Invasive non-native trees in Natura2000 sites of Sicily: relevance and management issues

Invasive non-native trees (INNTs) are an ever-increasing component of natural and seminatural communities worldwide. However, for the high competitive ability of INNTs and their tendency to cover and dominate over large areas, such a trend is commonly associated with a reduction of biodiversity along with a simplification and banalization of ecosystems. These detrimental ecological effects are likely to impact more on protected sites, established with the main aim to preserve native ecosystems and species. In this general framework, we assessed the abundance and spread of the main INNTs occurring in the Special Areas of Conservation of Sicily, being part of the Natura2000 network and designed according to the Habitats Directive (92/43/EEC). In particular, we accessed the management plans of all SACs present in Sicily, that is about 200 protected sites. We selected the INNTs having a higher ability to invade natural and seminatural habitats in Sicily, including forest systems: Ailanthus altissima, Acacia saligna, Eucalyptus camaldulensis, Parkinsonia aculeata, Robinia pseudoacacia and Vachellia karroo. We also took into consideration the inclusion in the list of invasive alien species of Union concern pursuant to Regulation (EU) 1143/2014. Within the management plans, we found three main information types concerning INNTs: presence/absence, abundance level and invasiveness status. The results of the research will help to identify the most widespread INNTs as well as some patterns of tree invasion in Natura2000 sites of Sicily. Furthermore, we assessed whether well-known invasive tree species are adequately considered as serious threats in the management efforts addressed to biodiversity conservation in protected sites of Sicily.