Asset Accounts

TG-3.1 Section 3: Compiling Ocean Accounts from Relevant Data Applied Draft TG-3.1 Applied Draft Section 3 Section 3: Compiling Ocean Accounts from Relevant Data asset accounts opening stock closing stock cultivated assets natural resources physical stocks SEEA produced assets non-produced assets SEEA EA SNA SNA 2025 blue carbon mangrove mangroves overfished overfishing stock status condition indicator normalisation pH

Circular ID	TG-3.1
Version	0.9.1
Badge	Applied
Status	Draft
Last Updated	September 2026

Circular TG-3.1 · Section 3: Compiling Ocean Accounts from Relevant Data · 1 September 2026

Asset Accounts

Builds asset accounts for ocean resources — the structured records that track what you have, what you gained, what you lost, and what remains.

Version

0.9.1

Status

Draft

Stability

Applied

Last updated

September 2026

Responsible officer

Dr Jordan Gacutan

Drafting

AI-assisted drafting from GOAP Secretariat source materials; source list to be published at the close of consultation.

Contents

1. 1. Outcome
2. 2. Requirements
3. 3. Guidance Material
   1. 3.1 Physical Asset Accounts
   2. 3.2 Compilation Procedure for Asset Accounts
   3. 3.3 Monetary Asset Accounts
   4. 3.4 Individual Environmental Assets
   5. 3.5 Ecosystem Assets
   6. 3.6 Produced Assets in the Ocean Domain
   7. 3.7 Worked Example: Coastal Ecosystem Asset Accounts
   8. Implementation Considerations
4. 4. Acknowledgements
5. Footnotes

About this circular

Recommended citation

Asset Accounts (2026) (GOAP Technical Guidance on Ocean Accounting, TG-3.1, v0.9.1). GOAP Secretariat. https://guidance.oceanaccounts.org/circulars/section-3/3-1-assets/

© 2026 Global Ocean Accounts Partnership. Licensed under CC BY-NC 4.0.

Builds asset accounts for ocean resources — the structured records that track what you have, what you gained, what you lost, and what remains.

Version

0.9.1

Status

Draft

Stability

Applied

Last updated

September 2026

Responsible officer

Dr Jordan Gacutan

Drafting

AI-assisted drafting from GOAP Secretariat source materials; source list to be published at the close of consultation.

Read first

TG-0.1 General Introduction to Ocean Accounts, TG-0.2 Overview of Relevant Statistical Standards, TG-0.7 Quality Assurance Principles, TG-1.9 Safe Usage of Monetary Valuation, TG-4.1 Remote Sensing and Geospatial Data, TG-4.6 Data Harmonisation and Interoperability

After this circular

TG-1.8 OA and Project-Level Finance, TG-2.1 Aggregate Biophysical Indicators of Environmental State, TG-2.2 Macro-economic Dependencies on Ocean Ecosystems (forthcoming), TG-2.4 Environmental (including Ecosystem) Goods and Services, TG-2.9 Disaster Risk Indicators (forthcoming), TG-3.2 Flows from Environment to Economy ·

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TG-3.4 Flows from Economy to Environment, TG-3.8 Combined Presentations, TG-3.9 Aquaculture Accounts, TG-3.10 Offshore Energy Accounts, TG-3.11 Sub-National Ocean Accounts, TG-6.1 Coral Reef Ecosystem Accounting, TG-6.2 Mangrove and Coastal Wetland Accounting, TG-6.3 Seagrass Ecosystem Accounting, TG-6.4 Kelp Forest and Temperate Reef Accounting, TG-6.5 Pelagic and Open Ocean Accounting, TG-6.6 Deep Sea and ABNJ Accounting, TG-6.7 Fisheries Accounting: Integrating Stock Assessment, TG-6.11 Coastal Infrastructure Accounting, TG-3.16 Quality Assurance and Quality Control of Ocean Asset Accounts

Standards this circular implements

• Implements SEEA Central Framework: SEEA CF physical asset account (opening, additions, reductions, closing) — records ocean environmental assets in physical units and depletion when extraction exceeds sustainable yield, so price change cannot mask physical draw-down. — §3.1
• Implements SEEA Central Framework: SEEA CF aquatic resources (Table 5.22; natural vs cultivated; extraction as gross catch including discards) — treats wild stocks as non-produced assets and farmed stocks as produced, with illegal non-resident catch as uncompensated seizure. — §3.4.1
• Implements SEEA Central Framework: SEEA CF mineral and energy resource classes A–C — classifies offshore deposits by commercial viability so a shift into recoverability is a reclassification, not a discovery. — §3.4.2
• Implements SEEA Central Framework: SEEA CF water-resource asset boundary (freshwater and brackish inland waters; seawater stocks excluded as too large to be meaningful) — tracks coastal-aquifer saltwater intrusion but not open-ocean water as an asset. — §3.4.3
• Implements SEEA Ecosystem Accounting: SEEA EA Table 4.1 and paras 4.10–4.15 ecosystem extent account — compiles marine ecosystem extent with managed versus unmanaged expansion and reduction, and records conversions as reclassifications that net to zero across types. — §3.5.1
• Implements IUCN Global Ecosystem Typology: IUCN GET marine biomes (M1 Marine Shelf, M2 Pelagic, M3 Deep Sea Floors, MFT brackish tidal, MT shorelines) — columns of the extent account and seabed-based delineation on the shelf follow GET functional groups (e.g. M1.1 seagrass, M1.3 photic coral reefs). — §3.5.1
• Implements Ecosystem Condition Typology: SEEA EA Ecosystem Condition Typology (Table 5.1 classes A1–C1) — organises marine condition variables (SST, pH, live coral cover, connectivity) into the six ECT classes, with Tables 5.2–5.4 as the variable, indicator and index accounts. — §3.5.2
• Implements SNA 2025: SNA 2025 depletion of natural resources as a cost of production, analogous to consumption of fixed capital — values physical depletion at mid-period prices so net income is not overstated when harvest liquidates the stock. — §3.1
• Implements SNA 2025: SNA capital account for produced assets — records vessels, ports, aquaculture infrastructure and offshore energy installations as produced ocean wealth alongside environmental stocks, with a decommissioning memorandum. — §3.6

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1. Outcome

1After working through this Circular, you will be able to build asset accounts for ocean resources — the structured records that track what you have, what you gained, what you lost, and what remains. These capabilities connect directly to the budget processes described in TG-1.1 OA and National Budget Processes, where asset accounts provide the evidence base for allocating public resources to ocean conservation and sustainable use. They also underpin the depletion-adjusted income measures that indicate whether economic growth is coming at the expense of natural capital.

2Section 3.5.3 additionally specifies the choices that govern any net present value valuation of an ecosystem asset — perpetuity against finite horizon, and the functional form linking a change in condition to a change in service capacity — together with ecosystem degradation, damage cost, and the offset requirement and restoration equivalence unit that no-net-loss policies rest on. Those specifications are normative for the publication; the service-level valuation methods they discount are in TG-2.4 Environmental (including Ecosystem) Goods and Services Section 3.10.

3Ocean accounts answer to two disciplines at once. Accounting requires that numbers balance, whilst ecology describes fish populations whose dynamics resist neat categorisation. This Circular sets out how to satisfy both: maintaining the accounting identities that ensure internal consistency whilst respecting the ecological behaviour of marine systems.

2. Requirements

1Essential prerequisites:

• 2TG-0.1 General Introduction to Ocean Accounts: conceptual framework and domain structure
• 3TG-0.2 Overview of Relevant Statistical Standards: SNA/SEEA accounting architecture

4Helpful background:

• 5TG-0.7 Quality Assurance Principles: data quality and uncertainty management

6Framework Position

7This Circular addresses the stock side of the Ocean Accounts Framework — asset accounts that record the state of marine and coastal assets across all three stock domain groups. SNA produced assets (SG1) are subject to capital formation and depreciation through economic flows (E3). Environmental assets (SG3) supply ecosystem services to the economy (E9) and support intermediate ecological processes (E11). In the Ocean Accounts Framework (TG-0.1 Figure 0.1.2):

Edge	Direction	Description
E3	FG1↔SG1	Economic flows interacting with SNA assets (Applied)
E9	SG3→FG1	Environmental assets supplying ecosystem services to economy (Applied)
E11	FG3↔SG3	Environmental assets supporting intermediate ecosystem services (Applied)

8Scope. TG-3.1 owns the asset account tables — physical and monetary, individual environmental assets and ecosystem assets — their rows, columns and accounting identities, and the compilation procedure that populates them. It cross-refers for the sector-specific method that produces an entry: fisheries stock assessment and sustainable yield to TG-6.7, aquaculture to TG-3.9 and TG-6.8, offshore energy to TG-3.10 and TG-6.9, pelagic delineation to TG-6.5; for the measurement of the variables it records to Section 4, in particular TG-4.1 for extent and TG-4.8 and TG-4.9 for condition; and for the service-level valuation methods its NPV calculations discount to TG-2.4 Section 3.10.

3. Guidance Material

1Asset accounts record what you hold and what you have used. They give the stock of marine assets at the beginning and end of an accounting period and every change in between — growth, extraction, natural losses, discoveries, and measurement revisions¹. This structured bookkeeping allows the central question to be answered: whether ocean capital is being drawn down faster than it regenerates.

2Two complementary accounting frameworks apply to ocean assets. The SEEA Central Framework provides the methodology for accounting for individual environmental assets — fish stocks, seabed minerals, water resources — each tracked separately. SEEA Ecosystem Accounting extends this by treating ecosystems as integrated spatial units: a coral reef or seagrass meadow as a whole rather than only the fish or carbon within it. For ocean accounting, you will typically need both. The individual asset approach records how many tonnes of fish remain, whilst the ecosystem asset approach records whether the reef that supports those fish is expanding or contracting.

3This section examines the structure and accounting entries for physical and monetary asset accounts, before addressing the specific requirements for individual environmental assets (Section 3.4), ecosystem assets (Section 3.5), and produced assets in the ocean domain (Section 3.6). Section 3.2 provides a compilation procedure detailing the steps from data collection to account entry, whilst Section 3.7 presents a worked example with synthetic data demonstrating how to populate asset accounts for a hypothetical coastal area. The methodology presented here provides the basis for the thematic circulars on coral reef accounts (TG-6.1), mangrove and wetland accounts (TG-6.2), and seagrass accounts (TG-6.3).

3.1 Physical Asset Accounts

1Physical asset accounts are where you count what you have in tangible units — tonnes of fish, hectares of seagrass, cubic metres of sand. They record whether marine resources are growing or shrinking in physical terms, before any monetary valuation is applied². This matters because price changes can mask physical depletion: a fish stock can be worth more in dollar terms even as the population collapses, since scarcity drives up prices. Physical accounts separate the volume change from the price change.

Basic structure

1Every physical asset account follows the same logic³:

1. 2Opening stock — what you had at the start of the year
2. 3Additions to stock — everything that increased the stock during the year, including natural growth, discoveries, upward reappraisals, and reclassifications
3. 4Reductions in stock — everything that decreased the stock, including extractions, natural losses, catastrophic losses, downward reappraisals, and reclassifications
4. 5Closing stock — what you have at the end of the year

6The closing stock must equal the opening stock plus total additions minus total reductions. If it does not balance, something is missing from your records — unreported catch, an unobserved storm event, or a measurement error. This accounting identity is your quality control mechanism: it forces you to account for every change (Figure 3.1.1).

Figure 3.1.1 SEEA Central Framework environmental-asset accounts follow one stock-flow identity: opening stock plus additions minus reductions equals closing stock. Extraction/harvest is the only economy-side reduction; contrast the ecosystem extent account in Figure 3.1.2. Source: SEEA CF Table 5.2 (physical asset account structure by type of asset); SEEA CF paras 5.43-5.46; TG-3.1. Adapted from: SEEA CF Table 5.2, recast as a stock-flow identity diagram for TG-3.1.

Additions to stock

1Natural growth is the primary addition for renewable resources like fish stocks. It encompasses recruitment — new fish joining the stock — and biomass increase as existing individuals grow⁴. Natural growth is driven by biological processes that vary with environmental conditions, stock size, and species characteristics. For a fisheries manager, natural growth sets the sustainable harvest ceiling: the largest catch that can be taken without reducing the stock’s long-term productivity⁵. An accurate measure of natural growth therefore allows harvest limits to be set that keep the stock stable.

2Discoveries apply primarily to non-renewable resources. In ocean accounting, this means identification of new oil and gas deposits, seabed mineral resources such as polymetallic nodules and seafloor massive sulphides, and rare earth elements in marine sediments⁶. Discoveries can also apply to aquatic resources when previously unknown fish stocks are identified and assessed — though this is rare in well-surveyed waters.

3Upward reappraisals record cases where the estimate of stock size increased but the stock itself did not physically change⁷. The distinction separates a real change in the ocean from an improvement in measurement. For fish stocks, a reappraisal occurs when a stock assessment model is updated with new data and produces a revised biomass estimate. The SEEA CF acknowledges that for fish stocks, “it may not be possible to attribute the changes to natural causes or harvesting activity” and in such cases “only a regional or national aggregate resource value will be produced”⁸. Compilers should therefore document whether a stock change reflects biological dynamics or improved measurement, even where the boundary between the two is indistinct.

4Reclassifications record transfers between asset categories without any physical change⁹. A common ocean example: when a wild fish stock becomes subject to aquaculture operations, it transfers from natural aquatic resources to cultivated aquatic resources. The SEEA CF emphasises that “in cases where stocking with cultured seeds is regularly conducted, as commonly observed in freshwater resources, it is important to include the amount of released seeds as a reclassification from cultivated aquatic resources”¹⁰. Misclassification matters for policy: it can make wild stocks appear to be growing when they are in fact being supplemented by hatchery production.

