OA and Marine Spatial Management (including MPAs)

1. Outcome

This Circular provides operational guidance on using Ocean Accounts to support marine spatial management decisions, including Marine Protected Area (MPA) designation and effectiveness assessment, adaptive management approaches, and integration of conservation finance. Readers will understand how to apply ecosystem accounting frameworks--specifically ecosystem extent accounts, condition accounts, and ecosystem services accounts--to address three core decision contexts: (1) MPA designation--identifying priority areas for protection using extent and condition baselines; (2) effectiveness monitoring--tracking conservation outcomes through time-series condition accounts and comparing protected versus unprotected areas; and (3) economic impact assessment--quantifying how spatial restrictions affect ecosystem service flows and economic dependencies. The Circular demonstrates the downward connections from policy questions through accounting structures to specific indicators, enabling practitioners to move from high-level conservation targets (Kunming-Montreal Global Biodiversity Framework 30x30, SDG 14.5) to measurable account entries and back to evidence-based management adjustments.

The guidance builds on the foundational concepts presented in TG-0.1 General Introduction to Ocean Accounts and supports the indicator derivation framework described in TG-2.1 Aggregate Biophysical Indicators, which addresses how aggregate condition indices derived from the accounting structures described here can inform protected area management and monitoring. For the broader spatial planning context within which MPAs are embedded, see TG-1.2 Marine Spatial Planning.

2. Requirements

• TG-0.1 General Introduction to Ocean Accounts -- provides foundational understanding of Ocean Accounts components, including the distinction between ecosystem assets, environmental assets, and ecosystem services.

3. Guidance Material

3.1 Marine spatial management and MPAs

Marine spatial management encompasses the governance mechanisms through which human activities in marine areas are planned, regulated, and monitored. This includes Marine Spatial Planning (MSP), which organizes the spatial allocation of ocean activities, and the designation and management of Marine Protected Areas (MPAs), which restrict or regulate activities in specific geographic areas to achieve conservation objectives^[1]. The United Nations Convention on the Law of the Sea (UNCLOS) establishes the legal framework for marine protection, requiring States to take measures to "protect and preserve the marine environment" (Part XII, Article 192) while recognizing sovereign rights over resources within Exclusive Economic Zones (EEZs)^[2].

MPAs serve multiple conservation objectives: protecting biodiversity and habitat, enabling recovery of depleted fish stocks, maintaining ecosystem services such as coastal protection and carbon sequestration, and supporting scientific research and environmental education. However, the effectiveness of MPAs varies substantially depending on management intensity, design characteristics, enforcement capacity, and the degree to which they are integrated into broader spatial planning frameworks^[3]. Achieving conservation targets set by international agreements--including the Kunming-Montreal Global Biodiversity Framework target to protect 30% of marine areas by 2030--requires robust information systems to guide MPA designation, monitor outcomes, and support adaptive management^[4].

Ocean Accounts provide a structured approach to organizing information relevant to marine spatial management. As noted in TG-0.1, Ocean Accounts can be applied to "particular areas within national jurisdictions (e.g., bays, protected areas)" and constitute "a statistical framework for measuring the ocean, its importance to people, and what people are doing to change it." This Circular applies the general framework to the specific context of MPAs and marine spatial management, drawing primarily on SEEA Ecosystem Accounting (SEEA EA) methodology. The relevance of ocean accounts for marine conservation is also recognized in CBD Decisions 15/24 (2022) and 16/1 (2024), which call on countries to implement ocean accounts as a basis for conservation and sustainable management of marine resources^[5].

3.2 Decision use cases for Ocean Accounts

Ocean Accounts support MPA management through three primary decision contexts, each requiring specific account types and analytical approaches.

3.2.1 Use Case 1: MPA designation and target tracking

Decision context: Countries must identify priority areas for protection to meet international commitments (Kunming-Montreal GBF Target 3: 30% of marine areas by 2030; SDG 14.5: at least 10% coverage) while ensuring ecological representativeness and connectivity. Designation decisions require baseline information on ecosystem distribution, condition, and irreplaceability.

