Abstract
Invasive alien species (IAS) are widely recognized as a major threat to ecosystems globally. Despite the growing interest and research effort on biological invasions, the impact of IAS on both terrestrial and aquatic subterranean habitats remains considerably under-studied in comparison to other environments. The Convention on Biological Diversity (CBD) has established global targets to mitigate the impacts of IAS, emphasizing the need for countries, organizations, and the scientific community to identify gaps in knowledge, monitoring, and management strategies for IAS. To this end, we mapped knowledge gaps in biological invasions of subterranean habitats that emerged from the first systematic surveys of the available information. We suggest that there are five main gaps restricting our ability to understand and tackle biological invasions in subterranean ecosystems. Given the vulnerability of subterranean ecosystems and the lack of attention they have received in conservation policies, it is crucial to increase research emphasis on IAS. This opinion paper aims to stimulate such efforts and contribute to the preservation of these ecosystems.