Restoring Rocky Intertidal Habitats in Santa Monica Bay
The decline of flora and fauna of rocky intertidal habitats along wave-exposed coasts has been observed globally. Over the past ten years, researchers have showed links between organism population change and human visitation disturbance. The rocky intertidal zone in Los Angeles County, CA, is especially vulnerable to visitation disturbance due to its large human population coupled with the importance of the ocean as a recreation center.
This study investigated recreational activity patterns and intensity of use by visitors along the rocky intertidal zone at ten sites in the Santa Monica Bay, Los Angeles County, California. Use varied from 0.4 visitors hr-1 to 42.7 visitors hr-1. Estimates of use, conservatively extrapolated from samples taken at low tides during daylight hours, indicate that >20,000 people visited the most highly used sites each year. Surveys of visitor activities indicate that approximately 50% of the visitors walked at the site without engaging in more destructive activities. Fishers were infrequent at most of the surveyed sites. Collectors were most frequent at White’s Point. The most commonly collected species included mussels, sea stars, owl limpets, urchins, snails, crabs, and sea slugs. Sitters/standers, walkers, and fishers tend to spend a majority of their time in one activity. Handlers and collectors, on the other hand, spend a relatively equal amount of time sitting/standing, walking, handling, and in the case of collectors, collecting. Intensity and patterns of human use can provide useful information required to design an effective management strategy to protect vulnerable species.
Current management practices appear ineffective in protecting rocky intertidal flora and fauna from human disturbance since collecting, trampling, and handling occur intensively. In sites that are protected by law from collecting activities, enforcement was virtually absent. Enforcement may be more effective if concentrated on the most visited sites and on weekends when visitation is highest.
Restoration of rocky intertidal habitats requires that the cause of degradation first be identified and eliminated or reduced. As we and others have demonstrated, the collection of organisms from Santa Monica Bay rocky intertidal habitats is widespread. We have focused on assessment of restoration alternatives on techniques to reduce impacts from trampling, handling and collecting.
Four main classes of restoration alternatives are discussed:
- Reducing the trampling of intertidal organisms followed by passive recovery
- Reducing the handling of intertidal organisms followed by passive recovery
- Reducing the collection of intertidal organisms followed by passive recovery of the community
- Active restoration of target species (accompanied by the protection of these species from further impacts)
Our recommendations for approaches to be used for restoring Santa Monica Bay rocky intertidal habitats include:
- Establish or expand an education program
- Establish or expand docent programs
- Expand enforcement activities, including educating enforcement personnel
- Establish a pilot exclusion area
- Monitor trends in surfgrass abundance in Malibu