An Integrated Ecological and Geophysical Approach to Habitat Mapping and its Application in Marine Conservation

Global biodiversity is in decline, with the marine environment experiencing significant and increasing anthropogenic pressures. As a response, very large (105–106 km2) marine protected areas (MPAs) have become the dominant form of environmental protection in the marine environment. At present, however, paucity in scientific sampling makes prioritising which regions of the ocean to protect, especially over such large spatial scales, particularly problematic. One such very large MPA, covering an area of over 1 million Km2, is located at the sub-Antarctic South Georgia and South Sandwich Islands (SGSSI). This study uses the SGSSI MPA as a model system to assess the application of benthic habitat mapping as an evidence-based framework for the spatial prioritisation of marine conservation.This study presents an interdisciplinary methodology to marine landscape mapping, as a top-down, objective statistical approach to hierarchically partition and map the benthic environment into physical habitats types. Ordination analysis demonstrates a statistically significant relationship between environmentally-derived landscape mapping clusters and the composition of benthic species data from the region, thus attributing ecological relevance to the marine landscape map. Furthermore, this study adopts a bottom-up approach to habitat mapping, using an ensemble of habitat suitability models. Potential distributions are modelled for a range of benthic faunal attributes relevant to marine management, based on taxonomic classification, functional traits and vulnerability to disturbance. These modelled distributions are used to describe, for the first time, the bio-physical characteristics of SGSSI’s benthic environment. Synthesising both top-down and bottom-up approaches to habitat mapping, this study assesses the physical landscape clusters and modelled distribution results in relation to the spatial protection currently enforced at SGSSI. This synthesis addresses, (i) whether marine spatial planning in the region is representative in terms of the habitats and fauna it protects; and (ii) whether this interdisciplinary methodology at SGSSI can inform on MPA design and designation more universally, in what is an increasingly exploited, yet still poorly understood marine environment