Reductions in stock

1Extraction (or harvest, for biological resources) is the removal of natural resources for use in economic activity¹¹. For fish stocks, extraction corresponds to gross catch — the total live weight of fish caught, including discarded catch but excluding pre-catch losses¹². Countries use gross catch rather than landings because discards still remove fish from the ocean, even though they never reach port. The FAO defines the stages of catch as¹³:

• 2Gross removal: total live weight of fish caught or killed during fishing operations
• 3Gross catch: gross removal less pre-catch losses
• 4Retained catch: gross catch less discarded catch
• 5Landings: net weight of quantities landed at port
• 6Nominal catch: live weight equivalent of landings

7Normal losses (natural mortality for biological resources) are decreases from natural processes — death from age, predation, disease, and accidents¹⁴. For fish stocks, natural mortality is a key parameter in stock assessment models. It must be estimated alongside fishing mortality to understand population dynamics, because a stock with high natural mortality can tolerate less fishing pressure than one where most individuals die of old age.

8Catastrophic losses are “exceptional and significant reductions in the natural resource”¹⁵ due to discrete events — storms, disease outbreaks, toxic algal blooms, mass coral bleaching, or oil spills. The distinction from normal losses matters for two reasons. First, if catastrophic losses are increasing in frequency, that is a warning sign that environmental conditions are deteriorating. Second, catastrophic losses are unpredictable and fall outside the scope of normal management, so they need to be tracked separately to avoid distorting assessments of whether routine management is working.

9Downward reappraisals and reclassifications mirror their counterparts in additions, recording accounting adjustments from improved information or transfers between categories.

Depletion

1Depletion is the central sustainability signal in the asset account. It records whether a renewable resource is being harvested faster than it can regenerate, and by how much. For a policy-maker, depletion answers whether current consumption is drawing down the productive base itself.

2For renewable resources, depletion occurs when “the extraction of the natural resource is occurring at a level greater than that of regeneration”¹⁶. The formula is straightforward:

Depletion = max(0, Extraction - Sustainable yield)

3When extraction stays at or below sustainable yield, depletion is zero — the stock can absorb the harvest. When extraction exceeds sustainable yield, every tonne above that threshold is depletion — a reduction in the stock’s future productive capacity¹⁷. For non-renewable resources such as mineral deposits, there is no regeneration, so depletion equals extraction: every barrel of offshore oil extracted is permanently removed from the stock.

4Depletion links the physical and monetary accounts. In the 2025 SNA, depletion of natural resources is treated as a cost of production analogous to depreciation of produced assets, reducing net measures of income and product¹⁸. A country reporting high GDP from fisheries alongside high depletion is therefore overstating its true income, since part of what appears as earnings is the liquidation of natural capital. The SEEA CF notes that “since the drivers for changes in populations of aquatic resources can only be modelled, it may be difficult to obtain precise and consistent measures of sustainable yield over time”¹⁹. For methodological guidance on estimating sustainable yield and depletion for fisheries, see TG-6.7 Fisheries Accounting: Integrating Stock Assessment.

3.2 Compilation Procedure for Asset Accounts

1This section walks through the step-by-step procedure for compiling ocean asset accounts, beginning with the assembly of raw data and ending with balanced accounts that integrate with the broader national accounting system. Following these steps ensures that your accounts are internally consistent and comparable across asset types.

Step 1: Data collection and source identification

1Start by identifying the data sources you need for each asset type. Different marine assets draw on distinct data sources:

2For individual environmental assets (fish stocks, seabed minerals):

• 3Stock assessment reports from fisheries management agencies, providing estimates of spawning stock biomass, recruitment, natural mortality, and fishing mortality (see TG-6.7 Fisheries Accounting: Integrating Stock Assessment)
• 4Geological surveys and commercial exploration reports for mineral and energy resources, including estimates of proven reserves and probabilistic resource classifications (see TG-3.10 Offshore Energy Accounts)
• 5Catch statistics from fisheries agencies and international databases (FAO FishStatJ), recording landings, gross catch, and discards by species and fishing zone

6For ecosystem assets (coral reefs, seagrass meadows, mangroves):

• 7Remote sensing imagery (Sentinel-2, Landsat, MODIS) processed to classify ecosystem extent and detect changes over time (see TG-4.1 Remote Sensing and Geospatial Data)
• 8Field survey data from ecological monitoring programmes, providing measurements of ecosystem condition variables such as coral cover, seagrass shoot density, mangrove canopy height, and water quality parameters (see TG-4.2 Survey Methods for Ocean Economic Activity)
• 9National spatial databases delineating protected areas, coastal zone boundaries, and ecosystem type classifications consistent with the IUCN Global Ecosystem Typology

10Assess data quality following TG-0.7 Quality Assurance Principles. Pay particular attention to three things: temporal consistency (are opening and closing stocks measured on a comparable basis?), spatial coverage (do the data cover the full accounting area?), and measurement uncertainty (what are the confidence intervals, and are they documented?).

Step 2: Classification and mapping to asset categories

1Next, map your source data to the asset classification system used in the accounts. Getting this right matters because it determines how your numbers aggregate and compare with other countries. The SEEA CF classifies environmental assets into major categories including aquatic resources, mineral and energy resources, water resources, timber resources, land, and soil resources²⁰. For ocean accounting, the relevant categories are:

• 2Natural aquatic resources (wild fish, shellfish, and other uncultivated aquatic organisms)
• 3Cultivated aquatic resources (farmed fish, shellfish, and seaweed)
• 4Mineral and energy resources (offshore oil and gas, seabed minerals, marine aggregates)
• 5Water resources (coastal aquifers subject to saltwater intrusion, and seawater abstraction is recorded as an abiotic flow rather than an asset stock)

6SEEA EA ecosystem assets are classified using the IUCN Global Ecosystem Typology. Table 3.2.1 below summarises the marine ecosystem types.

IUCN GET code	Ecosystem types covered
M1 Marine Shelf	Seagrass meadows, kelp forests, coral reefs, shellfish beds, subtidal rocky reefs.
M2 Pelagic Ocean Waters	Epipelagic, mesopelagic, bathypelagic zones.
M3 Deep Sea Floors	Abyssal plains, submarine canyons, hydrothermal vents.
MFT Brackish Tidal Systems	Mangroves, saltmarshes, coastal brackish lagoons.
MT Shorelines	Rocky shores, sandy beaches.

7If your country uses a national ecosystem type classification that differs from the IUCN GET, document the correspondence between the two. This ensures that your ecosystem extent can be aggregated to standard categories for international comparison.

Step 3: Measurement and quantification

1With data sources identified and classifications established, you can quantify opening stocks, additions, reductions, and closing stocks in physical units appropriate to each asset type.

2For fish stocks, stock assessment models provide estimates of total biomass (or spawning stock biomass) at the beginning of the accounting period (opening stock). Natural growth is estimated from recruitment models and individual growth rates. Extraction is measured as gross catch from fisheries statistics. Natural mortality is estimated from stock assessment parameters. The accounting identity (opening stock + growth - mortality - catch = closing stock) serves as your reconciliation tool. Where stock assessment provides direct estimates of both opening and closing stock, the identity becomes a consistency check, and discrepancies may indicate data errors or unobserved changes requiring reappraisal entries.

3For ecosystem extent, remote sensing analysis provides the primary measurement of opening and closing extent, typically expressed in hectares or square kilometres. Change detection algorithms identify areas where ecosystem type has changed (conversions), distinguishing managed changes (restoration, conversion to aquaculture) from natural changes (storm damage, succession). Ground-truthing surveys validate remotely sensed classifications and provide confidence ratings. The SEEA EA recommends recording extent changes in a structured account showing managed expansion, natural expansion, managed reduction, and natural reduction separately²¹.

4For ecosystem condition, the measurement process involves selecting condition variables for each ecosystem type following the SEEA EA Ecosystem Condition Typology (ECT), measuring variable values from field surveys or remote sensing, and normalising these values into indicators relative to reference conditions. Condition accounts record the raw variable values rather than derived indicators, whilst the indicator derivation is addressed in TG-2.1 Aggregate Biophysical Indicators of Environmental State.

Step 4: Account entry and balancing

1Once physical quantities have been measured, enter them into the asset account structure. The account must balance: closing stock = opening stock + total additions - total reductions. Any imbalance signals an error — either a data fault or a missing entry (unreported extraction, unobserved natural changes, or a needed reappraisal adjustment).

2For marine assets, three issues require particular attention:

• 3Spatial boundaries: Ensure that opening and closing stocks cover the same geographic area. If jurisdictional boundaries or accounting area definitions changed during the period, record those changes as reclassifications rather than real changes. Otherwise, you will attribute administrative decisions to ecological processes.
• 4Unit consistency: Keep all entries for a given asset in the same measurement unit. For fish stocks, this typically requires converting landings (wet weight) to live weight equivalent, and converting different life stages to a common biomass measure.
• 5Temporal alignment: Ensure all entries refer to the same accounting period. Where stock assessments use different time periods or reference dates than the calendar year accounting period, adjustments may be needed.

Step 5: Monetary valuation (for monetary accounts)

1For monetary asset accounts, you translate physical stock quantities into monetary values. This is the step where accounting and ecology are most in tension, since pricing a fish stock or a mangrove forest requires assumptions about a future that ecology renders uncertain.

2For fish stocks and other renewable natural resources, the net present value (NPV) of expected future resource rents provides the standard valuation approach²². The NPV calculation requires:

1. 3Resource rent estimation: Calculate the annual resource rent as the difference between the value of harvest and all costs (including labour, capital, intermediate inputs, and normal return on produced assets). This isolates the economic surplus that the natural resource itself contributes.
2. 4Discount rate selection: Determine an appropriate discount rate reflecting the time value of money and asset-specific risk factors (see TG-1.9 Safe Usage of Monetary Valuation for detailed guidance). Higher discount rates reduce asset values, so this choice matters for policy.
3. 5Asset life assumption: Estimate the expected duration of the resource rent stream. For sustainably managed renewable resources, this may be assumed to be perpetual.

6For ecosystem assets, the monetary value is estimated as the NPV of expected future ecosystem service flows. This requires:

1. 7Service quantification: Measure the physical supply of ecosystem services from the asset (see TG-3.2 Flows from Environment to Economy)
2. 8Service valuation: Apply appropriate valuation methods to estimate unit prices for each ecosystem service
3. 9NPV calculation: Discount the stream of future service values to present value

10Changes in monetary value are decomposed into three components:

• 11Changes due to physical volume changes (additions and reductions in stock)
• 12Changes due to updated expectations about future rents or service flows (reappraisals)
• 13Changes due to price movements (revaluations)

14This decomposition matters because it prevents price effects from masking physical depletion. A fish stock can be worth more in dollar terms this year than last, even as the population declines, provided prices rose enough. Separating the two effects keeps the monetary account aligned with the underlying physical change.

Step 6: Integration with balance sheets and other accounts

1The final step is integrating asset accounts with national balance sheets and with other ocean accounts. The balance sheet presents the stock of all assets (produced assets, non-produced natural assets, ecosystem assets, financial assets) and liabilities at a single point in time, enabling calculation of net worth²³. Changes in net worth during the accounting period are explained by saving, capital transfers, and holding gains/losses recorded in the revaluation account.

2For ocean accounting, integration ensures that:

• 3Depletion entries in asset accounts correspond to depletion costs in production accounts and adjustments to net domestic product
• 4Extraction entries in asset accounts correspond to natural resource inputs in physical supply-use tables (TG-3.2 Flows from Environment to Economy)
• 5Ecosystem service flows are consistent with the capacity to supply services implied by ecosystem extent and condition (as illustrated in the worked example below)
• 6Investment in ocean infrastructure (such as aquaculture facilities and offshore energy) is recorded as gross fixed capital formation in produced assets, enabling joint analysis of natural and produced capital stocks

7Cross-stack connections upward to policy circulars include:

• 8TG-1.1 National Ocean Budgets uses asset values and depletion estimates to inform natural capital budgeting
• 9TG-2.1 Aggregate Biophysical Indicators of Environmental State derives extent change indicators and condition indices from asset accounts
• 10TG-2.2 Productivity Indicators uses fish stock biomass and sustainable yield estimates to calculate indicators of resource productivity

11Cross-stack connections downward to data circulars include:

• 12TG-4.1 Remote Sensing and Geospatial Data provides methods for extent mapping that populate ecosystem extent accounts
• 13TG-4.2 Survey Methods for Ocean Economic Activity provides protocols for condition variable measurement
• 14TG-4.3 Administrative Data Sources provides the spatial framework for delineating ecosystem assets and aggregating data

15Asset accounts therefore operate as an integrated component of the broader ocean accounting system rather than a standalone exercise.

3.3 Monetary Asset Accounts

1Monetary asset accounts translate the physical stocks and changes described in Section 3.1 into economic values. This translation enables three things that physical accounts alone cannot do: aggregate across different asset types (you cannot add tonnes of fish to hectares of seagrass, but you can add their monetary values), compare environmental assets with produced and financial assets on common terms, and calculate depletion-adjusted income measures that reveal whether economic growth is genuine or is partly the liquidation of natural capital²⁴. For detailed guidance on valuation methods applicable to ocean assets, see TG-1.9 Safe Usage of Monetary Valuation.

Structure of monetary asset accounts

1The structure parallels physical accounts, with one important addition — a revaluation entry²⁵:

1. 2Opening stock value — the monetary value of the asset at the beginning of the accounting period
2. 3Additions to stock value — value of growth, discoveries, and upward reappraisals
3. 4Reductions in stock value — value of extractions, normal losses, catastrophic losses, and downward reappraisals
4. 5Revaluations — changes in value due to price changes, distinct from physical changes
5. 6Closing stock value — the monetary value at the end of the accounting period

7The revaluation entry captures holding gains and losses — changes in asset value attributable to changes in prices rather than physical quantities²⁶. This separation is essential: without it, a rise in asset value cannot be attributed to an improvement in the ecosystem rather than a shift in market prices.

Valuation approaches

1Environmental assets are typically not traded in markets, so no observable price exists. The SEEA CF describes several approaches to address this²⁷:

2Net present value (NPV) is the preferred approach for valuing natural resources. You estimate the stream of expected future resource rents — the economic surplus accruing to the resource owner after all costs and normal returns are deducted — and discount this stream to the present²⁸. For natural resources:

Value = Resource rent x Discount factor

3where the discount factor adjusts for the time value of money and the expected duration of the income stream. The SEEA CF describes the discount factor (Omega) as linking “future resource rents to the present value of the asset”²⁹. Key considerations for discount rate selection include the real rate of interest, expected asset life, and country-specific factors³⁰.

