Kelp Forest and Temperate Reef Accounting

1. Outcome

This Circular provides guidance on compiling ecosystem accounts for kelp forests and temperate rocky reef ecosystems within the ocean accounting framework. These ecosystems represent highly productive habitats in temperate and polar coastal waters, supporting complex food webs, significant biodiversity, and a range of ecosystem services including fisheries habitat, coastal protection, and emerging contributions to carbon cycling. However, methodological development for accounting of these systems remains less advanced than for tropical marine ecosystems such as coral reefs and mangroves. This Circular is classified as Emerging to reflect both the ecological importance of these systems and the current limitations in standardised measurement approaches. Unlike TG-6.1 Coral Reef Accounts or TG-6.2 Mangrove and Coastal Wetland Accounts which build on more established monitoring frameworks, kelp and temperate reef accounting lacks comparable standardised approaches, and users should interpret guidance as indicative rather than prescriptive.

Readers will gain an understanding of the ecological characteristics that define kelp forests and temperate reefs, the challenges associated with measuring their extent and condition, the ecosystem services they provide, the step-by-step procedures for compiling accounts, and the priority areas for methodological development. This Circular also demonstrates upward connections from biophysical accounts to decision-relevant indicators for marine protected area management, kelp restoration targeting, and fisheries habitat assessment. The extent and condition accounting methods presented here build on the foundational asset accounting framework established in TG-3.1 Asset Accounts, while the ecosystem services treatment follows the measurement and valuation approaches described in TG-2.4 Ecosystem Goods and Services and TG-1.9 Valuation. For comparison with other marine ecosystem types, see TG-6.1 Coral Reef Accounts and TG-6.3 Seagrass Accounts. Given the emerging status of this guidance, uncertainty in methods and data is explicitly acknowledged, and users are encouraged to document methodological choices transparently and contribute to the evolving knowledge base.

Decision use cases

Kelp forest and temperate reef accounts support several priority decision contexts:

Kelp restoration prioritisation: Extent and condition accounts identify degraded areas suitable for restoration intervention. Condition indicators tracking canopy density, urchin barrens extent, and species richness provide baseline data for restoration site selection and success monitoring. The kelp-to-barren transition dynamics documented in Section 3.1 inform restoration feasibility assessment, as areas recently transitioned to barren states may be more amenable to recovery than long-established barrens with hysteresis dynamics.

Urchin barren remediation: Phase shift dynamics between kelp-dominated and urchin barren states (Section 3.1) inform management interventions. Condition accounts tracking urchin density and predator abundance guide culling programmes and predator reintroduction efforts. The hysteresis effects documented here indicate that threshold-based management is required: prevention of kelp loss requires lower urchin densities than recovery from established barrens.

Temperate reef fisheries support: Extent accounts quantifying reef area and connectivity inform fisheries management plans for reef-associated species (rock lobster, abalone, temperate reef fish). Condition indicators for herbivore biomass and structural complexity (rugosity) provide early warning of trophic cascade effects that may reduce fisheries productivity. Integration with fisheries accounts (TG-6.7 Fisheries Accounting) enables assessment of habitat-fisheries linkages.

Marine protected area effectiveness: Condition accounts compiled inside and outside marine protected areas support quantitative evaluation of protection effectiveness. Kelp extent change and condition indicator time series reveal whether protected areas are achieving conservation objectives for temperate reef ecosystems. The comparison approach is analogous to that described for coral reef MPAs in TG-6.1 Coral Reef Accounts Section 3.2.

Climate change vulnerability assessment: Temperature anomaly indicators (Section 3.2) and extent change attributable to marine heatwaves (Section 3.1) provide spatially explicit climate impact metrics. These indicators support upward connection to national climate reporting obligations and inform climate adaptation planning for ocean ecosystems. For guidance on linking biophysical indicators to climate policy frameworks, see TG-2.1 Biophysical Indicators Section 3.4.

2. Requirements

This Circular requires familiarity with:

• TG-0.1 General Introduction to Ocean Accounts -- provides foundational understanding of Ocean Accounts components and the conceptual framework linking environmental, economic, and social dimensions of ocean accounting.

• TG-3.1 Asset Accounts -- for the foundational methodology of ecosystem extent, condition, and asset accounting on which kelp forest and temperate reef accounts are structured, including the standard extent account format and condition indicator framework.

