Asset Accounts

1. Outcome

This Circular provides comprehensive guidance on compiling asset accounts for ocean accounting, covering both physical and monetary accounts for individual environmental assets (natural resources) and ecosystem assets. Asset accounts are fundamental to ocean accounting, recording the opening and closing stocks of marine assets and the changes occurring during accounting periods. They provide the statistical foundation for measuring ocean wealth, assessing the sustainability of resource use, and tracking degradation or enhancement of marine and coastal ecosystems.

Asset accounts serve critical decision use cases for governments managing ocean resources. They inform natural capital budgeting by quantifying the value of ocean assets and changes in that value, enabling governments to assess whether economic growth is achieved at the expense of depleting natural capital. They support depletion tracking for net domestic product (NDP), ensuring that resource extraction beyond sustainable levels is recognized as a cost reducing national income. They enable sustainable yield management by comparing actual extraction against the regenerative capacity of renewable marine resources such as fisheries, guiding quota-setting and conservation measures. These functions connect directly to the budget processes described in TG-1.1 National Ocean Budgets, where asset accounts provide the evidence base for allocating public resources to ocean conservation and sustainable use.

This Circular integrates the individual asset approach of the SEEA Central Framework with the ecosystem asset approach of SEEA Ecosystem Accounting, demonstrating how both perspectives can be applied to ocean domains. By understanding asset accounting methodology, readers will be equipped to compile robust asset accounts for fish stocks, seabed minerals, marine ecosystem types, and produced assets in the ocean domain, and to interpret changes in these assets over time. For guidance on the valuation methods referenced throughout this Circular, see TG-1.9 Valuation.

2. Requirements

This Circular requires familiarity with:

• TG-0.1 General Introduction to Ocean Accounts -- for the conceptual framework and key components of Ocean Accounts
• TG-0.2 Overview of Relevant Statistical Standards -- for the methodological foundations provided by SNA 2025, SEEA CF, and SEEA EA
• TG-0.7 Quality Assurance -- for data quality considerations applicable to asset measurement

3. Guidance Material

Asset accounts are a core component of environmental-economic accounting, recording the stock of assets at the beginning and end of an accounting period and the changes during that period^[1]. The SEEA Central Framework provides the foundational methodology for accounting for individual environmental assets, while SEEA Ecosystem Accounting extends this to treat ecosystems as integrated spatial units. For ocean accounting, both approaches are relevant: the individual asset approach is applied to fish stocks, seabed minerals, and other natural resources within marine areas; the ecosystem asset approach captures coral reefs, seagrass meadows, mangroves, and other marine ecosystem types as spatially bounded accounting units.

This section examines the structure and accounting entries for physical and monetary asset accounts, before addressing the specific requirements for individual environmental assets (Section 3.3), ecosystem assets (Section 3.4), and produced assets in the ocean domain (Section 3.5). Section 3.2 provides a compilation procedure detailing the steps from data collection to account entry, while Section 3.6 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

Physical asset accounts record stocks and changes in stocks in physical measurement units appropriate to the asset type--tonnes, cubic metres, hectares, number of individuals, or other relevant units^[2]. These accounts provide the foundation for understanding the physical dimension of ocean wealth and are essential for assessing sustainability, as they reveal whether resource extraction exceeds natural regeneration or whether ecosystem extent is declining.

Basic structure

The general structure of a physical asset account consists of^[3]:

1. Opening stock -- the quantity of the asset at the beginning of the accounting period
2. Additions to stock -- increases during the period, including natural growth, discoveries, upward reappraisals, and reclassifications
3. Reductions in stock -- decreases during the period, including extractions, natural losses, catastrophic losses, downward reappraisals, and reclassifications
4. Closing stock -- the quantity of the asset at the end of the accounting period

The closing stock equals the opening stock plus total additions minus total reductions. This accounting identity provides the logical structure for reconciling stock estimates with observed changes and ensures completeness of recording.

Figure 3.1.1: Physical asset account identity

Additions to stock

For renewable natural resources such as fish stocks and timber resources, the primary addition to stock is natural growth, encompassing recruitment (new individuals joining the stock) and biomass increase (growth of existing individuals)^[4]. Natural growth is determined by biological processes that vary with environmental conditions, stock size, and species characteristics. For renewable resources under effective management, natural growth provides the basis for sustainable yield--the largest harvest that can be taken without reducing the long-term productivity of the stock^[5].

