The Ocean Economy

Every year the ocean regulates climate, produces oxygen, protects coastlines and cycles water for the whole planet. Economists call this flow of free work ecosystem services. The best known global estimate, by Costanza and colleagues in 2014, valued all of Earth's ecosystem services, land and sea together, at about 125 trillion dollars a year (2007 dollars); the ocean and coasts are only part of that total, and the method is debated. National accounts only register the ocean economy that moves through markets: shipping, fishing, tourism, energy. The OECD estimated its value added at about 1.5 trillion dollars in 2010. A WWF study put annual gross marine product near 2.5 trillion, a different measure. The gap between the two numbers is not a rounding error. It reflects a choice, made by accounting systems built centuries ago, to ignore anything that does not pass through a cash register. Natural capital that regenerates quietly in the background has no owner, no invoice and no line in a spreadsheet, so markets treat it as if it were free. A resource treated as free gets used as if it were infinite.

Thinking of the ocean as natural capital means treating it like any other productive asset: a stock that, managed well, generates a steady flow of returns. Fish stocks can be harvested indefinitely if catch stays below the rate of reproduction. Coastal wetlands can keep filtering water and storing carbon for centuries if they are not drained or paved over. The trouble starts when withdrawals exceed regeneration. Overfishing, pollution and habitat destruction are not separate problems, they are different ways of running down the same balance sheet. Because externalities like pollution or reef damage usually carry no price, no single actor bears the full cost of degrading the asset, so the incentive to protect it is weak. This is the core failure the chapter returns to: without a price, there is no feedback signal to stop overuse until the stock is visibly collapsing.

If the core problem is that ocean value goes unpriced, the obvious response is to build mechanisms that price it. Natural capital accounting adds environmental assets and their depletion to national statistics alongside GDP, so a government can see when economic growth is being bought by running down a reef or a fish stock. Carbon markets for coastal ecosystems, often called blue carbon credits, pay landowners or communities for protecting mangroves or seagrass meadows that store carbon. Insurance markets are starting to price coastal risk more realistically as storms intensify. None of these tools is complete. Measuring an ecosystem's value is harder than measuring a barrel of oil, and markets can be gamed or can commodify things better left to regulation. But each step toward pricing an externality makes it a little more visible to decision makers who currently see it as free.

Shipping is the biggest ocean sector by volume because it is the cheapest way to move heavy cargo across long distances. Grain, cars, copper, lithium, even the blades of wind turbines travel by sea because no other mode can match its cost per tonne. Around this core sit flag registries, giant port hubs such as Rotterdam, Shanghai and Singapore, and shipbuilding concentrated in South Korea, Japan and China. The sector is capital intensive, increasingly automated and heavily dependent on fuel, which is also its biggest weakness. Ships still mostly burn heavy fuel oil, a legacy fuel that is cheap but carbon intensive and hard to clean up at sea. The industry is now testing methanol, ammonia and hydrogen as alternatives, alongside slower sailing speeds, optimised routing and electrified ports. None of these fixes is simple, because new fuels need new infrastructure and new safety standards built almost from scratch.

Offshore platforms, ultra deepwater drilling and subsea pipeline networks built offshore oil and gas into one of the most capital intensive and highest value industries on the ocean. For most of the twentieth century it generated more economic value per worker than almost any other maritime activity, concentrated in basins such as the Gulf of Mexico, the North Sea, the Persian Gulf and West Africa. The sector is now in relative decline as the broader energy system shifts toward renewables, though it remains enormous in absolute terms and continues to attract investment in regions with large untapped reserves. The transition is not sudden. Offshore infrastructure, skilled labour and engineering expertise built for oil and gas are increasingly being redirected toward offshore wind, which uses many of the same vessels, ports and subsea skills. The sector's decline is therefore also partly a transformation of its workforce and supply chains into the next generation of marine energy.

Marine and coastal tourism, including cruises, beach tourism, diving and recreational boating, ranks among the two or three largest ocean sectors by revenue and is often the single largest source of coastal employment. It carries a structural paradox: its product is the health of the marine environment, but when it scales up without limits it degrades the very asset it sells. A pristine reef draws divers until overcrowding, anchor damage and runoff from hotels push it past recovery. The tension between mass tourism and a more careful, regenerative model runs through the whole sector. Regenerative approaches, such as dive quotas, visitor caps and revenue sharing with local conservation, are gaining traction because operators increasingly understand that a degraded destination earns less over time, not more. The lesson echoes the chapter's opening argument: an asset that is treated as inexhaustible eventually proves that it is not.

Fisheries and aquaculture generate less financial value than shipping, offshore energy or tourism, but their role in food security makes them indispensable. Fish provides a primary source of animal protein for more than 3 billion people, and the sector employs about 600 million people directly and indirectly along supply chains from boat to market. The sector splits into two very different stories. Wild capture fishing is in structural decline in many regions because of decades of overexploitation, while aquaculture keeps growing and now supplies more seafood than wild catch worldwide. Within aquaculture, outcomes vary enormously between intensive industrial models that can pollute coastal waters and regenerative multi species systems that restore them. A central governance problem cuts across both: destructive practices such as bottom trawling and illegal, unreported and unregulated fishing undermine stock recovery and make sustainable management far harder to enforce even where good rules exist on paper.

