Pathogens on the horizon: enhancing understanding of invasive alien entomopathogens and impacts on biodiversity

Horizon-scanning, the systematic examination of future potential threats and opportunities, leading to prioritisation of invasive alien species (IAS) threats is an essential component of IAS management. Consensus methods have been used to undertake IAS horizon scanning for Great Britain; 30 species considered a high risk with respect to arriving, establishing and posing a threat to native biodiversity were identified. Information on microbes is often lacking from alien species databases and so pathogens were excluded from this consensus approach. There is a significant gap in our knowledge in relation to risk posed to biodiversity by “alien” microorganisms. We organised a workshop of 40 experts with five subgroups (terrestrial invertebrates, aquatic, plants, wildlife diseases and vectors of disease) to specifically consider invasive alien pathogens that have the potential to impact on biodiversity in the EU. The aim was to undertake a cross-cutting review of pathogen life histories to enhance understanding of threats, methods and knowledge gaps within natural and semi-natural systems, and to identify invasive alien pathogens that will impact on biodiversity in Europe. We identified key barriers to our understanding of the introduction, establishment and impact of invasive alien pathogens through two distinct phases; 1) preliminary consultation between experts prior to the workshop, 2) consensus-building across the expert groups during the workshop. We highlight the results of this consensus approach by examining the top 10 barriers identified. We then detail specific examples from the terrestrial invertebrate and aquatic sub-groups that exemplify these barriers and indicate how this may inform pan-European policy.