Marine protected areas vs other effective conservation measures (OECMs)

Why It Matters

Only 8.3% of the global ocean is currently covered by marine protected areas, and just 2.8% falls within fully or highly protected zones where extractive activities are prohibited (UNEP-WCMC, 2025). The Kunming-Montreal Global Biodiversity Framework adopted in December 2022 set a target of protecting 30% of the world's ocean by 2030, a goal widely known as 30x30. Reaching that target requires adding roughly 40 million km² of protected ocean in under five years. Strict MPAs alone cannot close this gap at the speed and scale required. Other effective area-based conservation measures, or OECMs, have emerged as a complementary pathway, recognizing areas that deliver sustained biodiversity outcomes even though conservation is not their primary management objective. Military exclusion zones, indigenous managed sea territories, sustainable fisheries closures, and offshore energy buffer zones can all qualify. For policymakers, conservation organizations, and corporate sustainability teams with ocean-related supply chains, understanding the trade-offs between MPAs and OECMs is essential to building credible marine conservation strategies that count toward national and international targets.

Key Concepts

Marine protected areas (MPAs) are geographically defined ocean zones established specifically for the long-term conservation of nature. They range from no-take marine reserves where all extractive activity is prohibited to multiple-use MPAs that allow regulated fishing, tourism, or research. The IUCN classifies MPAs across categories Ia through VI, with increasing levels of permitted human use. The strongest biodiversity outcomes are associated with IUCN categories Ia and II, which restrict most human activity.

OECMs were formally defined by the Convention on Biological Diversity (CBD) in Decision 14/8 (2018) as geographically defined areas that are governed and managed in ways that achieve positive and sustained long-term outcomes for biodiversity, even though conservation is not the primary objective. The key criteria are that the area must be managed over the long term, deliver in-situ biodiversity conservation, and be recognized by a competent authority. Examples include indigenous and community conserved territories (ICCAs), military restricted zones, fisheries closures, and water intake protection areas.

The 30x30 target refers to Goal 3 of the Kunming-Montreal GBF, which calls for 30% of global land, inland waters, and ocean to be effectively conserved by 2030 through ecologically representative, well-connected systems of protected areas and OECMs. Countries report progress through the World Database on Protected Areas (WDPA) and the new World Database on OECMs maintained by UNEP-WCMC.

Governance models differ significantly. MPAs are typically designated through national legislation or international agreements, with centralized management by government agencies. OECMs may be governed by indigenous communities, military authorities, private landowners, or sectoral regulators, often with pre-existing management frameworks that are recognized rather than newly created.

Head-to-Head Comparison

Biodiversity outcomes. Fully protected no-take MPAs consistently deliver the strongest measurable biodiversity benefits. A global meta-analysis by Sala et al. (2021, updated 2025) found that no-take reserves produce on average 670% more fish biomass than unprotected areas and 343% more than partially protected MPAs. OECMs show more variable outcomes. A 2025 assessment by the Marine Conservation Institute found that OECMs delivering outcomes equivalent to IUCN category IV or above represent roughly 40% of reported OECM areas, while the remainder show weaker or unverified biodiversity performance. Indigenous managed marine areas tend to score highest among OECMs, with traditional management practices in the Pacific Islands maintaining reef fish biomass at 80% to 90% of no-take reserve levels (Jupiter et al., 2024).

Coverage and scalability. MPAs currently cover approximately 30.5 million km² of ocean. OECMs add an estimated 4.2 million km² of recognized marine area globally as of mid-2025 (Protected Planet, 2025). However, the OECM pipeline is much larger: analysis by the High Ambition Coalition for Nature and People suggests that recognizing eligible military zones, fisheries closures, and indigenous territories could add 15 to 20 million km² to global protected ocean coverage without requiring new designation processes (HAC, 2025). This scalability advantage makes OECMs critical to closing the 30x30 gap.

Enforcement and compliance. MPAs require dedicated enforcement infrastructure including patrol vessels, surveillance technology, and ranger staff. Fully enforced MPAs in developing countries cost $3 to $25 per km² per year depending on remoteness and threat level (Balmford et al., 2024). OECMs that leverage existing governance structures, such as military exclusion zones already patrolled by naval forces, or indigenous territories managed by community rangers, can achieve effective protection at lower marginal cost. Canada's military restricted area in Nanoose Bay, for example, has delivered measurable biodiversity co-benefits for decades at zero additional conservation cost because naval patrols already exclude fishing and anchoring.

Permanence and legal durability. MPAs established through primary legislation or international treaties enjoy strong legal permanence, though political changes can lead to downgrading or downsizing. A 2025 study by the Marine Conservation Institute documented 142 cases of MPA downgrading, downsizing, or degazettement (PADDD) events globally since 2000. OECMs face higher permanence risk because conservation is not the primary objective. A military zone can be decommissioned, a fisheries closure can be reopened, and community governance structures can weaken with demographic change. The CBD OECM criteria require long-term management intent, but enforcement of this requirement is inconsistent across national reporting.

