As countries endeavor to reach their 30×30 goals— the plan to conserve 30% of the Earth’s land and water by 2030– evaluating the efficacy of current conservation efforts is critical to setting future priorities for conservation.
Marine Protected Areas (MPAs) – regions of the ocean where human activities, like fishing, are banned or restricted – are a primary marine conservation tool. MPAs can protect biodiversity, provide marine habitat connectivity, and buffer against climate change.
Currently, MPAs cover 8.4% of the ocean, meaning countries must protect much more of the ocean in order to reach their 30% goal. However, the percent of ocean covered by MPAs doesn’t fully reveal their efficacy. MPAs may vary in their value to biodiversity conservation based on the level of restrictions on activities like fishing, on local environmental variables, and on social compliance with restrictions.
Caldwell, I.R., McClanahan, T.R., Oddenyo, R.M., Graham, N.A., Beger, M., Vigliola, L., Sandin, S.A., Friedlander, A.M., Randriamanantsoa, B., Wantiez, L. and Green, A.L. 2024. Protection efforts have resulted in~ 10% of existing fish biomass on coral reefs. Proceedings of the National Academy of Sciences, 121(42), p.e2308605121.
In a new study, researchers modeled the extent to which current marine protection efforts have impacted fish conservation efforts on coral reefs. Human activities, like pollution and overfishing, have degraded coral reefs. Degraded coral reefs impact not only marine wildlife, but human livelihoods, too.
Researchers compiled underwater visual surveys of fish at 1,244 tropical reef sites around the globe and used survey data to estimate fish biomass. This allowed them to compare fish biomass at current protections to fish biomass under a scenario of no protections. They modeled these gains in fish biomass based on protections at each site, allowing them to incorporate local environmental and socio-economic variables into the models.
They found that, without current protections, there would be 10.2% less fish biomass on coral reefs. Gains in biomass varied by local socio-economic and environmental variables. For example, reefs located on slopes and crests had higher gains in fish biomass than reef flats. The context dependency of fish biomass gains means placing MPAs in favorable locations can have a greater impact on marine conservation.
To investigate the potential for future gains, the researchers compared the current protection scenario to one in which 30% of the MPAs fully banned fishing (versus some having only restricted fishing). Under this 30×30 scenario, researchers found that fish biomass would be 17% higher if MPAs were randomly selected, and 28% higher if MPAs were placed in favorable locations. This means that strategic selection of protected areas could lead to 50% more fish biomass.
These results provide empirical evidence that 30×30 conservation efforts are working. They also provide guidance for how to prioritize future protections. Favorable local environmental and socio-economic conditions can maximize the value of protections. Other considerations, like encouraging connectivity between protected areas, could enhance protection efforts, too.
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