Ocean Currents

Noted Scientists Debate Value of Large-Scale MPAs

© Alec Perkins

Two ocean experts went head to head this week over the value and environmental impact of creating large no-take zones – such as Australia’s recently designated 500,000-km2 no-take area in the Coral Sea. They took part in an online debate on Tuesday Oct. 8, which was sponsored by, MPA News, and the EBM Tools Network.

In one corner was Callum Roberts, a professor of marine conservation biology at York University (UK), who argued that the total environmental impact of large no-take areas is positive.

In the other corner was Ray Hilborn, a professor in the School of Aquatic and Fishery Sciences at the University of Washington, who argued that the total environmental impact of large no-take areas may be negative due to the need to make up food production in another way, either at sea or on land.

“Imagine we closed all the oceans to fishing,” opened Hilborn. “If 80 million tons of lost fish production was made up by chopping down rain forest to grow cattle, I think the global environment would be worse off.” Hilborn’s main argument throughout the debate was that making up ocean food production elsewhere would be environmentally damaging.

The problem with this rationale is that no one is proposing closing the entire ocean to fishing. Most scientists who support marine protected areas (MPAs) believe the right percentage is somewhere between 20-30% of no-take areas in our ocean.

In fact, most large MPAs are being proposed in remote places with little fishing. Roberts astutely pointed out that these MPAs actually ‘cost’ very little in terms of lost fishing yield. He went on to estimate that, for 10% cover of very large MPAs, he would expect a short-term loss of about 0.1% to 1% production. So a large MPA does not necessarily mean increased reliance on terrestrial sources of protein, such as beef.

This is why, regardless of size, when looking at MPAs we have to be careful in making assumptions about the correlation between the amount of ocean that restricts fishing and the amount of lost fishing opportunities. Location matters and so do factors like habitat type and existing uses. While some fishermen may need to hang up their gear if an important fishing spot gets closed and there are no alternatives, most fishermen tend to be opportunistic and fish in other nearby places when new protections take effect.

So why designate large MPAs if they’re not being fished anyway? Large protected areas in more remote locations ensure that the marine life inside will continue to thrive into the future, regardless of advances in fishing technology and gear. Meanwhile, scientific research from around the world has shown that marine reserves in more heavily used areas can increase the production of fish – and lead to long-term benefits both for marine wildlife and for fishermen.

A smart global MPA policy would therefore mean setting aside a mix of larger protected areas in these remote places, along with complementary smaller reserves in more heavily used locales that have enhanced recovery potential, like those in California.

Of course the protections need to be real – we can’t just create MPAs and walk away. Implementation, monitoring and enforcement are at least as important as the designation itself. That’s why California—and thousands of volunteers who are committed to the health of their local MPAs—is dedicated to the long-term implementation and monitoring of its MPAs.

For more information, check out the transcript of this debate, along with the comments and questions of the more than 700 people who participated as audience members.

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