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Hagger V, Stewart-Sinclair P, Rossini R, Waltham NJ, Ronan M, Adame MF, Lavery P, Glamore W and Lovelock CE (2022). Coastal wetland restoration for blue carbon in Australia. Values-based approach for selecting restoration sites. Report to the Reef and Rainforest Research Centre. Cairns, Queensland.
Diverse forms of coastal wetlands contribute significantly to global carbon stores and climate change mitigation. Opportunities to incentivise coastal wetland restoration by leveraging carbon markets is growing in Australia as methods become available and markets emerge. However, little is known of the feasibility of blue carbon restoration at scale, or the quantities of ecological and social co-benefits that could accompany restoration.
This project quantified the blue carbon restoration potential in three geographically unique case study regions across Australia. It used a multi-stage approach that identified the biophysical suitability of coastal wetland restoration sites, their carbon abatement and co- benefits, and their economic feasibility using a cost-benefit analysis under different carbon pricing and other financial factors. Sites were identified by intersecting restorable land (productive agriculture on historic coastal wetlands) within the highest astronomical tide levels and determining the presence of drains and tidal barriers, and thus with potential for tidal restoration. A set of metrics were identified and quantified for ancillary ecosystem services, or co-benefits, including biodiversity, fisheries, water quality, and coastal protection. Cultural benefits were identified as the potential for leadership and collaboration by Indigenous land managers at sites. Cost-effectiveness analyses were then performed, to identify sites that were profitability under different carbon prices and maximised the provision of co-benefits under different possible stakeholder weightings.
We reveal that identifying blue carbon restoration opportunity is more complex than identifying biophysically suitable sites. Opportunities for blue carbon projects with tidal restoration varies among regions, with variation in tidal range, land-uses, and hydrology impacting abatement forecasts. The presence of threatened species can modify what land is deemed as suitable for restoration, for example from avoiding disturbance to the critically endangered Capricorn Yellow Chat on banked habitats in the Fitzroy Basin region in central Queensland. Or where a restoration site has low profitability or carbon abatement it may be attractive because it supports threatened species and community recovery (e.g. temperate salt marsh in the Peel-Harvey and Purple-crowned fairy wren habitat in the Ord River).
We identified 13,874 ha of land as potentially restorable via the Australian Government blue carbon tidal restoration method across the Fitzroy Basin region with much less in the Peel- Harvey region in south-west Western Australia (348 ha). In the Ord River region in east Kimberley Western Australia, 24,123 ha of land was identified as potentially restorable via restoration activities other than tidal restoration, such as removal of cattle to prevent coastal wetland degradation. Restoration of all potential sites in the Fitzroy Basin and Peel-Harvey would equate to a net carbon abatement of 162,000 Mg CO2-e yr-1 and 4,312 CO2-e yr-1, respectively. Though not eligible under the blue carbon tidal restoration method, conservative estimates of avoided emissions for the Ord River suggest another 7,237 Mg CO2-e yr-1 could be abated if methods that allow rehabilitation of degraded natural wetlands were available.
Carbon price and permanence period impacted profitability in the Fitzroy Basin, but not Peel- Harvey. Forty-eight Fitzroy Basin sites (51% of area) became profitable under a high carbon price and 21 sites (7% of area) over 100 years, whilst no Peel-Harvey sites were profitable
under any scenario because sites were small (additionally input data was limited in this case study region).
Traditional Custodians were interested in restoring coastal wetlands and many wetlands hold significant cultural value. We did not find exclusive Native Title across the potential restoration sites, however there are areas of non-exclusive Native Title in the Fitzroy Basin sites and Native Title is currently being resolved in the Peel-Harvey region, with opportunities for land purchase. There is potential for First Nations people to benefit from long-term blue carbon projects that are led by Traditional Custodians by enhancing connection to Country and culture, protecting cultural sites, and maintaining Indigenous food systems. The Ord River region has high restoration potential but is not eligible under the blue carbon tidal restoration method, and other methods that focus on reducing disturbance and enhancing condition of coastal wetlands might be more useful for Traditional Custodians to engage and implement blue carbon projects.
Our results indicate that high carbon prices are needed to make projects feasible on land used for beef production. A combination of lower restoration costs and lower farm gross margins from reduced agricultural productivity in areas affected by seawater intrusion may create greater incentives for implementing blue carbon projects in the future. There are a range of data deficiencies in accurately predicting the feasibility of blue carbon projects, including higher resolution tidal planes, accurate income data from different land-uses, accurate costing of restoration, and mapping of hydrological modifications.
Importantly, we found that carbon abatement and many co-benefit metrics covaried and that trade-offs were limited. Therefore, there is potential to find hotspots where multiple ecosystem services can be bundled to attain higher carbon prices for restoration projects with co-benefits, or to undertake projects under other emerging markets, such as biodiversity stewardship. Increasing the range of case study regions that encompass different characteristics would help in understanding potential trade-offs.
There is significant opportunity to incentivise coastal wetland restoration under blue carbon markets to enhance Australia’s carbon stocks and associated co-benefits. Our analysis highlights that identifying potential sites must go beyond biophysical attributes and consider the range of factors that will impact the long-term profitability and sustainability. It also highlights the rich ecological and cultural benefits that could be produced. Each region was unique in the characteristics of sites, the data available to inform decision making, and profitability outcomes. Our research indicates that a framework to select sites for coastal wetland restoration for blue carbon in Australia should be regionally specific, creating an approach that inherently engages Traditional Custodians and incorporates local knowledge.