Adaptive management of the Great Barrier Reef: a globally significant demonstration of the benefits of networks of marine reserves.

The Great Barrier Reef (GBR) provides a globally significant demonstration of the effectiveness of large-scale networks of marine reserves in contributing to integrated, adaptive management. Comprehensive review of available evidence shows major, rapid benefits of no-take areas for targeted fish and sharks, in both reef and nonreef habitats, with potential benefits for fisheries as well as biodiversity conservation. Large, mobile species like sharks benefit less than smaller, site-attached fish. Critically, reserves also appear to benefit overall ecosystem health and resilience: outbreaks of coral-eating, crown-of-thorns starfish appear less frequent on no-take reefs, which consequently have higher abundance of coral, the very foundation of reef ecosystems. Effective marine reserves require regular review of compliance: fish abundances in no-entry zones suggest that even no-take zones may be significantly depleted due to poaching. Spatial analyses comparing zoning with seabed biodiversity or dugong distributions illustrate significant benefits from application of best-practice conservation principles in data-poor situations. Increases in the marine reserve network in 2004 affected fishers, but preliminary economic analysis suggests considerable net benefits, in terms of protecting environmental and tourism values. Relative to the revenue generated by reef tourism, current expenditure on protection is minor. Recent implementation of an Outlook Report provides regular, formal review of environmental condition and management and links to policy responses, key aspects of adaptive management. Given the major threat posed by climate change, the expanded network of marine reserves provides a critical and cost-effective contribution to enhancing the resilience of the Great Barrier Reef.

Can juvenile corals be surveyed effectively using digital photography?: implications for rapid assessment techniques.

The widespread decline of coral reefs requires integrated management measures across whole regions. Knowledge of demographic processes of reef organisms is important for informed management, yet current techniques for assessing such processes are time consuming, making it impractical to gather relevant information over large scales. We tested the usefulness of digital still photography as a rapid assessment technique to estimate coral recruitment--an important process in coral reef recovery. Estimates of the density and diversity of juvenile hard corals from digital images were compared with direct visual estimates from the same plots made in the field. Multiple plots were sampled on four reefs from a range of locations on Australia's Great Barrier Reef. On average, estimates of juvenile densities from photographic images were lower, in both absolute and relative terms, than that estimated from images. This was the case whether colonies <20 mm or <50 mm in diameter were considered. Overall differences between methods were generally greater at reefs where recruitment was higher, though proportional differences (density from images/density from direct visual census) still varied among reefs. Although the ranking of taxa, in terms of their densities, from the two methods were similar, the density of common genera was generally underestimated in images, and the occurrence of 'unknown' taxa was higher. We conclude that photographic images do not constitute a reliable rapid assessment method for estimating the spatial patterns in the density or diversity of juvenile hard corals.