4Discount rate selection can affect asset valuations substantially, particularly for long-lived assets such as fish stocks under perpetual management regimes. A lower discount rate makes long-term sustainability more economically visible, whilst a higher rate assigns less weight to the distant future. The SEEA CF provides extensive guidance on discount rate methodology in Annex A5.2, covering asset life assumptions, risk adjustments, and country-specific factors³¹. For detailed guidance on discount rate selection and its implications for marine asset valuation, see TG-1.9 Safe Usage of Monetary Valuation.

5Market prices may be used where environmental assets or rights to extract them are traded. For aquatic resources, long-term fishing licences and individual transferable quotas (ITQs) may provide market-based valuations³². Markets for environmental assets are, however, often thin or non-existent, and the approach therefore has limited applicability. The SEEA CF notes that “in many cases, where the government hands the access rights to fishermen, trading in these access rights is prohibited and there is therefore no directly observable market valuation”³³.

Deriving resource rent for a wild-capture fishery

6Resource rent per tonne. Resource rent is the surplus remaining after deducting all costs of fishing from the gross value of catch. It is estimated as:

7$$\text{Resource rent per tonne} = \frac{\text{Gross value of landings} - \text{(Operating costs + Depreciation + Normal return to capital)}}{\text{Total catch (tonnes)}}$$

8Normal return to capital is estimated as the risk-free rate applied to the replacement value of the fishing fleet (SEEA CF para 5.114).

9If gross value of landings is USD 28.8 million (24,000 tonnes at USD 1,200 per tonne average price), and total fishing costs are USD 18 million (including labour, fuel, vessel depreciation, normal return to capital), resource rent is USD 10.8 million. Resource rent per tonne is USD 10.8 million / 24,000 tonnes = USD 450 per tonne.

10The rent estimated here is the total rent generated by the fishery, only part of which accrues to government as access payments or royalties. Where those receipts are also compiled in the governance revenue tables (TG-3.7 Table 3.7.10b), the two must be reconciled rather than added; presenting government rent receipts alongside a depletion-adjusted net income measure without reconciliation double counts the same flow. The budget use of the resulting figure is in TG-1.1 Section 3.4.

11Restoration cost approaches estimate the cost of restoring an ecosystem asset to a reference condition. This approach is described in SEEA EA as a complement to NPV-based valuation, particularly for ecosystem degradation³⁴. It answers a different question: the cost of replacing what has been lost, which is distinct from the worth of the ecosystem itself. See TG-1.9 Safe Usage of Monetary Valuation for detailed comparison of valuation approaches.

Structural template — monetary asset account

1Table 1b is the blank counterpart to the physical templates in Section 3.4, for individual environmental assets in monetary terms. The revaluation row is what distinguishes it from the physical account and is the row most often omitted; without it a price movement is indistinguishable from a change in the resource.

2Table 1b: Monetary asset account — structural template (after SEEA CF Table 5.17)

Accounting entry	Asset class 1	Asset class 2	…	Total
Opening stock value	[value]	[value]	…	[Σ]
Additions to stock value
— Growth in stock	[value]	[value]	…	[Σ]
— Discoveries	[value]	[value]	…	[Σ]
— Upward reappraisals	[value]	[value]	…	[Σ]
— Reclassifications in	[value]	[value]	…	[Σ]
Total additions	[Σ]	[Σ]	…	[ΣΣ]
Reductions in stock value
— Extraction	[value]	[value]	…	[Σ]
— Normal losses	[value]	[value]	…	[Σ]
— Catastrophic losses	[value]	[value]	…	[Σ]
— Downward reappraisals	[value]	[value]	…	[Σ]
— Reclassifications out	[value]	[value]	…	[Σ]
Total reductions	[Σ]	[Σ]	…	[ΣΣ]
Revaluation (price change only)	[+/-]	[+/-]	…	[+/-]
Net change in value	[+/-]	[+/-]	…	[+/-]
Closing stock value	[value]	[value]	…	[Σ]
Memorandum: depletion at constant prices	[value]	[value]	…	[Σ]

3Table 1b: Structural template of a monetary asset account. The identity is Closing = Opening + total additions — total reductions + revaluation. The memorandum line carries depletion valued at the average of opening and closing prices, which is the figure adjusted income measures deduct; it is a memorandum rather than an account entry because its value is already inside the reduction rows.

Valuation of depletion

1The monetary value of depletion is calculated by multiplying physical depletion by the appropriate asset price³⁵. Following the conventions in the SNA and SEEA CF, depletion should be valued at the average of opening and closing prices:

Monetary depletion = Physical depletion x (P_opening + P_closing) / 2

2This mid-period valuation “is consistent with the rules in the SNA for the valuation of consumption of fixed capital”³⁶: depletion of a fish stock is treated on the same footing as depreciation of a factory. Both represent the using-up of productive capacity, and both should be deducted from income.

3.4 Individual Environmental Assets

1Individual environmental assets are “those environmental assets that may provide resources for use in economic activity”³⁷ — the specific natural resources that can be named and counted, such as fish stocks, oil deposits, and sand reserves. For ocean accounting, the principal categories include aquatic resources (Section 3.4.1), mineral and energy resources (Section 3.4.2), and water resources (Section 3.4.3).

3.4.1 Aquatic resources

1Aquatic resources include fish, crustaceans, molluscs, shellfish and other aquatic organisms such as sponges and seaweed, as well as aquatic mammals such as whales³⁸. These organisms are subject to harvest for commercial, subsistence, and recreational purposes. The SEEA CF distinguishes between:

• 2Natural aquatic resources — wild fish and other aquatic organisms not under direct cultivation
• 3Cultivated aquatic resources — organisms raised in aquaculture facilities, including fish, shellfish, seaweed, and other species

4This distinction determines how the assets are classified in the accounts: natural aquatic resources are non-produced assets (nature made them), whilst cultivated aquatic resources are produced assets (fixed assets for breeding stocks, and inventories for stocks held for sale)³⁹. The distinction matters for policy because the management interventions differ: a wild fishery is managed by controlling extraction, whereas aquaculture is managed by controlling production inputs. Detailed guidance on aquaculture accounting is provided in TG-3.9 Aquaculture Accounts.

5What the asset account requires of a stock assessment. The account needs four things, whatever method produced them: an opening and a closing estimate of the total stock on a consistent basis, natural growth and natural mortality as separate entries, extraction measured as gross catch, and a documented statement of which of these were estimated independently and which were derived. Where the assessment supplies both endpoints directly, the accounting identity becomes a consistency check rather than a derivation, and any residual is entered as a reappraisal rather than absorbed silently.

6Stock assessments commonly distinguish total stock, spawning stock biomass and exploitable stock⁴⁰. The asset account takes the total stock; the other two are management reference points, and substituting one for another between periods breaks the time series without any change in the ocean. Where only a relative index such as catch per unit effort is available, the account cannot be closed on that index alone⁴¹ and the limitation must be recorded in metadata; the index still carries a signal, since a declining CPUE trend “may be a signal that the rate of harvest is exceeding the renewal rate of the fish stock”⁴², ⁴³.

7The choice of assessment method — virtual population analysis, surplus production, tag-recapture, acoustic or trawl survey — and the treatment of CPUE standardisation and technological creep are matters for TG-6.7 Fisheries Accounting: Integrating Stock Assessment, which also gives the tier mapping from assessment type to the account entries each can support.

8Classification of catch types. The SEEA CF recommends using gross catch as the measure of extraction from natural aquatic resources⁴⁴. Gross catch is defined as the total live weight of fish caught, comprising:

• 9Retained catch — fish brought to shore as landings
• 10Discarded catch — fish returned to the water, typically dead or dying

11Using gross catch rather than landings matters because discards still remove fish from the ocean. In some fisheries, discards constitute a substantial fraction of total catch, so ignoring them would understate the impact on fish stocks. The SEEA CF notes that “the measurement of discarded catch is an important contributory factor to a full understanding of the linkages between economic activity and the impact on aquatic resources”⁴⁵. Omitting discards would understate that impact.

12Where direct measurement through at-sea observer programmes is unavailable, discard rates may be estimated using species-specific discard ratios from comparable fisheries, gear-type-specific discard rates from regional studies, or logbook-based self-reporting validated against observer data. For guidance on survey methods applicable to discard estimation, see TG-4.2 Survey Methods for Ocean Economic Activity.

13Physical asset account for aquatic resources. Table 1 presents the structure of a physical asset account for aquatic resources, distinguishing between cultivated and natural resources.

Accounting entry	Cultivated aquatic resources	Natural aquatic resources	Total
Opening stock	12,000	180,000	192,000
Additions to stock
— Growth in stock	3,500	28,000	31,500
— Upward reappraisals	—	5,000	5,000
— Reclassifications	200	—	200
Total additions	3,700	33,000	36,700
Reductions in stock
— Gross catch/harvest	3,200	24,000	27,200
— Normal losses	400	15,000	15,400
— Catastrophic losses	—	2,000	2,000
— Uncompensated seizure	—	800	800
— Downward reappraisals	—	—	—
— Reclassifications	—	200	200
Total reductions	3,600	42,000	45,600
Closing stock	12,100	171,000	183,100

14Table 1: Structure of physical asset account for aquatic resources, with illustrative synthetic values in tonnes (adapted from SEEA CF Table 5.22)⁴⁶

15The table includes “uncompensated seizure” to record illegal fishing by non-residents, following the SEEA CF treatment⁴⁷. In this example the natural aquatic stock is declining (closing stock 171,000 < opening stock 180,000), driven by extraction and losses exceeding growth. Cultivated resources record modest growth, the pattern expected where aquaculture is expanding whilst wild fisheries are under pressure.

Combined physical asset account template

1Table 1a provides a broader template that compilers can use to record all major categories of marine natural resources within a single accounting structure. It distinguishes natural aquatic resources (fish and other wild aquatic organisms), ecosystem assets (spatially defined marine ecosystem types measured by extent), and mineral and energy resources (seabed deposits). Each asset class follows different dynamics: fish grow and reproduce, ecosystems expand and contract, and minerals only deplete. The template captures these differences.

Entry	Natural Aquatic Resources	Ecosystem Assets	Mineral Resources
	(tonnes)	(hectares)	(tonnes)
Opening stock	180,000	72,000	5,200,000
Additions
Natural growth	28,000	N/A	N/A
Natural expansion	N/A	120	N/A
Managed expansion	N/A	350	N/A
Discoveries	5,000	N/A	200,000
Upward reappraisals	5,000	80	100,000
Reclassifications in	—	50	—
Total additions	38,000	600	300,000
Reductions
Extraction/Harvest	24,000	N/A	180,000
Natural reduction	15,000	400	N/A
Catastrophic losses	2,000	600	N/A
Managed reduction	N/A	200	N/A
Downward reappraisals	—	—	—
Reclassifications out	200	50	—
Total reductions	41,200	1,250	180,000
Closing stock	176,800	71,350	5,320,000
Derived entries
Sustainable yield	22,000	N/A	N/A
Depletion	2,000	N/A	180,000

2Table 1a: Combined physical asset account template for marine natural resources with illustrative synthetic values (integrating SEEA CF Table 5.4, SEEA EA Table 4.1, and SEEA CF Table 5.22)⁴⁸

3Note: Illustrative values are synthetic. In practice, discoveries of entirely new fish stocks are rare, and stock revisions are typically recorded as reappraisals rather than discoveries.

4The “Derived entries” section highlights depletion as a key sustainability indicator. For renewable resources, depletion occurs only when extraction exceeds sustainable yield (24,000 - 22,000 = 2,000 tonnes in this example). For non-renewable resources, all extraction constitutes depletion — there is no regeneration to offset it. For natural aquatic resources, stock assessment models provide the primary input (see TG-6.7 Fisheries Accounting: Integrating Stock Assessment). For ecosystem assets, remote sensing and spatial survey provide extent mapping (see TG-4.1 Remote Sensing and Geospatial Data). For mineral resources, geological surveys and commercial assessments provide stock estimates.

5Sustainable yield and depletion. For fisheries management, sustainable yield represents the maximum catch that can be taken without reducing the stock’s long-term productivity. When gross catch exceeds sustainable yield, depletion occurs and should be recorded. Conversely, when catch is below sustainable yield, the excess regeneration contributes to stock growth rather than depletion⁴⁹. The practical test: compare your catch to your sustainable yield estimate each year. If the gap is widening, management intervention is needed. The SEEA CF recommends that “estimates from biological models be compared with indicators of stock size, such as CPUE, and also that estimation be carried out on an ongoing basis so that the dynamics of the various populations (natural growth, natural losses, etc.) can be better understood”⁵⁰.

6Capture fishing by non-residents. Under the SNA and SEEA CF, production is attributed to the country of residence of the harvesting operation, not the location of the resource⁵¹. For asset accounts, in contrast, the focus is on changes in the national aquatic resource. The SEEA CF states that “the total catch from the country’s aquatic resources—including any resources on the high seas over which ownership rights exist, regardless of the residency of the harvesting operation”⁵² must be recorded as reductions in the national stock. Foreign-flagged vessels fishing in your waters therefore reduce your asset account even though their production appears in another country’s GDP.

7Illegal fishing. The SEEA CF addresses illegal fishing explicitly: “If residents harvest aquatic resources beyond the scope of their licence, they are harvesting illegally. Nonetheless, following the principles of the SNA, this harvest should still be recorded as production with an income accruing to the fisherman”⁵³. For illegal fishing by non-residents, the physical removals should be recorded as “uncompensated seizures”⁵⁴. Excluding illegal catch from the asset account would overstate the closing stock, since the fish are removed regardless of whether they were caught legally.

8Monetary valuation of aquatic resources. The SEEA CF describes two main options for valuing natural aquatic resources⁵⁵:

1. 9Using the value of long-term fishing licences and quotas where realistic market values are available
2. 10Applying the NPV of expected resource rents

11Where individual transferable quotas (ITQs) are used and traded, the total market value of all quotas may approximate the value of the aquatic resource⁵⁶. Quota markets are, however, often imperfect, and quota values may not reflect the full value of the underlying resource. The SEEA CF notes that “because of market imperfections (barriers to entry in the form of specialized fixed assets, knowledge of fishing grounds, etc.), a lack of liquidity in the markets, and uncertainties in the statistical assumptions required for net present value calculations”, different approaches “are unlikely to give the same result in practice”⁵⁷. Compilers should therefore document which method they used and why, rather than assuming that any single approach yields the “right” answer.

