Das Interview: Fisheries, ecosystem function and biodiversity in a human dominated world.

Ralph O. Schill met Dr. Sebastian Ferse from the Leibniz Centre for Tropical Marine Research (ZMT) in Bremen, Germany, on a “dive”…

In a study published this week in the scientific journal „Science“, researchers investigate the question of whether and how socio-economic and ecological goals can be achieved simultaneously through protective measures for coral reefs. An international team of 38 scientists led by Prof. Joshua Cinner from the Australian James Cook University compiled a unique data set from around 1800 reef sites worldwide and simulated the effects of various management approaches. I talked with my colleague, Dr. Sebastian Ferse, coral reef ecologist at the Leibniz Centre for Tropical Marine Research (ZMT) in Bremen, who also participated in the study.

Ralph Schill: Tropical coral reefs provide a livelihood for around 500 million people. However, especially along densely populated coasts, they are exposed to a variety of problems caused by humans. There are now more than 2800 protected areas worldwide that restrict or completely prohibit the use of reef resources. What is the motivation for setting up protected areas?

Sebastian Ferse: The motivation for setting up protection measures can vary – in many places the aim is to preserve reef biodiversity or to support fishing, but in some cases it is also to protect certain ecosystem functions. Keeping reef conservation areas functioning is associated with great financial and human effort and depends on the acceptance of the coastal inhabitants to whom the reefs provide an income. It must therefore be carefully considered whether such an effort is worthwhile and likely to succeed under the conditions prevailing at a given site.

Ralph Schill: What is different about the new study compared to other studies?

Sebastian Ferse: The extent of the dataset is unprecedented. Our data spans 10 years and more than 1800 tropical reef sites worldwide, and we have extensive data on the socio-economic conditions, environment and ecological status of reefs. Usually only a single response to management is looked at, e.g. fish biomass or coral cover. We considered three representative management objectives at the same time: the biomass of large fish, the grazing potential of parrotfish, and the diversity of specific reef fish traits such as their food source, home range and schooling behavior.

Ralph Schill: Can you tell me more about the role of parrotfish?

Sebastian Ferse: Parrotfish fulfill an important function for the reproduction of corals. They scrape surfaces free of algae and thereby provide space for coral larvae to settle.

Ralph Schill: What else have you recorded in order to determine the human influence on the reefs?

Sebastian Ferse: We also recorded data on socio-economic characteristics of each site, such as population density, the development status of the respective country and the distance and accessibility of markets. Finally, the protection status of the reefs was also noted when they were located in a marine protected area. With these data we fed a model that calculated which factors are major drivers of the three parameters fish biomass, parrotfish grazing potential and trait diversity, and what are the effects of implementing different degrees of management. The model showed that the effectiveness of conservation measures varies considerably depending on the context and the objectives.

Ralph Schill: Can you tell us more about your results?

Sebastian Ferse: The local level of human influence is a strong driver of fish biomass and functional diversity, and determines the effect of management measures. The results are partly sobering. Four out of five fished reefs in our survey had less than a quarter of the fish biomass they could reach. For half of these, the situation would not change even if strict management was implemented. This is because of the high level of human influence at those locations, which strongly affects the effects management can have. For example, where there is strong human influence, even very restrictive protection measures, so-called „no take zones“, achieve only a low fish biomass, while in reefs with little human influence the biomass is high even without protected areas. For the other parameters studied, there was little difference between very strict or less strict rules in meeting management objectives. Only 2% of openly fished reefs simultaneously scored high for all three parameters, and to meet all three management objectives together, management has the highest chance in places with very low human impact. With our extensive dataset, we can assess under which circumstances it is worth investing resources in conservation measures and what effects coastal managers can realistically expect from such measures. National and international protection programmes can thus better focus on specific objectives and set priorities.

Ralph Schill: Thank you very much, Sebastian, for this summary.

Original publication:
Cinner J.E., J. Zamborain-Mason, G.G. Gurney, N.A.J. Graham, M.A. MacNeil, A.S. Hoey, C. Mora, S. Villéger, E. Maire, T.R. McClanahan, J.M. Maina, J.N. Kittinger, C.C. Hicks, S. D’agata, C. Huchery, M.L. Barnes, D.A. Feary, I.D. Williams, M. Kulbicki, L. Vigliola, L. Wantiez, G.J. Edgar, R.D. Stuart-Smith, S.A. Sandin, A.L. Green, M. Beger, A.M. Friedlander, S.K. Wilson, E. Brokovich, A.J. Brooks, J.J. Cruz-Motta, D.J. Booth, P. Chabanet, M. Tupper, S.C.A. Ferse, U.R. Sumaila, M.J. Hardt & D. Mouillot: Meeting fisheries, ecosystem function, and biodiversity goals in a human dominated world. Science 368: 307-311. Doi: 10.1126/science.aax9412