Account types required:

• Ecosystem extent accounts (SEEA EA Chapter 4) -- record the spatial distribution and area of each ecosystem type within the Ecosystem Accounting Area (EAA), providing the foundation for calculating protected area coverage and assessing representativeness. For marine applications, extent accounts distinguish coastal and marine ecosystem types following the IUCN Global Ecosystem Typology, including seagrass meadows (M1.1), kelp forests (M1.2), photic coral reefs (M1.3), shellfish beds (M1.4), subtidal rocky reefs (M1.6), mangroves (MFT1.2), and pelagic water column ecosystems^[6].
• Ecosystem condition accounts (SEEA EA Chapter 5) -- document baseline ecosystem health at the time of designation using the Ecosystem Condition Typology (ECT), enabling identification of high-integrity areas warranting protection and degraded areas requiring restoration-focused management.
• Governance accounts (SEEA EA Chapter 13, Section 13.4) -- record existing MPA designations by IUCN category, management effectiveness ratings, and spatial overlap with ecosystem types.

Key indicators derived:

• MPA coverage as percentage of total marine area by ecosystem type
• Representation index showing which ecosystem types are under- or over-represented in protected areas
• Baseline condition index for newly designated MPAs

Operational procedure: Compilers should first establish the EAA corresponding to national marine waters (territorial sea and EEZ). Ecosystem extent accounts are compiled using the IUCN GET marine ecosystem classification, with Basic Spatial Units (BSUs) at a resolution sufficient to distinguish MPA boundaries (typically 100m-1km for coastal areas, coarser for offshore). Each BSU is attributed to an ecosystem type and protection status (IUCN categories Ia-VI, or unprotected). The extent account aggregates BSU areas by ecosystem type and protection status, producing a cross-tabulation that reveals coverage gaps. Condition accounts are compiled for a subset of high-priority ecosystem types (typically coral reefs, seagrass, mangroves) using available monitoring data. Reference conditions should be established using historical baselines, comparison with protected reference sites, or ecological modelling. The resulting extent and condition data inform spatial prioritization, with high-condition unprotected areas and low-representation ecosystem types identified as designation priorities.

3.2.2 Use Case 2: MPA effectiveness monitoring

Decision context: MPA managers and conservation agencies must assess whether protection is achieving intended outcomes--maintaining or improving ecosystem condition--and whether management interventions (zoning, enforcement, restoration) require adjustment. Effectiveness assessment requires comparison of outcomes against expectations or counterfactuals.

Account types required:

• Ecosystem condition accounts (time-series) -- track changes in condition variables within MPAs across accounting periods, distinguishing abiotic characteristics (physical and chemical state), biotic characteristics (compositional, structural, and functional state), and seascape characteristics (connectivity, fragmentation). The time-series enables detection of trends and attribution of changes to management interventions versus external drivers^[7].
• Ecosystem asset accounts (SEEA EA Chapter 10) -- record ecosystem degradation (decline in condition) and ecosystem enhancement (improvement in condition) in monetary terms, enabling integration with economic accounts and assessment of whether protection is maintaining the natural capital base.
• Ecosystem services accounts (SEEA EA Chapter 6) -- measure changes in ecosystem service flows (fish provisioning, coastal protection, carbon sequestration, recreation) associated with changes in extent and condition, linking conservation outcomes to human wellbeing.

Key indicators derived:

• Ecosystem Condition Index (ECI) trends for protected versus unprotected areas
• Area under effective protection (combining extent with condition criteria)
• Change in ecosystem service capacity attributable to protection

Operational procedure: Effectiveness monitoring requires establishing a baseline condition account at or near the time of MPA designation, followed by periodic re-compilation (annually for intensively monitored sites, every 3-5 years for standard monitoring). Condition variables are selected from the ECT based on data availability and policy relevance, with priority given to variables responsive to management interventions (e.g., coral cover, fish biomass, water quality for marine reserves). Each condition variable is normalized against its reference value to produce a condition indicator on a 0-1 scale, with indicators aggregated into an overall Ecosystem Condition Index using area-weighted averaging. Comparing ECI trends inside versus outside MPAs provides evidence of protection effectiveness. Where condition is improving, this is recorded as ecosystem enhancement in the asset account; where declining, as degradation. For robust effectiveness assessment, compilers should establish comparable condition accounts for unprotected control sites matched to MPA characteristics, enabling counterfactual comparison.

