Comparative Intertidal Study and User Survey for Point Pinos, California
- Scott Kimura
End Date: September 01, 2003
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 a 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.
During summer 2002 we completed sampling to develop a database to evaluate visitor impacts. We sampled species abundances over broad areas 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.
Summary to DateWe 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) 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 this impact, foot traffic did not create barren pathways through the intertidal. The high topographic relief of the shoreline and the lack of flat rock platforms makes it unlikely that visitor use would be concentrated enough to form such well-worn paths.
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, which 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.
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 may occur naturally. Natural physical disturbances (e.g., boulder rolling from storm waves, sand scour) affect species abundances, but also contribute to the diversity of marine life by maintaining a mix of habitats that are in turn used by a greater variety of species. Furthermore, 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. We found that the Point Pinos shoreline is as diverse as adjoining shorelines that had very little visitor use. This lack of a difference is probably related to the high natural variability in the area, which can overwhelm minor differences due to visitor impacts.
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 and monitoring programs at Point Pinos may be warranted in light of the findings of this study, because visitor use will likely increase in the future.
- Statistically significant differences were detected in total algal cover between the high and low use areas, with the high use area having about 25 percent less total algal cover. The difference was due mainly to reduced coverage of rockweeds and turf algae in the visitor use area, relative to the reference area. The areas affected were in the upper intertidal near public access points, so one explanation for the reduced algal cover is increased foot traffic (trampling) from visitors that erode the algae and limit recruitment.
- No statistically significant differences were detected in the invertebrates and fishes, with the exception of purple sea urchins. The abundance of purple sea urchins was significantly lower in the Point Pinos tidepools, relative to the reference area tidepools. While sea urchins may be of interest and curiosity to visitors, they are difficult to collect, since they have spines and are often tightly nestled in crevices and small depressions in the rocks. The difficulty in collecting these animals, combined with the lack of statistically significantly lower abundances of other invertebrates susceptible to visitor impacts, reduces the likelihood that visitor impacts were the primary cause for the lower abundance of only purple sea urchins.
- Abalone and owl limpets are often collected for human consumption. Because we had no baseline data on abundances, we examined collecting effects by determining whether visitor use areas had lower numbers of large animals, relative to areas with less visitor use. There were no significant differences in the mean sizes or numbers of black abalone and owl limpets between high and low visitor use areas. The similarity in shell sizes for the two areas indicates that there was no difference in harvesting levels for these species between areas.
- Almost 85 percent of the people observed in the study were in the parking lots and on the cliff banks. Only 15 percent of the people observed were down on the seashore, representing approximately 50,000 people that step into the Point Pinos intertidal zone annually. Research indicates that visitor use is over twice this amount at other popular rocky intertidal areas in California. However, 18 percent of the people in the intertidal zone were observed handling organisms, turning rocks, and displacing animals.
- Habitat association
- Size structure
Figures and Images
Figure 1. Location of biological sampling stations.
Figure 2. Relative visitor use of the Point Pinos intertidal zone by season.
Figure 3. Placement of shoreline segments surveyed for the visitor counts portion of the study. See Figure 4 (below) for percent frequency per segment.
Figure 4. Distribution (percent frequency) of visitors along the coast in the rocky intertidal zone (excludes beaches).
- Tenera Environmental (2003)A comparative intertidal study and user survey, Point Pinos, California.
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