Scuba Diver Australasia + Ocean Planet
MARINE PROTECTED AREAS CAN BENEFIT MARINE LIFE, BUT IMPACTS ARE UNEVEN
outside. Halpern further analysed a subset of 17 studies that had information from before the reserves were established, and concluded that fish density and biomass increased within one to three years of the creation of the reserves.
But the reserves affect different species in different ways, Halpern wrote. Slow-growing, long-lived species like cod tend to respond to protection more gradually than fast-growing, short-lived species like scallops. Similarly, heavily exploited species are likely to respond to protection more quickly than those that are not fished, because fishing – the main activity impacting their survival – is suddenly removed from the reserve.
In a more recent study published last year, George Mason University’s Gill and his colleagues compared fish data from 218 MPAs with matching unprotected areas to weed out potential rival explanations.
The team found that, on average, fish biomass inside the protected areas was 1.6 times higher than in similar unprotected areas. “We lost about a quarter of our dataset because we did not find appropriate protected and unprotected matches, but by doing this, we were also more confident about our results,” Gill said.
Overall, researchers say that there is quite a lot of evidence to show that MPAs can benefit species, particularly those that have been threatened historically within the protected area boundaries.
But some recent studies have found that merely creating an MPA does not mean that biodiversity conservation goals will be achieved. They have to be done right in order to work.
In a study published in 2014, for example, the University of Tasmania’s Edgar used data from 87 MPAs collected largely by trained recreational scuba divers, and found that the levels of fish biomass in more than half of the protected areas were not very different from adjacent fished locations. These MPAs were simply “paper parks,” he wrote in The Conversation, “lines on the map that fail to achieve desired conservation outcomes.”
“This is a very worrying statistic in terms of biodiversity conservation goals,” Edgar told Mongabay. “I think most of the public is misled in the sense that they consider [the] establishment of a marine protected area as being an important conservation goal but the reality is that there are very little biodiversity benefits from most marine protected areas. The public is getting quite a wrong impression in terms of the safeguards for marine biodiversity.”
He deemed only 10 percent of the parks he studied “effective” based on their having very high numbers of large fish like sharks. All these protected areas had five recurring features, he found: They had no-fishing zones, were well-enforced, more than 10 years old, relatively large in area, and isolated from fished areas.
Similarly, Gill’s study found that protected areas that had adequate staff performed nearly three times better than parks that did not.
In short, if marine protected areas, or networks of marine protected areas, are large enough relative to the range size of species of interest, away from sources of stress that marine protected areas can’t control, such as land-based pollution from rivers, and well-enforced, they provide dramatic benefit towards biodiversity conservation Benjamin Halpern
By closing off areas of the ocean to fishing and other extractive activities, MPAs, especially marine reserves that ban all or most such activities, are expected to help species recover.
A great deal of research has looked into whether they do, although much of it is not of the highest quality: Many studies do not have rigorous designs and cannot definitively attribute observed changes to the MPA itself.
When considering the studies Mongabay reviewed, though, most studies suggest that MPAs can be good for marine life.
In a meta-analysis published in 2003, for example, Benjamin Halpern of the University of California,
Santa Barbara combined survey data from 89 studies and found that population densities, biomass, diversity and size of fish were generally considerably higher inside marine reserves than