Compilers will also benefit from familiarity with TG-4.1 Remote Sensing Data for mapping approaches applicable to subtidal ecosystems, TG-2.1 Biophysical Indicators for deriving condition indicators from biophysical measurements and connecting accounts to policy indicators, and TG-0.7 Quality Assurance for uncertainty documentation and quality management. As methodological development progresses, derivative circulars (for example, specialised kelp carbon accounting guidance) may be developed when carbon sequestration methods mature.

3. Guidance Material

Kelp forests and temperate rocky reefs are among the most productive marine ecosystems, supporting high biodiversity and providing essential ecosystem services to coastal communities^[1]. The IUCN Global Ecosystem Typology classifies kelp forests as Functional Group M1.2 within the Marine Shelf biome (M1), while subtidal rocky reefs are classified as M1.6^[2]. Both ecosystem types occur in nearshore rocky substrates in temperate and polar waters, with kelp forests distinguished by the presence of large brown macroalgae that form canopy structures analogous to terrestrial forests^[3].

Despite their ecological and economic importance, accounting for kelp forests and temperate reefs presents significant methodological challenges. Unlike coral reefs, which have been the focus of extensive monitoring programmes and satellite-based mapping, kelp and temperate reef ecosystems have received less systematic attention in environmental-economic accounting contexts^[4]. This section provides guidance on extent accounting (Section 3.1), condition assessment (Section 3.2), ecosystem services (Section 3.3), account compilation procedures (Section 3.4), and identifies priority data and methodological gaps (Section 3.5). For the foundational ecosystem accounting methodology upon which this guidance builds, see TG-3.1 Asset Accounts. For comparison with tropical biogenic marine ecosystems, see TG-6.1 Coral Reef Accounts and TG-6.3 Seagrass Accounts.

3.1 Extent Accounting

Ecosystem extent accounts record the area of kelp forests and temperate reef ecosystems and changes in this area over accounting periods, following the structure described in TG-3.1 Asset Accounts^[5]. For these subtidal ecosystems, extent measurement presents particular challenges related to their subsurface nature, dynamic boundaries, and seasonal variability.

Ecosystem type definitions

Kelp forests (IUCN GET M1.2) are characterised by dense canopies of large brown macroalgae of the Order Laminariales^[6]. Key genera include Macrocystis (giant kelp), Laminaria, Ecklonia, Lessonia, and Eisenia. These kelps can grow to over 30 metres in length and grow rapidly (up to 0.5 metres per day), producing substantial biomass that supports complex trophic networks^[7]. Kelp forests occur on hard rocky substrates in the photic zone, typically to depths of 30 metres, though this varies with water clarity^[8]. They are limited to temperate and polar waters, being absent from warm tropical waters except in upwelling zones off Peru, the Galapagos, Namibia, Oman, and Cape Verde^[9].

Subtidal rocky reefs (IUCN GET M1.6) are characterised by hard minerogenic substrates supporting communities of macroalgae, sessile invertebrates, and associated mobile fauna^[10]. Unlike kelp forests, rocky reefs lack dense macroalgal canopies, with algal growth kept in check by herbivory, storm disturbance, and depth-related light limitation^[11]. Mosaics of turf algae, encrusting organisms, and bare rock are typical, with community composition varying along gradients of depth, exposure, and herbivore abundance.

For accounting purposes, the boundary between kelp forests and rocky reefs may be dynamic, as kelp canopies can expand or contract in response to environmental conditions and herbivore populations^[12]. The distinction between M1.2 and M1.6 is ecologically important but may be difficult to operationalise in practice. Compilers should establish clear criteria for distinguishing these ecosystem types, document the canopy density thresholds or classification rules applied, and record the rationale for any reclassification decisions. National standards may vary, and transparency about classification choices is essential for comparability.

Mapping challenges

Mapping the extent of kelp forests and temperate reefs is complicated by several factors:

Subtidal location. Unlike intertidal or emergent ecosystems, subtidal kelp and rocky reef habitats cannot be directly observed from above the water surface in most conditions. This limits the applicability of conventional aerial and satellite remote sensing^[13].