3.4.2 Mineral and energy resources

1Mineral and energy resources in the ocean domain include offshore oil and gas deposits, seabed minerals (including polymetallic nodules, cobalt-rich ferromanganese crusts, and seafloor massive sulphides), sand and gravel, and other extractable minerals⁵⁸. Unlike fish stocks, these resources do not regenerate on human timescales — every unit extracted is permanent depletion.

2Classification of resources. The SEEA CF classifies mineral resources based on commercial viability, which determines how they enter the accounts⁵⁹. Table 3.4.2 below summarises the three classes.

Class	Description
Class A — Commercially recoverable	Economically viable to extract under current conditions.
Class B — Potentially commercially recoverable	May become viable with technological advances or price changes.
Class C — Non-commercial and other known deposits	Not currently viable.

3This classification matters because movements between classes (a deposit becoming commercially viable as technology improves) are recorded as reclassifications, not discoveries. Understanding this distinction prevents double-counting.

4Physical asset accounts for minerals. Asset accounts for mineral and energy resources record the opening stock, discoveries, extractions, reappraisals, and closing stock⁶⁰. Because these are non-renewable resources with no natural growth, depletion equals extraction. Measurement units vary by resource type (barrels for oil, cubic metres for gas, tonnes for minerals).

5For deep-sea minerals in areas beyond national jurisdiction (ABNJ), the regulatory framework under the International Seabed Authority (ISA) continues to develop. The BBNJ Agreement, which entered into force on 17 January 2026, establishes new governance arrangements for biodiversity in ABNJ that may have implications for asset accounting boundaries. Compilers should note that mineral resources in ABNJ are designated as the “common heritage of mankind” under UNCLOS and are administered by the ISA. Asset accounts for ABNJ minerals should reflect the access and benefit-sharing provisions of the applicable regulatory framework. For further guidance on deep-sea and ABNJ accounting, see TG-6.6 Deep-Sea and ABNJ.

6Monetary valuation. The NPV approach is typically applied, using the expected resource rent — the surplus after all extraction costs and normal returns to produced assets have been deducted⁶¹. Resource rent can be estimated as a residual from operating surplus or from royalty payments where these approximate market rent. For detailed guidance on resource rent estimation, see TG-1.9 Safe Usage of Monetary Valuation.

3.4.3 Water resources

1The SEEA CF defines water resources as “freshwater and brackish water in inland water bodies, including groundwater and soil water”⁶². Seawater is excluded from the asset boundary because “the stocks are too large to be meaningful for analytical purposes”⁶³. The open ocean is therefore not tracked as an asset, whilst the interfaces between freshwater and marine systems remain important.

2For coastal areas, groundwater in coastal aquifers may be subject to saltwater intrusion, and estuarine systems represent transitional zones where freshwater and marine systems interact. Asset accounts for water resources should capture these coastal dynamics where relevant. The SEEA CF notes that “water is in continuous movement through the processes of precipitation, evaporation, run-off, infiltration and flows to the sea”⁶⁴, and this hydrological connectivity must be considered in coastal accounting. A coastal aquifer losing freshwater to saltwater intrusion is an asset account reduction that directly affects the communities and agriculture that depend on that aquifer.

3.5 Ecosystem Assets

1SEEA Ecosystem Accounting extends asset accounting to treat ecosystems as integrated spatial units: the whole living system, of which the fish or minerals within it are components⁶⁵. An ecosystem asset is defined as “contiguous spaces covered by a specific ecosystem type characterized by a distinct set of biotic and abiotic components and their interactions”⁶⁶. For ocean accounting, ecosystem assets include coral reefs, mangrove forests, seagrass meadows, kelp forests, coastal wetlands, and the various pelagic and deep-sea ecosystem types.

2This ecosystem-level view captures something that individual asset accounts omit: the interdependence of marine systems. A coral reef supplies coastal protection, supports tourism, sequesters carbon, and maintains biodiversity, alongside its fish. Tracking the reef as a whole records whether these combined services are being sustained or degraded. The relationship between ecosystem assets and the individual environmental assets described in Section 3.4 is addressed in TG-0.2 Overview of Relevant Statistical Standards.

3.5.1 Ecosystem extent accounts

1Ecosystem extent is the size of an ecosystem asset, measured in units of area (or, for some marine ecosystems, length or volume)⁶⁷. Extent accounts answer a basic question: how much of each ecosystem type do you have, and is it growing or shrinking? The extent account uses the same opening-plus-additions-minus-reductions identity as the Central Framework natural-resource account (Figure 3.1.1), but adds an attribution of every addition and reduction by cause — managed change from direct human activity versus unmanaged change from natural processes (Figure 3.1.2).

Figure 3.1.2 SEEA Ecosystem Accounting keeps the Central Framework stock-flow identity and adds managed versus unmanaged cause attribution for each change. Colour marks the cause split on shared CF structure; illustrated for extent (area conversions). Same attribution applies in carbon and monetary ecosystem asset accounts. Source: SEEA EA 2024 para 13.63 (shared CF asset-account form); paras 4.14-4.27 and Table 4.1 (extent account, managed/unmanaged); paras 10.2.2-10.2.3 (enhancement/degradation); TG-3.1. Adapted from: SEEA EA 2024 Table 4.1, recast to highlight the concepts SEEA EA adds to the shared Central Framework asset-account identity for TG-3.1.

2Structure of extent accounts. The structure follows the standard asset account format⁶⁸:

Accounting entry	Ecosystem Type A	Ecosystem Type B	…	Total
Opening extent	15,000	8,500	…	72,000
Additions to extent
— Managed expansion	250	100	…	350
— Natural expansion	80	40	…	120
Total additions	330	140	…	470
Reductions in extent
— Managed reduction	150	50	…	200
— Natural reduction	300	100	…	400
Total reductions	450	150	…	600
Net change in extent	-120	-10	…	-130
Closing extent	14,880	8,490	…	71,870

3Table 2: Structure of ecosystem extent account with illustrative synthetic values in hectares (adapted from SEEA EA Table 4.1)⁶⁹

4Structural template — opening/closing extent account (SEEA EA Table 4.1). Table 2a presents the same account as a blank structural template, ready to be populated. The row structure follows the standard SEEA asset-account logic (opening stock, additions, reductions, closing stock), whilst the columns are the ecosystem types selected for the accounting area⁷⁰. Compilers should populate one column per ecosystem type in the EAA, using a consistent unit of area (e.g., hectares or square kilometres) throughout. The accounting identity is: Opening extent + Total additions — Total reductions = Closing extent, and the sum of closing extents across all ecosystem types should equal the total area of the EAA⁷¹.

5Table 2a: Opening/closing extent account — structural template (after SEEA EA Table 4.1)

Accounting entry	Ecosystem type 1	Ecosystem type 2	…	Ecosystem type n	Total
Opening extent (start of period)	[area]	[area]	…	[area]	[Σ area]
Additions to extent
— Managed expansion	[area]	[area]	…	[area]	[Σ area]
— Unmanaged expansion	[area]	[area]	…	[area]	[Σ area]
Total additions	[Σ]	[Σ]	…	[Σ]	[ΣΣ]
Reductions in extent
— Managed reduction	[area]	[area]	…	[area]	[Σ area]
— Unmanaged reduction	[area]	[area]	…	[area]	[Σ area]
Total reductions	[Σ]	[Σ]	…	[Σ]	[ΣΣ]
Net change in extent	[+/-]	[+/-]	…	[+/-]	[+/-]
Closing extent (end of period)	[area]	[area]	…	[area]	[Σ area = total EAA]

6Table 2a: Structural template of an ecosystem extent account; cells are left blank to be populated by the compiler with no synthetic values. Row labels follow SEEA EA paras 4.10 and 4.15; column structure follows SEEA EA paras 4.11—4.13.⁷⁰, ⁷¹

7The accounting entries are defined by the SEEA EA as follows (para 4.15)⁷¹:

• 8Opening extent and closing extent — the total area of ecosystem assets for a given ecosystem type at the beginning and end of the accounting period (generally one year).
• 9Additions to extent — increases in the area of an ecosystem type, separated where possible into:
  • 10Managed expansions — increases due to direct human activity (e.g., land reclamation, reforestation), including the unplanned effects of such activity.
  • 11Unmanaged expansions — increases resulting from natural processes (e.g., seeding, sprouting, succession), which may be influenced by human activity (e.g., climate-driven shifts) or result from land abandonment.
• 12Reductions in extent — decreases in the area of an ecosystem type, separated where possible into:
  • 13Managed reductions — decreases due to direct human activity (e.g., deforestation, urban expansion), including unplanned or illegal activity.
  • 14Unmanaged reductions — decreases associated with natural processes (e.g., loss of coral reefs to climate change, abandonment).

15Where data availability does not permit the managed/unmanaged split, SEEA EA para 4.14 advises that it is sufficient to record opening and closing extents and the net change⁷². Revisions arising from updated input data or methods are not recorded as a distinct entry. Instead, opening/closing extents and additions/reductions are altered and time series revised (para 4.17)⁷².

16Ecosystem conversions. Changes in ecosystem extent are termed ecosystem conversions — situations where “for a given location, there is a change in ecosystem type involving a distinct and persistent change in ecological structure, composition and function”⁷³. Conversions may be human-induced (such as clearing mangroves for aquaculture ponds) or natural (such as succession of wetland types). Within the extent account, the total area of all ecosystem types should equal the total ecosystem accounting area: what one type loses, another type gains.

17Conversions are recorded in the extent account, not beside it. A conversion changes the ecosystem type of an area that remains inside the accounting area, so it is not a reduction in the same sense as an area lost from the accounting area altogether. Where conversions are material, add a reclassification block to Table 2a between additions and reductions:

Accounting entry	Ecosystem type 1	Ecosystem type 2	…	Total
Reclassifications
— Conversions from other ecosystem types	[area]	[area]	…	[Σ area]
— Conversions to other ecosystem types	[-area]	[-area]	…	[-Σ area]
Net reclassification	[+/-]	[+/-]	…	0

18Table 2b: Reclassification block for the ecosystem extent account. Net reclassification sums to zero at the total level: an area converted out of one ecosystem type is an area converted into another.

19The distinction that governs which row an event enters is whether the area changes type or leaves the accounting area. Kelp lost to storm damage where the substrate is exposed but not yet colonised is an unmanaged reduction; kelp that becomes an urchin barren is a reclassification, because the area is still accounted for, under a different type. Compilers who cannot yet support a reclassification block should record conversions in a separate ecosystem type change matrix and state in account metadata that they have done so, but the block above is the preferred presentation because it keeps the conversion inside the account that has to balance.

20Marine ecosystem delineation. For marine ecosystems, the SEEA EA recommends that within the continental shelf, “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”⁷⁴. This seabed-based approach accommodates the three-dimensional nature of marine ecosystems whilst providing a practical basis for area measurement. The SEEA EA also 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”⁷⁵. Mapping therefore proceeds from the seabed upward: the seabed type defines the ecosystem boundary, even though the living system extends through the water column above it.

21The IUCN Global Ecosystem Typology (GET) provides the reference classification for marine ecosystem types, with the Marine Shelf biome (M1) encompassing key functional groups including seagrass meadows (M1.1), kelp forests (M1.2), photic coral reefs (M1.3), shellfish beds and reefs (M1.4), and subtidal rocky reefs (M1.6)⁷⁶. For guidance on mapping marine ecosystem extent using remote sensing and spatial data, see TG-4.1 Remote Sensing and Geospatial Data.

22The seabed-based delineation approach presents challenges for pelagic ecosystems that are not clearly associated with specific seabed areas. Epipelagic, mesopelagic, and bathypelagic ecosystem types (IUCN GET M2.1—M2.4) require alternative delineation approaches, potentially using water mass characteristics, depth zones, or biogeochemical provinces as boundaries. These challenges are addressed in TG-6.5 Pelagic and Open Ocean Accounts.

3.5.2 Ecosystem condition accounts

1Ecosystem condition refers to the quality of an ecosystem — how well it is functioning, as distinct from how much of it exists⁷⁷. A hectare of degraded coral reef is still a hectare in the extent account, but its capacity to deliver services (coastal protection, fish habitat, tourism value) may be a fraction of a healthy reef’s. Condition accounts capture this quality dimension.

2Structure of condition accounts. The SEEA EA describes a three-stage measurement approach⁷⁸, summarised in Table 3.5.2 below.

Stage	Description
Condition variable accounts	Record raw values of condition characteristics (e.g., live coral cover percentage, species richness count, water temperature).
Condition indicator accounts	Transform variables into comparable indicators, typically scaled against a reference condition (e.g., coral cover as a percentage of reference condition).
Condition indices	Aggregate indicators into composite measures for communication to policy-makers (optional).

3Selection of condition variables. Condition variables should be selected based on their relevance to the ecosystem type, data availability, and connection to ecosystem integrity⁷⁹. For marine ecosystems, the SEEA EA identifies key drivers of condition including bathymetric profile, climate factors (temperature, acidification), substrate type, ocean circulation, salinity, and human pressures⁸⁰. The SEEA EA groups condition characteristics into six classes⁸¹:

• 4Physical state (including water temperature, salinity)
• 5Chemical state (including ocean acidification, nutrient levels, pollutant concentrations)
• 6Compositional state (including species diversity, community composition)
• 7Structural state (including habitat complexity, biomass)
• 8Functional state (including productivity, ecosystem processes)
• 9Landscape/seascape context (including connectivity, fragmentation)

10For guidance on indicators derived from ecosystem condition accounts, see TG-2.1 Aggregate Biophysical Indicators of Environmental State.

Relationship between extent, condition, and service capacity

1The capacity of an ecosystem to deliver services depends on both its extent and its condition — area multiplied by quality. A large, healthy reef delivers more services than a small, degraded one. SEEA EA Figure 6.1 illustrates this relationship: ecosystem extent determines the spatial scale of potential service delivery, whilst ecosystem condition determines the quality and intensity of service flow per unit area⁸². Together, they determine the overall capacity to deliver ecosystem services, which is then realised through actual service flows to economic units.