Several sectors round out the ocean economy map, each strategically significant despite being less visible than shipping or tourism. Subsea cables carry more than 95 percent of international data traffic, and subsea pipelines move oil and gas between continents, making this infrastructure a frequent flashpoint in geopolitical tension. Marine renewable energy, led by offshore wind with fixed turbines in shallow water and floating turbines reaching deeper sites, is the fastest growing sector by projected rate even though it remains small in absolute volume today. Desalination is expanding fast under global water stress, mature in reverse osmosis technology but limited by its high energy footprint, a constraint increasingly addressed by pairing desalination plants with offshore renewables. Maritime security spans navies, coastguards, satellite surveillance and a growing fleet of autonomous underwater vehicles. The most contested newcomer is deep sea mining, which targets polymetallic nodules, hydrothermal sulfides and ferromanganese crusts rich in cobalt, nickel, manganese and rare earths needed for the energy transition, forcing a direct trade off between decarbonisation materials and poorly understood deep ecosystems.

National waters extend only about 200 nautical miles from shore under the exclusive economic zone system. Beyond that line lies the high seas, international waters that make up about 64 percent of the ocean's surface and belong to no single state. For decades this area lacked any comprehensive management framework, even though it hosts fisheries, shipping lanes, subsea cables and increasingly deep sea mining interest. Fragmented rules covered specific issues, such as fishing quotas for particular species, but no single instrument protected biodiversity across the whole area. The Agreement on Biodiversity Beyond National Jurisdiction, usually called the High Seas Treaty, was adopted in 2023 after almost two decades of negotiation. It is widely seen as the most significant advance in high seas governance in a generation, creating a legal pathway for marine protected areas in international waters. Its ambition is real, but its implementation will take years, and enforcement across such a vast, largely unmonitored area remains an open problem.

Good policy needs good models, and good models need good data. The ocean fails that test in basic ways. Only about 27 percent of the seafloor had been mapped to modern standards by June 2025, and the share keeps growing, meaning most of the planet's largest surface is known less precisely than the surface of the Moon or Mars. Biodiversity data is similarly patchy, concentrated near wealthy coastal nations and major research stations while vast stretches of open ocean and deep sea remain almost unobserved. This is not a minor technical gap. Climate models, fisheries management and conservation planning all depend on baseline data about where species live, how currents move and what the seafloor looks like. Without that baseline, policymakers are often forced to act on incomplete pictures, or not act at all until problems become visible at the surface, by which point underlying damage may already be severe. International efforts such as the Seabed 2030 initiative aim to close the mapping gap by the end of the decade.

Some ocean changes are gradual and reversible. Others cross thresholds, called tipping points, after which the system settles into a new and largely irreversible state. Melting Arctic sea ice reduces the reflective surface that cools the planet, accelerating further warming through the albedo effect. A weakening Atlantic Meridional Overturning Circulation could disrupt heat transport that currently keeps parts of Europe temperate. Mass coral bleaching, once occasional, is becoming permanent across large reef systems as ocean heat accumulates. Dead zones, areas starved of oxygen by nutrient runoff, are expanding and in some cases becoming permanent features rather than seasonal events. Current climate scenarios generally do not model a positive outcome for ecosystems or economies if these thresholds are crossed. Alongside these physical tipping points sit uncounted externalities: plastic pollution, underwater noise and nutrient runoff all impose real costs that rarely appear in any sector's financial statements, though coastal insurers are starting to price some of that risk explicitly.

Three sectors sit at the sharpest edge of the ocean economy's tensions: fishing, offshore oil and gas, and deep sea mining. Each is extractive in the strict sense, removing a finite or slow renewing resource from the ocean, and each now faces converging pressures. Regulation is tightening, from stricter catch limits to emissions rules to seabed mining moratoria proposed by a growing number of states. Alternatives are becoming more competitive, as aquaculture substitutes for wild catch and renewables substitute for offshore fossil fuels. And public and investor tolerance for ocean extraction is falling, visible in divestment campaigns and in the reputational risk that now attaches to destructive practices. None of this means these sectors will disappear quickly, since global demand for protein, energy and minerals remains large. But the transition away from a purely extractive model is unlikely to be smooth or linear, and sectors that adapt early, by investing in selective gear, lower emission fuels or stricter environmental standards, are better placed to retain both resources and legitimacy.

