Marine Protected Areas: how to prioritise conservation objectives?
Why protect the oceans?
Oceans support an enormous biodiversity, play a key role in climate regulation, and provide a wide range of benefits to humans . However, oceans are under great threat due to anthropogenic pressures that compromise the safeguard of biodiversity, and the support of human communities. The declaration of marine protected areas (or MPA) is one of the most recognized long-term strategies for protecting and managing oceans facing human-induced pressures, with specific management and conservation objectives .
However, in 2021, only 7% of the total ocean area is designated as MPAs, from which only 2.7% is actively protected . This low proportion can be explained in part by the presence of conflicts between economic and conservation interests that can exist around the declaration and implementation of MPAs.
In this context, a study published this year by a team of researchers coordinated by Dr. Enric Sala sought to provide new answers. This paper identifies priority areas around the world for the creation of MPAs that could maximize the benefits of one or multiple management objectives . In particular, the three targeted objectives are biodiversity conservation, food supply and carbon storage.
Marine Protected Areas with single objectives
The first part of the analysis concerns the identification of priority areas to be protected for increasing the benefits of single objectives.
If the main goal is to conserve biodiversity, it would be sufficient to protect 21% of the oceans to achieve 90% of the potential related benefits, including minimizing the risk of species extinction and preserving the evolutionary history of marine species. From this 21%, most is located in Exclusive Economic Zones (EEZs), in the national territories managed by states, and a minority in the high seas, including seamounts areas and Antarctic ecosystems, amongst others.
Regarding food supply, to achieve 90% of the maximum benefit in terms of fish catches, 5.3% of the ocean should be protected, of which more than 90% is within national jurisdictions.
As for ocean carbon storage, trawling is identified as the main factor impacting the carbon stocks in the seabed. However, all activities that disturb the seabed have an effect on the release of marine CO2, such as deep-sea mining, for which information on spatial distribution is more limited . Nevertheless, the authors’ results show it would be sufficient to protect 3.6% of the oceans to control the disturbance to the carbon pool in 90%.
Marine Protected Areas with multiple objectives
A second part of the study focuses on identifying areas of interest for the creation of MPA with multiple management objectives, in order to increase the benefits.
The first approach is made by identifying areas where 90% of the benefits of two or three objectives are achieved simultaneously. The results show that the protection of 2.7% and 0.3% of the ocean could maximize the benefits from two or three objectives at the time (red and orange areas respectively in fig 1).
Fig 1: Priority areas for achieving 90% of the maximum benefits for one (yellow), two (orange) or three (red) conservation objectives at the same time. In blue, existing Marine Protected Areas. Source: .
Another approach presented by the authors allows to give different levels of importance to each objective. This offers scenarios, according to the interests of the stakeholders (Fig). For example, if biodiversity conservation is targeted with the same importance as food supply (scenario c Fig. 2), protecting 45% of the ocean would provide 71% and 92% of the maximum benefits of each objective respectively. On the other hand, if biodiversity conservation is set as a low priority, and food supply as the main objective (scenario b Fig. 2), 28% of the ocean could provide the maximum benefit to fisheries.
If this tool was made available to the actors of marine conservation, it could help them prioritize conservation areas that could maximize the several benefits, depending on their needs.
Fig 2: Prioritization of several conservation objectives with different possible preferences. (a) Each point is a scenario with benefits related to the weight given to objectives. Food supply benefits on the Y-axis; biodiversity conservation benefits on the X-axis; colors are for carbon benefits; size of dots is the proportion of ocean protected. (b), (c ) and (d) are possible scenarios. Source: .
An international collaboration
Based on the analysis at the global level, the authors were able to estimate how collaboration between countries for the implementation of MPAs can contribute to achieving conservation goals. Under a strategy that is solely national in scope, the proportion of the ocean to be protected would need to be larger, in order to maximize the benefits. However, if the strategy is based on internationally coordinated efforts, 90% of the biodiversity benefits could be achieved with less than half the area to be protected. In other words, collaboration between countries to implement MPAs would make the efforts much more effective.
Regardless of what are the priorities of the ocean stakeholders, Salas and his team emphasize the urgency of increasing investment in MPAs around the world for the creation of new areas, but especially for the enforcement of existing ones for the protection of the oceans in order to halt current and future crises. This would help achieve conservation goals and maintain benefits for human communities such as tourism revenues, food security and climate change mitigation. In this sense, international collaboration and local acceptance are fundamental to the effectiveness of MPAs and the support of human communities.
Written by Florina Jacob and Coralie Barrier.
For more information:
 Marine Conservation Institute. (2020) The Marine Protection Atlas. Ressource virtuelle : http://mpatlas.org
 Day J., Dudley N., Hockings M., Holmes G., Laffoley D., Stolton S. & S. Wells, 2012. Application des catégories de gestion aux aires protégées : lignes directrices pour les aires marines. Gland, Suisse: UICN. 36 pp.
 Sala, E., Mayorga, J., Bradley, D. et al. Author Correction: Protecting the global ocean for biodiversity, food and climate. Nature 592, E25 (2021). https://doi.org/10.1038/s41586-021-03371-z
 Stratmann, T., Lins, L., Purser, A., Marcon, Y., Rodrigues, C. F., Ravara, A., Cunha, M. R., Simon-Lledó, E., Jones, D. O. B., Sweetman, A. K., Köser, K., and van Oevelen, D.: Abyssal plain faunal carbon flows remain depressed 26 years after a simulated deep-sea mining disturbance, Biogeosciences, 15, 4131–4145, https://doi.org/10.5194/bg-15-4131-2018.