2Figure 3.1.3 shows the relationship between ecosystem extent, condition, and service capacity (adapted from SEEA EA Figure 6.1).

Figure 3.1.3 Ecosystem extent and condition jointly determine capacity -- the potential sustainable supply realised as final service flows to the economy. Extent, condition, and capacity are supporting accounts; the final service flow crosses the Environment--Economy boundary.

3This framework has direct implications for ocean accounting. A decline in coral reef extent (recorded in the extent account) reduces the total area available for service delivery. Simultaneously, degradation in reef condition (recorded in the condition account) reduces the service flow per hectare. Both effects are captured when compiling ecosystem service flow accounts as described in TG-3.2 Flows from Environment to Economy.

Illustrative marine condition variables by ECT class

1To support the selection of condition variables for marine ecosystem types, Table 3 maps illustrative variables to the six classes of the SEEA EA Ecosystem Condition Typology (ECT)⁸³. The ECT provides a universal structure for organising condition characteristics across all ecosystem types, and groups them into abiotic, biotic, and landscape-level categories.

ECT Group	ECT Class	Marine condition variables (illustrative)
Group A: Abiotic	A1. Physical state	Sea surface temperature (°C), salinity (PSU), turbidity (NTU), microplastic concentration (particles/m³)
	A2. Chemical state	Ocean pH, dissolved oxygen (mg/L), chlorophyll-a (μg/L), nutrient concentrations (N, P)
Group B: Biotic	B1. Compositional state	Species richness (number), abundance of key species (individuals/area), invasive species presence
	B2. Structural state	Live coral cover (%), seagrass canopy height (cm), mangrove canopy density (%), fish biomass (kg/ha)
	B3. Functional state	Net primary productivity (gC/m²/yr), trophic index, recruitment rates
Group C: Landscape	C1. Landscape/seascape	Habitat connectivity index, fragmentation (patch count), distance to pressure sources (km)

2Table 3: Illustrative marine condition variables structured by ECT class (based on SEEA EA Table 5.1)⁸³

3The SEEA EA recommends selecting at least one variable for each of the six ECT classes for each ecosystem type, which sets a minimum level of coverage⁸⁴. Each variable should be compared against a reference condition representing “good” or “natural” state, so that it can be transformed into condition indicators that are comparable across ecosystem types and accounting periods. Based on evaluation of existing ecosystem condition accounts, a set of approximately 6 to 10 well-selected indicators for a given ecosystem type should provide sufficient information to assess the overall condition of an ecosystem asset⁸⁵. For biome-specific indicative variables, including those relevant to marine shelf, pelagic, and deep-sea biomes, compilers should consult the indicative variable sets presented in SEEA EA Table 5.7⁸⁶.

4Reference conditions. Condition indicators are typically expressed relative to a reference level representing “good” or “natural” condition⁸⁷. The reference condition may be a historical baseline, a minimally impacted area, or a policy target, and the choice should be clearly documented. A reef measured against a pristine 1950s baseline may record a 60% decline, whilst the same reef measured against a 2010 baseline may appear stable. The choice of reference therefore shapes how the account is interpreted. The SEEA EA links condition to the concept of ecosystem integrity: “the ecosystem’s capacity to maintain its characteristic composition, structure, functioning and self-organization over time within a natural range of variability”⁸⁸.

The three condition account tables

1The three stages produce three account tables. Compilers should publish all three: the variable account is the auditable record, the indicator account is what can be compared across ecosystem types, and the index is what reaches a policy reader. Publishing only the index hides the choices that produced it.

2Stage 1 — condition variable account. Records each selected variable in its own measured units, unrescaled, for the opening and closing of the accounting period, together with the upper and lower reference levels against which it will be rescaled. The reference levels are fixed at the start of the time series and held constant (TG-4.8 Section 3.1).

3Table 3a: Ecosystem condition variable account — structural template (after SEEA EA Table 5.2)

ECT class	Condition variable	Unit	Polarity	Lower reference L	Upper reference U	Opening value	Closing value
A1 Physical state	[variable]	[unit]	Normal / Inverse	[L]	[U]	[value]	[value]
A2 Chemical state	[variable]	[unit]	Normal / Inverse	[L]	[U]	[value]	[value]
B1 Compositional state	[variable]	[unit]	Normal / Inverse	[L]	[U]	[value]	[value]
B2 Structural state	[variable]	[unit]	Normal / Inverse	[L]	[U]	[value]	[value]
B3 Functional state	[variable]	[unit]	Normal / Inverse	[L]	[U]	[value]	[value]
C1 Landscape/seascape	[variable]	[unit]	Normal / Inverse	[L]	[U]	[value]	[value]

4Table 3a: Structural template of an ecosystem condition variable account, one table per ecosystem type in the accounting area. Cells are blank for compiler population. Row structure follows the ECT classes in Table 3; the reference-level and polarity columns carry the parameters the Stage 2 rescaling consumes.

5Stage 2 — condition indicator account. Rescales each variable to a dimensionless 0—1 indicator against its reference levels. The transformation is not defined here. It is normative in TG-2.1 Aggregate Biophysical Indicators of Environmental State Section 3.4.1 — Indicator = (V - L) / (U - L) for normal polarity, (L - V) / (L - U) for inverse polarity, with the categorical step deduction for pH and other logarithmic-scale variables — and compilers must use that transformation without local variation.

6Table 3b: Ecosystem condition indicator account — structural template (after SEEA EA Table 5.3)

ECT class	Condition indicator	Opening indicator (0—1)	Closing indicator (0—1)	Change	Data tier
A1 Physical state	[indicator]	[0—1]	[0—1]	[+/-]	1 / 2 / 3
A2 Chemical state	[indicator]	[0—1]	[0—1]	[+/-]	1 / 2 / 3
B1 Compositional state	[indicator]	[0—1]	[0—1]	[+/-]	1 / 2 / 3
B2 Structural state	[indicator]	[0—1]	[0—1]	[+/-]	1 / 2 / 3
B3 Functional state	[indicator]	[0—1]	[0—1]	[+/-]	1 / 2 / 3
C1 Landscape/seascape	[indicator]	[0—1]	[0—1]	[+/-]	1 / 2 / 3

7Table 3b: Structural template of an ecosystem condition indicator account. Every value is dimensionless and bounded on [0, 1], which is what makes rows comparable across ecosystem types and periods. The data tier column carries the quality flag defined in TG-4.8 Section 3.2 and TG-4.9 Section 3.4.

8Stage 3 — condition index. Aggregates the indicators, first to a class-level sub-index and then to a single index for the ecosystem type. SEEA EA describes three aggregation rules in common use: the (weighted) arithmetic mean, the (weighted) geometric mean, and one-out-all-out, in which the index takes the value of its worst-performing indicator. The choice matters and is not neutral: an arithmetic mean lets a strong indicator mask a collapsed one, a geometric mean penalises imbalance, and one-out-all-out is the precautionary rule used in several regulatory regimes. TG-2.1 Section 3.6 sets the publication default and is normative; the weights and the rule applied must be recorded in the account.

9Table 3c: Ecosystem condition index — structural template (after SEEA EA Table 5.4)

Level	Component	Weight	Opening	Closing	Change
Class sub-index	A1 Physical state	[w]	[0—1]	[0—1]	[+/-]
Class sub-index	A2 Chemical state	[w]	[0—1]	[0—1]	[+/-]
Class sub-index	B1 Compositional state	[w]	[0—1]	[0—1]	[+/-]
Class sub-index	B2 Structural state	[w]	[0—1]	[0—1]	[+/-]
Class sub-index	B3 Functional state	[w]	[0—1]	[0—1]	[+/-]
Class sub-index	C1 Landscape/seascape	[w]	[0—1]	[0—1]	[+/-]
Ecosystem condition index	All classes	—	[0—1]	[0—1]	[+/-]

10Table 3c: Structural template of an ecosystem condition index. Record the aggregation rule and the weights alongside the table; an index published without them cannot be reproduced or challenged.

11The closing index in Table 3c is the value the degradation calculation in Section 3.5.3 consumes, and the change column is the index-point decline that formula takes as its input. A compiler who has not produced Table 3c cannot produce a defensible degradation entry.

3.5.3 Monetary ecosystem asset accounts

1Monetary ecosystem asset accounts record the value of ecosystem assets in currency units. The SEEA EA presents two main valuation approaches⁸⁹:

1. 2NPV of ecosystem services — summing the discounted future flows of all ecosystem services supplied by the asset
2. 3Restoration cost — the cost of restoring an ecosystem to a reference condition

4The NPV approach aligns with valuation methods for other natural assets but requires monetary valuation of ecosystem services, which remains methodologically challenging, particularly for non-market services such as coastal protection and biodiversity maintenance. The restoration cost approach provides an alternative that does not require service valuation but may not reflect the full economic value of the asset. A coral reef may cost a certain amount to restore, whilst its actual value to the economy and society may be far higher. For detailed guidance on valuation of ecosystem services, see TG-1.9 Safe Usage of Monetary Valuation and TG-2.4 Ecosystem Goods and Services.

Structure of monetary ecosystem asset accounts

1The SEEA EA monetary ecosystem asset account (Chapter 10) records the monetary values of all ecosystem assets within an ecosystem accounting area at the beginning and end of each accounting period, together with the changes in those values⁹⁰. Table 4 presents the standard structure.

Accounting entry	Ecosystem Type A	Ecosystem Type B	…	Total
Opening value	84,000	42,500	…	360,000
Ecosystem enhancement	1,200	300	…	1,500
Ecosystem degradation	-2,500	-800	…	-3,300
Ecosystem conversions (additions)	400	200	…	600
Ecosystem conversions (reductions)	-600	-250	…	-850
Other changes in volume
— Catastrophic losses	-1,500	-400	…	-1,900
— Reappraisals	800	100	…	900
Revaluation	1,100	400	…	1,500
Net change in value	-1,100	-450	…	-1,550
Closing value	82,900	42,050	…	358,450

2Table 4: Structure of monetary ecosystem asset account with illustrative synthetic values in thousand currency units (adapted from SEEA EA Table 10.1)⁹⁰

3The account balances on the identity Closing value = Opening value + enhancement — degradation + conversions (additions) — conversions (reductions) + other changes in volume + revaluation, and the net change row makes that visible. In this illustration degradation and catastrophic losses together exceed enhancement, reappraisals and holding gains, so the closing value is below the opening value: the accounting area ended the period with less ecosystem wealth than it started with. That is the signal the account exists to carry, and it is the one a compiler should check first.

4The accounting entries distinguish five broad types of change in the monetary value of ecosystem assets⁹¹:

• 5Ecosystem enhancement records increases in monetary value associated with improving condition during the accounting period. This includes the effects of active restoration, reductions in harmful activities that allow recovery, and natural improvements in condition. A positive enhancement entry indicates that investment in ecosystem health is generating economic returns.
• 6Ecosystem degradation records decreases in monetary value associated with declining condition. Degradation plays an analogous role to depletion for individual natural resources: it represents a cost that should be deducted in calculating adjusted income measures. Consistently large degradation entries indicate an economy drawing down its ecosystem capital.
• 7Ecosystem conversions record additions and reductions resulting from changes in ecosystem type at a given location. When mangroves are cleared for aquaculture, a decrease in value is recorded for mangroves and an increase for the new aquaculture pond ecosystem. There is no expectation that these will be offsetting in monetary terms, as mangroves typically provide far more total ecosystem services than the aquaculture ponds that replace them.
• 8Other changes in volume capture two categories: catastrophic losses, which are decreases in value due to large-scale, discrete events that cause significant loss in ecosystem condition — significant losses in structure, function or composition — such as a mass bleaching event, a cyclone or an oil spill (SEEA EA paras 10.24, 10.37); and reappraisals, which record changes in value due to updated information about expected future demand for ecosystem services or changed expectations about future condition (SEEA EA para 10.38)⁹². Where such an event is severe enough that the ecosystem is considered to have changed its type, the loss is recorded as an ecosystem conversion, not as a catastrophic loss (SEEA EA para 10.37). The line therefore turns on whether condition fell or type changed, not on how much extent was affected.
• 9Revaluation records changes in monetary value due solely to movements in the unit prices of ecosystem services, distinct from any physical changes in the asset. Following the SEEA CF convention, changes in value resulting from changes in the quantity or quality of future flows of ecosystem services are not revaluations and should be recorded under the appropriate entry above (SEEA EA para 10.41)⁹³.

10The distinction between reappraisals and revaluation is essential for interpreting changes in ecosystem asset values. Reappraisals concern changes in expectations — for example, revised demographic projections that alter the expected future demand for ecosystem services, or rezoning decisions that change the expected pattern of ecosystem use. Revaluations, by contrast, concern changes in unit prices only and are conceptually equivalent to the holding gains and losses recorded for other asset types in the SNA.

11For marine contexts, monetary values of ecosystem assets can be estimated using the NPV of expected future ecosystem service flows. For market services such as fish provisioning and blue carbon sequestration, resource rent methods may be applied. For non-market services such as coastal protection, water purification, and recreational amenity, replacement cost or avoided damage cost methods from the preference hierarchy in TG-2.4 Environmental (including Ecosystem) Goods and Services Section 3.10.2 should be used.

12The UN Statistical Commission, in adopting the SEEA EA in 2021, identified “outstanding methodological concerns related to chapters 8 to 11 on valuation” (SEEA EA Preface para 8). Accordingly, the valuation chapters have the status of “internationally recognised statistical principles and recommendations” rather than a full international statistical standard. Compilers should be aware that monetary ecosystem asset valuation methods continue to evolve, and should document the methods and assumptions used in their valuations transparently.

Horizon and condition-to-service scaling

13Two choices govern any NPV-based ecosystem asset valuation and should be recorded in account metadata.

14Apply the condition adjustment once. A condition-adjusted asset value is built by adjusting the physical service flow for observed condition — treating a literature-derived or reference-condition service rate as the reference value and scaling it by the composite condition index — and then discounting the resulting condition-adjusted flow. The condition index enters at the service-flow step and not again at the discounting step. Applying it at both steps squares the adjustment and understates the asset, and it is a common error because each step looks defensible in isolation. Where condition is on a declining trajectory, project the service flow forward using the trend rather than applying a perpetuity to a single adjusted flow, and record the projected trajectory, its source and the horizon in account metadata.