3.2.3 Use Case 3: Economic impact assessment of spatial restrictions

Decision context: Policymakers must assess the economic implications of MPA restrictions on fishing, tourism, and other marine uses, balancing conservation benefits against livelihood impacts and economic opportunity costs. This requires integrated environmental-economic analysis.

Account types required:

• Ecosystem services supply and use accounts (SEEA EA Chapter 6) -- record flows of provisioning services (wild fish, genetic resources), regulating services (coastal protection, climate regulation), and cultural services (recreation, education) from marine ecosystems to economic beneficiaries, enabling quantification of service flows before and after spatial restrictions.
• Monetary ecosystem services accounts (SEEA EA Chapter 9) -- value ecosystem services in monetary units consistent with SNA conventions, enabling comparison of ecosystem service values with GDP contributions from extractive industries.
• Extended supply-use tables (SEEA EA Chapter 11) -- integrate ecosystem services with conventional economic production, revealing dependencies of ocean-based industries on ecosystem service inputs and distributional effects of spatial restrictions across sectors.

Key indicators derived:

• Ecosystem service value per hectare by protection status
• Economic dependency ratio (ocean industry GDP / ecosystem service value)
• Distributional incidence of MPA restrictions across sectors and communities

Operational procedure: Economic impact assessment begins with ecosystem services supply accounts that quantify service flows in physical units (tonnes of fish provisioned, volume of coastal protection service, recreation visitor-days). Supply is attributed to specific ecosystem assets (MPAs, adjacent fishing grounds) using spatial models that link ecosystem characteristics to service generation. Use accounts record which economic units (fishing enterprises, tourism operators, coastal households) receive these services. Monetary valuation applies methods consistent with SEEA EA Chapter 9: exchange values for provisioned fish, avoided damage cost for coastal protection, travel cost or contingent valuation for recreation. Comparing service values before and after MPA designation reveals net economic effects. Where MPA restrictions reduce extractive service flows (reduced fishing area) but enhance long-term service capacity (stock recovery, habitat restoration), the extended supply-use framework enables integrated assessment of short-term costs versus long-term benefits. For detailed guidance on ecosystem services valuation, see TG-2.4 Ecosystem Goods and Services.

3.3 Information needs for MPA management

Effective MPA management requires comprehensive information across multiple dimensions. Decision-makers need data to support: (1) designation decisions--identifying areas of high conservation value or management priority; (2) baseline establishment--documenting ecosystem condition and services at the time of protection; (3) performance monitoring--tracking changes in ecosystem health and effectiveness of management interventions; (4) adaptive management--adjusting management strategies based on observed outcomes; and (5) reporting--communicating results to stakeholders and contributing to national and international assessments^[8].

These information needs align closely with the accounting structures defined in SEEA EA. The framework identifies four categories of accounts particularly relevant to MPA management:

Ecosystem extent accounts record the area of different ecosystem types within the accounting area (SEEA EA Chapter 4). For MPAs, extent accounts can document the spatial coverage of marine ecosystem types such as coral reefs, seagrass meadows, kelp forests, mangroves, and pelagic waters. The IUCN Global Ecosystem Typology (GET) provides a standardized classification for marine ecosystem functional groups, including the Marine Shelf biome (M1) with categories such as 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)^[6:1].

Ecosystem condition accounts track the health and integrity of ecosystems relative to a reference condition (SEEA EA Chapter 5). Condition accounts are organized according to the Ecosystem Condition Typology (ECT), which distinguishes abiotic characteristics (physical state such as sea surface temperature and current patterns; chemical state such as pH and dissolved oxygen), biotic characteristics (compositional state such as species diversity; structural state such as coral cover; functional state such as primary productivity), and landscape/seascape characteristics (spatial configuration, connectivity, fragmentation)^[7:1].

Ecosystem services accounts measure the contributions of ecosystems to people, organized through supply-use frameworks (SEEA EA Chapter 6). Relevant marine ecosystem services include provisioning services (wild fish provisioning), regulating services (coastal protection, global climate regulation through carbon sequestration, water purification), and cultural services (recreation, tourism, spiritual and educational values)^[9].

