Dunes under attack: untangling the effects of landscape changes on Iceplant invasion (Carpobrotus spp., Aizoaceae) in Mediterranean coasts

Invasive alien plants (IAPs) are a great challenge for biodiversity conservation and management. Temporal landscape analysis has a great potential for describing plant invasion process; however, conservation solutions accounting of landscape dynamics are still limited. This research aims to explore the spatial-temporal pattern of Carpobrotus spp. by analysing the IAP expansion and reduction processes in relation with landscape changes on Mediterranean coastal dunes. Based on detailed Carpobrotus spp. and local land-cover maps of the years 2011 (T0) and 2019–20 (T1), we described coastal dune landscape changes on invaded areas using transition matrices and identified areas of IAP expansion and reduction. We then calculated a set of class and landscape pattern metrics and explored the spatial configuration of invaded patches through trajectory analysis. We also analysed the relationship between Carpobrotus spp. patches and landscape pattern over time examining their respective temporal delta values, by Random Forest (RF) models followed by Partial Dependence analysis. The spatial-temporal characteristics of invaded patches and their contextual landscapes varied across coastal tracts experiencing IAP expansion or reduction. Trajectory analysis for IAP expansion areas evidenced an increased Carpobrotus spp. cover, accompanied by a rise in patch size, number and connectivity. According to RF models, these trends are related to a morphodynamical stable seashore and increased artificial surfaces. In contrast, trajectory analysis of IAP reduction area evidenced a decline in Carpobrotus spp. cover, with patches shrinking into smaller, more regularly-shaped forms. RF models suggest that this reduction is linked to coastal erosion, which compresses dunes against static infrastructures present in the foredune (e.g. roads, building etc.). Temporal landscape analysis provides a sound framework for understanding invasion dynamics across coastal mosaics shaped by the combined effects of factors, such as seashore dynamics and urban sprawl. This approach offers valuable insights for developing tailored management strategies that account for specific contextual nuances and enable informed planning of recovery actions.