Discoveries apply primarily to non-renewable resources such as mineral and energy resources. In the marine context, discoveries include identification of new oil and gas deposits, seabed mineral resources (including polymetallic nodules and seafloor massive sulphides), and rare earth elements in marine sediments^[6]. Discoveries also apply to aquatic resources when previously unknown fish stocks are identified and assessed.

Upward reappraisals record revisions to estimates of stock size that result from improved information or measurement methods, rather than actual physical changes^[7]. For fish stocks, reappraisals occur when stock assessment models are updated with new data, leading to revised estimates of biomass or abundance. It is important to distinguish reappraisals (accounting adjustments) from actual growth or discoveries (physical changes). For fish stock accounting, the SEEA CF notes that "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].

Reclassifications record transfers of assets between categories within the classification system without any actual physical change^[9]. For example, a reclassification occurs when a natural fish stock becomes subject to aquaculture operations and is transferred 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].

Reductions in stock

Extraction (or harvest, for biological resources) represents the removal of natural resources from the environment for use in economic activity^[11]. For aquatic resources, extraction corresponds to the gross catch--the total live weight of fish caught, including discarded catch but excluding pre-catch losses^[12]. The SEEA CF recommends using gross catch rather than landings as the measure of extraction, as this provides a more complete picture of the impact on aquatic resources. The FAO defines the stages of catch as^[13]:

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

Normal losses (or natural mortality for biological resources) represent decreases in stock due to natural processes such as death from age, predation, disease, and accidents^[14]. For fish stocks, natural mortality is a key parameter in stock assessment models and must be estimated alongside fishing mortality to understand population dynamics.

Catastrophic losses represent "exceptional and significant reductions in the natural resource"^[15] due to discrete events such as storms, disease outbreaks, toxic algal blooms, or mass mortality events. For marine ecosystems, catastrophic losses may result from coral bleaching events, oil spills, or extreme weather. These are distinguished from normal losses by their exceptional and unpredictable nature.

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

Depletion

Depletion is a derived measure of particular importance for sustainability analysis. For renewable resources, depletion occurs when "the extraction of the natural resource is occurring at a level greater than that of regeneration"^[16]. Depletion equals extraction minus sustainable yield:

Depletion = Extraction - Sustainable yield

When extraction equals or is less than sustainable yield, depletion is zero. When extraction exceeds sustainable yield, the stock is being depleted and future productive capacity is being reduced^[17]. For non-renewable resources such as mineral deposits, depletion equals extraction, as there is no regeneration.

The concept of depletion provides a critical link between 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 product^[18]. This treatment provides stronger signals about the sustainability of resource-based economic activities. The SEEA CF describes the relationship between depletion, income, and sustainability: "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 Stock Assessment.

3.2 Compilation Procedure for Asset Accounts

This section outlines the step-by-step procedure for compiling ocean asset accounts, from data collection through account entry and balance sheet reconciliation. Understanding this workflow is essential for translating source data into accounting entries and maintaining consistency across the full accounting system.

Step 1: Data collection and source identification

The compilation process begins with identifying and assembling the data sources required to measure opening stocks, additions, reductions, and closing stocks for each asset type. For individual environmental assets such as fish stocks and seabed minerals, primary data sources include:

• Stock assessment reports from fisheries management agencies, providing estimates of spawning stock biomass, recruitment, natural mortality, and fishing mortality (see TG-6.7 Fisheries Stock Assessment)
• Geological 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)
• Catch statistics from fisheries agencies and international databases (FAO FishStatJ), recording landings, gross catch, and discards by species and fishing zone

For ecosystem assets such as coral reefs, seagrass meadows, and mangroves, primary data sources include:

• Remote sensing imagery (Sentinel-2, Landsat, MODIS) processed to classify ecosystem extent and detect changes over time (see TG-4.1 Remote Sensing Data)
• Field 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)
• National spatial databases delineating protected areas, coastal zone boundaries, and ecosystem type classifications consistent with the IUCN Global Ecosystem Typology

Data quality should be assessed following TG-0.7 Quality Assurance, with particular attention to temporal consistency (ensuring opening and closing stocks are measured on a comparable basis), spatial coverage (ensuring data represent the full accounting area), and measurement uncertainty (documenting confidence intervals and data quality ratings).

