The Great Barrier Reef Marine Park was rezoned in 2004, greatly increasing the extent of no-take or green zones to about one third of the Park’s area. But what do we know about the biological benefits of this major change in allowed activities, particularly fishing?

Our new study, led by Kerrie Fraser and published in Biological Conservation, found that biological sampling in the Great Barrier Reef Marine Park was limited in providing evidence of the impact of the Park’s no-take zones. Impact is the difference between the outcome of an intervention, such as establishing no-take zones, and the counterfactual, or the outcome expected without the intervention. Impact evaluation aims to determine the extent to which changes in, for example, biological indicators are directly attributable to an intervention and not to other causes. 

We reviewed available data on measures of biological impact from ‘new’ no-take zones established in the 2004 rezoning of the Marine Park, and those established under previous zoning. We found that, in comparisons of biological indicators in no-take zones with fished areas, impacts were largely neutral (57%) or positive (33%). Of 159 impact measurements, 48 supported causal relationships between new no-take zones and improvements in indicators. However, the biological indicators and trophic levels benefiting from protection were limited. Current conservation monitoring and evaluation approaches used in the Marine Park do not adequately adhere to the key principles of impact evaluation that would enable these studies to draw convincing causal inferences.

Limited knowledge of conservation impact in the Great Barrier Reef Marine Park, one of the most intensively studied marine regions, is likely to apply to many other marine parks around the world. We provide recommendations for improved impact evaluation of marine parks generally.

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