Estimating the greenhouse gas emission abatement potential of tidal introduction in Australia

Abstract Introduction Coastal wetlands store higher amounts of organic carbon and sequester it at higher rates in soil relative to terrestrial ecosystems. However, they have been extensively drained, excavated, or modified, often to allow agriculture. Restoring degraded coastal wetlands can be an important contribution to climate change mitigation by reducing greenhouse gas emissions and recovering sequestration processes. Objectives We generated continental‐scale estimates of the quantity of abatement (greenhouse gas emission reduction and enhanced sequestration) expected from tidal restoration in Australia. Methods We used continental‐scale datasets for elevation, tidal height and land use, and applied calculations legally required by the Tidal Restoration of Blue Carbon Ecosystems method of the Australian Carbon Credit Unit ( ACCU ) Scheme. We integrated costs of restoration and the long‐term profitability of agricultural land uses to estimate economic feasibility at a range of carbon prices. Results Approximately 276,000 ha of agricultural land could potentially be restored across Australia through tidal introduction. Doing so could generate 58.9 Mt CO 2 ‐e of abatement over 25 years. Land used for grazing and flooded agricultural land accounted for most of the area (91%) and potential abatement (84%). Economic feasibility was sensitive to establishment costs: over half the projected abatement (>30 Mt CO 2 ‐e) was feasible only if establishment costs were low (AUD$100 per ha). With higher establishment costs, 24.8–25.0 Mt CO 2 ‐e was economically feasible only if carbon prices were high ($65–80 per t CO 2 ‐e). Conclusion This study provides an initial continental‐scale estimate of the potential abatement expected from tidal restoration in Australia, along with the jurisdictions and land uses that could generate the highest abatement. The realization of abatement potential through carbon credits will require finding ways to lower costs and achieve higher carbon prices.