Alterations in human visitation patterns and behaviors in southern California rocky intertidal ecosystems over two-decades following increased management efforts

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In urbanized regions, such as southern California, USA, marine rocky intertidal habitats are frequented by large numbers of human visitors. Visitor activities, such as trampling, rock turning, and collecting, can harm rocky shore flora and fauna, including reducing their abundances, diversity, and reproductive output, shifting their size/age structure, and altering normal ecosystem functioning. Research characterizing human use of these ecosystems in 1995–96 at 8 sites in Orange County, California, revealed that levels of visitation and collecting were high at some sites, despite collecting being prohibited in these Marine Protected Areas, and that these behaviors have adversely affected some organisms. Over the decade following, the Orange County Marine Protected Area Council (OCMPAC), a local conservation collaborative, implemented education, outreach, and enforcement strategies to reduce the harmful activities of visitors. To determine whether human visitation and behaviors have changed over the last two-decades, during a period of increased management associated with OCMPAC efforts, we compared human use patterns between 1995–96 and 2013–14. Comparisons revealed a decrease in the frequency of detrimental activities, such as collecting and fishing, possibly due to management strategies. However, increases in visitation frequency over time, which often includes the detrimental impacts of trampling on organisms, highlights that some activities are increasing and will remain difficult to manage in the future. Comparisons of the size structures of Lottia gigantea, an exploited limpet herbivore, over the same time period, reveal an increase in size, possibly indicative of reduced collecting pressure, potentially as a result of OCMPAC management. While some adaptive management is necessary to improve enacted management strategies, it is recommended that the conservation model set by OCMPAC be introduced to other coastal regions exhibiting high levels of human visitation in order to better manage rocky intertidal ecosystems.