Functional diversity of marine megafauna in the Anthropocene

Marine megafauna, the largest animals in the ocea, serve key roles in ecosystem functioning. Yet, one-third of these animals are at risk if extinction. To better understand the potential consequences of megafauna loss, here we quantify their current functional diersity, predict future changes under different extinction scenarios, and intoduce a new metric [functionally unique, speciallized and endangered (FUSE) that identifies threatened species of partcular importance for functional diversity. Simulated extinction scenarios forecast marked declines in functional richness if current trajectories are maintained during the next century (11% globally uo to 24% regionnally) with more marked reductions (48% gloallly up to 70% at the poles) beyond random expectations if all threatened species eventually go extinct. Among the megafaunal groups, sharks will incur a disproportionate loss of functional richness. We identify top FUSE species and suggest a renewed focus on these species to preserve the ecosystem functions provided by marine megafauna.