The land molluscs of North Ronaldsay, Orkney: human intervention and island faunal diversity

A survey in July 2001 found 23 species of land mollusc on the island of North Ronaldsay, Orkney. A total of 26 have been recorded since 1965. While this species richness is roughly as predicted from the island's area and latitude, the species composition of the fauna differs markedly fromthose of the Hebridean islands of Colonsay and Ulva. The fauna contains many anthropochorous species and lacks several species typical of wetland and woodlands which are present on the Hebridean islands. These results are discussed in relation to the islands' histories and their agricultural status.