Recent global conservation efforts, such as the UN’s Kunming-Montreal Global Biodiversity Framework and updates to the UN Convention on the Law of the Sea, have put ocean conservation under the spotlight. These agreements provide more opportunities for area-based conservation planning, but also necessitate a better understanding of which marine environments are most in need of protection.
Jacquemont, J., Loiseau, C., Tornabene, L. and Claudet, J. 2024. 3D ocean assessments reveal that fisheries reach deep but marine protection remains shallow. Nature Communications 15(1): 4027.
However, many conservation efforts are built around a two-dimensional view of the ocean, and focus on shallow waters that are the most used and studied by people. Given that the ocean is inherently three-dimensional, this means that vast portions of the deep ocean are often under-represented or ignored when marine conservation and use policies are enacted. The vertical connectivity between different ocean depths plays a critical role for fish spawning and feeding, climate refugia, and carbon cycling, and deeper waters are increasingly exploited by the fishing industry.
A recent assessment of global oceans captures this lack of representation in ocean protections across the globe, and emphasizes a framework to identify conservation gaps and priority areas across depths. Commonly used two-dimensional marine ecoregions were combined with depth realms that represent main ecological units across depths. This combined framework allowed for a more meaningful assessment of whether marine protected areas are effective across both space and depth, particularly in the context of high fishing pressure.
The results show that marine protections are uneven, with shallow waters (0-30m) the best protected depth realm. Although these waters suffer the highest fishing pressure, they represent only 2% of the ocean’s surface. In addition, the three dimensional footprint of fisheries extends across most depths in most ecoregions of the world, with almost 40% of total fishing effort overlying depths greater than 300 m. This means that even when fishing occurs in upper depths, it is still likely having significant impacts on deep marine ecosystems.
Protection coverage of three-dimensional realms was also negatively correlated with fishing pressure, meaning that ocean conservation efforts are often biased towards marine areas that are the least impacted. Overall, less that 0.7% of the ocean has high or full protection status under IUCN classification, and these protections are not evenly distributed and mostly occur in areas with little fishing pressure.
These results lead to two suggestions for further conservation work. First, efforts to conserve biodiversity in the ocean should include depth representation. Since humans are naturally biased toward shallow waters and often lack information on deeper waters, using depth as a blanket category to represent areas for conservation could be an effective way to capture unknown biodiversity. Second, depth should be recorded when making measurements of ecological representation, so that in the future there is better data on how different ocean depths can be incorporated into area-based conservation measures.
By shifting to a more three-dimensional view of the ocean, we can better protect and connect diverse marine ecoregions. As more policies put legal frameworks into place, it’s necessary to take a broader view in order to protect more than just the part of the ocean that people can see.
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