Visitation and Rocky Intertidal Monitoring at Cabrillo National Monument

Background/Question/Methods

Cabrillo National Monument is a 0.64 km2 park located in San Diego, CA (USA) that attracts nearly 1,000,000 visitors annually. A proportion of visitors traverse a 1 km stretch of rocky intertidal habitat managed by the park. To make natural resource management decisions about this sensitive habitat, we assessed patterns in (1) visitation and (2) dominant intertidal taxa to determine if shifts have occurred over time. Coastal area visitation was quantified using infrared counters deployed at trail entrances (2011-2019). Rocky intertidal community assessments were conducted annually (1990-2020) with Multi-Agency Rocky Intertidal Network (MARINe) protocols, which involve repeated measurements of marked plots and transects. Percent cover of target taxa (Mytilus, Silvetia, Pollicipes, Phyllospadix, Egregia, Chthamalus/Balanus, and red algal turf) and 41 associated taxa (1990-2019) were recorded.

Results/Conclusions

Trail counter results demonstrate that between 2011 and 2019, coastal area visitation increased from 224,104 to 321,898 annual visitors. While weekends and holidays attracted more visitors, low tides did not. Highlights from 30 years of community assessments include: a steady pattern of high Phyllospadix abundance and precipitous Mytilus declines followed by slight recovery. Other target taxa exhibited high variation. Results presented highlight the vital connection between long-term monitoring programs and natural resource management.