Ecosystem asset accounts track changes in the value and stock of ecosystem assets over time, including degradation (decline in condition) and enhancement (improvement in condition). These accounts enable assessment of whether management interventions are maintaining or improving the natural capital base within protected areas (SEEA EA Chapter 10)^[10].

3.4 Ocean accounts for monitoring ecosystem health

Ocean Accounts support MPA monitoring by providing standardized frameworks for data compilation, enabling comparison across sites and over time. The accounting approach emphasizes completeness (covering all relevant ecosystem types within the MPA boundary), consistency (applying the same classifications and methods across accounting periods), and coherence (ensuring data from different sources can be integrated)^[11].

3.4.1 Establishing baseline accounts

When an MPA is designated, compiling baseline accounts establishes the starting point against which future changes can be measured. Baseline ecosystem extent accounts document the spatial distribution of ecosystem types at the time of protection, providing the foundation for monitoring changes in habitat coverage--for example, detecting expansion or contraction of seagrass meadows or coral reef area.

Baseline ecosystem condition accounts document the health status of ecosystems at designation. For marine ecosystems, relevant condition variables may include:

• Abiotic physical state: Water temperature, salinity, turbidity, current patterns, bathymetric characteristics
• Abiotic chemical state: Dissolved oxygen, pH (ocean acidification), nutrient concentrations, pollutant levels
• Biotic compositional state: Species richness, community composition, abundance of indicator species, presence of threatened species
• Biotic structural state: Coral cover percentage, seagrass canopy height and density, kelp forest biomass, mangrove stem density
• Biotic functional state: Primary productivity, fish recruitment rates, trophic structure, decomposition rates
• Seascape characteristics: Habitat patch size distribution, connectivity between reef systems, fragmentation of coastal wetlands

SEEA EA recommends measuring condition relative to a reference condition that reflects, where possible, the natural or undegraded state of the ecosystem (SEEA EA para 5.69)^[12]. For marine ecosystems, establishing appropriate reference conditions may require drawing on historical data, scientific literature, expert knowledge, or comparison with similar unimpacted areas.

Table 1 illustrates a simplified ecosystem condition account structure for an MPA.

Table 1: Illustrative ecosystem condition account for a marine protected area

Note: Condition index calculated as observed value divided by reference value. Values less than 1 indicate degradation relative to reference condition.

3.4.2 Condition indices and aggregation

Individual condition variables can be aggregated into composite condition indices to provide summary assessments of ecosystem health. The accounting framework supports aggregation through the Ecosystem Condition Index (ECI), which summarizes condition across multiple variables relative to the reference condition. An ECI value of 1 indicates reference condition, while values below 1 indicate degradation^[13].

For MPA management, condition indices can be constructed at different scales: individual ecosystem assets (e.g., a specific reef), ecosystem types within the MPA (e.g., all coral reef area), or the entire protected area. Tracking changes in these indices over time provides a quantitative basis for assessing whether management interventions are achieving conservation objectives. The methodology for constructing aggregate condition indices is detailed in TG-2.1 Aggregate Biophysical Indicators, including guidance on aggregation approaches (arithmetic mean, geometric mean, weighted mean) and their implications for interpretation.

Figure 1.3.1 illustrates how condition indices can be tracked over time to assess MPA effectiveness. The illustrative time series shows an ecosystem condition trajectory for a hypothetical MPA, demonstrating how observed condition can be compared against a target threshold to evaluate whether management interventions are achieving their intended outcomes.

Figure 1.3.1: Illustrative MPA ecosystem condition trajectory showing observed condition index (blue line) with 95% confidence interval (shaded area) relative to target condition threshold (green dashed line)^[14]

3.5 Measuring MPA effectiveness

Ocean Accounts support assessment of MPA effectiveness by providing a framework for comparing outcomes inside protected areas against expectations or against conditions outside protected areas. Effectiveness assessment addresses the central question: are the restrictions and management interventions associated with MPA designation achieving their intended conservation outcomes?

