Plant invasions in Natura 2000 habitats in Poland are driven primarily by macroclimatic factors

Invasive plants pose an ecological threat around the world. Their influence can also be observed in protected areas such as the European Ecological Network Natura 2000. Although invasions can endanger protected habitats, the specific impact of invasive species in such areas and the factors that determine their spread remain understudied. This study aimed to analyse the factors influencing the probability of plant invasion in five groups of habitat types protected under the EU Habitats Directive, based on Polish State Monitoring of Natura 2000 data. A total of 2,096 monitoring sites, with a balanced distribution across the country, were analysed, belonging to broadleaf forests, riverine habitats, dry grasslands, mesic and wet grasslands, and mires. The study confirmed the presence of 45 invasive species and two potentially invasive species. The most frequently observed species were Impatiens parviflora , Prunus serotina , Solidago gigantea , Erigeron canadensis , Solidago canadensis , and Bidens frondosa . The correlation between the presence of invasive species in monitored Natura 2000 sites and 38 variables was then analysed. The probability of invasion was much higher in regions with milder and wetter winters and, at the same time, in areas with a more continental climate. The importance of large rivers and their valleys and major roads as corridors facilitating plant invasions was also confirmed. Moreover, this study demonstrated the effectiveness of the State Monitoring Programme in detecting invasive species and analysing invasions. The programme could be used to inform the planning of future invasion management and prevention strategies.