Step 2: Classification and mapping to asset categories

Once source data are assembled, they must be mapped to the asset classification system used in the accounts. The SEEA CF classifies environmental assets into major categories including aquatic resources, mineral and energy resources, water resources, timber resources, land, and soil resources^[20]. For ocean accounting, the relevant categories are:

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

SEEA EA ecosystem assets are classified using the IUCN Global Ecosystem Typology, with marine ecosystem types including:

• 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)

Compilers should document the correspondence between national ecosystem type classifications (if different from IUCN GET) and the reference classification, ensuring that ecosystem extent can be aggregated to standard categories for international comparison.

Step 3: Measurement and quantification

With data sources identified and classifications established, the next step is to quantify opening stocks, additions, reductions, and closing stocks in physical units appropriate to each asset type.

For 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) is used to reconcile these components. Where stock assessment provides direct estimates of both opening and closing stock, the identity serves as a consistency check; discrepancies may indicate data errors or unobserved changes requiring reappraisal entries.

For 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 separately^[21].

For 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; the indicator derivation is addressed in TG-2.1 Biophysical Indicators.

Step 4: Account entry and balancing

Once physical quantities have been measured, they are entered into the asset account structure following the standard format. The account must balance, with closing stock = opening stock + total additions - total reductions. Any imbalance indicates either data error or missing entries (such as unreported extraction, unobserved natural changes, or required reappraisal adjustments).

For marine assets, particular attention should be given to:

• Spatial boundaries: Ensuring that opening and closing stocks are measured for the same geographic area. Changes in jurisdictional boundaries or accounting area definitions should be recorded as reclassifications rather than real changes.
• Unit consistency: Ensuring that all entries for a given asset are expressed 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.
• Temporal alignment: Ensuring that 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)

For monetary asset accounts, the physical stock quantities are valued at appropriate asset prices. For fish stocks and other renewable natural resources, the net present value (NPV) of expected future resource rents provides the standard valuation approach^[22]. The NPV calculation requires:

1. Resource rent estimation: Calculating the annual resource rent as the difference between the value of harvest and all costs (including labor, capital, intermediate inputs, and normal return on produced assets)
2. Discount rate selection: Determining an appropriate discount rate reflecting the time value of money and asset-specific risk factors (see TG-1.9 Valuation for detailed guidance)
3. Asset life assumption: Estimating the expected duration of the resource rent stream, which for sustainably managed renewable resources may be assumed to be perpetual

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

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

Changes in monetary value are decomposed into:

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

This decomposition ensures that monetary asset accounts remain consistent with physical asset accounts while also capturing the economic dimension of asset value changes.

Step 6: Integration with balance sheets and other accounts

The final step in the compilation procedure 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 worth^[23]. Changes in net worth during the accounting period are explained by saving, capital transfers, and holding gains/losses recorded in the revaluation account.

For ocean accounting, integration ensures that:

• Depletion entries in asset accounts correspond to depletion costs in production accounts and adjustments to net domestic product
• Extraction entries in asset accounts correspond to natural resource inputs in physical supply-use tables (TG-3.2 Flows from Environment to Economy)
• Ecosystem service flows are consistent with the capacity to supply services implied by ecosystem extent and condition (as illustrated in the worked example below)
• Investment 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

Cross-stack connections upward to policy circulars include:

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

Cross-stack connections downward to data circulars include:

• TG-4.1 Remote Sensing Data provides methods for extent mapping that populate ecosystem extent accounts
• TG-4.2 Survey Methods provides protocols for condition variable measurement
• TG-4.3 Geospatial Data Integration provides the spatial framework for delineating ecosystem assets and aggregating data

These linkages ensure that asset accounts are not compiled in isolation but function as an integrated component of the broader ocean accounting system.

3.3 Monetary Asset Accounts

Monetary asset accounts record the value of environmental assets and the changes in value during an accounting period. These accounts enable aggregation across different asset types, comparison with produced assets and financial assets, and calculation of depletion-adjusted income measures^[24]. For detailed guidance on valuation methods applicable to ocean assets, see TG-1.9 Valuation.

Structure of monetary asset accounts

The structure of monetary asset accounts parallels that of physical accounts^[25]:

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

The revaluation entry captures holding gains and losses--changes in asset value attributable to changes in prices rather than physical quantities^[26]. This separation is essential for distinguishing real changes in wealth from price effects.