Floating offshore wind is the clear front runner among marine energy technologies, able to reach strong, steady winds far from shore in waters too deep for fixed turbine foundations. Behind it come several technologies still scaling up: tidal stream turbines that harness predictable currents, wave energy converters that extract power from surface motion, and ocean thermal energy conversion, which generates electricity from the temperature difference between warm surface water and cold deep water. None of these rivals offshore wind in scale yet, but each offers something wind cannot, particularly the predictability of tides, which can be forecast years in advance with high precision. Submarine energy storage, including compressed air and pumped systems built into subsea infrastructure, is also emerging to smooth out supply. Taken together, these technologies reframe the ocean not just as a resource to extract from, but as active infrastructure for generating and storing the clean power the rest of the economy needs.

Coastal ecosystems are some of the planet's most efficient carbon sinks, often outperforming land forests per hectare. Mangroves, amphibious coastal forests, can hold up to about four times more carbon per hectare than most tropical forests, mostly in their soils, while also buffering coastlines from storms and serving as nurseries for fish. Seagrass meadows are slow growing underwater plants with very high sequestration capacity, but they are highly vulnerable to anchoring damage and nutrient pollution. Salt marshes, intertidal wetlands, accumulate carbon densely in their sediments yet are frequently destroyed by coastal development. Together these coastal ecosystems are called blue carbon, a narrower idea than the whole ocean carbon cycle. Protecting them does not automatically create tradable credits. A credit needs an approved methodology and registry, a baseline of what would happen otherwise, proof of additionality, measures against reversal and leakage, regular measurement and verification, no double counting, and respect for community rights with fair benefit sharing. Carbon credits also differ from biodiversity credits and from direct payments for ecosystem services.

Marine protected areas restrict certain activities, from all extraction in fully protected reserves to limited fishing in sustainable use zones, to let ecosystems recover and function with less human pressure. The global 30x30 target, protecting 30 percent of the ocean by 2030, has become the headline benchmark for ocean conservation policy, adopted as part of the Kunming Montreal Global Biodiversity Framework. The case for protection is not only ecological. A well documented spillover effect shows that fish populations inside reserves grow and reproduce, then move beyond reserve boundaries, boosting catches in adjacent fished waters. This turns marine protected areas into an economic tool for fisheries, not just a conservation one. The hardest governance problem is extending meaningful protection to the high seas, where enforcement is difficult and no single state has jurisdiction, which is precisely the gap the 2023 High Seas Treaty aims to help close by creating a legal pathway for protected areas beyond national waters.

Against the industrial, intensive model of fish farming, a different approach is emerging that improves the ecosystem while producing food. Seaweed, mussels and oysters are filter feeders or filter effects by nature, so farming them at scale can measurably improve local water quality by removing excess nutrients, the same nutrients that cause the dead zones described earlier in this volume. Polyculture systems combine several species in a single farm, imitating the layered structure of a natural reef and reducing the waste and disease risk that plague single species intensive farms. Integration with offshore renewables, growing seaweed or shellfish around the base of wind turbines, is an emerging model that shares infrastructure and permitting costs between two regenerative sectors. None of this replaces the need for careful siting and management, since even regenerative aquaculture can cause local problems if poorly planned, but the direction is clear: aquaculture is increasingly positioned as a bridge sector between food production and marine restoration rather than a purely extractive industry.

Tourism's relationship with the ocean does not have to repeat the overtourism pattern described earlier in this volume. When designed well, visitor activity can become a direct funding source for conservation rather than a pressure on it. Quota based diving limits the number of visitors to a reef or wreck site per day, protecting the resource while often allowing operators to charge a premium for a less crowded, higher quality experience. Scientific tourism invites paying visitors to participate in research expeditions, from coral monitoring to whale tracking, funding fieldwork that would otherwise struggle for budget. Coastal communities that hold direct stewardship over a reef or mangrove, often through locally managed marine areas, have strong incentives to protect the resource that sustains their income, turning conservation into a local economic interest rather than an externally imposed rule. These models remain the exception rather than the norm, and mass tourism continues to dominate many coastal economies, but they demonstrate a workable alternative where destination, visitor and ecosystem interests align.

The regenerative shift will not look the same everywhere. The North Atlantic combines high maturity in offshore renewables, deep historical fishing pressure and strong institutional capacity to manage the transition. The Mediterranean holds exceptional biodiversity alongside mass tourism, chronic overfishing and governance fragmented across many bordering states. The Caribbean and tropical Atlantic face reefs under extreme stress and economies heavily dependent on coastal tourism, but carry real potential in blue carbon restoration. The western Indian Ocean, along East Africa's coast, combines large scale artisanal fisheries, fast population growth and pressure on mangroves, with clear opportunity in sustainable aquaculture. The tropical Pacific holds the largest ocean surface on the planet, governed by small island states with enormous exclusive economic zones but limited institutional capacity relative to that scale. The Arctic and Antarctic hold unique, fast changing ecosystems under especially complex governance, with growing pressure from energy and mineral interests. The North Pacific and East Asia host the world's largest fishing fleets, the largest aquaculture production and the largest shipbuilding industry, operating at a scale and speed with no real parallel elsewhere.