is also an indicator of a healthy kelp forest ecosystem. Scientists plan to monitor the restored sites to know how many fish, invertebrates, and kelp plants are returning.

For more information on the project, check out:



-Gabrielle Dorr, MSRP Outreach Coordinator