Valuation approaches

Environmental assets are typically not traded in markets, creating challenges for valuation. The SEEA CF describes several approaches^[27]:

Net present value (NPV) is the preferred approach for valuing natural resources. The NPV method estimates the stream of expected future resource rents (the economic surplus accruing to the resource owner after all costs and normal returns are deducted) and discounts this stream to the present^[28]. For natural resources:

Value = Resource rent x Discount factor

where 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 factors^[30].

Discount rate selection can significantly affect asset valuations, particularly for long-lived assets such as fish stocks under perpetual management regimes. The SEEA CF provides extensive guidance on discount rate methodology in Annex A5.2, covering asset life assumptions, risk adjustments, and country-specific factors^[31]. For detailed guidance on discount rate selection and its implications for marine asset valuation, see TG-1.9 Valuation.

Market 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 valuations^[32]. However, markets for environmental assets are often imperfect or non-existent, limiting the applicability of this approach. 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].

Restoration 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 degradation^[34]. See TG-1.9 Valuation for detailed comparison of valuation approaches.

Valuation of depletion

The monetary value of depletion is calculated by multiplying physical depletion by the appropriate asset price^[35]. 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

This treatment ensures consistency with the valuation of consumption of fixed capital (depreciation) for produced assets. The SEEA CF notes that this mid-period valuation "is consistent with the rules in the SNA for the valuation of consumption of fixed capital"^[36].

3.4 Individual Environmental Assets

Individual environmental assets are "those environmental assets that may provide resources for use in economic activity"^[37]. 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

Aquatic resources comprise all fish, crustaceans, molluscs, shellfish, aquatic plants, and other organisms living in water that are of economic importance or have the capacity to provide economic benefits in the future^[38]. The SEEA CF distinguishes between:

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

Natural aquatic resources are classified as non-produced assets, while cultivated aquatic resources are produced assets (fixed assets for breeding stocks; inventories for stocks held for sale)^[39]. Detailed guidance on aquaculture accounting is provided in TG-3.9 Aquaculture Accounts.

Measuring fish stocks. Estimating the absolute size of fish stocks is challenging and requires biological assessment methods. Common approaches include virtual population analysis (VPA), tag-recapture studies, and acoustic or trawl surveys^[40]. When absolute stock estimates are unavailable, catch per unit effort (CPUE) may provide an indicator of relative stock size, assuming that population density correlates with catch rates^[41]. The SEEA CF cautions that "a declining trend in the CPUE may be a signal that the rate of harvest is exceeding the renewal rate of the fish stock"^[42].

Stock assessments should ideally distinguish between the total stock, the spawning stock biomass (the portion of the stock capable of reproduction), and the exploitable stock (the portion subject to harvest)^[43]. For accounting purposes, estimates of the total stock and changes therein are required. Remote sensing and other spatial data sources may support stock assessment; see TG-4.1 Remote Sensing Data for guidance on satellite-derived inputs.

Classification of catch types. The SEEA CF recommends using gross catch as the measure of extraction from natural aquatic resources^[44]. Gross catch is defined as the total live weight of fish caught, comprising:

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

Using gross catch rather than landings provides a more complete measure of the impact on fish stocks and on marine ecosystems, as discards may constitute a significant portion of total catch in some fisheries. 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].

The treatment of discards varies across fisheries and jurisdictions. Where 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.

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

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

Note that the table includes "uncompensated seizure" to record illegal fishing by non-residents, following the SEEA CF treatment^[47]. The synthetic values illustrate a natural aquatic stock experiencing decline (closing stock 171,000 < opening stock 180,000), driven by extraction and losses exceeding growth, while cultivated resources show modest growth.

Comprehensive physical asset account template

Table 1a provides a broader physical asset account template that compilers can use to record all major categories of marine natural resources within a single accounting structure. The template 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), reflecting the different dynamics that govern each asset class.

Table 1a: Comprehensive 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]

The bracketed entries indicate the data sources or estimation methods typically used for each row. For natural aquatic resources, stock assessment models provide the primary input (see TG-6.7 Fisheries Stock Assessment). For ecosystem assets, remote sensing and spatial survey provide extent mapping (see TG-4.1 Remote Sensing Data). For mineral resources, geological surveys and commercial assessments provide stock estimates. The "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.

