Environment

Marine Protected Areas Do More For The Ocean Than We Originally Thought

The number of Marine Protected Areas (MPAs) around the world has increased over the last decade. As of May 2nd, 2019, there are 14,882 (figure updated monthly) Marine Protected areas worldwide, some of which are in the Caribbean.

Countless studies have been published about MPAs and their ability to restore biodiversity (the variety of life in a particular area) and species population to a region. However, a new study that looks at Marine Protected Areas’ effect on predation and herbivory (the state of eating plants) was recently published.

Hammerheads off Cocos Island, Costa Rica  © Barry Peters CC BY 2.0

Brian S. Cheng, Assistant Professor at the University of Massachusetts Amherst, along with his colleagues conducted a meta-analysis that compared rates of predation and herbivory on 32 species across 30 MPAs.

Findings

They found that (1) MPAs significantly increases predation risk on animals and (2) no evidence of increased herbivory on macroalgae and seagrass.

The study defines ‘predation risk’ as the odds of prey being eaten. It suggests that increases in predation risk is due to predator abundance and biomass within MPAs. Predation risk, however, was dependant on the overall success of the MPA.

The study stated that in successful MPAs with the greatest predator accumulation, the odds of predation increased to nearly 49:1, as opposed to 1:1 at MPAs where predators actually declined. The success of an MPA is contingent upon a number of biological and non-biological factors.

Cheng and his colleagues also found correlation between the decline of predation risk and an increase in sea-surface temperature.

As it relates to herbivory, the study suggests that the lack of change is due to functional redundancy (when a number of species from different taxonomy groups share the same or similar roles in an ecosystem) and the inability of MPAs to increase herbivore abundance relative to fished zones in the studies samples.

What does this mean? 

Green Sea turtle in Marine Protected Area courtesy of the Foreign & Commonwealth Office -CC BY-ND 2.0

MPAs ability to restore biodiversity to near depleted ecosystems and its surrounding areas has been a leading push for their implementation all around the world.

Now restoration of predation, a critical ecosystem function can be added to list of benefits of MPAs.

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