Range contractions, fragmentation, species extirpations, and extinctions of commercially valuable molluscs in the Mediterranean Sea—a climate warming hotspot

Abstract The Mediterranean Sea is a global hotspot of climate warming and biodiversity loss where molluscs have provided valuable ecosystem services, such as provisioning and cultural value, since pre-historic times. A high rate of warming and range shift limitations due to the semi-enclosed nature of the basin raise concerns about molluscan population persistence in future climate scenarios. We modelled the future distribution of 13 Mediterranean species of molluscs subject to industrial fisheries exploitation on both the Mediterranean and Atlantic European coasts. We tested the hypothesis that range contractions, fragmentation, and species extirpations will become increasingly severe in the Mediterranean by modelling mid-century and end-century species distributions for four IPCC climate change scenarios. Already under mild emissions scenarios, substantial range contractions and fragmentation are projected in the Mediterranean, suggesting global extinctions by end-century for most endemic species. Colder deep waters do not act as refugia, contrary to expectations. Species also occurring along the Atlantic European coasts may benefit from warming through range expansions to higher latitudes or deeper waters. Most of the modeled species are already over-exploited, but their eradication from the Mediterranean will imply substantial financial losses and a profound cultural change in coastal communities.