Overview of Relevant Statistical Standards

This Circular provides a reference overview of the international statistical standards that underpin Ocean Accounts: the System of National Accounts 2025 (SNA 2025), the System of Environmental-Economic Accounting Central Framework (SEEA CF), and SEEA Ecosystem Accounting (SEEA EA). It also covers the classification systems required for consistent and comparable ocean accounts. For the conceptual framework and key components of Ocean Accounts, see TG-0.1 General Introduction to Ocean Accounts. Key terms are defined in TG-0.6 Glossary.

This Circular requires familiarity with:

• TG-0.1 General Introduction to Ocean Accounts — for the conceptual framework and key components of Ocean Accounts, including the relationship between environmental and economic accounting frameworks and the spatial boundaries relevant to ocean accounting.

The SNA provides the overarching framework for economic accounting. The SEEA extends this framework to measure interactions between the economy and the environment. Within the SEEA family, the Central Framework addresses individual environmental assets and physical flows, whilst SEEA Ecosystem Accounting measures ecosystems as integrated spatial units. Ocean Accounts build upon all three, adapting their concepts and methods to the marine and coastal domain.

3.1 System of National Accounts 2025

The System of National Accounts (SNA) is the internationally agreed set of standards for measuring economic activity. It provides the conceptual framework, classifications, and accounting rules that countries use to compile their national accounts statistics. The 2025 SNA, adopted by the United Nations Statistical Commission at its 56th session in March 2025, strengthens linkages with environmental accounting and introduces new concepts directly relevant to ocean accounts.

The SNA defines a “whole set of standards, including extended/thematic accounts and supplementary items”. Its integrated framework consists of the sequence of economic accounts, supply and use tables, and balance sheets. The 2025 SNA refers to thematic and extended accounts (replacing the earlier “satellite account” terminology used in SNA 2008) to better reflect the integrated nature of these compilations.

Key concepts for ocean accounting

The sequence of economic accounts records production of goods and services, generation, distribution and redistribution of income, and capital accumulation, culminating in balance sheets showing stocks of assets and liabilities. For the ocean economy, this sequence enables measurement of gross value added by ocean industries, income flows to households in ocean sectors, government expenditure on fisheries management, and investment in ocean infrastructure. Application to ocean economy thematic accounts is in TG-3.3 Economic Activity Relevant to the Ocean.

Treatment of natural resources

The 2025 SNA explicitly recognises natural resources as a separate asset category, including renewable energy resources. It identifies five categories: land, mineral and energy resources, biological resources, water resources, and other natural resources. For ocean accounting, this encompasses seabed minerals, offshore energy resources (including offshore wind and tidal energy), aquatic biological resources such as fish stocks, and coastal land.

The 2025 SNA introduces natural capital, defined as “the combination of natural resources and ecosystem assets”. This definition bridges the SNA’s treatment of individual natural resources with the ecosystem approach in SEEA Ecosystem Accounting. Asset accounting applying this concept is in TG-3.1 Asset Accounts.

Depletion as a cost of production

The 2025 SNA treats depletion of natural resources as a cost of production. When fish stocks are harvested beyond sustainable levels, the resulting depletion is recorded as a cost reducing net measures of production. The SNA now emphasises that “the volume change of net domestic product (NDP) is identified as the conceptually preferred measure of economic growth, not replacing but to be used alongside the volume change of gross domestic product (GDP)”.

• Tier 1 — Where depletion data for all major marine natural resources exist, report both Gross Ocean GVA and Net Ocean GVA.
• Tier 2 — Where depletion data exist for some resources only, report Gross Ocean GVA with a qualitative note identifying the resources for which depletion could not be calculated and estimating the likely direction of bias.
• Tier 3 — Where no depletion data are available, report Gross Ocean GVA only, flag depletion data as a priority data gap, and cross-reference TG-0.7 Quality Assurance for data gap documentation guidance.

Aquaculture production is included in ocean economy gross value added (ISIC Division 03) reported in TG-3.3. Natural growth of wild fish stocks is recorded as an addition to stock in the physical asset account in TG-3.1 Table 7.

Natural resources are included in the SNA’s balance sheets “provided that institutional units are exercising effective ownership rights over them, that is, are actually in a position to be able to benefit from them”. Resources within a country’s Exclusive Economic Zone (EEZ) are generally within scope. High seas resources “over which no ownership rights can be exercised” are excluded. The SNA explicitly recommends compilation of ecosystem accounts according to SEEA Ecosystem Accounting.

