A new study in PNAS challenges the widely cited figure that 10% of the world's oceans are protected. Using observational data from shallow reefs and modeling for thousands of other sites, researchers estimate that only about a fifth of that designated area actually doubles fish biomass—the threshold they define as ecologically effective. That translates to just 2% of the global ocean, a stark gap between official designations and real-world conservation impact.
The main culprit is weak enforcement. Many MPAs allow some fishing, and even in fully protected zones, violations are common. The lead author notes that compliance officers themselves have been seen fishing inside protected areas, drawn by the abundance of large fish. Such behavior reflects a systemic problem: governments often create "paper parks" that exist on maps but lack the management needed to restore ecosystems.
The findings raise questions about the UN's 30×30 goal, which aims to protect 30% of land and ocean by 2030. That target is area-based, easy to measure and communicate, but it ignores whether protections are working. The authors argue for shifting focus from square mileage to ecological outcomes, such as fish population recovery, to ensure conservation dollars actually help marine life.