In last month’s MPA News, we examined the ongoing debate over the value of large vs. small MPAs: whether MPA designations should focus on large offshore sites or smaller inshore ones. This debate has been going on for many years, and we’ve reported on aspects of it several times. 

In the introduction to the article, I inserted the statement that “if the world is to reach Aichi Target 11 under the UN Convention on Biological Diversity (that 10% of marine areas are effectively conserved by 2020) […] then large MPAs are a necessity.”

That statement was criticized by some readers who felt that MPA News was taking a political stand in favor of large MPAs, and against small ones. I recognize now that I should have done a better job of explaining why I said what I did. In fact the statement had nothing to do with politics and everything to do with math.

As long-time readers of MPA News may recall, we published an article in 2012 that examined how the MPA field could reach the 10% target by 2020. We broke it down mathematically. Ten percent of the ocean equals roughly 36 million km2. The median size of MPAs worldwide is somewhere around 3 km2 these days. (This means half of MPAs are larger than that, half smaller.) If you do the math, we would need 12 million median-sized MPAs to reach the 10% target. For comparison: there are just 15,000 MPAs today. (Indeed, even if the median size of MPAs were a hundred times greater – 300 km2 – we would still need 120,000 of them.)

The 20 largest MPAs in the world make up 70% of global MPA coverage. If none of these large MPAs existed, the global MPA coverage would currently be around 2%. And if no more large MPAs were designated, the field would never get to 10%.

That is why I phrased that sentence as I did. I was saying if we want to meet the numerical target of Aichi Target 11, then we obviously must have at least a few very large MPAs. I was not saying large MPAs are good or bad, or numerical targets are good or bad. They both have their strengths and weaknesses, as we’ve covered in MPA News many times. (Small MPAs have their strengths and weaknesses, too.)

If any readers find fault with the math I’ve presented above or my reasoning, I invite you to please write in. I am open to being shown to be wrong. My goal is only to serve the field by raising important issues for consideration.

One last note: The discussion in last month’s article was among the most thoughtful and nuanced I have seen on the topic of large vs. small MPAs, and on numerical targets for MPA coverage. If you have not read it yet, I hope you have time to do so. Thanks.

John Davis,
Editor, MPA News