Marine Invertebrates

Marine invertebrates have the greatest abundance and biomass of animals in the Earth system. As a result, they exert a major influence on the structure and function of marine ecosystems through food-web interactions and as ecosystem engineers. Marine invertebrates are also important in terms of the ecosystem services they provide to humankind. In this chapter we review Red List assessments for marine invertebrates, summarise the levels of extinction threat within this group of animals and examine the drivers of decline in affected species. Our findings suggest that only a small fraction of marine invertebrate species have been assessed for extinction threat and even within ‘well’-assessed groups a large proportion of species are categorised as Data Deficient. We find that the proportion of species threatened with extinction can be extremely high (33% in reef-forming corals), with lower levels found for other, less comprehensively assessed groups. The main drivers of extinction risk include habitat loss or degradation through coastal development, pollution or other human activities, overexploitation of species for fisheries, or other purposes, and climate change. Approaches to improve the conservation of marine invertebrates are discussed.