The importance of incorporating fine-scale habitat data into the design of an intertidal marine reserve system

There is concern about the reliability of surrogate measures to represent biodiversity and the use of such measures in the design of marine reserve systems. Currently, surrogate measures are most often based on broad-scale (100–1000s of km) bioregional frameworks that define general categories (sandy beach, rocky shore) for intertidal systems. These broad-scale categories are inadequate when making decisions about conservation priorities at the local level (10–100s of m). In this study, ‘shoreline types’, derived using physical properties of the shoreline, were used as a surrogate for intertidal biodiversity to assist with the identification of sites to be included in a representative system of marine reserves. The use of local-scale shoreline types increased the likelihood that sites identified for conservation achieved representation goals for the mosaic of habitats and microhabitats, and therefore the associated biodiversity present on rocky shores, than that provided by the existing marine reserve protection. These results indicate that using broad-scale surrogate measures (rocky shore, sandy beach) for biodiversity (habitats, microhabitats and species) are likely to result in poor representation of fine-scale habitats and microhabitats, and therefore intertidal assemblages in marine reserves. When additional fine-scale data were added to reserve selection the summed irreplaceability of 24% (for spatial extent of habitats), and 29% (for presence/absence of microhabitats) of rocky shore sites increased above 0, where a value close to 1 means a site is necessary, for inclusion in a reserve system, to meet conservation targets. The use of finer-scale physical data to support marine reserve design is more likely to result in the selection of reserves that achieve representation at habitat and microhabitat levels, increasing the likelihood that conservation goals will be achieved.