An examination of the effectiveness of estuarine conservation management tools and their theoretical underpinnings

Estuarine ecosystems provide a wide range of valuable ecosystem services including the provision of food and raw materials, shoreline protection, carbon sequestration and recreational opportunities. These ecosystem services are underpinned by local biodiversity, which determines resistance and resilience in the face of environmental perturbations. However, estuarine biodiversity is under increasing pressure from coastal development and anthropogenic climate change . The protection of estuarine ecosystem services requires conservation measures that ensure the persistence of biodiversity. This thesis examines: 1) the utility of key ecological theories in informing estuarine conservation planning ; 2) the applicability of ecosystem - level risk assessment s to estuaries ; and 3 ) the applicability of existing estuarine typologies and ecological metrics of community structure to the implementation and monitoring of conservation interventions in estuaries. Using meta - analysis of existing literature, I show qualified support for the application of island biogeographic theory to estuarine habitats. However, field studies reveal that the spatial arrangement of habitat patches in estuarine mosaics affect community structure in ways that extend beyond the covarying effects of habitat patch size and isolation . The proximity of different habitats to one another may facilitate greater abundance in habitat patches through the addition of nutrients or allowing mutualist relationships that would otherwise not exist. These effects are not currently incorporated in estuarine conservation planning. Through a retrospective risk analysis of Chesapeake Bay, U SA, I show that the International Union for the Conservation of Nature 's Red List of Ecosystems may in some instances overestimate the risk of collapse in estuarine ecosystems and that criteria based on abiotic and biotic change, rather than ecosystem area, may be more appropriate for such systems. I use existing data to demonstrate that an Australian estuarine typology for estuaries, based on geomorphological and hydrological factors, is effective at describing the habitat mosaics present. Such typologies, may therefore, be of use to estuarine conservation planners in identifying groups of estuaries across ecological processes may be similar. Finally, I test the ability of zeta diversity, a recently developed metric of community structure, to provide a simple and low - cost method of monitoring estuarine seascapes for habitat homogenisation. Overall, these results show that existing conservation tools are effective in the management of estuarine ecosystems but could be made more effective through adaptation.