Ecosystem accounting to support coastal restoration decision-making

Ecosystem accounting is a structured approach to compiling environmental and economic information, but accounts are most often used to report past trends and current ecosystem states rather than to evaluate future management options. We used the System of Environmental-Economic Accounting - Ecosystem Accounting (SEEA EA) to examine current ecosystem extent, condition and service flows, and to compare prospective restoration scenarios for tidal marshes, mangroves and seagrass meadows in Port Phillip and Western Port, two large metropolitan bays in south-eastern Australia. We focused on a subset of ecosystem services for which regionally relevant data were available: fisheries, recreational fishing, carbon sequestration, nitrogen sequestration and coastal protection. We do not estimate total ecosystem value; rather, we show how a selected set of ecosystem service indicators and restoration cost data can be integrated to support decision-making. The assessed services contributed AUD 89.7 million per year. We then evaluated restoration of historically lost tidal marsh and mangrove ecosystems across 114 feasible sites (1,689 ha) using three management options: fencing, levee removal, and fencing combined with levee removal. Restoring all feasible sites would require an estimated AUD 8.5 million investment and deliver AUD 146 million in benefits over 50 years, equivalent to a net benefit of AUD 137 million and an investment benefit ratio of 16.2. The results demonstrate how ecosystem accounts can move beyond retrospective reporting to provide a transparent and repeatable framework for comparing restoration options and informing investment decisions.