Exploring the Contribution of a Generalist Citizen Science Project for Alien Species Detection and Monitoring in Coastal Areas. A Case Study on the Adriatic of Central Italy

Coastal areas are biodiversity hotspots, providing essential ecosystem services, yet they are among the most threatened systems, particularly by alien species invasion. The European regulation on invasive alien species (IAS) highlights early detection as a key prerequisite for effective containment or eradication strategies. Traditional monitoring methods are costly and time-consuming, and Citizen Science (CS) may be a promising alternative. We assessed the contribution of the generalist CS project “Wild Coast Adriatic” (WCA) developed on the iNaturalist platform to the detection of alien species (AS) along the Central Adriatic coast. Using WCA, we extracted alien occurrences and explored AS seasonal patterns, geographic origins, dangers (EU regulation), and distributions inside protected areas (Natura 2000 and LTER sites). Between 2020 and 2023, WCA gathered 2194 research-grade observations of 687 species, including 139 records of 50 AS, five of which are of European concern. Asteraceae and Fabaceae (plants) as well as insects and mollusks (fauna) were the most abundant aliens. The observations increased over time, with more records concentrated in autumn and summer. Most AS come from the Americas and occurred outside the protected areas. Our results underline the contribution of CS data for detecting AS in coastal ecosystems, offering a valid support for early warning, monitoring, and management strategies.