15Perpetuity or finite horizon. A perpetuity is appropriate where there is no foreseeable terminal date for the ecosystem asset, governance arrangements are stable, and any management mandate over the area is continuously renewed. A finite-horizon NPV is required where the arrangement that sustains the service flow has a time-limited mandate, a sunset clause, or uncertain renewal — a protected area designated for a fixed term, or a concession-dependent management regime. The choice materially changes the asset value, and the rationale must be documented.

16Condition-to-service scaling. Where a change in the composite condition index is used to infer a change in service flow, compilers should not assume a linear relationship as a default. The relationship between condition and service capacity is service-specific: coastal protection, carbon sequestration and fishery support functions each have distinct functional forms, and several are known to be non-linear near ecological thresholds. Compilers should apply the best available ecological or economic evidence for the service in question, and document the functional form and its source. A linear scaling may be used as a screening-level approximation where no calibrated relationship is available, provided it is labelled as such and the direction of likely bias is stated. TG-1.6 OA and Environmental Impact Assessment Section 3.5 sets out how an assessor applies these conditions in practice, and why a damage cost must be reported as a range.

Ecosystem degradation, damage cost and offsets

17Degradation is the decline in the monetary value of an ecosystem asset arising from a decline in its condition during the accounting period. This subsection specifies how it is calculated, when the simplified approach is defensible, and how the same extent-and-condition arithmetic supports offset requirements under no-net-loss policies.

Applicability of the simplified linear approximation

18Before applying the degradation formula below, practitioners should confirm that the linear approximation is appropriate for their context. The simplified linear formula is appropriate only where all three of the following conditions are met:

19(a) Condition decline is 20 percentage points or less, that is, the absolute change in the condition index does not exceed 0.20. This cut-off is indicative compiler judgement rather than a SEEA-specified threshold, and practitioners should adjust it where domain-specific evidence supports a different value. Larger declines are more likely to involve non-linear service losses.

20(b) No threshold responses are documented in the relevant ecosystem literature for the ecosystem type and service combination being valued. If published studies indicate that condition decline triggers disproportionate service loss at any intermediate point within the predicted range, the linear approximation will underestimate damage.

21(c) A single dominant service type drives asset value (i.e., one service accounts for more than approximately 70% of total annual service flow value per hectare, an indicative threshold that is not SEEA-specified). Where multiple services of roughly equal weight respond differently to the same condition change, separate service-specific calculations should replace the aggregated formula.

22Decision checklist:

• 23 Is absolute condition decline 0.20 or less? If no, use an ecosystem-specific biophysical model (see the Guidelines on Biophysical Modelling cited below).
• 24 Does the ecosystem literature document threshold responses within the predicted condition range? If yes, use biophysical model or apply conservative non-linear adjustment (e.g., service loss proportional to condition decline squared). Consult the Guidelines on Biophysical Modelling for Ecosystem Accounting⁹⁴.
• 25 Does one service type account for more than approximately 70% of asset value? If no, calculate degradation separately for each major service.

Degradation formula

26Degradation (simplified linear approximation) = (Condition decline) × (Present value of affected service flows)

27Definition of “condition decline”: In this formula, “condition decline” means the absolute change in the condition index, expressed in index points. For example, if the condition index falls from 0.72 to 0.60, the condition decline is 0.12 (not the proportional change of 16.7% relative to opening condition). Practitioners must use the absolute index-point change consistently throughout all calculations.

28The formula is applied to project-level impact assessment in TG-1.6 OA and Environmental Impact Assessment Section 3.5. Consider a coastal development expected to reduce coral reef condition index from 0.75 to 0.60 (a decline of 0.15 index points) across 100 hectares. If the reef provides coastal protection services valued at USD 10,000/ha/year and biodiversity habitat services valued at USD 2,000/ha/year, and using a 4% discount rate for perpetual service flows (consistent with social discount rates used in several OECD national accounting frameworks, and practitioners should substitute their national treasury or green book rate):

29Worked calculation:

• 30Annual service flow per hectare = USD 12,000/ha/year
• 31Asset value per hectare (perpetual annuity) = USD 12,000 / 0.04 = USD 300,000/ha
• 32Total reef asset value (100 ha) = USD 30,000,000
• 33Degradation (0.15 index-point condition decline) = 0.15 × USD 30,000,000 = USD 4,500,000

34Discount rate sensitivity: As the choice of discount rate affects damage cost estimates, practitioners should present results across a range of rates. For the worked example above (USD 30,000,000 total asset value at 4%, condition decline = 0.15):

Discount rate	Asset value (100 ha)	Degradation cost (0.15 decline)
2%	USD 60,000,000	USD 9,000,000
4%	USD 30,000,000	USD 4,500,000
7%	USD 17,143,000	USD 2,571,000

35If engineering solutions to reduce reef impacts would cost USD 4,000,000, the cost-benefit comparison at the 4% rate suggests such measures are economically justified. Discount rate selection is covered in Section 3.3 of this Circular and in TG-2.4 Section 3.10; TG-1.9 Safe Usage of Monetary Valuation sets out how the resulting figures should be presented and caveated.

36Important methodological considerations:

37Service-specific responses: Different ecosystem services may respond differently to the same condition change. For example, coral cover decline may reduce coastal protection services linearly but reduce biodiversity habitat services exponentially if critical shelter structures are lost. Degradation estimates should separately assess each major service type.

38Uncertainty: Both condition predictions and service valuations involve uncertainty. Practitioners should propagate uncertainty through calculations and present results as ranges rather than point estimates where feasible.

Offset requirement and restoration equivalence

39Extent and condition accounts provide the quantitative foundation for environmental offset and no-net-loss policies, which apply in a growing number of marine regulatory contexts. The regulatory and procedural side of offsetting is covered in TG-1.6 OA and Environmental Impact Assessment Section 3.7; the measurement definitions are set out here so that they are available to compilers and regulators approaching from the accounts. Ecosystem extent and condition accounts establish the quantitative baselines against which offset requirements can be calculated. The offset requirement formula uses the condition index of the habitat that is lost (or degraded), not the condition gain from a restoration action. Consider a port expansion that will result in the loss of 5 hectares of seagrass at condition index 0.80. The offset requirement is:

Offset requirement = (Lost extent) × (Condition of lost habitat) × (Multiplier)

40Note on the multiplier: The multiplier is determined by the relevant regulatory authority and is not prescribed by the Ocean Accounts framework. Ocean Accounts provide the input data for the formula (extent and condition metrics) but do not set the multiplier. The illustrative example in this section uses a 2:1 multiplier, whilst the worked example in TG-1.6 Section 3.8 uses a regulator-specified 3:1 multiplier. Practitioners should apply the multiplier required by the applicable regulatory regime.

41Applying a 2:1 multiplier (illustrative only) to account for implementation risk and time lag:

Offset = 5 ha × 0.80 × 2 = 8 ha-equivalents of seagrass at reference condition

42The restoration equivalence unit for delivery of the offset is defined as:

ha-equivalents delivered = (Restored area) × (Condition gain)

43where condition gain is the absolute increase in condition index achieved by the restoration action. Using this definition consistently with the requirement formula: restoration of 10 hectares of degraded seagrass from condition 0.60 to 0.80 delivers 10 × 0.20 = 2.0 ha-equivalents, which is insufficient to meet the 8 ha-equivalent requirement. Restoring 10 hectares from 0.50 to 0.80 (gain of 0.30) would deliver 10 × 0.30 = 3.0 ha-equivalents, still insufficient. The offset could instead be achieved through protection of 8 hectares of high-quality seagrass at risk of loss.

44Side-by-side equivalence check (illustrative seagrass example):

Side	Formula	Values	Result
Requirement	Lost extent × Condition of lost habitat × Multiplier	5 ha × 0.80 × 2	8.0 ha-equivalents required
Delivery (option A)	Restored area × Condition gain	10 ha × 0.20 (from 0.60 to 0.80)	2.0 ha-equivalents delivered (shortfall)
Delivery (option B)	Restored area × Condition gain	10 ha × 0.30 (from 0.50 to 0.80)	3.0 ha-equivalents delivered (shortfall)
Delivery (option C)	Area protected × Condition preserved	8 ha at reference condition	8.0 ha-equivalents (meets requirement)

45Both sides of the equivalence calculation must use the same condition metric definition (absolute index points) to produce comparable results. Ecosystem service flow accounts enable assessment of whether proposed offsets adequately compensate for lost service flows, in addition to habitat area. If the 5 hectares of lost seagrass provided coastal stabilisation services valued at USD 2,000/ha/year and fish nursery services valued at USD 1,500/ha/year, the offset must provide equivalent service flows:

Required service compensation = 5 ha × USD 3,500/ha/year = USD 17,500/year

46The offsetting actions must demonstrably provide this level of service flow to achieve functional equivalence. Using the asset valuation approach set out above, the present value of the lost asset is:

Lost asset value = (Annual service flow) / (Discount rate) Lost asset value = USD 17,500 / 0.04 = USD 437,500

47This provides a quantitative basis for determining financial compensation where physical offsetting is not feasible.

48Temporal discounting of offset delivery: Marine restoration offsets typically take 5—20 years to deliver the promised condition gain, whilst the impact occurs immediately. A nominal 1:1 equivalence at eventual full achievement understates the interim loss of ecosystem services during the restoration period. Some regulatory frameworks address this through temporal discounting provisions or by requiring upfront financial assurance (e.g., surety bonds or in-lieu fee arrangements) that compensate for the time lag. Practitioners should consult their applicable regulatory framework for guidance on whether temporal provisions apply. Where none exist, the multiplier (see above) partly serves this function by requiring over-delivery on the offset.

49Time series data support assessment of whether offsets achieve their intended outcomes over the long term. Post-implementation monitoring should track condition variables and service flows using the same methods as the accounts. This supports objective assessment of offset success and triggers adaptive management responses if targets are not met.

50Countries implementing marine offset policies should ensure that offset accounting is consistent with their broader Ocean Accounts framework to maintain coherence between project-level compensation and national ecosystem reporting⁹⁵.

51The multiplier in the offset requirement is set by the regulator, not by the accounts. Ocean Accounts supply the extent and condition metrics on both sides of the equivalence; the policy parameters — multiplier, temporal discounting of delayed delivery, and whether financial compensation may substitute for physical offset — are matters for the applicable regulatory regime.

52Degradation. In SEEA EA, ecosystem degradation represents the decline in condition multiplied by the associated loss of future ecosystem service flows, valued in monetary terms⁹⁶. It is the ecosystem equivalent of depletion: the cost of using an ecosystem harder than it can sustain. The SEEA EA states that the approach “involves measuring the value of degradation in terms of loss in future value of ecosystem services due to a decline in ecosystem condition”⁹⁷. For a policy-maker, degradation measures what ecosystem decline is costing the economy.

Recording losses from discrete events: catastrophic losses and conversions

53A disaster — a cyclone, a mass bleaching event, an oil spill — is recorded differently from the gradual decline that degradation measures, and the two rules that govern it are the opposite of what intuition suggests.

54Physical accounts. The treatment differs between the two account types, and conflating them is a common error. For individual environmental assets — fish stocks, timber, mineral resources — the SEEA CF physical asset account carries “Catastrophic losses” as a named line within reductions, covering “exceptional and significant reductions in the natural resource” that result from discrete events (SEEA CF para 5.49(c)). For ecosystem extent accounts, SEEA EA provides no standalone catastrophic-losses line: the reductions side is managed contraction and unmanaged contraction, and catastrophic losses are allocated between them according to whether the reduction was a deliberate management action, though SEEA EA notes they “could be separately identified” as a memorandum component. Report a disaster loss in an extent account as an identified component of unmanaged contraction, so the account still reconciles with the standard structure.

55A catastrophic loss is a loss of ecosystem condition, not of extent. SEEA EA records under catastrophic losses the decreases in value due to “large-scale, discrete and recognizable events that cause a significant decline in the condition of an ecosystem asset, that is, significant losses in structure, function or composition”, naming earthquakes, bushfires, cyclones and industrial disasters as the events in scope (paras 10.24, 10.37).

56Where the event changes the ecosystem type, it is a conversion. “Where the effects of large-scale events are significant enough for the ecosystem to be considered to have changed its type, this should be recorded as an ecosystem conversion” (para 10.37). Mangrove stand that a cyclone destroys outright, leaving open water or bare mudflat, is a conversion, not a catastrophic loss.

What the event did	Recorded as
Reduced condition of a surviving ecosystem asset (structure, function, composition)	Catastrophic losses
Changed the ecosystem type at that location	Ecosystem conversions
Gradual condition decline from ongoing management and use	Ecosystem degradation

57Degradation is not the disaster line. Degradation records decline in condition attributable to “the current and expected patterns of ecosystem management and use and expected patterns of environmental variation” (paras 10.22—10.23). A discrete, unforeseeable event is carved out of it precisely because its timing, location and magnitude cannot be anticipated. Routing disaster damage into degradation overstates the entry that feeds adjusted income measures.

58The value recorded for a catastrophic loss is the fall in asset value attributable to the condition decline, derived through the same condition-to-service-flow-to-NPV chain as degradation, above. The value recorded for a conversion is the value of the converted extent, less any value of the ecosystem type that replaces it. Neither represents consumption of fixed capital or depletion: they reduce the value of the asset without arising from its use in production.

3.6 Produced Assets in the Ocean Domain

1Whilst this Circular focuses primarily on environmental (non-produced) assets, ocean accounts must also include produced assets — the infrastructure, vessels, and equipment built for ocean-based activities. Produced assets are “assets that have come into existence as outputs of production processes”⁹⁸. Recording them alongside environmental assets gives a full account of total ocean wealth and exposes the interdependencies between the two.

Types of produced assets in the ocean domain

1Key categories include:

2Aquaculture fixed assets — cages, pens, nets, and other infrastructure used for raising cultivated aquatic resources, as well as breeding stocks held as fixed assets⁹⁹. These are produced assets resulting from deliberate investment decisions. For detailed guidance, see TG-3.9 Aquaculture Accounts.