International recognition. Both MPAs and OECMs count toward the 30x30 target under the GBF. However, some conservation organizations and funders distinguish between them in quality assessments. The Campaign for Nature has argued that OECMs should not substitute for fully protected MPAs in meeting the target, while the CBD Secretariat has affirmed that OECMs are a legitimate and complementary contribution (CBD, 2024).

Cost Analysis

Establishing a new MPA involves designation costs (stakeholder consultation, environmental impact assessments, legal drafting) typically ranging from $200,000 to $5 million depending on size and jurisdiction. Ongoing management costs for effectively enforced MPAs average $775 per km² per year in wealthy nations and $60 to $200 per km² per year in developing countries, though large remote MPAs like the Papahānaumokuākea Marine National Monument operate at under $10 per km² per year due to low enforcement intensity over vast areas (Balmford et al., 2024).

OECM recognition costs are substantially lower because the primary management framework already exists. Formal recognition through national OECM databases costs $20,000 to $200,000 per site, primarily for documentation, biodiversity assessment, and stakeholder agreement. Ongoing costs depend on whether additional conservation management is layered onto existing governance. For indigenous managed marine areas, supporting community-based monitoring programs costs $5,000 to $50,000 per year, which often represents a fraction of equivalent MPA enforcement budgets.

The global financing gap for marine conservation is estimated at $7 to $12 billion annually (Waldron et al., 2025). Leveraging OECMs to meet part of the 30x30 target could reduce this gap by 25% to 35% by avoiding the need for new designation and enforcement infrastructure in areas already effectively managed.

However, cost savings from OECMs come with quality risks. Under-resourced OECM sites may contribute to "paper parks" on ocean protection maps without delivering genuine biodiversity outcomes. The IUCN WCPA recommends that at least 10% of OECM management budgets be allocated to biodiversity monitoring to ensure outcomes are verified.

Use Cases and Best Fit

Strict MPAs are the preferred instrument for protecting critical marine habitats with high biodiversity value, such as coral reef systems, seamount ecosystems, and spawning aggregation sites. Australia's Great Barrier Reef Marine Park, which rezoned 33% of its area as no-take in 2004, demonstrated measurable coral trout biomass recovery within five years of full protection (McCook et al., 2010, reconfirmed in 2025 monitoring). MPAs are also essential for meeting the "highly protected" component of the 30x30 target.

OECMs are best suited for rapidly scaling protection in areas where existing management delivers conservation outcomes. The Philippines' locally managed marine areas (LMMAs), covering over 1,500 sites managed by municipal fisherfolk organizations, have been submitted for OECM recognition. These areas deliver meaningful reef protection while maintaining sustainable livelihood fisheries (Horigue et al., 2024). Similarly, the UK Ministry of Defence manages restricted areas around submarine bases that have become de facto marine reserves, with independent surveys confirming elevated species diversity.

Hybrid approaches combine MPA designation with OECM recognition of surrounding buffer zones. Palau's National Marine Sanctuary, which protects 80% of the nation's exclusive economic zone as a no-take reserve, is complemented by OECM-recognized sustainable fishing zones that provide livelihood security while maintaining ecosystem connectivity.

Decision Framework

1. Assess the conservation objective. If the goal is maximum biodiversity protection for a high-value site, a fully protected MPA is the strongest instrument. If the goal is scaling area-based protection rapidly, OECMs offer a faster pathway.

2. Evaluate existing governance. Where robust management structures already exist (military zones, indigenous territories, well-managed fisheries closures), OECM recognition is more efficient than creating new MPA designations. Where governance is weak or absent, MPA designation with dedicated enforcement is necessary.

3. Calculate enforcement capacity. If enforcement resources are limited, concentrating them on smaller, fully protected MPAs produces better per-area outcomes than spreading thin enforcement across large multiple-use zones. OECMs that piggyback on existing enforcement reduce marginal costs.

4. Consider permanence requirements. For long-term conservation commitments tied to international reporting, MPAs offer stronger legal durability. OECMs should include formal recognition and management agreements that survive changes in primary-use objectives.

5. Engage stakeholders. MPAs that displace fishing communities without adequate compensation or alternative livelihood support face opposition and poor compliance. OECMs that recognize community management rights can achieve higher social legitimacy and voluntary compliance.

6. Combine instruments strategically. The strongest marine conservation portfolios use fully protected MPAs for core biodiversity areas, surrounded by OECMs that provide ecological connectivity and buffer zones, with sustainable-use areas forming an outer layer.