For resources in areas beyond national jurisdiction (ABNJ), the Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction (BBNJ Agreement), which entered into force on 17 January 2026, may provide new frameworks for accounting treatment as its governance structures develop. The BBNJ Agreement establishes new institutional arrangements for marine genetic resources, area-based management tools, environmental impact assessments, and capacity-building in ABNJ, which may clarify the institutional attribution of benefits from high seas resources and inform asset accounting boundaries. Guidance on deep-sea and ABNJ accounting is in TG-6.6 Deep-Sea and ABNJ.

Ecosystem services, the contributions of marine and coastal ecosystems to human welfare, largely remain outside the SNA production boundary: the natural growth of wild fish stocks, coastal protection by mangroves, and carbon sequestration by seagrass are not recorded as production unless directly transacted in markets. SEEA Ecosystem Accounting addresses this gap directly: it “complements the estimates of output based on the SNA production boundary” by measuring ecosystem services in both physical and monetary terms.

The 2025 SNA “strengthens the linkages with the System of Environmental Economic Accounting (SEEA)”, describes the SEEA as providing “a comprehensive set of monetary and non-monetary accounts covering natural resources and ecosystem assets”, and “strongly encourages” compilation of ecosystem accounts according to SEEA Ecosystem Accounting. The 2025 SNA also explicitly identifies ocean accounting as an application of its thematic accounting framework.

The SEEA Central Framework (SEEA CF) is “a multipurpose conceptual framework that describes the interactions between the economy and the environment, and the stocks and changes in stocks of environmental assets”. Adopted as an international statistical standard in 2012, the SEEA CF extends the SNA’s economic accounts to systematically record physical flows between the environment and the economy and to measure stocks of individual environmental assets. An update is currently underway, with adoption anticipated in March 2028, to ensure alignment with SNA 2025.

The SEEA CF defines environmental assets as “the naturally occurring living and non-living components of the Earth, together constituting the biophysical environment, that may provide benefits to humanity”. These assets are classified into seven main categories: mineral and energy resources; land; soil resources; timber resources; aquatic resources (including wild fish and aquaculture); other biological resources; and water resources. For ocean accounting, the aquatic resources category is most important, encompassing both cultivated aquatic resources (aquaculture) and natural aquatic resources (wild fish, crustaceans, molluscs, and aquatic plants).

The SEEA CF scope includes “all natural resources, cultivated biological resources and land within a country of reference (including resources within a country’s exclusive economic zone)”. For high seas resources, scope is more limited: “While some aquatic resources on the high seas are included as part of individual environmental assets (e.g., fish stocks attributable to countries on the basis of international agreements on access rights), the overall scope of the asset boundary in the SEEA Central Framework is narrower”.

The SEEA CF Physical Supply and Use Tables (PSUTs) record flows between the environment and the economy in physical units (tonnes, cubic metres, joules). For ocean accounting, these enable measurement of fish catches and other aquatic harvests; extraction of seabed minerals and energy resources; use of marine water; and inputs of marine renewable energy. The SEEA CF also provides frameworks for recording residual flows—emissions and waste returned to the environment—which are needed for understanding pressures on marine ecosystems from pollution. Detailed guidance is in TG-3.2 Flows from Environment to Economy.

Asset accounts in the SEEA CF record the opening stock of an environmental asset, additions and reductions during the period, and the closing stock. For aquatic resources, additions include natural growth (recruitment and biomass increase), whilst reductions include catches, natural mortality, and catastrophic losses. The SEEA CF defines physical depletion as “the decrease in the quantity of the stock of a natural resource over an accounting period that is due to the extraction of the natural resource by economic units occurring at a level greater than that of regeneration”. Depletion is a function of the net change in stock: it arises when extraction exceeds regeneration, causing the stock to decline.

A simplified comparison of catch against a sustainable yield estimate is insufficient, because the SEEA CF anchors depletion to the actual net stock change rather than to any single yield reference point. The full derivation is: depletion = gross catch − (natural growth − natural mortality − catastrophic losses − net stock change), consistent with SEEA CF para 5.75—5.83. For sourcing sustainable yield conventions and stock assessment data, see TG-6.7 Fisheries Stock Assessment (planned circular).

