Solanum elaeagnifolium (Solanaceae) Invading One in Five Natura 2000 Protected Areas of Greece and One in Four Habitat Types: What Is Next?

Invasive alien plants have severe impacts on biodiversity and ecosystem services worldwide. To assess the invasion of Solanum elaeagnifolium Cav. (a major alien invasive plant; Solanaceae) in Greek protected areas (PAs), we conducted an extensive drive-by survey across the country crossing half of the Greek Natura 2000 sites. The occurrence data were then linked in GIS with (i) the boundaries of the Natura 2000 sites, (ii) the mapped habitat types in the invaded sites, and (iii) the Corine land cover, from which we calculated the ecosystem services. The results showed that approximately 24% of the investigated PAs were invaded by S. elaeagnifolium to varying degrees of extension and density of the populations. A variety of 29 different habitat types of Annex I of the Directive 92/43/EEC (including a priority habitat and seven habitat types of national importance) were found to be invaded (one in four habitat types present in Greece). In the invaded Natura 2000 sites, we recorded human activities/threats that were mostly related to agricultural activities of high intensity, while the potential in ecosystem service provision was relatively low for the category of regulating services in the invaded sites. Our study provides the first nationwide report of the distribution of S. elaeagnifolium in Natura 2000 sites of Greece, providing baseline maps and information for future monitoring. Our results highlight the need of an effective management strategy across the Natura 2000 network to effectively protect the local biodiversity, which should include management measures for invasive species, mitigating habitat fragmentation, and soil degradation, as well as the adaptation of eco-enhancing management strategies for the provision of multiple ecosystem services in agriculture.