Protecting the sea, feeding people
How can we reconcile the imperative need to protect coral reefs without penalizing the many human populations living off the sea's resources? According to a study conducted by researchers from the UM, IRD, CNRS and the University of New Caledonia and published in Science on April 17, placing certain reefs under "partial" protection, combined with good fisheries management, could be an interesting compromise.
Since the 1980s, some 2,000 marine protected areas (MPAs) have been set up to protect coral reefs from the pressure exerted by human activities, particularly overfishing. There are several levels of protection, from "no-take" or integral MPAs, which prohibit all harvesting, to "partial" MPAs where fishing activities are only restricted. Although they currently cover only 6% of the world's coral reefs, the UN plans to multiply these MPAs fivefold by 2030. A necessity, given that they are home to 6,000 species of fish and account for 70% of known marine biodiversity.
Current status of coral reefs
Researchers from an international consortium comprising laboratories in the USA, Canada, Australia, the UK and France have focused on this sustainable development objective. Among them are specialists from CNRS,IRD, theUniversity of New Caledonia and the University of Montpellier, with the Marbec laboratory (marine biodiversity, exploitation and conservation). The aim of the study? To draw up an inventory of coral reefs and simulate their protection, in order to determine where to place these MPAs to make them both effective in protecting biodiversity and compatible with the survival of the many human populations for whom the sea is a source of food and income.
The researchers studied the fish populations living on 1,800 coral reefs (106 of which are MPAs) in the Caribbean, Indian and Pacific Oceans, located at varying distances from the coast. Three conditions have been identified as essential for maintaining biodiversity and providing services to mankind: the maintenance of a high biomass of commercial species such as grouper; the preservation of herbivory pressure, i.e. the presence of species such as parrotfish which, by eating the algae developing on the corals, promote their growth. Finally, the presence of species that perform different ecological functions (functional diversity) and thus contribute to the resistance and resilience of coral ecosystems.
Effective MPAs away from men
The first finding is that only 5% of the reefs observed performed well on the three reference conditions.These reefs are located over 1,000 kilometers from the coast," explains David Mouillot, researcher at the Marbec laboratory. "They are still in good condition and represent the last refuges for many marine species, particularly large predators such as sharks, swordfish and tuna" (see article Trop proches humains, LUM magazine no. 8). For Laurent Vigliola, researcher at the IRD and co-author of the study, "It isimperative that these very rare isolated reefs are protected. This is the case of the Parc Naturel de Mer de Corail, which has placed all the isolated reefs off the coast of New Caledonia under an integral MPA."
The study's second conclusion: the ineffectiveness of marine protected areas on reefs that have been subjected to excessive human pressure due to their proximity.These reefs are doing very badly, and the creation of marine protected areas brings only marginal benefits," notes David Mouilllot. When there's too much human pressure around them, even complete sanctuary is not enough. We therefore need to lower our objectives in theseareas.
A possible compromise
On a more positive note, half of the sites studied and currently located outside MPAs could benefit from real improvement by being placed under protection. "These arereefs located 5 or 6 hours' sail from the coast. They are affected by human activity, but their degradation is reversible.It'sin these areas that we really need to fight," says David Mouillot. While total protection would obviously be desirable, the need to take into account societal issues, and in particular the food security of many countries in economic difficulty, points towards partial protection which, combined with good fisheries management, could pave the way for a genuine balance between man and marine biodiversity.