How can marine areas to be protected be most effectively defined by reconciling several SDGs?
Coral reefs, which cover only 0.1% of the oceans, are home to more than 6,000 species of marine fish and contain 70% of known marine biodiversity. These fish also provide a vital source of food and income for many human populations. How can these two objectives be reconciled in a sustainable way?
To combat excessive pressure, more than 2,000 Marine Protected Areas (MPAs), covering only 6% of the world’s coral reefs, have been established since the 1980s. These areas combine several levels of protection: from no-take or full MPAs (where no harvesting is allowed) to partial MPAs (where fishing activities are only restricted).
10% of maritime areas to be protected
According to the UN, the surface area of these MPAs would have to increase fivefold by 2030 to reach Target 5 of Sustainable Development Goal 14: 10% of the world’s marine habitats with a protected status. To achieve this, policy-makers are considering where to place new MPAs effectively.
It is in this context that an international consortium, bringing together French, Australian, American, British and other countries organizations, has studied the capacity of coral reefs to ensure several beneficial objectives for both humans and nature: maintaining a large biomass of commercial species; conserving the herbivory pressure by fish, which limits the growth of algae and allows coral development; and ensuring functional diversity, ensuring the resistance and resilience of the functioning of coral ecosystems.
5% of reefs in good condition
By studying fish communities on 1,800 coral reefs around the world (Indian and Pacific Oceans, Caribbean Sea), 106 of which are MPAs, researchers have shown that only 5% of reefs simultaneously provide a good level (>75% of reference conditions) of biomass, herbivory and functional diversity.
“This first result highlights the difficulty of reconciling protection and exploitation of reefs when they are close to humans, even in MPAs,” says David Mouillot, from the University of Montpellier. “We need to protect the very rare isolated reefs, which are the only ones capable of meeting all three objectives at the right level. This is the case of the Coral Sea Natural Park, which has placed all the isolated reefs off the coast of New Caledonia in integral MPAs,” says Laurent Vigliola, a researcher at the IRD and co-author of the study.
Reconciling biodiversity and food security
Researchers then turned their attention to developing countries, which have to reconcile ecological requirements with food security and thus find a compromise between resource use and biodiversity conservation. To do this, they simulated the effect on the 3 objectives of a (full or partial) implementation of MPAs for the world’s sites without any level of protection.
Result: when these reefs are already overexploited, very few could reach the threshold of 75% of the reference state, even with full protection. However, for half of these sites currently outside MPAs, protection could greatly improve the level of these targets. “The ideal would be a full MPA, which offers the best results for all three objectives. But a partial MPA remains very interesting, especially for biomass in commercial species and herbivory,” says Josh Cinner of James Cook University in Australia.
Acceptable partial protection
Thus, the restoration of fish populations that meet both biodiversity protection and fishing objectives seems illusory near densely populated areas or on reefs that are already badly damaged. But protection preferentially targeting reefs under more limited human pressure would have a positive effect, even with partial restriction. In order to reconcile societal issues (food security, economy) and biodiversity conservation, partial MPAs can be an interesting compromise.
This post is adapted from a release by IRD.