Water column effects. Light penetration through the water column is affected by depth, turbidity, and surface conditions. Remote sensing of benthic habitats requires correction for water column effects, which adds uncertainty to extent estimates^[14]. The SEEA EA notes that marine ecosystems extend "throughout the water column and include the underlying sediment and seabed"^[15], creating three-dimensional complexity that area-based extent measures may not fully capture.

Canopy structure variability. Some kelp species form floating surface canopies (e.g., Macrocystis), while others have subsurface canopies (e.g., Laminaria, Ecklonia). Surface-canopy kelp can be detected using satellite imagery, but subsurface kelp requires different approaches^[16].

Seasonal dynamics. Kelp biomass can vary substantially across seasons, with growth in spring and summer followed by senescence and storm-related losses in winter. Extent estimates from single time points may not capture the full annual range^[17]. To address this challenge in annual accounting, compilers should consider standardising the observation period--for example, recording extent at the late summer maximum--or applying multi-temporal averaging approaches that integrate observations across seasons. The choice of approach and its rationale should be documented. This issue is less acute for coral reefs, which show less pronounced seasonality.

Recommended approaches

Given these challenges, a tiered approach to extent mapping is recommended:

Tier 1 (basic): Use existing global or regional habitat maps, such as the UN Environment World Conservation Monitoring Centre's Ocean Data Viewer or national marine habitat mapping programmes. Accept that spatial resolution and temporal currency may be limited^[18].

Tier 2 (intermediate): Combine satellite remote sensing of surface-canopy kelp with acoustic surveys or diver transects for subsurface habitats. Use multi-temporal imagery to account for seasonal variation^[19]. For guidance on remote sensing data acquisition and processing, see TG-4.1 Remote Sensing Data.

Tier 3 (advanced): Develop high-resolution benthic habitat maps using multibeam sonar, underwater video transects, and species distribution modelling. Integrate with satellite time series for surface-canopy kelp to track interannual changes^[20].

Extent account structure

The structure of the extent account follows the standard format for ecosystem assets^[21]:

Table 1: Structure of ecosystem extent account for kelp forests and temperate reefs (adapted from SEEA EA Table 4.1)

Transitions between ecosystem types. A distinctive feature of kelp and reef systems is the potential for phase shifts between alternative stable states. Kelp forests can transition to "urchin barrens"--rocky substrates dominated by sea urchins with minimal macroalgal cover--when herbivore populations increase following the loss of predators^[22]. These trophic cascades represent significant ecosystem conversions that should be recorded in extent accounts. The classification of urchin barrens is currently unresolved, with options including: (a) treating barrens as degraded M1.6 rocky reef; (b) creating a separate category such as "M1.6b Urchin barrens"; or (c) tracking the kelp-to-barren transition as a condition variable rather than an extent change. Different choices have implications for how kelp recovery would be recorded in accounts. Compilers should document their chosen approach and its rationale, recognising that international guidance on this classification may evolve.

Phase shift dynamics

The transition between kelp-dominated and urchin barren states is characterised by nonlinear dynamics and hysteresis, meaning that the conditions required to trigger degradation differ from those required for recovery. The following table summarises the key characteristics of each phase state:

Table 2: Kelp-urchin phase shift characteristics

Recovery from urchin barrens requires temperature decrease OR urchin removal AND kelp reseeding. The recovery threshold is higher than the degradation threshold (hysteresis), meaning that simply reversing the conditions that caused degradation is often insufficient to restore the kelp-dominated state. Compilers should note that phase shifts may result in persistent ecosystem state changes that affect both extent and condition accounts over multiple accounting periods.

3.2 Condition Assessment

Ecosystem condition accounts record the quality of kelp forest and temperate reef assets using indicators that reflect their biotic and abiotic characteristics^[23]. Condition assessment for these systems should address both structural attributes (canopy extent, biomass) and functional characteristics (productivity, community composition), as well as key stressors affecting ecosystem integrity. For the general methodology of ecosystem condition accounting, see TG-3.1 Asset Accounts Section 3.4.2. For guidance on deriving biophysical indicators from condition accounts and connecting them to policy frameworks, see TG-2.1 Biophysical Indicators.

