Non-marine molluscs stand out as the major animal group under the most severe threat. Among the 8664 mollusc species evaluated for the IUCN Red List (version 2019-1), 300 are considered Extinct out of a total 872 listed Extinct species. However, only ~10% of molluscs have been evaluated and other assessments of the number of extinct species are much higher, 3000 to over 5000, almost exclusively non-marine species. As for most other groups, threats faced by non-marine molluscs are habitat loss, probably the most important, but also impacts of introduced species, exploitation, generally of less concern, and climate change, likely to have serious effects into the future. Oceanic island species, often narrowly endemic, are especially threatened and constitute a high proportion of recorded extinctions. Anthropogenic activities have caused non-marine mollusc extinctions since prehistory, but threats have increased greatly over the last few centuries and will probably continue to increase. Most mollusc species for which a population trend has been evaluated by IUCN are stable or declining; those few that are increasing are primarily introduced and invasive. Most threatened are oceanic island snails, North American and other freshwater bivalves, and the diverse and highly endemic micro-snails of Southeast Asian limestone outcrops. |