3.5.1 Accounting for ecosystem degradation and enhancement

SEEA EA provides explicit accounting treatments for changes in ecosystem condition. Ecosystem enhancement is defined as "the increase in the value of an ecosystem asset over an accounting period that is associated with an improvement in the condition of the asset during that accounting period" (SEEA EA para 10.15), while ecosystem degradation is defined as "the decrease in the value of an ecosystem asset over an accounting period that is associated with a decline in the condition of the ecosystem asset during that accounting period" (SEEA EA para 10.21)^[15]. These accounting entries enable tracking of whether ecosystems within MPAs are improving (net enhancement), stable (no net change), or declining despite protection (net degradation).

The accounting framework distinguishes between changes due to human activity (recorded as degradation or enhancement) and changes due to natural processes (recorded as other changes in volume). This distinction is analytically important for MPA assessment--for example, distinguishing coral decline due to reduced local pressures (management success) from decline due to thermal stress associated with climate change (external driver). The operational approach involves attributing observed condition changes to drivers through expert assessment, scientific literature, or statistical attribution studies. Where decline is observed in both protected and unprotected areas, and scientific evidence links the decline to climate-driven thermal stress, the change is attributed to natural processes (other volume changes) rather than management failure. Where decline is observed only in poorly enforced MPAs but not in well-enforced sites experiencing similar environmental conditions, the differential is attributed to management effectiveness and recorded as anthropogenic degradation.

3.5.2 Ecosystem services as effectiveness indicators

Changes in ecosystem services flow provide another dimension for assessing MPA effectiveness. Accounts can track whether protection is maintaining or enhancing the capacity of marine ecosystems to deliver services such as:

• Fish provisioning: Monitoring fish biomass and catch per unit effort in areas adjacent to no-take zones to assess spillover effects
• Coastal protection: Measuring changes in wave attenuation capacity of reef systems or mangrove forests within the MPA
• Carbon sequestration: Quantifying carbon storage in seagrass meadows, mangroves, and other blue carbon ecosystems
• Recreation and tourism: Recording visitor numbers, satisfaction levels, and economic contributions from MPA-based tourism

The extended supply-use tables in SEEA EA enable integration of ecosystem services data with economic accounts, facilitating analysis of how changes in MPA ecosystem health translate into economic outcomes for dependent communities and industries (SEEA EA Chapter 11)^[16]. For detailed guidance on compiling ecosystem services accounts for marine ecosystems, see TG-2.4 Ecosystem Goods and Services. The combined presentation of ecosystem and economic accounts is addressed in TG-3.8 Combined Presentations.

3.5.3 Counterfactual analysis

Robust effectiveness assessment often requires counterfactual analysis--comparing outcomes within the MPA against what would have occurred without protection. Accounting frameworks support this by enabling compilation of comparable accounts for unprotected control sites, or by establishing time-series that show changes before and after MPA designation. The standardized structure of accounts facilitates such comparisons by ensuring consistent measurement approaches across sites and time periods.

The counterfactual approach requires selecting control sites that are comparable to the MPA in terms of baseline ecosystem characteristics, environmental conditions, and human pressure levels, but differ in protection status. Condition accounts are compiled for both MPA and control sites using identical variable selection, reference conditions, and aggregation methods. The difference in condition trends between MPA and control sites provides an estimate of the treatment effect attributable to protection. Where baseline data exist from before MPA designation, a before-after-control-impact (BACI) design can be applied, comparing the change in MPA condition (after minus before) with the change in control site condition over the same period. This design controls for environmental variability and regional trends that affect both protected and unprotected areas.

3.6 Linking accounts to conservation targets

Ocean Accounts serve as an information system that connects local MPA management to national and international conservation commitments. This "accounts-to-targets" linkage operates at multiple levels.

3.6.1 SDG 14 and marine conservation

The 2030 Agenda for Sustainable Development includes SDG 14 "Life Below Water" with targets directly relevant to marine spatial management. SDG Target 14.5 calls for countries to "conserve at least 10 per cent of coastal and marine areas, consistent with national and international law and based on the best available scientific information," with indicator 14.5.1 measuring "coverage of protected areas in relation to marine areas"^[17]. SDG Target 14.2 addresses sustainable management and protection of marine and coastal ecosystems, monitored through indicator 14.2.1 on "proportion of national exclusive economic zones managed using ecosystem-based approaches."