Condition variables

The SEEA EA identifies six classes of condition characteristics applicable to marine ecosystems: physical state, chemical state, compositional state, structural state, functional state, and landscape/seascape context^[24]. For kelp forests and temperate reefs, recommended condition variables include:

Physical and chemical state:

• Sea surface temperature and subsurface temperature profiles
• Nutrient concentrations (nitrate, phosphate)
• Dissolved oxygen levels
• Sedimentation rates

Compositional state:

• Kelp species diversity and relative abundance
• Presence/absence of key canopy-forming species
• Abundance of herbivores (particularly sea urchins)
• Abundance of apex predators (e.g., sea otters, large fish)
• Invasive species presence

Structural state:

• Canopy extent (for kelp forests)
• Canopy height and density
• Understorey algal cover
• Sessile invertebrate cover
• Reef structural complexity (rugosity)

Functional state:

• Primary productivity
• Herbivory rates
• Recruitment of key species
• Kelp detritus export

Landscape context:

• Connectivity to adjacent ecosystem types
• Proximity to pollution sources
• Level of protection (marine protected area status)

Climate stressors

Climate change poses significant threats to kelp forests and temperate reefs, and condition accounts should incorporate indicators of climate-related stress^[25]. Climate stress indicators may overlap with pressures recorded in SEEA Central Framework physical flow accounts. Compilers should consider how condition accounts for kelp systems relate to broader climate indicators and pressure accounts, ensuring consistency and avoiding double-counting. For the relationship between ecosystem condition and climate-related pressures, see TG-2.1 Biophysical Indicators.

Ocean warming. Kelp forests have truncated thermal niches and are sensitive to elevated temperatures^[26]. Marine heatwaves have caused widespread kelp losses in multiple regions, including the documented decline of Ecklonia radiata forests in Western Australia following the 2011 marine heatwave^[27]. Temperature-related stress may manifest as reduced growth rates, increased susceptibility to disease, or range contractions.

Ocean acidification. While the direct effects of acidification on kelps are variable, reduced pH can affect calcifying organisms such as coralline algae, sea urchins, and shellfish that are integral components of reef communities^[28].

Storm regime changes. Kelps rely on strong holdfasts to resist wave action, but increased storm intensity can dislodge kelp and create gaps in canopy cover^[29]. Recovery from storm disturbance depends on recruitment success and may be impaired if environmental conditions have shifted.

Reference conditions

Condition indicators should be expressed relative to a reference level representing ecosystem integrity^[30]. For kelp forests and temperate reefs, establishing appropriate reference conditions is challenging because:

1. Long-term baselines are often lacking--systematic monitoring of these systems is relatively recent
2. Many systems have been affected by fishing pressure, pollution, and climate change for decades or centuries
3. Natural variability in these dynamic systems is high

Reference condition uncertainty is particularly acute for kelp systems. Unlike coral reefs where historical records and paleoecological data may be available, kelp forest baselines are often limited to recent decades. Compilers should clearly document the reference conditions applied and the rationale for their selection, recognising that historical reconstructions, minimally impacted reference sites, or modelled baselines may each be appropriate depending on context^[31]. Transparency about baseline limitations is essential for meaningful condition assessment.

Urchin barren transitions

A key indicator of condition degradation in kelp forests is the transition to urchin barrens^[32]. This phase shift occurs when predator removal (through overfishing or disease) releases sea urchin populations from top-down control, leading to intensive grazing that eliminates kelp canopy. Urchin barrens are characterised by:

• Absence or near-absence of canopy-forming kelp
• High densities of sea urchins (often in grazing fronts)
• Bare rock or encrusting coralline algae
• Reduced biodiversity compared to kelp forests

Once established, urchin barrens can persist as an alternative stable state, even if predator populations recover, due to positive feedback mechanisms. Condition accounts should track the area of kelp forests in degraded (barren) versus healthy states.

3.3 Ecosystem Services

Kelp forests and temperate reefs provide a range of ecosystem services to coastal communities and the broader economy. The SEEA EA framework for ecosystem services accounting applies to these systems, though quantification of some services remains methodologically challenging^[33]. For the general methodology of ecosystem service measurement and valuation, see TG-2.4 Ecosystem Goods and Services and TG-1.9 Valuation.