The treatment of discards is addressed at SEEA CF para 2.90: “During the extraction of some natural resource inputs, not all extraction is retained in the economy, for example, in fishing operations, there is an amount of discarded catch.” Detailed methodological guidance is in TG-3.1 Asset Accounts and TG-3.2 Flows from Environment to Economy.

Following SEEA CF Table 5.1, stock reappraisals are recorded as “revisions and reclassifications,” a distinct account row from “discoveries” (genuine identification of previously unknown resource occurrences). Conflating the two produces errors in the policy-relevant depletion measure. See SEEA CF para 5.55—5.57 for the full distinction.

Aquaculture versus wild capture

The SEEA CF maintains a clear distinction between cultivated and natural biological resources. “All cultivated biological resources are considered to be within the production boundary”, meaning aquaculture production is treated similarly to agricultural production. Natural biological resources (including wild fish) “are recorded as entering the economy at the point of harvest”. Changes in aquaculture stocks are recorded as changes in produced assets. Reductions in wild fish stocks through overfishing constitute depletion of natural resources. The physical asset account template in TG-3.1 Table 1a sets out cultivated and natural aquatic resources in separate columns.

Limitations for marine ecosystems

The SEEA CF does not treat the ocean itself as an environmental asset: it “does not include oceans and the atmosphere as part of environmental assets, since their stocks are too large to be meaningful for analytical purposes”. Marine ecosystems as integrated spatial units are outside the SEEA CF scope. SEEA Ecosystem Accounting is required for these.

3.3 SEEA Ecosystem Accounting

SEEA Ecosystem Accounting (SEEA EA) was adopted by the United Nations Statistical Commission in March 2021 “as an international statistical standard for the ecosystem accounting framework and physical ecosystem accounts, and presents internationally recognized statistical principles and recommendations for the valuation of ecosystem services and assets”. The SEEA EA extends the SEEA CF by treating ecosystems as integrated spatial units—ecosystem assets—that can be measured in terms of their extent, condition, and the services they provide.

The SEEA EA defines an ecosystem as “a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit”. An ecosystem asset is “contiguous spaces of a specific ecosystem type characterized by a distinct set of biotic and abiotic components and their interactions”, assigned to an ecosystem type that “reflects a distinct set of abiotic and biotic components and their interactions”.

Ecosystem services are “the contributions of ecosystems to the benefits that are used in economic and other human activity”, representing flows generated by ecosystems. The SEEA EA distinguishes between final ecosystem services (directly used by economic units or households) and intermediate services (inputs to the supply of other ecosystem services).

Five types of ecosystem account

The SEEA EA describes five types of ecosystem account:

The Statistical Commission noted “outstanding methodological concerns related to chapters 8 to 11 on valuation”. Accordingly, whilst the physical ecosystem accounts (chapters 3—7) were adopted as a full international statistical standard, the valuation chapters (8—11) were adopted at the level of “internationally recognized statistical principles and recommendations”. This distinction is relevant for ocean accounting applications involving monetary valuation of marine ecosystem services and assets. A worked example applying all five account types to coastal mangroves and seagrass is in TG-3.1 Asset Accounts Section 3.7.

The SEEA EA notes that “marine ecosystems are not concentrated near one surface (i.e. the air-land/water interface) but extend throughout the water column and include the underlying sediment and seabed”. The recommended delineation approach is: “for marine ecosystems within the continental shelf, it is recommended that ecosystem assets be delineated based on the areas of the different ecosystem types associated with the seabed, for example, seagrass meadows, subtidal sandy bottoms and coral reefs”.

The spatial boundary for ecosystem accounting aligns with the SEEA CF: “Consistent with the scope of the SEEA Central Framework, the scope of national jurisdictions for ecosystem accounting should include all ecosystems across the terrestrial, freshwater and marine realms to the boundary of the exclusive economic zone (EEZ)”. For areas beyond national jurisdiction, the SEEA EA notes these may be “the focus of regional or international accounting work”.

IUCN Global Ecosystem Typology

The SEEA EA adopts the IUCN Global Ecosystem Typology (GET) as its reference classification for ecosystem types. Detailed marine biome and ecosystem functional group classifications relevant to ocean accounting are described in Section 3.5 below.

Ecosystem condition is measured using a three-stage approach: presentation of condition variables, derivation of condition indicators, and optional derivation of composite indices. The SEEA EA links condition to ecosystem integrity: “the ecosystem’s capacity to maintain its characteristic composition, structure, functioning and self-organization over time within a natural range of variability”. For marine ecosystems, key drivers of condition include bathymetric profile, climate factors (including ocean acidification and temperature), substrate type, ocean circulation, salinity, and human activities.

