Should we be conserving and managing marine ecosystems in 3D? The latest thinking on vertical zoning | The Skimmer on – MEAM

Editor’s note: Several new papers have examined the feasibility and advisability of applying different management and conservation measures at different depths of the water column (aka ‘vertical zoning’). In this issue, with help from a couple of experts, The Skimmer takes a quick look at the history of vertical zoning and current thinking on where it can and should go next.

Are we going to use vertical zoning on the high seas?

Areas beyond national jurisdiction (ABNJ) make up 64% of the oceans’ surface. To provide for the conservation and sustainable use of biodiversity in these areas, the UN General Assembly is currently convening an intergovernmental conference to create a legally binding instrument under the United Nations Convention on the Law of Sea (UNCLOS). The conference held its first session in late 2018 and will have two additional sessions in 2019 and a final one in 2020.

UNCLOS currently has one level of stratification for ABNJ – the deep seabed which is governed by the concept of being “the common heritage of mankind” (with mineral extraction from the seabed governed by the International Seabed Authority) and the water column which is governed by the principle of “freedom of the seas” – which until now has allowed states freedoms of navigation, fishing, and scientific research with responsibilities in how those freedoms are exercised. Currently, areas with vulnerable marine ecosystems can be closed to bottom fishing while fishing is permitted in the water column above.

To learn more about what role vertical zoning may be playing in ABNJ negotiations, The Skimmer contacted Aria Finkelstein. Finkelstein is a Ph.D. candidate at MIT’s Department of Urban Studies and Planning and a guest student at the Woods Hole Oceanographic Institute’s Marine Policy Center and is researching efforts to implement MSP on the high seas.

According to Finkelstein, “To put it simply, vertical zoning is not currently playing a role in ABNJ negotiations.” She added, “So far, while the negotiations emphasize spatial management under the umbrella of area-based management tools (ABMTs), they have not explicitly addressed the importance of vertical striations within the high seas water column.”

She said:

“For example, one area that is hugely important and sorely understudied is the mesopelagic zone, or the twilight zone between 200 and 1,000 meters depth. The organisms that populate this low-light layer are so dense they were originally thought to be the bottom of the sea because they registered in soundings. These organisms constitute an enormous store of biomass and play a large role in global carbon cycles, actively sequestering carbon from surface waters via fecal pellet fall or mortality at depth.

These organisms have been notoriously difficult to harvest, but technologies to exploit them, especially for aquaculture feed and nutraceuticals, are developing quickly. Fully fledged mesopelagic fisheries are probably still a way in the future, but neglecting to provide a framework for regulating them now could spell a serious failure in preventing the erosion of our biological climate change regulation systems. So there is no question that 3D thinking is necessary for effective high seas management.”

She suggested that even if the ABNJ biodiversity negotiations do not address the desirability of or options for vertical zoning of high seas MPAs head-on, simply establishing a legal framework for high seas MPAs may “allow for case-by-case consideration of whether vertical zoning is appropriate or not.” If it does, she said, “there’s no doubt the requirements for doing so need to call for great caution, for example, by explicitly limiting it to systems in which benthic-pelagic linkages are demonstrably weak and ruling it out where these systems are more strongly connected or their relationship is still uncertain or unknown.”

At the moment, with our current, very limited understanding of deep sea dynamics and very limited ability to effectively monitor human activities and ecosystem status in the deep sea, Finkelstein concluded, “the importance of benthic-pelagic linkages for the health of marine ecosystems and global carbon cycles as a whole is a compelling reason to avoid vertical zoning, as it may fail to account for these relationships.”


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