Provisioning services

Fisheries habitat. Kelp forests and rocky reefs provide critical habitat for commercially important fish and invertebrate species, including rockfish, sea bass, abalone, lobster, and various bivalves^[34]. The complex three-dimensional structure of kelp canopies and reef substrates offers shelter for juvenile fish, foraging habitat for adults, and attachment surfaces for prey organisms. Fish production associated with these ecosystems contributes to both commercial and recreational fisheries.

For accounting purposes, the contribution of kelp forests and reefs to fisheries production can be approached as a habitat or nursery maintenance service, following the SEEA EA classification^[35]. Measurement may involve estimating the proportion of fish catch attributable to species dependent on these habitats. The SEEA EA describes nursery population and habitat maintenance services as intermediate services that support provisioning of biomass^[36].

Wild-harvested products. Kelp is harvested directly in some regions for use in food, fertiliser, animal feed, and industrial products (alginates, cosmetics). Sea urchins harvested from rocky reefs are a valuable food product, particularly in Asian markets^[37]. These harvests should be recorded as provisioning services, with physical flows measured in tonnes and valued using market prices where available.

Regulating services

Carbon sequestration (emerging research). Kelp forests are highly productive ecosystems with rapid carbon uptake through photosynthesis. However, the role of kelp in long-term carbon sequestration remains an active area of research and considerable uncertainty exists^[38].

Unlike seagrasses and mangroves, kelps do not accumulate carbon in sediments at the site of growth in the same manner as "blue carbon" ecosystems. Instead, kelp-derived carbon may be:

• Consumed by herbivores and respired
• Exported as drift material to other ecosystems, including deep sea sediments
• Remineralised in the water column

Recent research suggests that a significant proportion of kelp-derived carbon may reach the deep ocean where it can be sequestered on long timescales, potentially making kelp forests important for carbon cycling at regional and global scales^[39]. However, quantification methods are not yet standardised, and the SEEA EA notes that carbon sequestration assessments should only consider carbon stored long-term (at least several decades) in the ecosystem^[40]. Current evidence is insufficient to support inclusion of kelp in national blue carbon inventories at the same level of confidence as seagrass, mangrove, or saltmarsh ecosystems. Compilers who choose to include kelp carbon in ocean accounts should clearly flag the provisional nature of current methods and monitor developments in IPCC guidance, which does not currently include kelp in the wetlands supplement for national greenhouse gas inventories.

Coastal protection. Kelp canopies can dampen wave energy and reduce water turbulence, potentially contributing to coastal protection^[41]. However, the magnitude of this service is less well documented than for coral reefs or mangroves, and quantification methods specific to kelp systems are not well established.

Water quality regulation. Kelp forests take up nutrients from surrounding waters, and high kelp productivity can help mitigate eutrophication effects in nutrient-enriched coastal areas^[42].

Cultural services

Recreation and tourism. Kelp forests and temperate reefs are popular destinations for recreational diving and snorkelling, with associated economic activity in coastal communities^[43]. The charismatic megafauna associated with these systems (sea otters, seals, diverse fish assemblages) contributes to their attraction.

Scientific and educational value. These ecosystems are important sites for marine research and education. Long-term monitoring sites, such as those established by the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO), provide valuable scientific data^[44].

Cultural and spiritual significance. Kelp forests and rocky reefs may have cultural significance for coastal Indigenous communities, supporting traditional fishing practices, food security, and cultural identity^[45].

Service quantification challenges

For Emerging-status ecosystems, ecosystem service quantification faces particular challenges:

1. Limited spatial data on ecosystem extent constrains service estimation
2. Ecological production functions (linking ecosystem condition to service flows) are less developed than for coral reefs or mangroves
3. Beneficiary populations and their use of services may be poorly documented
4. Monetary valuation studies are less numerous, limiting benefit transfer approaches

Compilers should document the methods and assumptions used in service quantification and communicate uncertainty to users. For guidance on quality assurance and uncertainty documentation, see TG-0.7 Quality Assurance.

3.4 Compilation Procedure

This section provides step-by-step guidance for compiling kelp forest and temperate reef ecosystem accounts, from spatial delineation through to monetary valuation. The procedure assumes that compilers have access to the prerequisite frameworks described in TG-3.1 Asset Accounts and follow data quality protocols from TG-0.7 Quality Assurance.

