Ocean Governance: EEZs and Marine Protected Areas

Ocean governance is the system of laws, institutions and agreements that regulate human activity at sea; it is based on the UN Convention on the Law of the Sea (UNCLOS), which gives coastal states rights in exclusive economic zones (EEZs) and leaves the high seas open to all, and it uses tools such as marine protected areas (MPAs) to conserve ecosystems. In brief: national EEZs cover roughly a third of the ocean, and the remaining two thirds are the high seas and the seabed beyond national jurisdiction, where rules are weaker and harder to enforce. About 8% of the ocean is formally designated as protected, but only a small part is strongly protected. Governments agreed in 2022 to protect 30% of the ocean by 2030.

The ocean is shared, and its resources, shipping lanes and ecosystems cross borders, so governance needs cooperation. This guide explains the legal framework, the role of EEZs and the high seas, how marine protected areas work, the main institutions and gaps, compares MPA types in a table, works through coverage calculations, outlines the history and corrects common mistakes.

What is the legal framework?

UNCLOS, adopted in 1982 and in force since 1994, is often called the “constitution for the oceans.” It sets out the zones (territorial sea, contiguous zone, EEZ, continental shelf and high seas), the rights and duties of states, freedoms of navigation, rules for the protection of the marine environment and for scientific research, and the settlement of disputes through bodies such as the International Tribunal for the Law of the Sea. It is complemented by agreements and organizations that deal with specific activities:

• International Maritime Organization (IMO): shipping safety and pollution (MARPOL), including emission rules.
• Regional fisheries management organizations (RFMOs): groups of states that manage fish stocks, such as the Western and Central Pacific Fisheries Commission, and the FAO’s guidelines and codes.
• International Seabed Authority (ISA): regulates mineral activities on the seabed beyond national jurisdiction, treated as the “common heritage of mankind.”
• Regional seas conventions: such as the Barcelona Convention for the Mediterranean and OSPAR for the northeast Atlantic.
• Treaties on wildlife and trade: such as CITES and the Convention on Migratory Species, and agreements on whaling.

How do EEZs work in governance?

In its EEZ, which extends up to 200 nautical miles (370 km) from the coast, a state has sovereign rights over living and mineral resources and jurisdiction over environmental protection, marine research and artificial installations. EEZs cover about 30–35% of the ocean, but include around 90% of the world’s fish catch, and most offshore oil and gas. This gives coastal states a major responsibility, and also an advantage: small island states with large EEZs, such as Kiribati, Palau and the Cook Islands, control huge areas of ocean, and they earn income from fishing licenses and have established large marine protected areas. Challenges are the limited capacity for monitoring and enforcement, overlapping claims, illegal fishing by foreign vessels, and the sharing of fish stocks that migrate across boundaries. Neighboring states need to cooperate to manage shared stocks, and regional organizations and joint patrols can help.

How is the high seas governed?

Areas beyond national jurisdiction (ABNJ), about two thirds of the ocean, are open to all states, but with duties to cooperate and protect the environment. Governance there is fragmented: sectoral bodies (IMO, RFMOs, ISA) each regulate one activity, without an overall framework for conservation. In June 2023, countries adopted the Agreement on Biodiversity Beyond National Jurisdiction (BBNJ, or “High Seas Treaty”), which provides for marine protected areas on the high seas, environmental impact assessments, sharing of benefits from marine genetic resources and capacity building. It needs to be ratified by a sufficient number of states to take effect. Deep-sea mining is a current issue: the ISA is developing rules for the extraction of minerals such as polymetallic nodules, and many scientists and states call for caution or a moratorium because of the risks to poorly understood deep-sea ecosystems.

What are marine protected areas?

An MPA is a defined area of the sea in which human activities are managed or restricted to protect nature. They range from no-take reserves, where all extraction is banned (fully protected), to multiple-use areas, where some activities, such as fishing or tourism, are allowed under rules. Well-managed no-take reserves can increase the biomass of fish several times compared with fished areas, make larger and more fertile fish, restore habitats, increase resilience to climate change and “spill over” adults and larvae to nearby fishing grounds. Success depends on size, location, enforcement, funding and the involvement of local communities. Many MPAs are “paper parks” with little protection in practice.

Large MPAs include the Papahānaumokuākea Marine National Monument in Hawaii (about 1.5 million km²), the Ross Sea Region MPA in Antarctica (about 1.55 million km², agreed in 2016), and the Chagos Marine Protected Area in the Indian Ocean. About 8% of the ocean is covered by designated MPAs, but only about 3% is fully or highly protected. The Kunming-Montreal Global Biodiversity Framework (2022) set the target of conserving 30% of the ocean by 2030 (“30 by 30”), through effectively managed and well-connected systems of protected areas and other area-based measures, which include Indigenous and community conserved areas.

MPA types compared

Worked example: coverage and targets

The values are approximate and illustrate typical calculations.

1. EEZ and high seas: the ocean covers about 361 million km². If EEZs cover 35%, they are 0.35 × 361 = 126 million km², and the rest, 361 − 126 = 235 million km² (65%), is the high seas.
2. Protected area: if 8% of the ocean is in MPAs, the area is 0.08 × 361 = 28.9 million km².
3. The 30% target: 30% of the ocean is 0.30 × 361 = 108.3 million km². The gap is 108.3 − 28.9 = 79.4 million km², which means almost tripling the protected area, as 108.3 ÷ 28.9 = 3.7 times.
4. Strongly protected area: if 3% is fully or highly protected, it is 0.03 × 361 = 10.8 million km², so only 10.8 ÷ 28.9 = 37% of the area in MPAs is strongly protected.
5. Fish recovery: a no-take reserve raises fish biomass from 40 tonnes per km² to 160 tonnes, a 4-fold increase, or an increase of 300%. For a reserve of 500 km², the biomass rises from 20,000 to 80,000 tonnes.
6. Large MPA vs EEZ: a state with an EEZ of 3.5 million km² designates an MPA of 1.2 million km². This is 1.2 ÷ 3.5 = 34% of its EEZ, which meets the 30% target for its waters.

How has ocean governance developed?

For centuries, the sea was governed by the principle of freedom of the seas, with a narrow strip of coastal control, a position set out by Hugo Grotius in 1609. The Truman Proclamation (1945) and the claims of Latin American states to 200 nautical miles in the late 1940s and 1950s led to the UN conferences on the law of the sea in 1958, 1960 and 1973–1982, which produced UNCLOS. Environmental agreements followed, including MARPOL (1973) and the London Convention on dumping (1972). The first large marine reserves were created in the 2000s and 2010s, such as the Great Barrier Reef zoning in 2004 that protected a third of the park as no-take, and the expansion of Papahānaumokuākea in 2016. The UN Ocean Conferences (2017, 2022 and 2025) and the BBNJ treaty (2023) are recent steps. Governance has progressed, but gaps in enforcement, funding and coverage remain.

Which mistakes are common?

Mistake 1: Treating the high seas as lawless

The high seas are open to all, but are subject to UNCLOS and other rules. The gaps are in coordination and enforcement, not in the absence of law.

Mistake 2: Judging ocean protection by the percentage designated

A large share of MPAs allow extractive uses. Quality, enforcement and the level of protection matter as much as area.

Mistake 3: Assuming that an EEZ gives full ownership of the sea

States have sovereign rights over resources, but other states keep rights of navigation, overflight and cable laying.

Mistake 4: Seeing MPAs as opposed to fishing

Well-designed reserves can support fisheries by increasing the numbers and size of fish and by spillover to adjacent waters, and local fishers are often key partners.