David Mouillot: “Coral reefs are highly biodiverse ecosystems that serve as a source of income for local communities (fisheries, recreational activities, etc.). Increasingly, setting up new protected areas involves reaching a consensus with fishermen, NGOs and other institutions and local organisations – especially at sites with economic or food security challenges. Marine protected area (MPA) development strategies will therefore need to take stock of the local context, and consider synergies and compromises between conservation goals and human needs. Yet, as things stand, we have very little information about whether reefs can support what are, on the face of it, competing aims. That’s why our study looked at the capacity of 1,800 coral reefs worldwide – including 106 reefs in MPAs – to achieve simultaneously various goals supported by fish: commercial biomass, herbivory and functional diversity. Being an international consortium, we could access data on very remote reefs, reefs located near villages inhabited by active fishermen, or near regional capital cities, allowing to study a complete gradient of human impact while defining reference conditions.
D. M.: “We studied the reefs’ capacity to respond simultaneously to three key goals: biomass in terms of commercial fish, relevant to what is locally consumed or sold, the potential for herbivory of these fish on the reef, an essential function for the control of algae and maintenance of coral reef habitat, and the functional diversity (corresponding to the diversity of traits or fish communities found on the reef, essential component of biodiversity). We found very little correlation between these indicators. Our results showed that only 5% of reefs achieve a satisfactory level (above 75% of the reference condition) for all three of these objectives. Even some of the world’s most emblematic MPAs, such as those in the Coral Sea off the coast of Australia, score poorly on one or even two of the three indicators we looked at – especially when human populations are living nearby.”
D. M.: “There are two basic MPA models: fully protected, where no human activity is permitted, and partially protected, where limited commercial and/or recreational activities are allowed. We ran a series of simulations to assess the effect of creating these types of MPA at currently unprotected sites. The scenarios looked 5 or 10 years ahead, i.e. the amount of time it takes for conservation measures to produce effects on coral reefs, without seeking to make longer-term predictions.
For those reefs in the poorest condition (less than 25% of the reference condition), our simulations showed that, even with the implementation of a fully protected MPA, these reefs are unlikely to achieve a satisfactory level for the three indicators in the short term. However, we also found that creating an MPA would achieve an adequate level (above 50% of the reference condition) for these three indicators for half of the reefs we studied. In our simulations, the best performance was achieved by fully protected MPAs at coral reefs remote or relatively remote from human populations, but we also observed interesting results for partially protected MPAs (e.g. with regulated fishing gear) at sites relatively remote from human populations – especially for the commercial biomass and herbivory indicators.
Setting up partially protected MPAs could therefore be an interim step towards more ambitious conservation of marine ecosystems, and help strike a better balance between conservation imperatives and fisheries goals.
D. M.: “Our work underscores the need to adapt the objectives of MPAs, which are typically uniform across a given territory, to conditions at the site in question (near to or remote from human populations). Policy-makers will need to support MPA managers by setting realistic objectives based on the site’s location and the local socio-economic context, rather than looking to benchmark it against the best-performing site nearby. Securing buy-in from all stakeholders is another important step in MPA implementation. That’s why we’re keen to encourage the sharing of knowledge and best practice with stakeholders.
D. M.: “We’re continuing in the same line of research, aiming to develop more complex scenarios that incorporate both climate change and socio-economic factors (population increase, reef accessibility, etc.). That will help us identify longer-term reef restoration options. We’re also planning to cover a wider range of services provided by coral reefs, so we can identify how the decisions we make in relation to MPAs will influence a wider set of services in a given context.”