Study shows bias against protecting coral reefs in fishing areas

A new study out in the December issue of the ESA journal Ecological Applications has shown that human interests are having a disproportionate impact on the selection of marine protected areas, or MPAs, which are meant to protect biodiversity in marine ecosystems. Their paper shows a consistent bias in Australian and Tasmanian MPAs toward areas with little commercial resource value.

Volunteer diver undertaking fish transect in the Abrolhos Islands, Australia. Credit:  G. J. Edgar.

The study, led by Graham Edgar of the University of Tasmania, compared long-term trends for so-called “no-take” marine protected areas, where fishing is off-limits, to nearby marine areas that were unprotected and subject to fishing.  The 14 reef communities spanned the southern coasts of Australia and its neighboring southern island, Tasmania. He and his team surveyed the areas – by diving to the reef and visually inspecting along transects — from 1992 to 2008, collecting data on the presence and abundance of predatory fish, medium-sized fish and invertebrates. As Edgar says, the declaration of the MPAs in 1992 provided a unique large-scale natural experiment.

“Experiments of this kind are rarely undertaken at scales greater than a few square meters because of the difficulties in manipulating larger areas of seabed using scientific dive teams,” says Edgar. “The best opportunity to expand such experiments to regional scales is through monitoring changes that follow declaration of MPAs, because in each MPA we are effectively removing human predators from a patch of seabed.”

At the outset of the experiment, Edgar and his colleagues found that the MPAs had lower fish biomass (total estimated mass of fish in the area) and density than other reef areas nearby. Although these MPA became more diverse than their unprotected counterparts over time, Edgar wonders why they had lower biodiversity in the first place.

“When the boundaries of MPAs are drawn up, fishers and other stakeholders try to ensure that areas used by them are excluded from protected zones. This is often publicized as a ‘win-win’ situation because the MPA is declared with little impact on the activities of fishers, who continue fishing in their preferred areas,” Edgar says. “However, MPAs located in areas with little resource value also have relatively low value for biodiversity conservation because human activities continue largely unchanged and the community types most threatened by fishing remain unprotected. This bias seems to be widespread worldwide.”

Edgar says that to safeguard the full range of marine community types, some sanctuary zones need to be located in areas that are heavily fished.

“We cannot safeguard marine biodiversity by declaring sanctuary zones only at sites with little resource value,” he says. “Heavily-fished areas include the most highly threatened community types, so also need protection in MPA networks.”

Reporters and others interested in speaking to the authors can contact Christine Buckley at christine@nullesa.org.The article is open-access and can be accessed on the ESA web page here.
Edgar, G., Barrett, N., & Stuart-Smith, R. (2009). Exploited reefs protected from fishing transform over decades into conservation features otherwise absent from seascapes Ecological Applications, 19 (8), 1967-1974 DOI: 10.1890/09-0610.1