With less than 5% of the global terrestrial area, marine islands hold 20% of the world’s biodiversity. Biodiversity on marine islands is characterized by unique biogeographic, phylogenetic and functional characteristics, and plays a crucial role for sustaining ecosystem multifunctionality globally. However, marine islands are also experiencing a disproportionate loss of endemic species and a disproportionate gain of invasive species, due to increasing negative human impacts that make islands transitioned from primary through secondary to tertiary economies. In addition to habitat transformation and non-native species introduction, human-induced climate change and sea-level rise are emerging as new threats to biodiversity. Currently, islands are undergoing an unprecedented biodiversity remodeling, with some species going extinct, others changing in abundance, and non-native species becoming a part of many ecosystems. Undoubtedly, such species reassembly processes inevitably lead to unpredictable consequences on ecosystem multifunctionality. In this context, this session aims to stimulate a collaborative discussion to: 1) better understand how island biodiversity may respond to anthropogenic threats such as habitat loss, biological invasion, sea-level rise and climate change, and how the compositional and functional changes of biodiversity influence island ecosystem multifunctionality; and 2) develop new strategies for the protection and restoration of island biodiversity, including maintaining biological and cultural heritage through regenerative practices, mainstreaming biodiversity in cultural and production landscapes, and engaging with the reality of novel ecosystems.