Condition variables are selected from SEEA EA Table 5.7, which organises variables by characteristic class using full descriptive names (e.g., coral cover, bleaching prevalence, calcification rate, fish species richness, rugosity). See TG-6.1 Coral Reef Accounts for detailed guidance on condition variable selection for coral reef ecosystem assets.

Monetary ecosystem asset accounts and discount rate guidance

Monetary ecosystem asset accounts record the value of ecosystem assets as natural capital, derived by capitalising projected ecosystem service flows using a discount rate (SEEA EA Chapter 9). The discount rate is one of the most consequential inputs in ecosystem asset valuation. SEEA EA para 10.36—10.42 discusses appropriate approaches, including:

• The social discount rate, which reflects societal time preference and intergenerational equity considerations;
• The risk-free rate as a lower bound, typically approximated by long-term sovereign bond yields;
• Country-specific approaches where market data are available.

Any worked example applying a specific discount rate (such as the illustrative 4% in TG-3.1 Table 8) is illustrative only and does not constitute a GOAP recommendation. Compilers should select a rate appropriate to their national context following SEEA EA para 10.36—10.42. For countries without a sovereign yield curve, the SEEA EA recommends consulting regional comparators or applying a conservative social discount rate consistent with national planning frameworks. Full valuation methodology is in TG-3.1 Asset Accounts.

Standards status of content in this section

Content in this circular draws on sources with different levels of international endorsement. Compilers should distinguish:

1. Adopted international statistical standards — SNA 2025 (adopted March 2025), SEEA CF (adopted 2012, update anticipated March 2028), and SEEA EA physical accounts (Chapters 3—7, adopted March 2021). These carry full UN Statistical Commission authority.
2. Internationally recognised statistical principles and recommendations — SEEA EA valuation chapters (Chapters 8—11, adopted at principles level March 2021). These are authoritative guidance but carry a different level of endorsement than the physical accounts.

As the SEEA EA Preface para 8 notes, the Commission “noted that there are outstanding methodological concerns related to chapters 8 to 11 on valuation” and adopted these chapters as principles-level guidance.

When citing material from this circular in policy or official statistical publications, authors should identify which tier of authority applies to the specific methodology being cited.

The SEEA EA does not describe a separate “SEEA-Oceans” standard; rather, it describes ocean accounts as a thematic accounting application that builds upon SEEA EA and the SEEA Central Framework. No ocean-specific thematic guidance under the SEEA has yet been adopted by the United Nations Statistical Commission. The GOAP Technical Guidance provides an interim methodological framework applying the principles of SNA 2025, SEEA CF, and SEEA EA to the marine and coastal domain. As the international statistical community continues to develop ocean-specific methodology, this Technical Guidance will be updated to reflect any standards adopted by the Statistical Commission.

The SEEA EA describes ocean accounts as providing “a broad framework for connecting relevant elements of the SNA, the SEEA Central Framework and SEEA EA in order to harmonize priority ocean data covering economic, ecological, governance and social dimensions”. The framework adds governance, management and technology accounts alongside the environmental and economic accounts derived from SEEA.

Ocean accounts enable measurement of:

Challenges for ocean accounting

The SEEA EA acknowledges specific challenges for ocean accounting. Data on the ocean “is more fragmented than data for terrestrial and freshwater ecosystems and the understanding of the ecological and economic connections among marine ecosystems, coastal ecosystems and other ecosystems is less advanced, although the relationship is expected to be highly non-linear”. Additional challenges include appropriately reflecting the three dimensions of marine areas (depth in addition to area), accurately capturing changes in condition, and addressing transboundary issues for migrating fish stocks and shared ecosystems.

3.5 Related Classification Standards

The key classifications for ocean accounting span economic activities, products, government expenditure, environmental protection activities, and ecosystem types.

International Standard Industrial Classification (ISIC)

The International Standard Industrial Classification of All Economic Activities (ISIC) classifies economic activities. ISIC Revision 5 was endorsed by the UN Statistical Commission at its 55th session in March 2024 and organises activities into a four-level hierarchy: sections (alphabetic), divisions (2-digit), groups (3-digit), and classes (4-digit). Where national classifications have not yet adopted ISIC Rev.5, compilers should use the correspondence tables between ISIC Rev.4 and ISIC Rev.5 published by the UN Statistics Division and document the classification version applied in their metadata.

