Coastal wetland restoration for carbon accounting

The emerging global carbon markets are a potential opportunity to generate funds for wetland restoration efforts. These markets are designed to create emitter’ accountability and incentivise carbon abatement activities.

Carbon ‘credits’ are bought by emitters, from other organisations that oversee activities that facilitate the capture and storage of atmospheric carbon. When the capture is associated with oceans, coasts and wetlands, it is known as ‘blue carbon’. One carbon credit equals one tonne of facilitated carbon dioxide abated, or the equivalent in other greenhouse gases. Once a carbon credit is traded, it becomes an ‘offset’.

In Australia, despite aspirations to use carbon market capital for broadscale wetland re-establishment, this cannot proceed without accurate quantification of the carbon-capture potential of restored wetlands, and feasibility studies; these have not been available.

This project addressed these shortfalls.

Approach and findings

Approach

Three geographically unique, historically modified wetland regions within highest-tide reaches, were selected for study: the Fitzroy Basin in central-east Queensland; the Peel-Harvey and South West catchments in south-west Western Australia; and the Ord River floodplain in east Kimberly, north-east Western Australia. Specific sites with restoration potential were identified in each area.

A set of metrics were identified, quantified and then assessed for each site, including: biophysical suitability for restoration; co-benefits to biodiversity, fisheries, water quality, coastal protection; Indigenous heritage values; potential benefits to Traditional Custodian communities; regulation and policy constraints; and, economic feasibility within carbon markets under different carbon prices.

Findings

From the metrics, a site selection process for blue carbon eligible wetland restoration was developed encompassing projections based on various carbon abatement and carbon credit price scenarios, and co-benefit outcomes.

Sites within the Fitzroy Basin and the Peel-Harvey case study regions (in total 13,874 ha and 348 ha, respectively) were identified as potentially restorable under the Australian Government blue carbon restoration requirement for rewetting of historical wetlands by removing artificial drains and tidal barriers. These would achieve a net carbon abatement of 162,000 Mg CO2-e yr-1 and 4,312 CO2-e yr-1, respectively.

In the Ord River region, no potential restoration sites were identified as eligible under the blue carbon tidal restoration method, but 24,123 ha could potentially be recovered by cattle removal. This could abate 7,237 Mg CO2-e yr-1 of greenhouse gas emissions.

Variations in carbon price and the defined permanence obligation (the chosen period of guaranteed abatement) impacted profitability projections in the Fitzroy Basin, but not the Peel-Harvey. Under a high carbon price, with a permanence of 25 years, restoration of 51% of the Fitzroy Basin site area became profitable. However, if a 100-year permanence projection was used, this decreased to just 7%. Under the current average carbon price, tidal restoration of grazing land would not be economically feasible at any sites.

No Peel-Harvey sites were profitable under any scenario because sites were small, therefore economies of scale did not come into play.

Conclusions

The case studies confirm there are significant opportunities to incentivise coastal wetland restoration under blue carbon markets, and thereby enhance Australia’s carbon stocks while concurrently achieving rich ecological and cultural co-benefits. Notably, these opportunities increase significantly with projected one metre sea-level rise by 2100, and anticipated rises in carbon credit value.

The work demonstrated that, as well as biophysical attributes for restoration site selection, multiple other regionally specific factors that could impact long-term profitability and sustainability, must be considered. Of particular importance is Traditional Owners’ knowledge and participation in site selection.

This research uncovered current deficiencies in data and other factors that will continue to hinder the accuracy of feasibility projections for potential blue carbon projects unless addressed. These include: the level of resolution of tidal plane maps; accurate income data from different land-uses; accurate costing of restoration; mapping of hydrological modifications; detailed hydrology data for catchments; and, defined policy support.

Outcomes

• Economic and environmental restoration opportunities explored.
• Frameworks developed for selecting wetland restoration sites for carbon accounting.
• Support for Indigenous communities’ participation in carbon markets.

Project location