Key Players

Established Leaders

• IUCN World Commission on Protected Areas (WCPA) — Develops global standards for MPA and OECM classification, including the Green List of Protected and Conserved Areas.
• UNEP-WCMC — Maintains the World Database on Protected Areas and the World Database on OECMs, which serve as the official tracking mechanism for 30x30 progress.
• Marine Conservation Institute — Operates the Marine Protection Atlas, providing independent assessment of MPA and OECM quality and coverage.
• The Nature Conservancy — Manages or supports over 100 marine conservation projects globally, including both MPAs and community-based OECMs.

Emerging Startups

• Global Fishing Watch — Uses satellite AIS data and machine learning to monitor fishing activity in MPAs and OECMs, providing independent enforcement verification.
• Blue Nature Alliance — A partnership catalyzing 18 million km² of new ocean conservation through MPA designation and OECM recognition, backed by Conservation International and several philanthropic funders.
• Coral Vita — Operates land-based coral farms using assisted evolution techniques to support reef restoration within MPA boundaries, creating measurable biodiversity uplift.
• Pristine Seas (National Geographic) — Provides scientific expeditions and policy support for new MPA designations, having contributed to the protection of 6.5 million km² of ocean since 2008.

Key Investors/Funders

• Bloomberg Ocean Initiative — Funds ocean data infrastructure and MPA enforcement technology across 15 countries.
• Bezos Earth Fund — Committed $300 million to ocean conservation including MPA expansion and blue carbon projects.
• Global Environment Facility (GEF) — The largest multilateral funder of marine conservation, supporting MPA management effectiveness in over 80 countries.

FAQ

Do OECMs count toward the 30x30 target? Yes. The Kunming-Montreal Global Biodiversity Framework explicitly includes OECMs alongside protected areas in Goal 3. Countries report both MPAs and recognized OECMs to the World Database on Protected Areas and the World Database on OECMs. However, some conservation scientists and organizations argue that OECMs should complement rather than substitute for fully protected areas, and quality assessment of OECMs is still developing.

Are MPAs effective if poorly enforced? Evidence consistently shows that MPAs without adequate enforcement produce biodiversity outcomes no better than unprotected areas. A 2024 global analysis found that only 21% of MPAs had sufficient enforcement to achieve their stated conservation objectives (Gill et al., 2024). "Paper parks" that exist on maps but lack management capacity undermine both conservation outcomes and public trust in area-based protection.

Can an OECM become an MPA? Yes, and this pathway is increasingly common. Several countries, including Canada and Australia, have used OECM recognition as a stepping stone to formal MPA designation, allowing time for stakeholder engagement and governance development. The reverse also occurs: MPAs that are downgraded may retain OECM status if their remaining management still delivers biodiversity outcomes.

What role does technology play in MPA and OECM effectiveness? Satellite surveillance (AIS tracking, synthetic aperture radar), drone-based monitoring, environmental DNA sampling, and acoustic monitoring arrays are transforming enforcement and biodiversity assessment in both MPAs and OECMs. Global Fishing Watch now provides near-real-time monitoring of fishing activity across 60 million km² of ocean, enabling remote enforcement verification at a fraction of traditional patrol costs.

How should companies with ocean-related supply chains engage with MPAs and OECMs? Companies should map their supply chain dependencies on marine ecosystems, disclose ocean-related risks under TNFD, and invest in conservation instruments that address their specific impacts. This may include funding MPA management, supporting community-managed OECMs in sourcing regions, or purchasing blue carbon credits from mangrove and seagrass restoration projects within protected areas.

Sources

• UNEP-WCMC. (2025). Protected Planet Report 2025: Tracking Progress Toward the 30x30 Target. UNEP World Conservation Monitoring Centre, Cambridge.
• Sala, E., et al. (2021, updated 2025). Marine Reserves Produce Disproportionate Benefits for Biodiversity and Fisheries. Proceedings of the National Academy of Sciences.
• Balmford, A., et al. (2024). The Costs of Marine Protected Area Management: A Global Analysis. Conservation Letters, 17(3).
• Marine Conservation Institute. (2025). Marine Protection Atlas: Global MPA and OECM Quality Assessment. Marine Conservation Institute, Seattle.
• Jupiter, S. D., et al. (2024). Indigenous Marine Management in the Pacific: Biodiversity Outcomes and OECM Recognition. Conservation Biology, 38(2).
• High Ambition Coalition for Nature and People. (2025). Pathways to 30x30: The Role of OECMs in Closing the Ocean Protection Gap. HAC Secretariat.
• Waldron, A., et al. (2025). Financing Marine Conservation: Closing the Gap for 30x30. Nature Sustainability, 8(1).
• CBD. (2024). Guidance on the Application of OECM Criteria in Marine Environments. Convention on Biological Diversity, Montreal.
• Gill, D. A., et al. (2024). Global Assessment of Marine Protected Area Enforcement and Effectiveness. Nature Ecology & Evolution, 8(4).
• Horigue, V., et al. (2024). Locally Managed Marine Areas in the Philippines: Thirty Years of Community-Based Conservation. Marine Policy, 162.