Do academic students overestimate marine litter pollution? A threat analysis using plover birds as a target in a Mediterranean site

Marine litter is known to pose a threat to biodiversity. In this work, we wanted to verify if marine litter was overestimated as a threat by academic students when compared to other threats acting on a specific conservation target, a coastal bird of conservation concern, breeding on Mediterranean coastal dunes (Kentish Plover, Charadrius alexandrinus) in a site of central Italy (Maremma Regional Park, Tuscany). To test this hypothesis, before conducting any direct local survey (a priori), a panel of academic students in Ecotoxicology and Environmental Sustainability (Second cycle degree; Siena University) collected indirect information on a set of threats (trampling, coastal erosion, marine litter, presence of dogs and illegal plant collection), known as impacting on the target, assigning a score (from 1: low to 4: high) to two selected threat regime attributes (extent and intensity), and obtaining a magnitude score based the judgment only on general information communicated by park operators. After a field survey on the plover's breeding site, students were newly assigned a posteriori scores (`after' phase). The before-after comparison showed that no threat showed a significant difference in scores, except for marine litter, which was significantly a priori overestimated. Although marine litter is known to threatened plover birds, it has been significantly overestimated at the local level suggesting a prejudice in student evaluation. This biased overestimation could be due to the high media exposure of the marine litter as a threat, making it charismatic, affecting the a priori judgment.