Towards a National Ocean Account

The first edition of the National Ocean Account is a view on what will be possible for future publications. This edition publishes experimental methods and data on mangrove and seagrass extent, condition, carbon stocks and selected ecosystem services. Additional information on saltmarsh and kelp will be released later in 2022. While each of these datasets is a preliminary and broad estimate, they are an insight into what is feasible into the future.

This paper

This discussion article highlights what was learnt through the development of the current publication. It is also a call for comments on the functionality and use of the accounts in this format, the methodology employed to produce the estimates, and whether there is a need for more geographically detailed and repeatable accounts.

The Department of Climate Change, Energy, the Environment and Water, in partnership with the Australian Bureau of Statistics, is leading implementation of a National Strategy and Action Plan for Environmental-Economic Accounting. The National Ocean Ecosystem Account is funded as part of the $22.9 million commitment to support implementation of the Strategy.

In 2018 Australia became a member of High Level Panel for a Sustainable Ocean Economy (Ocean Panel). This panel aims to increase international understanding of how sustainable use of the oceans – and the ocean economy – can play a key role in meeting the world's most vital needs in the years to come. Accounting for the coastal/marine environment is a key component of Australia’s participation in the Ocean Panel. Ocean accounts provide organised environmental-economic information that describes our relationship with the ocean.

Since October 2021, the Department of Climate Change, Energy, the Environment and Water and the Australian Bureau of Statistics have been working in collaboration on the first Ocean Account, an Experimental National Ocean Ecosystem Account.  This Account has been compiled by the Australian Bureau of Statistics in accordance with the standards set out in the United Nations System of Environmental-Economic Accounting - Ecosystem Accounting.

Advice was sought from experts in the fields of marine ecology, seagrass, mangroves, saltmarsh and kelp to ascertain the most appropriate data sources and metrics to use in the accounts. Experts on environment economic accounting were also consulted on the form and main considerations of creating ecosystem accounts. As a result of an extensive consultation process, the following input data sources were selected:

Mangrove extent, characteristic of condition

 Digital Earth Australia (DEA) Mangrove Canopy Cover (Landsat) This product provides information about the extent and canopy density of mangroves for each year between 1987 and 2021 for the entire Australian coastline. 

Seagrass extent and condition

Seamap Australia – National Marine Benthic Habitat Map

Seamap Australia provides a synthesis of all national benthic habitat mapping data into one spatial data product using a national benthic marine classification scheme for the Australian continental shelf location. Seamap Australia – National Marine Benthic Habitat Map

Collation of spatial seagrass data (meadow extent polygons, species presence/absence points) from 1984 - 2014 for the Great Barrier Reef World Heritage Area (GBRWHA) (NESP TWQ 3.1, TropWATER, JCU) | eAtlas

This dataset summarises 30 years of seagrass data collection (1984-2014) within the Great Barrier Reef World Heritage Area. The Site data describes seagrass at 66,210 sites; while the Meadow data describes seagrass at 1,169 individual or composite meadows. The data includes information on species, meadow type and age and reliability of the data. The dataset is available as shapefiles, GIS layer packages, and/or a CSV file. Data represented in this dataset has been collected by the TropWATER Seagrass Group and CSIRO in a GIS database.

NESP MaC Project 1.13 – Synthesizing three decades of seagrass spatial data from Torres Strait and Gulf of Carpentaria 2021-2022 (JCU) | eAtlas

This data is an overview of the NESP Marine and Coastal Hub small-scale study - "Synthesizing three decades of seagrass spatial data from Torres Strait and Gulf of Carpentaria".

Carbon stocks

Carbon stocks were modelled using the estimates for the extend of seagrass and mangroves. The dataset used in the paper below was used to generate per hectare carbon estimates for mangrove and seagrass.

National scale predictions of contemporary and future blue carbon storage - PubMed (nih.gov)

Carbon sequestration

Carbon sequestration was modelled based on the BlueCAM carbon model, using the account extent estimates for seagrass and mangroves.

Blue carbon accounting model (BlueCAM) technical overview (cleanenergyregulator.gov.au)

BlueCAM uses Australian data to estimate abatement from carbon and greenhouse gas sources and sinks arising from coastal wetland restoration (via tidal restoration) and aligns with the Intergovernmental Panel for Climate Change guidelines for national greenhouse gas inventories. BlueCAM includes carbon sequestered in soils and biomass and avoided emissions from alternative land uses (Lovelock, Adame et al. 2022)  

Modelling was conducted to estimate coastal protection services of mangroves and carbon stocks and sequestration, which is described under the metrics section of this paper.

 More detail on the methodology and input dataset can be found in the methodology release associated with The National Ocean Account.

