AUS - Australia’s first National Ocean Accounts
The oceans are still a largely an undiscovered resource. While there are ongoing efforts across government and the scientific community to improve our knowledge, we are still far from having a comprehensive understanding.
A consistent understanding of our ocean ecosystems and their value allows us to better support the management of a healthy and resilient ocean, make informed decisions on a range of ocean-related policies, and measure their progress over time.
First released in August 2022, the National Ocean Accounts — a collaboration between the Australian Bureau of Statistics (ABS) and the Department of Climate Change, Energy, the Environment and Water (DCCEW) — provide an insight into some of Australia’s key blue carbon ecosystems including mangroves, saltmarsh and seagrass.
Blue carbon ecosystems are coastal or marine ecosystems that sequester (capture and store) large quantities of carbon in both the plants and the sediment below. The Ocean Accounts describe the extent and condition of each ecosystem, as well as some of the ecosystem services they provide — namely, carbon stock, carbon sequestration and coastal protection services.
Ocean accounts provide organised environmental-economic information that describes our relationship with the ocean. The Ocean Accounts are based on the United Nations System of Environmental-Economic Accounting – Ecosystem Accounting. This framework provides a standardised approach to uncovering the interactions between ecosystems and the economy by looking at how ecosystems contribute to human well-being in the form of identifiable ecosystem services.
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In 2018, Australia became a member of the High Level Panel for a Sustainable Ocean Economy. Accounting for the coastal and marine environment is a key component of Australia’s participation in this panel. Work on the Ocean Accounts began in October 2021, with an extensive stakeholder consultation process and advice sought from ecological experts to ascertain the most appropriate data sources and metrics to use in the accounts.
As a new account, the Ocean Accounts are experimental in nature and a main objective was to establish baseline estimates for future work.
Coastal geographies and Earth observation data
When producing any kind of environmental-economic account, it is necessary to define the scope of the area under investigation. The Ocean Accounts are presented at national, state and regional scales. They include Australia’s marine waters out to the Exclusive Economic Zone (EEZ), but exclude external territories such as Antarctica. State and territory boundaries for offshore areas were defined under the Offshore Petroleum and Greenhouse Gas Storage Act, while for regional-level reporting, we used Geoscience Australia’s Primary Sediment Compartments. These are part of a hierarchical structure that divides coastal zones on the basis of key environmental attributes to assist with coastal planning and management.
Data for the Ocean Account was integrated from a variety of sources, including Earth observation products, for each of the blue carbon ecosystems under investigation. For mangrove extent and condition accounts, we used the Mangrove Canopy Cover product from Digital Earth Australia (DEA), managed by Geoscience Australia. This dataset provides data about the extent and canopy density of mangroves for each year from 1987 to 2021 for the entire coastline of Australia. It consists of an annual sequence of 30-metre-resolution maps. These maps are generated by analysing the Landsat fractional cover product developed by the Joint Remote Sensing Research Program, and the Global Mangrove Watchlayers from the Japanese Aerospace Exploration Agency.
All extent datasets were reprojected to the Geocentric Datum of Australia 1994 (GDA94) with Australia Albers EPSG3577 projection and then combined on a per sediment region basis.
Coastal protection: a case study in mangroves
Mangroves thrive in salt and brackish water and form unique intertidal forests at the edge of land and sea. Almost exclusively tropical, they also occur in the subtropics. Mangroves provide coastal protection by acting as a living seawall, tempering floods during storm surges and slowing erosion. Mangrove forests also trap sediment, which helps the process of accretion, whereby coastal sediment returns to the visible portion of a beach or foreshore after a submersion event.