Ocean Accounts provide the information foundation for reporting against these targets. Ecosystem extent accounts can directly inform reporting on protected area coverage, while condition and services accounts support assessment of whether protection is achieving intended ecosystem management outcomes. The alignment between ocean accounts and SDG 14 indicators is detailed in TG-2.10 Multilateral Environmental Agreement Indicators.

3.6.2 Kunming-Montreal Global Biodiversity Framework

The Kunming-Montreal Global Biodiversity Framework, adopted at CBD COP15 in December 2022, establishes the ambition to protect 30% of marine areas by 2030 (Target 3) and to ensure that areas under protection are "effectively conserved and managed" through "ecologically representative, well-connected and equitably governed systems of protected areas"^[18]. The Framework explicitly calls for integration of biodiversity values into national accounting processes (Target 14), and related CBD decisions have specifically recognized the role of ocean accounts in supporting marine conservation^[5:1].

Ecosystem accounts provide a mechanism for operationalizing these commitments. Extent accounts track progress toward coverage targets. Condition accounts assess whether protected areas meet criteria for "effective conservation." Services accounts document the benefits that flow from protected marine ecosystems to people and economies. The explicit connection between SEEA EA and international biodiversity frameworks is described in SEEA EA Chapter 12, which addresses links to IPBES and other assessment processes^[19].

3.6.3 TNFD and corporate reporting

The Taskforce on Nature-related Financial Disclosures (TNFD) recommendations establish a framework for businesses to report on nature-related dependencies, impacts, risks, and opportunities. For organizations with marine operations or supply chain dependencies, Ocean Accounts compiled for MPAs provide relevant data on ecosystem condition and services that can inform TNFD disclosures, particularly through the LEAP (Locate, Evaluate, Assess, Prepare) approach to identifying nature-related issues^[20]. The TNFD framework aligns with ecosystem services concepts from SEEA EA, recognizing that "healthy ecosystems are a prerequisite for the sustained flow of ecosystem services that communities need to survive and flourish, and that business and finance depend on to generate cashflows and returns."

3.6.4 Adaptive management and decision cycles

Beyond static reporting, accounts support adaptive management by providing a systematic basis for tracking outcomes and adjusting strategies. The cyclical nature of accounting--with regular updates to extent, condition, and services data--aligns with adaptive management frameworks that emphasize learning from management interventions and adjusting approaches based on observed results.

For MPA managers, accounts can inform decisions such as:

• Zoning adjustments based on observed changes in ecosystem condition
• Resource allocation priorities based on identification of degraded areas requiring restoration
• Stakeholder engagement supported by clear communication of ecosystem trends
• Investment decisions supported by assessment of ecosystem services benefits

3.7 Worked Example: MPA Effectiveness Assessment

This section presents a synthetic worked example demonstrating how ecosystem condition accounts can be applied to assess MPA effectiveness using a before-after-control-impact (BACI) design. All data are hypothetical but structured to illustrate operational procedures.

3.7.1 Scenario

A coastal nation designated a 15,000-hectare marine protected area in 2018 to protect coral reef ecosystems. The MPA includes 3,500 ha of coral reef habitat, 4,000 ha of seagrass meadows, and 7,500 ha of pelagic water column. Management objectives include maintaining coral cover above 30%, improving fish biomass to within 20% of unfished levels, and ensuring water quality meets reference conditions for pH and nutrient levels. A control site of comparable size and baseline characteristics but without protection restrictions was identified 50 km away.

3.7.2 Baseline condition account (2018)

At the time of designation, baseline condition accounts were compiled for both the MPA and control site using field surveys, remote sensing, and water quality monitoring. The following condition variables were measured:

Table 2: Baseline condition variables for MPA and control site (2018)

Notes: DIN = dissolved inorganic nitrogen. Reference values based on regional historical data and comparison with remote pristine sites. Fish biomass reference is 30% of unfished biomass, following SEEA EA guidance on sustainable yield reference points.