The ecosystem accounts are based on the SEEA Ecosystem Accounting (SEEA EA). This framework uncovers the interactions between ecosystems and the economy by looking at ecosystems and their contribution to human well-being in the form of identifiable ecosystem services.  Figure 1 shows the ecosystem accounts and how they relate to each other (image taken from the United Nations SEEA-EA website. Ecosystem Accounting | System of Environmental Economic Accounting

Most ecosystems services are public goods that do not have clear market prices to allow their valuation. An advantage of an accounting framework is that it allows the contributions of ecosystems to be expressed in financial terms.

Ocean accounts provide a standardised and consistent framework for the integration of data, to enable the measurement of progress towards local, national, and global priorities. The accounts can inform on a range of ocean related policies and generally support the management of a healthy and resilient ocean, integrating biodiversity into planning, and going “Beyond GDP” to produce more holistic statistics and indicators to measure the contribution of oceans to society and the economy.

These accounts represent the most current and comprehensive data available at the national scale for mangrove and seagrass extent, condition, carbon stocks and sequestration and mangrove coastal protection services. While creating a time series for seagrass estimates is not possible from current data, these accounts provide a basis from which changes can be measured over time.

Experimental methods have been developed to integrate multiple data sources to compile these accounts where data exists, or to model metrics where it was feasible to do so. Further consultation will be undertaken with users and the scientific community to refine the models and data compilation processes with the aim of developing a set suite of methods that can be used to produce accounts into the future. This will not only ensure spatial and temporal consistency in the accounts, but also inform data providers of the standards and classifications required to provide ‘account ready’ data for account input.

An important component of creating ecosystem accounts is to highlight where there are significant data gaps that impact on our ability to create evidence-based policy.

This release includes ocean ecosystem accounts formatted as ideal accounts, with opening and closing stocks for each ecosystem asset account. However, the high number of NA (data not available) cells in the tables highlights the lack of nationally coherent data available to complete these accounts. If we are to have sufficient information to create robust and meaningful policy, these gaps must be filled through increased investment in research. The data gaps are particularly pronounced in seagrass meadow extent, where no reliable, current estimates exist at a national scale. Without this background data, estimates for carbon stock and sequestration and condition of seagrass cannot be produced with a high level of confidence.

A complete sequence of accounts is attractive from a statistical perspective because once complete they reflect a comprehensive integration of data from various sources that can convey a coherent narrative on economic, environmental and social changes. However, compiling accounts simply to present coherent data is not sufficient. It is important that the accounts meet the needs of users and can inform their decisions.

A human-centred design approach with end-users was (and continues to be) taken to develop accounts that are appropriate for their needs and aims.

Some of the questions that ocean accounts are designed to address are:

1. How much ocean resources are left?
2. What are the measures that can lead to a balanced discussion on trade offs?
3. Is Ocean health improving?
4. What services do Ocean ecosystems provide?
5. What are the impacts of development of coastal resources?

The overall scope of the National Ocean Ecosystem Account includes ecosystem extent, condition and carbon asset stocks for kelp, seagrass, saltmarsh and mangroves as well as two ecosystem services: carbon sequestration and coastal protection. The accounts will be released in two stages, with the second stage being released in November 2022. Table 1 outlines the ecosystem accounts to be included in the National Ocean Ecosystem Account. Stage 1 of the release focuses on accounts for Mangrove and Seagrass.

The National Ocean Ecosystem Account is presented at a range of geographic scales, including:

• national,
• state, and
• regional.

National Oceans Account boundary

This is the geographic extent of Australia, including Australia’s marine waters and excluding external territories such as Antarctica.

State and Territory boundaries

The state and territory boundaries for offshore areas is defined under the Offshore Petroleum and Greenhouse Gas Storage Act (OPGGSA). The boundaries are set out in a Schedule to the OPGGSA Act and are thus referred to as the Scheduled Areas Boundaries, the data can be downloaded from http://pid.geoscience.gov.au/dataset/ga/144572.

Regional boundaries

Based on user consultation, reporting based on ecological boundaries rather than administrative boundaries was determined to be the most appropriate division. Due to the spatial extent of the ecosystems in these accounts, a regional geography that encompassed both terrestrial and marine environments was required. Geoscience Australia’s Primary sediment compartments have been determined to be the most relevant divisions for substate reporting (figure 1). The data can be downloaded from: Australian_Coastal_Sediment_Compartments (MapServer) (ga.gov.au). Where these sediment compartments cover water that is outside Australia’s EEZ, this area has not been included in the accounts.

The Primary Coastal Sediment Compartment data set represents a regional (1:250 000 - 1:100 000) scale compartmentalisation of the Australian coastal zone into spatial units within (and between) which sediment movement processes are considered to be significant at scales relevant to coastal management. The data set was generated and attributed using expert panel knowledge of coastal geomorphology and processes, and represent compartment boundaries along the coast. Environmental attributes used to determine the location of compartment (point) boundaries are given in priority order below.

