Environment: Ocean protection could have triple benefits

A globally coordinated effort to protect ocean environments could boost the potential benefits to biodiversity, food provision and carbon storage, suggests a study in Nature this week.

Marine protected areas (in which extractive and destructive activities are restricted) can be an effective tool for restoring ocean biodiversity and ecosystem services. However, at present only around 7% of the ocean area has been designated or proposed as marine protected areas.

To identify how and where to protect the ocean to maximize benefits to the services it provides, Enric Sala and colleagues assess the trade-offs between strategies with the objectives of biodiversity preservation, food provision and carbon storage. They find that 90% of the maximum potential biodiversity benefits from marine protected areas could be achieved by strategically protecting 21% of the ocean. The authors also estimate that strategically placing marine protected areas that cover 28% of the ocean could increase food provisioning by 5.9 million metric tonnes. Some fishing practices, such as bottom trawling, release carbon stored in ocean sediments. However, decisions to halt such practices need to consider whether sediment carbon sources have already been exhausted. The authors suggest that only 3.6% of the ocean needs to be protected to achieve a 90% reduction of the present risk of carbon disturbance due to bottom trawling, although these estimates are based on limited data available on the impacts of trawling on the release of carbon from marine sediments.

Choosing the optimal protection strategy for all three benefits depends on which benefit is perceived to be the most important. If marine biodiversity and food provision benefits are considered to be of equal value, the optimal conservation strategy would protect 45% of the ocean, delivering 71% of the maximum possible biodiversity benefits, 92% of food provisioning benefits and 29% of carbon benefits. A globally coordinated effort could be twice as efficient as uncoordinated, national-level conservation planning, the authors add, calling for a greater level of investment and a cooperative approach to marine conservation.

After the embargo ends, the full paper will be available at: https://www.nature.com/articles/s41586-021-03371-z