Step 1: Define ecosystem accounting area (EAA)

Define the spatial boundary of the accounting area, typically aligned with national marine waters or a regional marine planning area. Document the coordinate system, vertical datum for depth measurements, and seaward boundary (territorial sea, EEZ, or other jurisdictional limit).

Step 2: Delineate ecosystem assets

2.1 Assemble spatial data layers:

• Bathymetric data (depth)
• Substrate classification (rocky vs. soft sediment)
• Water quality data (turbidity, nutrient levels)
• Existing habitat maps (national, regional, or global datasets)

2.2 Apply ecosystem type criteria:

• M1.2 Kelp forests: Rocky substrate + depth 3-30m + kelp canopy present
• M1.6 Temperate reefs: Rocky substrate + depth <50m + no kelp canopy or sparse kelp

2.3 Map ecosystem extent:

• Tier 1: Use existing habitat maps as baseline
• Tier 2: Supplement with satellite imagery for surface-canopy kelp; acoustic surveys for subsurface
• Tier 3: High-resolution multibeam sonar + underwater video transects + species distribution models

2.4 Address seasonal variation:

• Option A: Standardise observation to late summer (maximum canopy extent)
• Option B: Multi-temporal averaging across seasons
• Document chosen approach and rationale

2.5 Generate extent account:

• Calculate opening extent (t0) for each ecosystem type
• Identify additions and reductions during accounting period
• Calculate closing extent (t1)

Step 3: Select condition variables

3.1 Apply SEEA ECT framework:

• Select 1-2 variables per ECT class (A1 physical, A2 chemical, B1 compositional, B2 structural, B3 functional, C1 landscape)
• Aim for 6-10 variables total
• Prioritise variables with available data and policy relevance

3.2 Recommended minimum set:

• B2: Kelp canopy density (plants/m² or % cover)
• B1: Urchin barrens extent (% of reef area)
• B1: Species richness (fish + invertebrate count)
• A1: Water temperature anomaly (°C above baseline)
• B2: Reef rugosity index (structural complexity)
• C1: Connectivity to adjacent kelp patches (habitat fragmentation metric)

3.3 Data collection methods:

• Diver transect surveys for canopy density, species richness, rugosity
• Satellite SST data for temperature anomaly
• Acoustic surveys and video for urchin barren extent
• GIS analysis for connectivity

Step 4: Establish reference conditions

4.1 Select reference condition approach:

• Historical baselines: Pre-1950 or earliest available monitoring data
• Contemporary reference sites: Minimally impacted reefs within biogeographic region
• Modelled baselines: Species distribution models for pristine conditions
• Policy targets: National marine park standards or regional management targets

4.2 Assign reference levels:

• Upper reference level (VH): Value at reference condition (high integrity)
• Lower reference level (VL): Value at degraded/collapsed state

4.3 Example for kelp canopy density:

• VH = 14 plants/m² (historical maximum from reference sites)
• VL = 1 plant/m² (functional threshold below which recruitment fails)

4.4 Document rationale:

• Cite data sources for reference levels
• Explain biogeographic context
• Note limitations and uncertainties

Step 5: Derive condition indicators

5.1 Apply normalisation formula:

For variables where higher values indicate better condition:

Indicator = (V - VL) / (VH - VL)

For variables where lower values indicate better condition (e.g., temperature anomaly, urchin barrens extent):

Indicator = (VH - V) / (VH - VL)

5.2 Calculate indicators for each variable:

• Opening indicators (t0)
• Closing indicators (t1)
• Change in indicators

5.3 Aggregate to composite index (optional):

• Equal-weighted arithmetic mean across indicators
• Or apply ECT-weighted approach if ecological rationale supports differential weighting

Step 6: Quantify ecosystem services

6.1 Prioritise measurable services:

• Fisheries habitat (provisioning)
• Recreation and tourism (cultural)
• Coastal protection (regulating)
• Carbon sequestration (regulating, provisional)

6.2 Fisheries habitat:

• Estimate proportion of commercial catch attributable to kelp/reef habitat
• Apply resource rent method to isolate ecosystem contribution
• Physical units: tonnes of fish
• Monetary units: resource rent (catch value minus costs)