Sustainable 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 depletion^[49]. 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].

Capture 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 resource^[51]. However, for asset accounts, 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.

Illegal 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].

Monetary valuation of aquatic resources. The SEEA CF describes two main options for valuing natural aquatic resources^[55]:

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

Where individual transferable quotas (ITQs) are used and traded, the total market value of all quotas may approximate the value of the aquatic resource^[56]. However, quota markets are 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].

3.4.2 Mineral and energy resources

Mineral 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 minerals^[58].

Classification of resources. The SEEA CF adopts a classification based on commercial viability^[59]:

• Class A: Commercially recoverable resources -- resources that are economically viable to extract under current conditions
• Class B: Potentially commercially recoverable resources -- resources that may become viable with technological advances or price changes
• Class C: Non-commercial and other known deposits -- resources that are not currently viable

Physical asset accounts for minerals. Asset accounts for mineral and energy resources record the opening stock, discoveries, extractions, reappraisals, and closing stock^[60]. 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).

For 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.

Monetary 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 deducted^[61]. 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 Valuation.

3.4.3 Water resources

The 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]. However, abstraction of seawater and outflows to the ocean are recorded in the water asset account as reductions from and additions to inland water resources respectively.

For coastal areas, the interfaces between freshwater and marine systems are particularly important. Groundwater in coastal aquifers may be subject to saltwater intrusion, and estuarine systems represent transitional zones. 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.

3.5 Ecosystem Assets

SEEA Ecosystem Accounting extends asset accounting to treat ecosystems as integrated spatial units^[65]. An ecosystem asset is defined as a "contiguous space of a specific ecosystem type characterised 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. 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

Ecosystem extent is the size of an ecosystem asset, measured in units of area (or, for some marine ecosystems, length or volume)^[67]. Ecosystem extent accounts record the opening and closing extent of each ecosystem type and the changes during the accounting period.

Structure of extent accounts. The structure follows the standard asset account format^[68]:

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

Ecosystem 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"^[70]. Conversions may be human-induced (e.g., conversion of mangroves to aquaculture ponds) or natural (e.g., succession of wetland types). Within the extent account, the total area of all ecosystem types should equal the total ecosystem accounting area, such that additions to one type correspond to reductions in another.

Marine 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"^[71]. This seabed-based approach accommodates the three-dimensional nature of marine ecosystems while providing a practical basis for area measurement and mapping. 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"^[72].

The 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)^[73]. For guidance on mapping marine ecosystem extent using remote sensing and spatial data, see TG-4.1 Remote Sensing Data.

The 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

Ecosystem condition refers to the quality of an ecosystem measured in terms of its abiotic and biotic characteristics^[74]. Condition accounts record the state of ecosystem assets using a suite of condition variables and indicators, enabling tracking of ecosystem health and integrity over time.

Structure of condition accounts. The SEEA EA describes a three-stage measurement approach^[75]:

1. Condition variable accounts -- record raw values of condition characteristics (e.g., species richness, water quality parameters)
2. Condition indicator accounts -- transform variables into comparable indicators, typically scaled against a reference condition
3. Condition indices -- aggregate indicators into composite measures for communication (optional)

Selection of condition variables. Condition variables should be selected based on their relevance to the ecosystem type, data availability, and connection to ecosystem integrity^[76]. 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 pressures^[77]. The SEEA EA groups condition characteristics into six classes^[78]:

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

For guidance on indicators derived from ecosystem condition accounts, see TG-2.1 Biophysical Indicators.

Relationship between extent, condition, and service capacity

The capacity of an ecosystem to deliver services depends on both its extent and its condition. SEEA EA Figure 6.1 illustrates this relationship: ecosystem extent determines the spatial scale of potential service delivery, while ecosystem condition determines the quality and intensity of service flow per unit area^[79]. Together, they determine the overall capacity to deliver ecosystem services, which is then realised through actual service flows to economic units.

Figure 3.5.1: Relationship between ecosystem extent, condition, and service capacity (adapted from SEEA EA Figure 6.1)^[79:1]

This 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

To 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)^[80]. The ECT provides a universal structure for organising condition characteristics across all ecosystem types, grouping them into abiotic, biotic, and landscape-level categories.

