Baseline survey of the terrestrial invertebrate fauna of Barrow Island

Abstract

Barrow Island is Western Australia’s second largest offshore island and its flora and fauna have been able to evolve without major human disturbances. Chevron Australia Pty Ltd and its Joint Venture Participants made an application to construct a plant to liquefy natural gas on the island in 2001. One of the conditions under which approval was granted was the implementation of a rigorous biosecurity effort to ensure that no non-indigenous species (NIS) are introduced or allowed to establish on the island. To fulfil this condition it was first necessary to characterise what was already present on the island. A series of surveys have been performed using a purpose-designed sampling protocol in order to provide baseline data on the existing terrestrial invertebrates on Barrow Island. A total of 1,873 morphospecies were sampled but subsequent surveys and taxonomic developments have increased the count to 2,397. This compares with an estimated species richness of 2,481 terrestrial invertebrate species on the island. Composition of the fauna varied considerably between the wet and dry seasons and between years, even when samples were taken during the same month. Composition also varied with distance from the coast, which may be associated with soil type and vegetation association. Twenty five non-indigenous species and seven putative non-indigenous species have been found, all of which are believed to have been present prior to commencement of the Gorgon Gas Development project.