6.3 Recreation and tourism:

• Estimate person-visits to kelp/reef diving sites
• Apply simulated exchange value or travel cost method
• Physical units: person-visits
• Monetary units: consumer surplus or expenditure-based value

6.4 Coastal protection:

• Identify length of coastline protected by kelp/reef
• Estimate wave attenuation capacity (% reduction in wave height)
• Apply avoided damage cost method
• Physical units: km coastline protected
• Monetary units: expected annual damages avoided

6.5 Carbon sequestration (provisional):

• Estimate kelp biomass production (t dry weight/ha/year)
• Apply export coefficient (proportion reaching deep sea)
• Convert to CO2 equivalents
• Flag as provisional with high uncertainty

Step 7: Value ecosystem assets

7.1 Project future service flows:

• Assume stable condition: Use current service values for projection
• Assume degradation trend: Adjust service values based on condition change rate
• Scenario analysis: Model alternative management/climate scenarios

7.2 Select discount rate:

• Social discount rate typically 3-5% for ecosystem assets
• Document rate selection and sensitivity

7.3 Calculate net present value:

Asset value = Σ (Service value year t × Discount factor)

Or for stable flows over projection horizon:

Asset value = Annual service value × Present value annuity factor

7.4 Present value annuity factor (PVAF): For 25-year horizon at 4% discount rate: PVAF = 15.62

Step 8: Compile integrated accounts

8.1 Extent-condition-services linkage:

• Document how condition affects service capacity
• Link condition indicators to service quantification assumptions

8.2 Populate account tables:

• Extent account (Table 1 structure)
• Condition variable account
• Condition indicator account
• Ecosystem services flow account
• Monetary asset account

8.3 Quality assurance:

• Apply quality dimensions: accuracy, completeness, timeliness, coherence
• Document data sources, methods, and limitations for each account component
• Assign quality ratings per TG-0.7 Quality Assurance

Step 9: Connect to policy indicators

9.1 Derive policy-relevant indicators:

• Kelp extent change (% per annum) → MPA effectiveness indicator
• Urchin barren extent (%) → Restoration targeting indicator
• Composite condition index → Ocean health dashboard
• Temperature anomaly trend → Climate vulnerability indicator

9.2 Link to decision contexts:

• Reference decision use cases from Section 1
• Provide indicator time series and spatial maps
• Support management review cycles (e.g., MPA management plans)

For detailed guidance on connecting accounts to policy indicators, see TG-2.1 Biophysical Indicators Section 3.3.

3.5 Data and Methods Gaps

The Emerging status of this Circular reflects significant gaps in data availability and methodological development for kelp forest and temperate reef accounting. This section identifies priority areas for research and capacity building.

Extent mapping

Priority gaps:

• Globally consistent mapping of kelp forest extent remains incomplete
• Subsurface kelp species are poorly captured by current satellite-based approaches
• Temporal coverage is insufficient to distinguish long-term trends from natural variability
• Standardised protocols for classifying transitions between kelp forests, rocky reefs, and urchin barrens are lacking

Development priorities:

• Investment in satellite-based monitoring systems capable of detecting subsurface macroalgae
• Integration of acoustic survey methods with remote sensing
• Development of change detection algorithms suited to dynamic kelp systems^[46]
• Engagement with international research networks such as the Kelp Ecosystem Ecology Network (KEEN) and regional kelp monitoring programmes that may contribute standardised extent data as their outputs mature. The Emerging badge for this Circular may be revisited if major mapping advances emerge from these initiatives.

Condition assessment

Priority gaps:

• Reference conditions for many kelp and reef systems are poorly established
• Relationships between condition indicators and ecosystem integrity are not fully understood
• Monitoring of herbivore (urchin) populations is inconsistent across regions
• Climate change impact attribution methods need development

Development priorities:

• Establishment of long-term monitoring programmes in under-represented regions
• Development of composite condition indices suited to kelp and reef systems
• Improved understanding of phase shift dynamics and early warning indicators^[47]

Carbon accounting

Priority gaps:

• Fate of kelp-derived carbon remains uncertain
• Methods for quantifying carbon export to deep ocean are not standardised
• Inclusion of kelp in "blue carbon" accounting frameworks is debated
• IPCC does not currently include kelp in the wetlands supplement for national greenhouse gas inventories, and any inclusion of kelp carbon in ocean accounts should note this context and the provisional nature of current methods