Table 3: Illustrative marine condition variables structured by ECT class (based on SEEA EA Table 5.1)^[80:1]

The SEEA EA recommends that, 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, providing a minimum level of comprehensiveness in the full set of condition variables^[81]. Each variable should be compared against a reference condition representing "good" or "natural" state, enabling transformation 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 asset^[82]. 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 5.7^[83].

Reference conditions. Condition indicators are typically expressed relative to a reference level representing "good" or "natural" condition^[84]. The choice of reference condition--historical baseline, minimally impacted area, or policy target--has significant implications for interpretation and should be clearly documented. 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"^[85].

3.5.3 Monetary ecosystem asset accounts

Monetary ecosystem asset accounts record the value of ecosystem assets. The SEEA EA presents two main valuation approaches^[86]:

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

The 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. The restoration cost approach provides an alternative that does not require service valuation but may not reflect the full economic value of the asset. For detailed guidance on valuation of ecosystem services, see TG-1.9 Valuation and TG-2.4 Ecosystem Goods and Services.

Structure of monetary ecosystem asset accounts

The 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 values^[87]. Table 4 presents the standard structure of the account, classified by ecosystem type.

Table 4: Structure of monetary ecosystem asset account with illustrative synthetic values in thousand currency units (adapted from SEEA EA Table 10.1)^[87:1]

The accounting entries distinguish five broad types of change in the monetary value of ecosystem assets^[88]:

• Ecosystem enhancement records the increase in the monetary value of an ecosystem asset that is associated with an improvement in the condition of the asset during the accounting period. Enhancement incorporates the effects of activities--including reductions in harmful activities--that improve condition beyond merely maintaining it, as well as natural and unmanaged improvements in condition.
• Ecosystem degradation records the decrease in the monetary value of an ecosystem asset that is associated with a decline in the condition of the asset during the accounting period. Degradation represents a cost analogous to depletion for individual natural resources and should be deducted in calculating adjusted income measures.
• Ecosystem conversions record additions and reductions in monetary value resulting from changes in ecosystem type at a given location. A decrease in value is recorded for the ecosystem type from which area has been converted, and an increase for the type to which it has been converted; there is no expectation that these will be offsetting in monetary terms.
• Other changes in volume capture two categories: catastrophic losses, which are decreases in value due to large-scale, discrete and recognisable events that cause significant loss in ecosystem condition; 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)^[89].
• Revaluation records changes in the monetary value of ecosystem assets that are due solely to movements in the unit prices of ecosystem services, distinct from any actual 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)^[90].

The 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.

For 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-1.9 Valuation should be used.

It should be noted that the 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.

Degradation. In SEEA EA, ecosystem degradation represents the decline in condition multiplied by the associated loss of future ecosystem service flows, valued in monetary terms^[91]. Degradation plays an analogous role to depletion for individual assets, representing a cost that should be deducted in calculating net income measures. 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"^[92].

3.6 Produced Assets in the Ocean Domain

While the focus of environmental-economic accounting is on environmental (non-produced) assets, ocean accounts must also consider produced assets located in or used for ocean-based activities. Produced assets are "assets that have come into existence as outputs of production processes"^[93] and include fixed assets, inventories, and valuables.

Types of produced assets in the ocean domain

Key categories include:

Aquaculture fixed assets -- cages, pens, nets, and other infrastructure used for raising cultivated aquatic resources, as well as breeding stocks held as fixed assets^[94]. These are produced assets in the sense that they result from deliberate investment decisions. For detailed guidance, see TG-3.9 Aquaculture Accounts.

Offshore 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.

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

Coastal protection structures -- sea walls, groynes, revetments, and other engineered structures designed to protect coastal areas from erosion and flooding. These may be considered alongside natural coastal protection services provided by ecosystems such as mangroves and coral reefs^[95].

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

Accounting treatment

Produced 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 terms^[80:2].

For ocean accounting, the important linkages are between produced assets and environmental assets. For example:

• Aquaculture investment creates produced assets (infrastructure) that work in conjunction with environmental assets (water quality, marine ecosystems providing supporting services)
• Offshore oil and gas investment creates produced assets that enable extraction of environmental assets (mineral resources)
• Coastal infrastructure may protect inland assets but may also affect coastal ecosystem extent and condition

These 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

This section presents a worked example demonstrating 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), illustrating the compilation procedure described in Section 3.2 and the account structures presented in Sections 3.4 and 3.5.

