Research Technical Report
A PDF version of this report is available here:
A Comparative Intertidal Study and User Survey, Point Pinos, California
Tenera Environmental (July 2003)
Final Report, 274pp.
The purpose of this study was to investigate the effects of visitor use on the Point Pinos rocky shoreline located on the Monterey Peninsula in central California. Point Pinos receives high levels of visitor use because of its scenic values and easy accessibility from roads, adjoining parking lots, and trails. One of the main attractions of Point Pinos is the rich, diverse marine life along the rocky shore. Tidepools are common in the area, and small sandy beaches also occur along the upper shore. Point Pinos is within the Monterey Bay National Marine Sanctuary and the Pacific Grove Marine Gardens Fish Refuge.
There is substantial evidence in the scientific literature demonstrating that high levels of visitor use can negatively impact intertidal communities through rock turning, inadvertent trampling, and the collection and displacement of organisms. Although Point Pinos has legal statutes protecting it from some of these activities, the present and projected levels of visitor use have raised concerns on the effectiveness of the regulations in protecting the health and viability of marine life at this frequently visited section of coastline.
In this study we assess visitor use levels and activities at Point Pinos, and compare the condition of the shoreline biological community in areas of high and low use. Although numerous scientific studies have previously been completed at Point Pinos, there were no existing data that could be used as a baseline to make a definitive assessment on the current effects of visitor use. Therefore, during summer 2002 we completed sampline to develop a database to evaluate visitor impacts. We sampled species abundances over broad regions of shoreline habitat in areas of high and low visitor use using transects situated in the upper and low intertidal. We also sampled specific habitats, such as tidepools, as they represent focal points of interest and are exposed to visitor effects.
>We sampled over 150 species of invertebrates, algae, and intertidal fishes, and analyzed the data for differences in abundance between the visitor use areas of Point Pinos and reference areas. We did not find any conclusive evidence of effects from collecting. We found that lower coverage of some types of algae in the upper intertidal zone and around the margins of tidepools may have been caused by chronic trampling from visitors. All of the affected trampled areas were in the upper intertidal zone ( > +2 ft MLLW tide level) where our visitor surveys showed that people spend most of their time. Even though trampling may have contributed to the reduced algal cover on the upper surfaces of rocks at Point Pinos, these same species were found on the sides of rocks and in crevices that were not as exposed to trampling. Despite the lower abundances of some algal types, foot traffic had not resulted in barren pathways through the intertidal. This is mainly due to the high topographic relief of the shoreline and the lack of flat rock platforms that would otherwise tend to concentrate visitor use.
We also investigated whether local populations of owl limpets and black abalone have been affected by illegal harvesting for human consumption. Since large individuals in the population of these species are more susceptible to impacts from collecting, we measured shell sizes to determine whether there were fewer large animals at Point Pinos, relative to other areas with less visitor use. Although black abalone populations in particular have been affected historically by human harvesting and sea otter predation, there were no significant differences in size distributions between high and low use areas, including the nearby Hopkins Marine Life Refuge. The Hopkins Marine Life Refuge is treated in the present study as a low use area because it is fenced off from general public use, although it is an area of high scientific research activity. The research facility also has an on-site caretaker for security that further limits the possibility of poaching.
Aside from apparent trampling effects, disturbances that have likely occurred at some level from visitor use did not appear to exceed the range of disturbances that can occur naturally, as we found few differences between areas of high and low visitor use that presumable experience similar levels of natural disturbance. Natural physical disturbances (e.g., boulder rolling from storm waves, sand scour) affect species composition and abundance, but also contribute to the diversity of marine life by maintaining a mix of many species with varied age structures in their populations. Futhermore, many of the activities associated with visitor use, such as rock turning and trampling, are similar to the types of natural physical disturbances that the biological community is subjected to. Point Pinos is also located along a shoreline with naturally high algal productivity and growth from coastal upwelling that increases the habitat structure and food resources for associated invertebrates. The rocky shore is also contiguous with adjoining rocky areas supporting similar species assemblages, thus having nearby spore and larval supplies for recruitment. As a result, recovery potential can be high, reducing the effects of transitory disturbances, such as visitor use. We found that the Point Pinos shoreline is as diverse as adjoining shorelines that had very little visitor use, probably related to the high natural variability in the area, which also resulted in the difficulty to detect large differences from visitor impacts.
However, our studies of visitor use impacts had several limitations. First, the studies were observational in nature and did not include experimental manipulatins that could be used to establish relationships between the biological patterns and visitor use. Secondly, because biological communities are naturally variable, data from two areas (e.g., 'control' and 'impact' areas) will almost always have some statistically significant differences, and these differences may not necessarily be related to visitor use. The basis for concluding that the differences detected in a one-time observational study, are actually the effects of visitor use, is dependent on the magnitude of differences between control and impact areas and the consistency of the results from a variety of species that are susceptible to visitor impacts. In the present study, purple sea urchins were significantly less abundant in tidepools at the Point Pinos shore, but the absence of effects on other species that are also prone to collecting or damage from collecting reduces the likelihood that this single difference was due to visitor impacts. Finally, the short-term nature of the study could not account for seasonal or inter-annual variation in species abundances. Long-term monitoring at an increased number of sites in both visitor use and reference areas would help determine if there are any differences in the patterns of changes in species composition and abundance among areas.
An additional reason why we did not detect a greater number of visitor impacts may have been related to several resource conservation measures that had come into place several years prior to our studies, which allowed impacted species to recover. The Pacific Grove Police Department had increased their involvement in resource enforcement at Point Pinos. Educational signage explaining tidepool etiquette in three languages was placed at three locations along the Point Pinos shore. Bay Net, a Monterey Bay National Marine Sanctuary volunteer docent program, expanded their education outreach and conservation awareness instruction to Point Pinos and vicinity. Also, the Coalition to Preserve and Restore Point Pinos Tidepools, a public advocacy group, began education outreach at Point Pinos. Lastly, the California Department of Fish and Game issued a moratorium on scientific collecting in the area.
While the several year period of increased conservation measures that were implemented prior to our studies may have been sufficient for many species to recover, not all could have necessarily recovered completely in this period of time. Longer periods are generally required for species that do not readily recruit form limited reproduction and propagule dispersal, which includes slow growing, long lived species, such as owl limpets, abalone and sea stars. Accordingly, the lack of substantial findings of adverse visitor impacts may also indicate that the impacts were not large to begin with.
We estimate that approximately 50,000 people visit the Point Pinos intertidal zone annually, representing a small percentage of the total visitors to Point Pinos. Many other rocky intertidal zones in California that are near urban areas experience greater levels of visitation, and resource managers in these areas are confronted with similar issues of balancing resource conservation with continued access and uses. Accordingly, we feel that planning for additional resource conservation measures at Point Pinos, including monitoring, may be warranted in light of the findings of this study, because visitor use will likely increase in the future.