Development priorities:

• Research to quantify carbon sequestration pathways
• Development of accounting protocols that reflect current scientific understanding
• Coordination with IPCC and blue carbon initiatives^[48]

Valuation

Priority gaps:

• Economic valuation studies for kelp and temperate reef ecosystem services are limited compared to tropical systems
• Resource rent estimates for kelp-associated fisheries are rarely compiled
• Benefit transfer approaches lack locally calibrated studies

Development priorities:

• Primary valuation studies in key regions (North Pacific, Southern Ocean, North Atlantic)
• Integration of kelp forest values into broader natural capital assessments^[49]

3.6 Worked Example

This worked example demonstrates the compilation of kelp forest and temperate reef ecosystem accounts for a hypothetical coastal system in a southern Australian setting. The example follows the extent-condition-services-valuation sequence presented in Section 3 and illustrates the key accounting entries and calculations. Given the Emerging status of this Circular, compilers should treat the methods and values below as indicative rather than prescriptive.

Setting: A national ecosystem accounting area (EAA) containing 6,500 hectares of kelp forest (M1.2, dominated by Ecklonia radiata) and 2,500 hectares of subtidal temperate rocky reef (M1.6), totalling 9,000 hectares of temperate marine ecosystem along the southern continental shelf. The kelp forests extend from 3 to 25 metres depth, with rocky reef habitats occupying deeper and more exposed substrates.

Step 1: Extent account (year t to t+1)

Note: 250 hectares of kelp forest transitioned to urchin barrens following a marine heatwave event. This is recorded as a reclassification from M1.2 to M1.6 (degraded rocky reef), consistent with the phase shift dynamics described in Section 3.1. The net loss of 45 hectares reflects kelp area lost to natural reduction and infrastructure that was not offset by recovery and expansion.

Step 2: Condition account

Condition indicators are derived from diver transect surveys and satellite monitoring, using pre-2010 baselines as reference conditions:

Note: For urchin barrens extent and temperature anomaly, lower values indicate better condition. The indicator formula is inverted: Indicator = (VL - V) / (VL - VH).

Composite condition index (equal weights): (0.58 + 0.66 + 0.60 + 0.60) / 4 = 0.61

Interpretation: A composite condition index of 0.61 indicates that the kelp forest and temperate reef ecosystem is at 61% of reference condition. This moderate condition reflects the combined effects of canopy density reduction, expanding urchin barrens, and elevated water temperatures. The system retains substantial ecological integrity but shows clear degradation signals requiring management attention.

Step 3: Ecosystem services (annual flows)

Note: The carbon sequestration estimate is provisional, reflecting emerging research on kelp-derived carbon export to depth. This value should be interpreted with caution and clearly flagged in accounts, consistent with the guidance in Section 3.3.

Step 4: Asset valuation

Applying a 4% social discount rate over a 25-year projection horizon with stable service flows:

Asset value = 17,130,000 × present value annuity factor (4%, 25 years) Asset value = 17,130,000 × 15.62 = 267,600,000 USD

This worked example illustrates the full accounting sequence for kelp forest and temperate reef ecosystems. Actual compilations will require country-specific data, locally appropriate reference conditions, and primary valuation studies. The Emerging status of this Circular means that several methods--particularly carbon sequestration quantification and the treatment of urchin barren transitions--should be considered provisional. The urchin barren reclassification approach used here (kelp to rocky reef) is one of several possible treatments described in Section 3.1; compilers should document their chosen approach. The example values are illustrative and should not be used as benchmarks for specific national contexts.

Policy indicator derivation:

From this account, several policy-relevant indicators can be derived:

• Kelp extent change rate: -4.7% per annum (-305 ha / 6,500 ha opening extent)
• Urchin barren extent: 22% of reef area (early warning threshold typically 15-20%)
• Composite condition index: 0.61 (moderate condition requiring intervention)
• Climate stress indicator: Temperature anomaly +1.2°C (approaching stress threshold)

These indicators support the decision use cases outlined in Section 1, providing quantitative baselines for restoration targeting, MPA effectiveness assessment, and climate adaptation planning.

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

Reviewers: [To be confirmed]

5. References