Marine protected areas (MPAs) are an important tool for conserving ocean biodiversity. When they are effectively managed, MPAs can protect fish populations, maintain healthy reef ecosystems, and provide areas where species can reproduce and disperse.
Connected networks of MPAs can be especially valuable because many marine species move between habitats during their life cycles. However, simply designating an area as protected does not necessarily mean that it is providing meaningful ecological protection.
The Kunming-Montreal Global Biodiversity Framework includes the goal of effectively conserving at least 30% of the world’s oceans by 2030, commonly known as 30×30. Current estimates suggest that about 9.8% of the global ocean is within MPAs. But these estimates are largely based on the amount of area designated for protection and the regulations that are supposed to apply within those boundaries, without necessarily showing whether those protections are actually producing ecological benefits.
Clausius, E., Edgar, G.J., Mellin, C., Phillips, G.A., Bates, A.E., Benedetti-Cecchi, L., Brown, C.J., Cinner, J.E., Costello, M.J., Sanabria-Fernández, J.A. and Gill, D.A. 2026. At least a fivefold gap in effective global marine protection. Proceedings of the National Academy of Sciences, 123(38): e2611733123. DOI: 10.1073/pnas.2611733123
New research provides an empirical assessment of how effective the global MPA network is using standardized fish surveys from over 500 MPA zones on shallow tropical and temperate reefs around the world. Researchers compared observed fish biomass within MPAs with modeled estimates of what fish biomass would be expected in the absence of protection.
They then used information about MPA characteristics, including fishing restrictions and compliance, to predict effectiveness across the global network. MPAs were considered ecologically effective when observed fish biomass was at least twice as high as the modeled biomass expected without protection.
The results suggest that, at most, about one-quarter of the global MPA network is likely producing meaningful conservation outcomes. When these results are extrapolated across the global ocean, less than 2% of the ocean may currently be effectively protected, compared with the nearly 10% reported as protected. This estimate is substantially below the 30% target for 2030.
A major factor behind this difference was compliance with fishing restrictions. MPAs with stronger fishing regulations tended to be more effective, but regulations alone were not enough. Where fishing restrictions were poorly followed, protected areas often showed little ecological benefit. In other words, protection on a map does not necessarily translate into protection in the water.
These findings highlight an important challenge for achieving 30×30: expanding the network of MPAs is unlikely to reach global conservation targets if the areas are not effectively managed and enforced.
Effective MPAs can contribute to connected networks that support healthy populations and movement of marine species, but the connectivity of a network depends on the ecological function of the areas within it. Improving compliance, monitoring ecological outcomes, and understanding the social and management factors that make protections successful will be essential for turning the goal of 30×30 into meaningful conservation on the water.
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