MEPS 253:25-38 (2003)  -  doi:10.3354/meps253025

Opportunity cost of ad hoc marine reserve design decisions: an example from South Australia

R. R. Stewart1,*, T. Noyce2, H. P. Possingham1

1The Ecology Centre, Department of Zoology and Entomology, The University of Queensland, St Lucia, Queensland 4072, Australia
2Environment and Geographic Information Division, Department for Environment and Heritage, PO Box 550, Marleston, South Australia 5033, Australia

ABSTRACT: Like many states and territories, South Australia has a legacy of marine reserves considered to be inadequate to meet current conservation objectives. In this paper we configured exploratory marine reserve systems, using the software MARXAN, to examine how efficiently South Australia¹s existing marine reserves contribute to quantitative biodiversity conservation targets. Our aim was to compare marine reserve systems that retain South Australia¹s existing marine reserves with reserve systems that are free to either ignore or incorporate them. We devised a new interpretation of irreplaceability to identify planning units selected more than could be expected from chance alone. This is measured by comparing the observed selection frequency for an individual planning unit with a predicted selection frequency distribution. Knowing which sites make a valuable contribution to efficient marine reserve system design allows us to determine how well South Australia¹s existing reserves contribute to reservation goals when representation targets are set at 5, 10, 15, 20, 30 and 50% of conservation features. Existing marine reserves that fail to contribute to efficient marine reserve systems constitute Œopportunity costs¹. We found that despite spanning less than 4% of South Australian state waters, locking in the existing ad hoc marine reserves presented considerable opportunity costs. Even with representation targets set at 50%, more than half of South Australia¹s existing marine reserves were selected randomly or less in efficient marine reserve systems. Hence, ad hoc marine reserve systems are likely to be inefficient and may compromise effective conservation of marine biodiversity.

KEY WORDS: Marine reserves · Reserve selection · Efficiency · Decision theory · Representation targets · Irreplaceability · Biodiversity conservation · South Australia

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