3Offshore energy infrastructure — platforms, drilling equipment, pipelines, subsea facilities for oil and gas extraction, as well as wind turbines, wave energy converters, and tidal energy devices for marine renewable energy. For detailed guidance, see TG-3.10 Offshore Energy Accounts.

4Port infrastructure — wharves, jetties, breakwaters, dredged channels, container terminals, and other facilities for maritime transport and trade.

5Coastal protection structures — sea walls, groynes, revetments, and other engineered structures designed to protect coastal areas from erosion and flooding. These can be considered alongside the natural coastal protection services provided by ecosystems such as mangroves and coral reefs¹⁰⁰. Such comparisons often indicate that natural defences are more cost-effective than engineered ones.

6Vessels — fishing vessels, cargo ships, cruise ships, offshore service vessels, and other maritime transport equipment.

Accounting treatment

1Produced assets are accounted for following standard SNA methodology, with opening stocks, gross fixed capital formation (investment), consumption of fixed capital (depreciation), and closing stocks recorded in physical and monetary terms¹⁰¹.

2Table 10: Produced asset account — structural template (after the SNA capital account)

Accounting entry	Vessels	Aquaculture infrastructure	Offshore energy infrastructure	Port infrastructure	Coastal protection structures	Total
Opening stock (net)	[value]	[value]	[value]	[value]	[value]	[Σ]
Gross fixed capital formation	[value]	[value]	[value]	[value]	[value]	[Σ]
Consumption of fixed capital	[-value]	[-value]	[-value]	[-value]	[-value]	[-Σ]
Other changes in volume (incl. catastrophic loss)	[+/-]	[+/-]	[+/-]	[+/-]	[+/-]	[+/-]
Revaluation	[+/-]	[+/-]	[+/-]	[+/-]	[+/-]	[+/-]
Closing stock (net)	[value]	[value]	[value]	[value]	[value]	[Σ]
Memorandum: decommissioning provision	[value]	[value]	[value]	[value]	[value]	[Σ]

3Table 10: Structural template of a produced asset account for the ocean domain. Compiled on standard SNA methodology¹⁰¹; the decommissioning memorandum is specific to the ocean domain, where offshore energy and aquaculture infrastructure carry retirement obligations that the net stock does not show. Its treatment is in TG-3.10 Offshore Energy Accounts Section 3.6.

4For ocean accounting, produced assets interact with environmental assets in three ways:

• 5Aquaculture investment creates produced assets (infrastructure) that depend on environmental assets (water quality, marine ecosystems providing supporting services). If the environmental asset degrades, the produced asset becomes less productive.
• 6Offshore oil and gas investment creates produced assets that enable extraction of environmental assets (mineral resources). The produced asset depreciates through use, whilst the environmental asset depletes through extraction.
• 7Coastal infrastructure may protect inland assets but may also affect coastal ecosystem extent and condition — a sea wall can prevent erosion of property whilst destroying the beach ecosystem in front of it.

8These connections should be reflected in integrated accounts that present produced and environmental assets together, enabling analysis of total ocean wealth and its composition. Combined presentations of environmental and economic accounts are addressed in TG-3.8 Combined Presentations.

3.7 Worked Example: Coastal Ecosystem Asset Accounts

1This section demonstrates how to compile physical and monetary asset accounts for a hypothetical coastal area. The example uses synthetic data for three marine ecosystem types (mangroves, seagrass meadows, and continental shelf waters) and one individual environmental asset (fish stocks), following the compilation procedure from Section 3.2 and the account structures from Sections 3.4 and 3.5. Working through this example demonstrates how the components combine, and how physical declines can be masked by monetary gains.

Scenario description

1The accounting area is a coastal zone extending 12 nautical miles offshore and encompassing 500 km² of mangrove forest, 200 km² of seagrass meadows, and 15,000 km² of continental shelf marine waters. The area supports commercial fisheries targeting demersal fish species that depend on mangroves and seagrass as nursery habitat. The accounting period is calendar year 2025.

Step 1: Ecosystem extent accounts

1Extent data were compiled from Sentinel-2 satellite imagery processed using supervised classification algorithms, validated by field surveys at 150 ground-truth sites (see TG-4.1 Remote Sensing and Geospatial Data). Change detection analysis identified conversions between ecosystem types and losses to non-natural land cover.

2Physical extent account (area in km²)

Accounting entry	Mangroves	Seagrass	Shelf Waters	Total
Opening extent (1 Jan 2025)	500	200	15,000	15,700
Additions to extent
Managed expansion (restoration)	2.5	1.2	0	3.7
Natural expansion	0.8	0.3	0	1.1
Total additions	3.3	1.5	0	4.8
Reductions in extent
Managed reduction (conversion to aquaculture)	4.0	0.5	0	4.5
Natural reduction (storm damage, erosion)	2.5	1.8	0	4.3
Total reductions	6.5	2.3	0	8.8
Net change in extent	-3.2	-0.8	0	-4.0
Closing extent (31 Dec 2025)	496.8	199.2	15,000	15,696

3Table 5: Physical ecosystem extent account for coastal zone, 2025

4Reading the account. The coastal zone lost 3.2 km² of mangroves and 0.8 km² of seagrass during 2025. Managed reductions (conversion to aquaculture ponds) exceeded managed expansion (restoration projects): deliberate human decisions drove more loss than restoration could offset. Natural reductions from storm damage and coastal erosion added to the deficit. Continental shelf waters recorded no change in extent because the accounting area boundary remained fixed.

Step 2: Ecosystem condition accounts

1Condition data were compiled from 45 monitoring stations distributed across the three ecosystem types, measuring variables in each of the six ECT classes. Measurements were taken quarterly and averaged for the year.

2Condition variable account for mangroves (selected variables)

ECT class	Variable	Unit	Polarity	Lower reference L	Upper reference U	Opening value	Closing value
A1 Physical state	Sedimentation rate	mm/yr	Inverse	8.0	2.0	3.2	3.5
A2 Chemical state	Soil salinity	PSU	Inverse	35	15	18	19
B1 Compositional state	Tree species richness	count	Normal	2	12	8	8
B2 Structural state	Canopy density	% cover	Normal	20	85	72	70
B3 Functional state	Leaf litter production	g/m²/yr	Normal	150	550	480	465
C1 Landscape/seascape	Connectivity index	0—1	Normal	0.20	0.80	0.68	0.65

3Table 6: Ecosystem condition variable account for mangroves, 2025, in the Table 3a format

4Reading the account. Every variable sits between its two reference levels, and all but species richness are moving towards the lower one. Canopy density dropped from 72% to 70% against an upper reference of 85%. Connectivity between mangrove patches fell from 0.68 to 0.65, likely because the conversion of mangrove patches to aquaculture created gaps in the landscape. Leaf litter production, a proxy for ecosystem productivity, declined from 480 to 465 g/m²/yr.

5Condition indicator account. Each variable is rescaled on its own reference levels using the transformation in TG-2.1 Section 3.4.1 — (V - L) / (U - L) for normal polarity, (L - V) / (L - U) for inverse.

ECT class	Condition indicator	Opening	Closing	Change	Data tier
A1 Physical state	Sedimentation	0.80	0.75	-0.05	2
A2 Chemical state	Soil salinity	0.85	0.80	-0.05	2
B1 Compositional state	Tree species richness	0.60	0.60	0.00	1
B2 Structural state	Canopy density	0.80	0.77	-0.03	1
B3 Functional state	Leaf litter production	0.83	0.79	-0.04	2
C1 Landscape/seascape	Connectivity	0.80	0.75	-0.05	2

6Table 6a: Ecosystem condition indicator account for mangroves, 2025, in the Table 3b format

7Worked for one row: canopy density is normal polarity with L = 20% and U = 85%, so the closing indicator is (70 - 20) / (85 - 20) = 50 / 65 = 0.77.

8Condition index. Aggregated as an unweighted arithmetic mean of the six class indicators — the publication default in TG-2.1 Section 3.6. With one indicator per class the class sub-index equals the indicator.

Level	Component	Weight	Opening	Closing	Change
Class sub-index	A1 Physical state	1/6	0.80	0.75	-0.05
Class sub-index	A2 Chemical state	1/6	0.85	0.80	-0.05
Class sub-index	B1 Compositional state	1/6	0.60	0.60	0.00
Class sub-index	B2 Structural state	1/6	0.80	0.77	-0.03
Class sub-index	B3 Functional state	1/6	0.83	0.79	-0.04
Class sub-index	C1 Landscape/seascape	1/6	0.80	0.75	-0.05
Mangrove condition index	All classes	—	0.78	0.74	-0.04

9Table 6b: Ecosystem condition index for mangroves, 2025, in the Table 3c format

10The mangrove condition index fell 0.04 index points over the year. That figure — not a judgement about the variables — is what the degradation entry in Step 4 consumes. Had the aggregation rule been one-out-all-out rather than the arithmetic mean, the index would have been 0.60 in both periods and the change zero, because species richness is both the worst indicator and the only stable one. The rule is doing real work, which is why Section 3.5.2 requires it to be recorded in the account.

Step 3: Fish stock asset account

1Fish stock data were compiled from stock assessment models for the dominant demersal species complex, using data from commercial catch statistics, fishery-independent trawl surveys, and length-frequency analysis. The stock assessment estimated total biomass, natural mortality, recruitment, and fishing mortality using age-structured models.

2Physical asset account for fish stocks (biomass in tonnes)

Accounting entry	Value
Opening stock (1 Jan 2025)	42,000
Additions to stock
Natural growth (recruitment + growth)	8,500
Upward reappraisals	0
Total additions	8,500
Reductions in stock
Gross catch (commercial fisheries)	7,200
Natural mortality	4,800
Catastrophic losses (fish kill from hypoxia event)	500
Total reductions	12,500
Closing stock (31 Dec 2025)	38,000
Derived measures
Sustainable yield (MSY estimate)	6,500
Depletion (catch - sustainable yield)	700

3Table 7: Physical asset account for demersal fish stock, 2025

4Reading the account. The fish stock declined by 4,000 tonnes (9.5%) during 2025. Gross catch of 7,200 tonnes exceeded the sustainable yield estimate of 6,500 tonnes by 700 tonnes. That 700 tonnes is depletion, the amount by which the fishery is drawing down its capital base. The stock also experienced a catastrophic loss of 500 tonnes from a hypoxia event in coastal waters during summer, potentially linked to the nutrient loading and habitat fragmentation recorded in the mangrove condition data. The decline was driven by the combination of overfishing and environmental stress.

Step 4: Monetary valuation

1Monetary values were estimated for ecosystem assets using the NPV of expected future ecosystem service flows, and for fish stocks using the NPV of expected future resource rents.

2Mangrove ecosystem services valuation (values expressed per km² for this illustrative example):

• 3Coastal protection service: Replacement cost method based on equivalent seawall construction, estimated at USD 12,000 per km² per year
• 4Carbon sequestration service: Social cost of carbon (USD 50 per tonne CO2) applied to sequestration rate, USD 400 per km² per year
• 5Fish nursery service: Productivity change method estimating contribution to commercial fisheries, USD 800 per km² per year
• 6Total annual ecosystem service value: USD 13,200 per km² per year
• 7Discount rate: 4% real
• 8Asset value (perpetual annuity): USD 13,200 / 0.04 = USD 330,000 per km² (equivalent to USD 3,300 per hectare)

9Seagrass ecosystem services valuation (values expressed per km²):

• 10Carbon sequestration: USD 300/km²/yr
• 11Water filtration: Avoided treatment cost USD 150/km²/yr
• 12Fish nursery: USD 600/km²/yr
• 13Total annual service value: USD 1,050/km²/yr
• 14Asset value (4% discount): USD 1,050 / 0.04 = USD 26,250 per km² (equivalent to USD 262.5 per hectare)

15Fish stock valuation:

• 16Resource rent per tonne caught: USD 450 (gross value of landings USD 1,200/tonne, less all costs)
• 17Sustainable yield: 6,500 tonnes/yr
• 18Annual sustainable resource rent: 6,500 x USD 450 = USD 2,925,000
• 19Asset value (4% discount, perpetual): USD 2,925,000 / 0.04 = USD 73,125,000

20Monetary ecosystem asset account (values in USD thousand)

Accounting entry	Mangroves	Seagrass	Total
Opening value (500 km² x USD 3,300/ha; 200 km² x USD 262.5/ha)	165,000	5,250	170,250
Ecosystem enhancement (condition improvement from restoration, 2.5 km²)	825	0	825
Ecosystem degradation (condition index decline x opening value)	-6,600	-105	-6,705
Ecosystem conversions (additions)	0	0	0
Ecosystem conversions (reductions: -4.0 km², -0.5 km²)	-1,320	-13	-1,333
Catastrophic losses (storm damage value loss)	-825	-47	-872
Reappraisals	0	0	0
Revaluation (5% increase in unit service values)	8,250	263	8,513
Net change in value	330	98	428
Closing value	165,330	5,348	170,678

21Table 8: Monetary ecosystem asset account, 2025

22Where the degradation entry comes from. The mangrove figure is the condition index decline from Table 6b applied to the opening asset value, following Section 3.5.3: 0.04 x USD 165,000 thousand = USD 6,600 thousand. The seagrass figure is the same calculation on a parallel condition account not reproduced here, whose index fell 0.02 points: 0.02 x USD 5,250 thousand = USD 105 thousand. Both fall inside the applicability conditions for the simplified linear approximation set out in Section 3.5.3 — the decline is well under 0.20 index points, no threshold response is documented for these ecosystem types in this range, and coastal protection accounts for over 70 per cent of the mangrove service value per hectare. A compiler whose condition decline is larger, or whose asset value is split across services that respond differently, must use the service-specific route instead.

23Fish stock monetary asset account (values in USD thousand)

Accounting entry	Value
Opening value (1 Jan 2025)	73,125
Additions (natural growth valued at resource rent/tonne)	3,825
Reductions (extraction and mortality)	-5,400
Catastrophic losses (hypoxia event)	-225
Reappraisals (revised sustainable yield estimate)	0
Revaluation (10% increase in fish prices)	7,313
Closing value (31 Dec 2025)	78,638

24Table 9: Monetary fish stock asset account, 2025

25Reading the account — and what it can obscure. Holding gains do most of the work in this account. For mangroves, a 5% increase in unit service values (driven by updated coastal protection valuations following storm damage in a neighbouring region) generated USD 8.25 million, enough to more than offset USD 6.6 million of degradation, USD 1.32 million of conversion loss and USD 0.83 million of catastrophic loss, and to leave the mangrove closing value USD 0.33 million above its opening value. For fish stocks, a 10% price increase generated USD 7.3 million, more than offsetting the value of depletion, so that account too closes higher than it opened.