Gross lithological/geological changes (e.g. transition from sedimentary to igneous rocks).

Geomorphic (topographic) features characterising a compartment boundary (often bedrock-controlled) (e.g. peninsulas, headlands, cliffs).

Dominant landform types (e.g. large cuspate foreland, tombolos and extensive sandy beaches versus headland-bound pocket beaches).

Changes in the orientation (aspect) of the shoreline.

Table 3 shows the metrics produced in the account tables.

Hectares of mangrove and seagrass nationally, in each state and in each sediment compartment are reported for this metric. The scope for seagrass extent is limited to data with mapped seagrass extent, therefore it does not include some areas of seagrass further offshore for which there is no mapped data available.

Mangrove – Canopy cover change (characteristic of condition)     

The mangrove characteristic of condition account uses the Geoscience Australia DEA Mangrove Canopy Cover (Landsat) change product. The product presents change in mangrove cover from the previous year. For instance, the change in mangrove canopy cover from 1987 to 1988 gives the characteristic of condition category for 1988. These yearly characteristics of condition are compiled into a timeseries from 1989 onwards. 

Seagrass condition

Condition is represented by density of cover which is provided as a variable in the tropical seagrass data sourced from TropWATER (James Cook University). This data covers the Great Barrier Reef, the Torres Strait and the Gulf of Carpentaria. Regions outside of these areas will not have condition values for the first stage of the release. For the second stage of the release we expect to include seagrass threats into the accounts, which are outlined below.

Seagrass – Frequency of high rainfall event (threat to condition)

National scale condition of seagrass data is not available so a threat account will be produced as an alternative in the second stage of the release. River discharge poses a threat to seagrass through the increase in turbidity and/or pollutants and nutrients into the seagrass habitat.  As seagrass tolerance to river discharge differs depending on location and species, a relative measure will be used; which will be a percent increase above average level of river discharge into seagrass meadows. Thus meadows accustomed to a high level of river discharge will only be considered under threat if the discharge is significantly above what the meadow is acclimatised to.

Seagrass - Storm damage

In addition to river discharge, storm damage may be included as a threat to seagrass meadows. This compliments the river discharge data as there are a number of seagrass meadows in areas without river inputs.

Saltmarsh and kelp are being discussed in consultation with experts to determine the most appropriate metrics for condition or threat.

A model has been used to determine which mangroves provided coastal protection. Mangroves that were within 200m of the coastline and had a belt width of at least 90m were assumed to provide costal protection services. The protection afforded by these mangroves forests was considered to be 1km from the coastline.  Figure 2 shows how mangroves were determined to be in scope for protection services.

Figure 2. Section of coastline showing which mangroves were considered to provide coastal protection.  Yellow is total extent of mangroves in the area, green is mangrove forests with a width of at least 90m, and the purple lines are transects that extent 1km inland from the coast. Any meshblocks that the purple lines transect will be included in the count of coastal protection for people and property.

This is a measure of the length of total coastline that is covered by mangrove stands as described above. The accuracy of the length of coastline depends on the scale of the maps used to make the determination. Geoscience Australia’s DEA Coastlines Product (annualised shoreline 2020, in a GDA_1994_Australia_Ablers projection) was used to calculate length of the coastline that includes both mainland coastline and the length of all islands. As distinguished from mainland coastline. 

More information on total length of Australia's coastline as reported by Geoscience Australia can be found here Coastline lengths.

The cost to replace the service provided by the ecosystem is a recommended valuation technique in the United Nations SEEA Ecosystem Account standards (paragraphs 9.50-9.51) and was endorsed through user consolation as a suitable measurement of the ecosystem service. A model that estimates the value of coastal protection provided by mangroves and saltmarsh has been created by estimating the cost to maintain built infrastructure that would provide the same service.

The total replacement cost is estimated as the per meter cost of seawall construction, multiplied by the length of coastline that currently receives coastal protection services from mangroves.

The service replacement cost is estimated as the estimated annual capital depreciation of seawall infrastructure that would provide a similar service. Straight line depreciation has been assumed model.

Due to the variable nature of the coastline and seawall construction options a range of per meter values have been used based on estimates provided by Ware and Banhalmi-Zakar (2017), which were increased in line with the Producer Price Index to produce 2021 values. A mean of these values was used to simplify the model, producing a per meter value of seawall construction of $11600. Expected lifespan values of between 25 and 100 years were used, resulting in a minimum and maximum estimate. The mean estimated cost is based on a lifespan of 62.5 years

This metric is a count of the population and number of dwellings that are afforded protection by mangroves. The count was derived through counting the meshblocks that are within 1km of the coastline behind the in- scope mangrove patches, as shown in figure 2. The number of dwellings and population in these meshblocks was then summed for each sediment compartment and state. As some meshblocks are very large and cover more than the 1km radius considered in scope, in some cases this will lead to an over count of dwellings and population protected.

