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In line with global targets agreed under the Convention on Biological Diversity, the number of marine protected areas (MPAs) is increasing rapidly, yet socio-economic benefits generated by MPAs remain difficult to predict and under debate1,2. MPAs often fail to reach their full potential as a consequence of factors such as illegal harvesting, regulations that legally allow detrimental harvesting, or emigration of animals outside boundaries because of continuous habitat or inadequate size of reserve3,4,5. Here we show that the conservation benefits of 87 MPAs investigated worldwide increase exponentially with the accumulation of five key features: no take, well enforced, old (>10 years), large (>100 km2), and isolated by deep water or sand. Using effective MPAs with four or five key features as an unfished standard, comparisons of underwater survey data from effective MPAs with predictions based on survey data from fished coasts indicate that total fish biomass has declined about two-thirds from historical baselines as a result of fishing. Effective MPAs also had twice as many large (>250 mm total length) fish species per transect, five times more large fish biomass, and fourteen times more shark biomass than fished areas. Most (59%) of the MPAs studied had only one or two key features and were not ecologically distinguishable from fished sites. Our results show that global conservation targets based on area alone will not optimize protection of marine biodiversity. More emphasis is needed on better MPA design, durable management and compliance to ensure that MPAs achieve their desired conservation value.

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  • 12 February 2014

    Values denoting confidence limits off-scale have been added in Fig. 3.


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We thank the many Reef Life Survey (RLS) divers who contributed to data collection. Development of the RLS data set was supported by the former Commonwealth Environment Research Facilities Program, whereas analyses were supported by the Australian Research Council, a Fulbright Visiting Scholarship (to G.J.E.), the Institute for Marine and Antarctic Studies, and the Marine Biodiversity Hub, a collaborative partnership funded under the Australian Government’s National Environmental Research Program. Surveys were assisted by grants from the National Geographic Society, Conservation International, Wildlife Conservation Society, Winifred Violet Scott Trust, Tasmanian Parks and Wildlife Service, the Winston Churchill Memorial Trust, University of Tasmania, and ASSEMBLE Marine. We are grateful to the many park officers who assisted the study by providing permits and assisting with field activities, and to numerous marine institutions worldwide for hosting survey trips.

Author information


  1. Institute for Marine and Antarctic Studies, University of Tasmania, GPO Box 252-49, Hobart, Tasmania 7001, Australia

    • Graham J. Edgar
    • , Rick D. Stuart-Smith
    • , Stuart Kininmonth
    • , Neville S. Barrett
    • , Just Berkhout
    • , Colin D. Buxton
    • , Antonia T. Cooper
    • , Marlene Davey
    • , German Soler
    •  & Russell J. Thomson
  2. Institute of Marine Sciences, School of Biological Sciences, University of Portsmouth, Ferry Road, Portsmouth PO4 9LY, UK

    • Trevor J. Willis
  3. Stockholm Resilience Centre, Stockholm University, Kräftriket 2B, SE-106 91 Stockholm, Sweden

    • Stuart Kininmonth
  4. School of Plant Science, University of Tasmania, GPO Box 252, Hobart, Tasmania 7001, Australia

    • Susan C. Baker
  5. Charles Darwin Foundation, Puerto Ayora, Galapagos, Ecuador

    • Stuart Banks
  6. The Bites Lab, Natural Products and Agrobiology Institute (IPNA-CSIC), 38206 La Laguna, Tenerife, Spain

    • Mikel A. Becerro
  7. Elwandle Node, South African Environmental Observation network, Private Bag 1015, Grahamstown 6140, South Africa

    • Anthony T. F. Bernard
  8. Wildlife Conservation Society, Indonesia Marine Program, Jalan Atletik No. 8, Bogor Jawa Barat 16151, Indonesia

    • Stuart J. Campbell
  9. Department of Water, Perth, Western Australia 6000, Australia

    • Sophie C. Edgar
  10. Facultad de Recursos Naturales, Escuela de Ciencias del Mar, Pontificia Universidad Catolica de Valparaıso, Valparaıso, Chile

    • Günter Försterra
  11. Centro Nacional Patagonico, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Bvd Brown 2915, 9120 Puerto Madryn, Argentina

    • David E. Galván
    •  & Alejo J. Irigoyen
  12. Channel Islands National Park, United States National Park Service, 1901 Spinnaker Dr., Ventura, California 93001, USA

    • David J. Kushner
  13. Instituto de Biologia, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, Rio de Janeiro 21941-902, Brazil

    • Rodrigo Moura
  14. Scripps Institution of Oceanography, UC San Diego, Mail Code 0227, 9500 Gilman Dr., La Jolla, California 92093-0227, USA

    • P. Ed Parnell
  15. Leigh Marine Laboratory, University of Auckland, 160 Goat Island Road, Leigh 0985, New Zealand

    • Nick T. Shears
  16. Dipartimento di Scienze Biologiche, Geologiche ed Ambientali, Università di Bologna, Via San Alberto, Ravenna 163-48123, Italy

    • Elisabeth M. A. Strain


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G.J.E. and R.D.S.-S. conceived the project; G.J.E., R.D.S.-S., M.A.B., A.T.F.B., S.C.B., S.B., S.J.C., A.T.C., M.D., S.C.E., G.F., D.E.G., A.J.I., S.K., D.J.K., R.M., G.S., E.M.A.S. and many others collected the data; G.J.E., R.J.T., T.J.W., S.K. and S.C.E. prepared figures; G.J.E. drafted the initial manuscript; all authors contributed to analyses and interpretation.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Graham J. Edgar.

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  1. 1.

    Supplementary Table 1

    This table shows data associated with marine protected areas and ecoregions. Assessed levels for five key features for MPAs studied (l: low; m: medium; h: high), total number of NEOLI features, and observed and predicted species richness and biomass (per 250 m2 transect) for different ecological groups.

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