Strategic management to preserving coral reefs

Plain Language Summary – Meeting fisheries, ecosystem function, and biodiversity goals in a human-dominated world

Coral reefs provide ecosystem goods and services for millions of people in the tropics, but reef conditions are declining worldwide due to multiple human pressures including climate change. 

Productive and healthy coral reefs are clearly desirable to sustain both social and ecological benefits. To date, coral reef science has often focused on one single conservation target while key fisheries, ecological function, and biodiversity goals are needed simultaneously. 

Meeting multiple conservation targets on coral reefs

In our new paper published in Science, we examine around 1,800 tropical reefs across 41 countries or territories and determine the conditions of reefs that simultaneously support 3 key targets: 

  • high levels of fish stocks for multispecies coral reef fisheries;
  • scraping potential, a specialized ecological function performed by parrotfish which limits the growth of algae and promotes the provision of bare substrate for coral settlement and;
  • the diversity of fish traits which supports ecosystem productivity and stability. 

We highlight that the ability of local management to help meet these 3 targets is strongly related to human pressure. Not surprisingly, protected reefs with low human pressure are more likely to simultaneously sustain the 3 targets. More specifically, we show that only 5% of reef sites simultaneously have fish stocks, parrotfish scraping, and trait diversity at the highest rates (>75% of reference conditions). 

Overall, expected conservation gains change non-linearly with human pressure meaning that relatively small changes in management could have strong effects on key conservation targets. What are the conservation gains provided by fully protected MPAs when considering simultaneously fish stocks, parrotfish scraping, and trait diversity?

  • For the most ambitious conservation targets (>75% of reference conditions), the highest conservation gains are provided by fully protected MPAs placed where human pressure is low (left panel);
  • However, if less ambitious conservation targets (50 and 25% of reference conditions) are considered, fully protected MPAs provide the highest conservation gains where human pressure is intermediate (right panel). 
Estimated probability of reefs reaching the most ambitious (left) or less ambitious (right) conservation targets along a gradient of human pressure. Adapted from Cinner et al. 2020

How can the 3 conservation targets be realistically achieved with local management? 

We use statistical models to simulate the effect of the implementation of fully protected MPAs in openly fished sites on the 3 targets. 

For >50% of openly fished reefs, the implementation of a fully protected MPA is predicted to help achieve multiple goals. If only 1% of openly fished reefs are predicted to achieve high conservation targets (>75% of reference conditions), this likelihood increases for less ambitious conservation targets (25 and 50% of reference conditions). 

Additionally, in some openly fished reefs, the implementation of a fully protected MPA can provide reasonable conservation benefits for trait diversity and scraping potential while fishable biomass remains low. 

This emphasizes the importance of the broader seascape context in the effectiveness of MPAs. Thus, our study highlights conservation opportunities for effective management and the placement of new marine reserves while international action on climate change will be crucial for ensuring a future for coral-dominated reefs.

Read the paper in full here.

Read the French press release here.

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