Scenario description

The 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

Extent 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 Data). Change detection analysis identified conversions between ecosystem types and losses to non-natural land cover.

Physical extent account (area in km²)

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

Interpretation: The coastal zone experienced net loss of 3.2 km² of mangroves and 0.8 km² of seagrass during 2025. Managed reductions (conversion to aquaculture ponds) exceeded managed expansion (restoration projects). Natural reductions from storm damage and coastal erosion also contributed to extent loss. Continental shelf waters showed no change in extent, as the accounting area boundary remained fixed.

Step 2: Ecosystem condition accounts

Condition 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.

Condition variable account for mangroves (selected variables)

Table 6: Ecosystem condition variables for mangroves, 2025

Interpretation: Mangrove condition declined slightly during 2025, with canopy density decreasing from 72% to 70%, leaf litter production declining from 480 to 465 g/m²/yr, and connectivity index falling from 0.68 to 0.65. These changes suggest degradation pressure, likely associated with the conversion of adjacent mangrove areas to aquaculture and storm damage reducing patch size and increasing fragmentation.

Step 3: Fish stock asset account

Fish 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.

Physical asset account for fish stocks (biomass in tonnes)

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

Interpretation: The fish stock declined from 42,000 tonnes to 38,000 tonnes during 2025, a reduction of 4,000 tonnes (9.5%). Gross catch of 7,200 tonnes exceeded the sustainable yield estimate of 6,500 tonnes by 700 tonnes, indicating depletion. The stock also experienced a catastrophic loss of 500 tonnes from a hypoxia event in coastal waters during summer. The combination of overfishing and environmental stress contributed to stock decline.

Step 4: Monetary valuation

Monetary 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.

Mangrove ecosystem services valuation:

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

Seagrass ecosystem services valuation:

• Carbon sequestration: USD 50/tonne CO₂ x 6 tonnes CO₂/ha/yr = USD 300/ha/yr
• Water filtration: Avoided treatment cost USD 150/ha/yr
• Fish nursery: USD 600/ha/yr
• Total annual service value: USD 1,050/ha/yr
• Asset value (4% discount): USD 1,050 / 0.04 = USD 26,250 per hectare

Fish stock valuation:

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

Monetary ecosystem asset account (values in USD thousand)

Table 8: Monetary ecosystem asset account, 2025

Fish stock monetary asset account (values in USD thousand)

Table 9: Monetary fish stock asset account, 2025

Interpretation: Despite physical decline in ecosystem extent and fish stock biomass, monetary values increased slightly due to revaluation (holding gains from price increases). For mangroves, the 5% increase in unit service values (driven by updated coastal protection valuations following storm damage in a neighboring region) generated USD 8.25 million in holding gains, offsetting degradation and conversion losses. For fish stocks, a 10% increase in market prices generated USD 7.3 million in holding gains, offsetting the value of depletion.

This result illustrates an important distinction in asset accounting: price increases can mask physical depletion in monetary accounts. Adjusted income measures should deduct depletion at constant prices to avoid the misleading signal that rising resource prices can compensate for unsustainable extraction. The SEEA CF emphasizes that "depletion should be valued at the average of opening and closing prices" to provide a neutral mid-period valuation^[36:1], and changes in asset value due to price effects should be reported separately as revaluations rather than real income.

Step 5: Integration and policy implications

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

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

• TG-1.1 National Ocean Budgets: The USD 1.76 million in ecosystem degradation plus USD 225,000 in fish stock depletion (total USD 1.985 million 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.
• TG-2.1 Biophysical Indicators: The 0.64% 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.
• TG-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.

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

• TG-4.1 Remote Sensing Data: Sentinel-2 imagery provided the primary data source for extent change detection, demonstrating the operational feasibility of satellite-based ecosystem monitoring.
• TG-4.2 Survey Methods: Field monitoring at 45 stations provided condition variable measurements, highlighting the continuing need for in-situ data to complement remote sensing.
• TG-4.3 Geospatial Data Integration: 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.

Cross-account consistency:

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

This worked example illustrates how asset accounts provide a structured framework for organizing 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.

4. Acknowledgements

Authors: Jordan Gacutan (GOAP Secretariat), Mitchell Lyons (GOAP Secretariat)

Reviewers: Laura Friedrich, Jessica Andrews, Kirsten Oleson