3.7.3 Normalizing condition indicators

Each condition variable is normalized to a 0-1 scale using the reference value. For variables where higher values indicate better condition (water clarity, fish biomass, coral cover, seagrass density), the indicator is calculated as:

Indicator = Observed / Reference

For inverse variables where lower values indicate better condition (DIN), the polarity is reversed:

Indicator = (Reference - Observed) / (Reference - Lower threshold)

where Lower threshold is set at the value indicating fully degraded condition.

Table 3: Baseline condition indicators (2018)

The baseline Ecosystem Condition Index (ECI) is calculated as the arithmetic mean of the six condition indicators. Both sites show degraded condition (ECI < 1), with the MPA site marginally better than the control site.

3.7.4 Monitoring results (2024)

After six years of protection and enforcement, condition monitoring was repeated at both sites using identical protocols.

Table 4: Monitoring results and condition indicators (2024)

3.7.5 Effectiveness interpretation

The MPA site showed substantial improvement in condition (ECI increased from 0.64 to 0.79), while the control site showed slight decline (0.61 to 0.58). The treatment effect--the difference in change between MPA and control--is +0.18 points on the ECI scale, indicating that protection contributed approximately 18 percentage points of condition improvement beyond background environmental trends.

Breaking down by variable:

• Fish biomass showed the largest improvement (+0.27 points), consistent with expected responses to fishing restrictions
• Coral cover improved substantially (+0.20), suggesting reduced physical damage and improved water quality enabled coral recovery
• Water clarity and nutrient levels both improved, likely reflecting reduced sediment disturbance from fishing gear and lower nutrient inputs from restricted coastal development
• pH showed minimal change at both sites, as ocean acidification is driven by global atmospheric CO2 and is not amenable to local management

3.7.6 Ecosystem asset accounting

The condition improvement in the MPA is recorded as ecosystem enhancement in the monetary ecosystem asset account. Using the perpetuity valuation method described in SEEA EA Chapter 10, the present value of the ecosystem asset increased due to improved condition. The calculation proceeds as follows:

1. Baseline asset value (2018): The coral reef ecosystem within the MPA (3,500 ha) generated ecosystem services valued at $500/ha/year at baseline condition (ECI = 0.64). Using a 4% discount rate and perpetuity assumption, the baseline asset value = ($500/ha × 3,500 ha) / 0.04 = $43.75 million.

2. Current asset value (2024): After condition improvement to ECI = 0.79, the service flow increased proportionally to $618/ha/year (assuming linear relationship between condition and service capacity). The current asset value = ($618/ha × 3,500 ha) / 0.04 = $54.08 million.

3. Ecosystem enhancement: The increase in asset value attributable to improved condition = $54.08M - $43.75M = $10.33 million over the six-year period, or approximately $1.7 million per year on average.

This enhancement value quantifies the economic benefit of improved natural capital condition resulting from MPA management, and can be presented alongside management costs to assess return on conservation investment.

3.7.7 Limitations and caveats

This worked example simplifies several aspects of real-world MPA assessment:

• Attribution: The analysis assumes the difference between MPA and control outcomes is attributable to protection, but other factors (differential enforcement, community engagement, coincident management interventions) could contribute.
• Baseline comparability: Perfect matching of control sites is rarely achievable; residual differences in baseline characteristics may confound treatment effects.
• Spatial heterogeneity: Within-MPA variation in condition may be substantial; the example presents aggregate figures but operational assessments should examine spatial patterns.
• Temporal lags: Ecosystem responses to protection occur at different timescales; six years may be insufficient for slow-responding variables (e.g., structural complexity, apex predator recovery).

Despite these limitations, the accounting framework provides a structured, replicable approach to MPA effectiveness assessment that improves on ad-hoc monitoring by ensuring consistent measurement, explicit reference conditions, and integration with economic accounts.

4. Acknowledgements

This Circular has been approved for public circulation and comment by the GOAP Technical Experts Group in accordance with the Circular Publication Procedure.

Authors: Rekam Nusantara Foundation, Thauan Santos

Reviewers: Jordan Gacutan (GOAP Secretariat), Laura Friedrich, Rebecca Shellock (GOAP Secretariat)

5. References