Data for dwelling count and population count come from the 2021 census. The population count was based on Persons Usually Resident: This is the count of people where they usually live, which may or may not be where they were on Census Night.

For the dwelling count, a dwelling was defined as a structure which is intended to have people live in it, and which is habitable on Census Night. Unoccupied private dwellings are also counted with the exception of those in caravan parks, marinas and manufactured home estates.

Mangrove, saltmarsh and seagrass

Estimates of carbon stocks for mangrove, saltmarsh and seagrass have been calculated by Young et al. (2021) (see data section above). These data were used to produce an average value of carbon per hectare of mangrove or seagrass, which was then applied to the extent data to produce estimates of tonnes of carbon.

Kelp

Measurement of kelp carbon stocks is under discussion with scientific experts.

Mangrove, saltmarsh and seagrass –

Carbon sequestration of seagrass and mangrove have been calculated using the Blue Carbon Method (Lovelock, Adame et al. 2022), based on the extent of mangrove forests and seagrass meadows that we have produced in this publication.

The assumptions used for mangrove forests assumed a normal distribution of age centred around the mid-point of an expected life of mangrove (100 years). And growth was assumed to be incremental for the year measured. An age-stock estimate of mangroves would help to distribute sequestration more precisely but unlikely to be available in the near future.

The assumptions for seagrass meadows were based around the maturation age of most seagrass genus (10 years) and sequestration based on the increment over the year of that as a generalised assumption for measuring carbon sequestered.

Carbon sequestered in soil and vegetation were included in the calculation of final carbon sequestration services.

Kelp

Measurement of kelp carbon sequestration is under discussion with scientific experts

There are a number of challenges to compiling national ocean accounts.

The first release of the National Ocean Account focuses on four key blue carbon ecosystems, mangroves, saltmarsh, seagrass and kelp. Ideally the number of ecosystems would be expanded in the future to develop a full suite of ocean ecosystem accounts describing all ocean ecosystems in Australian waters. This could include an extended range of ecosystem services and their economic value, for example fishers and tourism services. This would provide Australia with a greatly improved knowledge base to manage oceans ecosystems, resources and economy. In order to produce this expanded range of accounts, increased focus is needed on collecting relevant data, and on developing methodologies to understand and evaluate ecosystem services.

Refining some of the methodology used in these experimental accounts will be a priority as the accounts develop. These accounts represent a first attempt to consolidate the available information on the blue carbon ecosystems included. Some of the simple models have been developed as a starting point to generate feedback from experts and users of the accounts, to determine if the metrics are useful and if the models need to be refined. For example, the mangrove coastal protection model has a fixed extent inland of protection from the mangrove forest. Further work could refine this model to include topological and hydrodynamic features that impact the distance inland that can be affected by wave damage.

The oceans are a largely undiscovered resource. While there are many ongoing efforts to fill in these gaps from across the world, there are still many areas that require further work. Relatively shallow water ecosystems such as seagrass are more accessible than deep ocean ecosystems, yet we still do not have a comprehensive understanding of the extent and condition of these ecosystems, let alone the services that they are providing for Australia. The seagrass extent account published here is based on survey data that has been collected over the span of 3 decades, and only covers seagrass meadows located in the most accessible sites. While this is useful to give an idea of the extent of areas that provide suitable habitat for seagrass, if we are to produce meaningful accounts into the future we need to understand how the extent of seagrass changes over time. For comprehensive ocean accounts to have meaning and practical applications, we need to reduce the uncertainty of measurements in these areas.

Accounts cannot change the way we interact with oceans. Changes are made by decision makers who have the spirit or the vision to maximise the potential of our natural resources. The challenge here is to understand how governments and investors will use information to make the best decisions, both in the interests of economic development and for maintaining oceans for future generations.

The second stage of the National Ocean Ecosystem Account will be released in November. This will include not only additional accounts for saltmarsh and kelp ecosystems, but also updates to the first stage release accounts. Prior to the next release we will be conducting further user consultation to gain feedback on the first phase accounts. We are also seeking feedback from the public on the methodology and metrics used in these accounts. If you would like to comment please refer to the feedback details at the bottom of the page.

Future releases will work closely with the scientific community to refine the methodology used to compile the accounts

If you would like to provide feedback on any aspect of the National Ocean Ecosystem Account, please contact environment@abs.gov.au.