For ocean accounting, the most directly relevant ISIC categories are:

Other ocean-relevant categories include shipbuilding, offshore support activities for petroleum and natural gas extraction, and recreational fishing services. Fish processing at land-based plants is classified in Division 10 (Food products).

Central Product Classification (CPC)

The Central Product Classification (CPC) classifies goods and services. CPC Version 3.0 was endorsed by the UN Statistical Commission at its 55th session in March 2024. Each CPC subclass corresponds to specific ISIC classes of industrial origin, enabling linkage between product statistics and industry statistics.

Division 04 (Fish and Other Fishing Products) provides detailed categories for live fish, fresh fish, crustaceans, molluscs, and other aquatic products, with distinctions between wild-caught and farmed products. Division 21 covers processed fish products. Transport services related to water are classified in Divisions 65 (water transport services) and 67 (port and waterway operation services).

Classification of Functions of Government (COFOG)

The Classification of Functions of Government (COFOG) classifies government expenditure by purpose. COFOG is currently under revision, with adoption expected in March 2028. For ocean accounting, the relevant COFOG categories are:

Interim guidance pending the March 2028 COFOG revision: Compilers preparing pilot ocean accounts before the revised COFOG is adopted should apply the existing COFOG (2000 version) codes with supplementary national detail and document allocation decisions in metadata. Where existing codes do not clearly distinguish ocean-related expenditures (for example, marine spatial planning or blue economy development expenditures not fitting clearly within Class 04.2.3), compilers should record a supplementary classification note alongside the COFOG code. Compilers should monitor the UNSD COFOG revision process at https://unstats.un.org/unsd/classifications/cofog/revision and consult TG-1.1 National Ocean Budgets for interim bridging conventions on government expenditure classification.

The Classification of Environmental Protection Activities (CEPA) and Classification of Resource Management Activities (CReMA) provide detailed categories for environmental expenditure and activities. Developed jointly by Eurostat and UNSD, these are international classifications with global applicability. SEEA CF Chapter 4 provides the overarching framework context. Compilers should note that CEPA and CReMA are in the process of being replaced by the new Classification of Environmental Purposes (CEP), which is progressing through UN adoption. Compilers implementing ocean accounts should monitor CEP development at the UNSD classifications portal.

For ocean accounting, relevant CEPA categories include wastewater management (CEPA 2) covering discharge to marine waters; protection and remediation of soil and water (CEPA 4) which “concerns surface water, groundwater and marine waters” including oil spill cleanup in coastal areas; and protection of biodiversity and landscapes (CEPA 6) covering marine species and habitat protection, marine protected area management, and fisheries quota enforcement. CReMA 13A covers production of energy from renewable sources including ocean energy (wave, tidal, thermal).

IUCN Global Ecosystem Typology

The IUCN Global Ecosystem Typology (GET) serves as the reference classification for ecosystem types in SEEA Ecosystem Accounting. For ocean accounting, the GET provides a typology of marine and coastal ecosystems organised into realms, biomes, and ecosystem functional groups. The Marine realm encompasses 20 ecosystem functional groups across four biomes, from seagrass meadows and coral reefs in the Marine Shelf biome to chemosynthetic-based ecosystems in the Deep Sea Floors biome. The transitional realms add further categories for shoreline systems, coastal wetlands, mangroves, estuaries, and other coastal ecosystem types.

ISIC identifies ocean-related industries (producers), CPC identifies ocean-related products (outputs), COFOG tracks government spending on ocean functions, CEPA/CReMA tracks environmental protection and resource management activities, and IUCN GET provides the ecosystem asset classification. Correspondences between classifications—such as the linkage between CPC subclasses and their ISIC classes of origin—facilitate integrated analysis. Gaps exist: ISIC does not separately identify marine mining from land-based mining, offshore renewable energy is not distinctly classified, and marine-specific environmental activities are often combined with terrestrial activities in CEPA and CReMA. These limitations may require supplementary classification detail for complete ocean accounts.

3.6 Standards Application Summary

Table 3.1 summarises how the international statistical standards described in this Circular are applied across the GOAP Technical Guidance, mapping each standard to the key concepts it provides, the ocean accounting applications it enables, and the specific circulars where detailed implementation guidance is provided.

Table 3.1: Application of statistical standards in ocean accounts

Authors: [To be confirmed]

Reviewers: [To be confirmed]