26Strip the revaluations out and the picture inverts. Mangroves lose USD 7.92 million at constant prices; the ecosystem account as a whole loses USD 8.09 million rather than gaining the USD 0.43 million the closing line reports; and the fish stock loses USD 1.80 million rather than gaining USD 5.51 million. The physical accounts said as much all along — declining fish stocks, shrinking mangroves, a condition index down 0.04 points — and it is the price column, not the ecosystem, that is carrying the closing balance.

27This is why the decomposition is not optional. Adjusted income measures should deduct depletion and degradation at constant prices, and changes in asset value due to price effects must be reported separately as revaluations rather than as real income. The SEEA CF requires depletion to be valued at the average of opening and closing prices to give a neutral mid-period valuation³⁶. An account that reports only opening and closing values, without the revaluation line, is capable of showing growth through an entire period of ecosystem collapse.

Step 5: Integration and policy implications

1The worked example demonstrates several key linkages in the ocean accounting system:

2Upward linkages to policy (TG-1.x and TG-2.x):

• 3TG-1.1 National Ocean Budgets: The USD 6,705 thousand in ecosystem degradation plus USD 315 thousand in fish stock depletion (700 tonnes above sustainable yield at USD 450/tonne resource rent, for a total of USD 7,020 thousand at constant prices) represents the natural capital cost of economic activity during 2025. This cost should be deducted from gross income measures to calculate environmentally adjusted net domestic product.
• 4TG-2.1 Aggregate Biophysical Indicators of Environmental State: The 0.025% decline in ecosystem extent (4.0 km² loss from 15,700 km² total) and 9.5% decline in fish stock biomass provide headline indicators of environmental state for policy monitoring.
• 5TG-2.4 Ecosystem Goods and Services: The estimated ecosystem service flows (coastal protection, carbon sequestration, fish nursery) quantified in the valuation step provide inputs to ecosystem service accounts.

6Downward linkages to data (TG-4.x):

• 7TG-4.1 Remote Sensing and Geospatial Data: Sentinel-2 imagery provided the primary data source for extent change detection.
• 8TG-4.2 Survey Methods for Ocean Economic Activity: Field monitoring at 45 stations provided condition variable measurements. In-situ data remains necessary to complement remote sensing.
• 9TG-4.3 Administrative Data Sources: Integration of extent, condition, and stock assessment data within a common spatial framework enabled consistent attribution of ecosystem services to ecosystem assets and analysis of nursery habitat contributions to fisheries.

10Cross-account consistency:

• 11Fish stock depletion of 700 tonnes corresponds to extraction recorded in physical supply-use tables (see TG-3.2 Flows from Environment to Economy)
• 12Ecosystem extent changes are reconciled with ecosystem conversion matrices
• 13Monetary degradation and depletion entries correspond to physical condition decline and stock reduction multiplied by appropriate unit values

14This worked example illustrates how asset accounts provide a structured framework for organising diverse data sources, maintaining accounting identities that ensure internal consistency, and deriving policy-relevant measures of sustainability. The procedure can be scaled to national accounting areas and extended to additional asset types following the same logical structure.

Implementation Considerations

1For minimum institutional capacity, data infrastructure, and human skills requirements for compiling these accounts, see TG-0.8 Implementation Readiness Assessment. For guidance on adapting these methods to sub-national scales, see TG-3.11 Sub-National Ocean Accounts.

4. Acknowledgements

1Authors: [To be confirmed]

2Reviewers: [To be confirmed]

Footnotes

1. 1

   SEEA CF, para 5.42. “Asset accounts record both the opening and the closing stock of assets and the changes over the accounting period.” ↩

2. 2

   SEEA CF, para 5.43 ↩

3. 3

   SEEA CF, para 5.44 ↩

4. 4

   SEEA CF, para 5.72. For renewable biological resources, “natural growth relates to the number of animals… or volume of plants… that have been added to the stock due to natural processes.” ↩

5. 5

   SEEA CF, para 5.82. “For any given population, it is possible to calculate the number of animals or volume of plants by age or size class that may be removed from the population without affecting the capacity of the population to regenerate itself.” ↩

6. 6

   SEEA CF, para 5.180 ↩

7. 7

   SEEA CF, para 5.51. “Reappraisals record changes in estimates of the stock due to revisions in the estimation techniques being applied.” ↩

8. 8

   SEEA CF, para 5.458 ↩

9. 9

   SEEA CF, para 5.52 ↩

10. 10

    SEEA CF, para 5.422 ↩

11. 11

    SEEA CF, para 5.47 ↩

12. 12

    SEEA CF, para 5.429 ↩

13. 13

    SEEA CF, para 5.428 ↩

14. 14

    SEEA CF, para 5.48 ↩

15. 15

    SEEA CF, para 5.50 ↩

16. 16

    SEEA CF, para 2.107 ↩

17. 17

    SEEA CF, Annex A5.1, para A5.28-A5.31 ↩

18. 18

    2025 SNA, Chapter 11, para 11.45 ↩

19. 19

    SEEA CF, para 5.431 ↩

20. 20

    SEEA CF, Chapter 5, Table 5.1. Classification of environmental assets. ↩

21. 21

    SEEA EA, Table 4.1 and para 4.10-4.22. Ecosystem extent account structure and accounting entries. ↩

22. 22

    SEEA CF, para 5.103-5.111 ↩

23. 23

    2025 SNA, Chapter 13, paras 13.1-13.15. Balance sheets record stocks of assets and liabilities, with net worth = assets - liabilities. ↩

24. 24

    SEEA CF, para 5.96 ↩

25. 25

    SEEA CF, para 5.97 ↩

26. 26

    SEEA CF, para 5.102 ↩

27. 27

    SEEA CF, para 5.103-5.111 ↩

28. 28

    SEEA CF, para 5.110. “Net present value is the value of an asset determined by estimating the stream of income expected to be earned in the future and then discounting the future income back to the present accounting period.” ↩

29. 29

    SEEA CF, Annex A5.1, para A5.15 ↩

30. 30

    SEEA CF, Annex A5.2, para A5.42-A5.76 ↩

31. 31

    SEEA CF, Annex A5.2, paras A5.42-A5.76. Discusses discount rate selection including the use of a rate “at the higher end of the range of observable rates on government and high-quality corporate bonds” adjusted for asset-specific risk. ↩

32. 32

    SEEA CF, para 5.444-5.452 ↩

33. 33

    SEEA CF, para 5.448 ↩

34. 34

    SEEA EA, para 12.30-12.39 ↩

35. 35

    SEEA CF, Annex A5.1, para A5.31 ↩

36. 36

    SEEA CF, Annex A5.1, para A5.27 ↩ ↩²

37. 37

    SEEA CF, para 5.11 ↩

38. 38

    SEEA CF, para 5.393 ↩

39. 39

    SEEA CF, para 5.395 ↩

40. 40

    SEEA CF, para 5.420-5.422 ↩

41. 41

    SEEA CF, para 5.423 ↩

42. 42

    SEEA CF, para 5.425 ↩

43. 43

    SEEA CF, para 5.457 ↩

44. 44

    SEEA CF, para 5.429 ↩

45. 45

    SEEA CF, para 5.429 ↩

46. 46

    SEEA CF, Table 5.22 ↩

47. 47

    SEEA CF, para 5.436 ↩

48. 48

    Physical asset account template integrating SEEA CF Table 5.4 (general structure of physical asset accounts for environmental assets), SEEA EA Table 4.1 (ecosystem extent account), and SEEA CF Table 5.22 (aquatic resources account). ↩

49. 49

    SEEA CF, para 5.431-5.432 ↩

50. 50

    SEEA CF, para 5.431 ↩

51. 51

    SEEA CF, para 5.433 ↩

52. 52

    SEEA CF, para 5.434 ↩

53. 53

    SEEA CF, para 5.435 ↩

54. 54

    SEEA CF, para 5.436 ↩

55. 55

    SEEA CF, para 5.442 ↩

56. 56

    SEEA CF, para 5.450 ↩

57. 57

    SEEA CF, para 5.443 ↩

58. 58

    SEEA CF, para 5.173 ↩

59. 59

    SEEA CF, para 5.175-5.178 ↩

60. 60

    SEEA CF, para 5.182-5.183 ↩

61. 61

    SEEA CF, para 5.113-5.114. “Resource rent is the economic rent that accrues in relation to environmental assets, including natural resources.” ↩

62. 62

    SEEA CF, para 5.474 ↩

63. 63

    SEEA CF, para 5.476 ↩

64. 64

    SEEA CF, para 5.469 ↩

65. 65

    SEEA EA, para 2.6 ↩

66. 66

    SEEA EA, para 2.11 ↩

67. 67

    SEEA EA, para 4.1 ↩

68. 68

    SEEA EA, para 4.10. “The structure of the rows reflects the general logic of asset accounts as described in the SEEA Central Framework.” ↩

69. 69

    SEEA EA, Table 4.1 ↩

70. 70

    UN SEEA EA (2021), paras 4.10—4.13 and Table 4.1. The row structure of the extent account follows the general asset-account logic of the SEEA Central Framework (opening stock, additions, reductions, closing stock); columns correspond to the classes of the selected ecosystem type classification. ↩ ↩²

71. 71

    UN SEEA EA (2021), para 4.15. Definitions of opening/closing extent, managed and unmanaged expansions, and managed and unmanaged reductions. The accounting identity that the sum of areas of all ecosystem types equals the total area of the EAA is stated in para 4.13. ↩ ↩² ↩³

72. 72

    UN SEEA EA (2021), paras 4.14 (minimum-detail recording where managed/unmanaged split is unavailable) and 4.17 (treatment of revisions arising from updated input data or methods; no distinct revision entry recorded). ↩ ↩²

73. 73

    SEEA EA, para 4.23 ↩

74. 74

    SEEA EA, para 3.32 ↩

75. 75

    SEEA EA, para 3.32 ↩

76. 76

    IUCN GET, M1 Marine Shelf biome ↩

77. 77

    SEEA EA, para 2.13 ↩

78. 78

    SEEA EA, para 5.5-5.8 ↩

79. 79

    SEEA EA, para 5.15-5.25 ↩

80. 80

    SEEA EA, para 3.35 ↩

81. 81

    SEEA EA, para 5.32, Table 5.1 ↩

82. 82

    SEEA EA, Figure 6.1 and para 6.18. The capacity to deliver ecosystem services is a function of both the extent and the condition of the ecosystem asset. ↩

83. 83

    SEEA EA, Table 5.1. Ecosystem Condition Typology (ECT) classes for organising condition characteristics. ↩ ↩²

84. 84

    SEEA EA, para 5.46. “Ideally, the compilation of ecosystem condition accounts should ensure that for each ecosystem type, at least one variable is selected for each of the six ECT classes.” ↩

85. 85

    SEEA EA, para 5.47. “A set of about 6 to 10 well-selected indicators for a given ecosystem type should provide sufficient information to assess the overall condition of an ecosystem asset.” ↩

86. 86

    SEEA EA, Table 5.7. Indicative set of ecosystem condition variables for biomes structured in accordance with the ECT. ↩

87. 87

    SEEA EA, para 5.35-5.48 ↩

88. 88

    SEEA EA, para 5.10 ↩

89. 89

    SEEA EA, Chapter 10 ↩

90. 90

    SEEA EA, Chapter 10, Table 10.1, paras 10.7-10.12. The monetary ecosystem asset account records the NPV of ecosystem services supplied by each ecosystem type. ↩ ↩²

91. 91

    SEEA EA, paras 10.15-10.41. Definitions of ecosystem enhancement (para 10.15), ecosystem degradation (para 10.21), ecosystem conversions (para 10.30), other changes in volume (para 10.36), and revaluations (para 10.41). ↩

92. 92

    SEEA EA, paras 10.36-10.39. Catastrophic losses are “large-scale, discrete and recognizable events that cause a significant loss in the condition of an ecosystem asset” (para 10.37). Reappraisals record changes due to “updated information that permits a reassessment of the expected condition of the ecosystem assets or the future demand for ecosystem services” (para 10.38). ↩

93. 93

    SEEA EA, para 10.41. “Revaluations are changes in the value of ecosystem assets over an accounting period that are due solely to movements in the unit prices of ecosystem services.” ↩

94. 94

    United Nations Environment Programme (2022). Guidelines on Biophysical Modelling for Ecosystem Accounting. UNEP, Nairobi. Provides methods for assessing ecosystem capacity and identifying threshold responses where the linear approximation is not appropriate. ↩

95. 95

    Countries implementing marine offset policies should ensure that offset accounting is consistent with their broader Ocean Accounts framework, so that project-level compensation and national ecosystem reporting remain coherent. ↩

96. 96

    SEEA EA, para 11.25 ↩

97. 97

    SEEA EA, para 12.30 ↩

98. 98

    SEEA CF, para 5.34 ↩

99. 99

    SEEA CF, para 5.395 ↩

100. 100

     SEEA EA, para 6.55 on coastal protection as an ecosystem service ↩

101. 101

     2025 SNA, Chapter 13 ↩ ↩²

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Cite this circular

Asset Accounts (2026) (GOAP Technical Guidance on Ocean Accounting, TG-3.1, v0.9.1). GOAP Secretariat. https://guidance.oceanaccounts.org/circulars/section-3/3-1-assets/

BibTeX

@techreport{goap_tg_3_1_2026,
  title = {Asset Accounts},
  institution = {Global Ocean Accounts Partnership Secretariat},
  series = {GOAP Technical Guidance on Ocean Accounting},
  number = {TG-3.1},
  year = {2026},
  version = {0.9.1},
  url = {https://guidance.oceanaccounts.org/circulars/section-3/3-1-assets/}
}

© 2026 Global Ocean Accounts Partnership. Licensed under CC BY-NC 4.0. Consultation drafts are not adopted GOAP guidance.