iNaturalist as a Supplementary Tool for Alien Species Monitoring: a South African Marine Protected Area Perspective

ABSTRACT Marine protected areas (MPAs) act as essential conservation tools. However, biological invasions directly undermine the ability of these important conservation areas to meet their objectives by negatively affecting biodiversity, ecosystem functions and service provisioning. Currently, data on the distribution of marine alien species in South Africa are scarce and often outdated, with little known about invasions in MPAs. This reflects the absence of long‐term monitoring programmes, a common challenge for many African countries. Recently, crowdsourced data platforms, including iNaturalist, have been used to support large‐scale data collection. Beneficial due to their accessibility, these platforms provide data that cover broad temporal and spatial scales while not requiring funding. This study assessed the status of iNaturalist records for species known to be alien in South Africa, with a focus on MPAs. A total of 952 records were recovered, with 568 retained for analysis following the application of a confidence metric. Alien species were documented in 14 of the 29 South African coastal MPAs, with most species (15) recorded in the Table Mountain National Park MPA. This study documented three ascidians ( Ciona robusta ; Clavelina lepadiformis ; Styela plicata ) in natural habitats for the first time and extended the known range of the maritime earwig Anisolabis maritima by more than 1500 km, highlighting the pervasive nature of alien species in MPAs. This study presents the first use of iNaturalist data in a marine invasion context in South Africa and demonstrates the potential of this approach to enhance monitoring in resource‐restricted under‐surveyed MPAs throughout Africa.