Spatially explicit ecosystem accounts for coastal wetland restoration

Coastal wetlands (i.e., mangroves, saltmarshes, and seagrasses) have been recognised as an efficient natural climate solution to help mitigate and adapt to climate change. These ecosystems are also known to provide additional ecosystem services to coastal communities (e.g., fisheries and biodiversity enhancement, nutrient removal). Despite their importance to coasts and coastal communities, we lack spatially explicit information on the values of these ecosystems and the estimated return on investment from coastal management activities to rehabilitate them. Here, we aligned an environmental economic accounting framework combined with a scenario analysis to develop a set of accounts for mangroves, saltmarshes, and seagrasses across the state of Victoria (Australia) as a case study, including the following ecosystem services: commercial and recreational fisheries, carbon and nitrogen sequestration, and coastal hazard mitigation. Importantly, we assessed the current extent, condition, and ecosystem services (physical and monetary) from these coastal ecosystems and examined how they could be improved through management actions. Overall, we found that the combined benefit (i.e., nitrogen and carbon sequestration, fisheries, and coastal hazard mitigation) provided by existing mangroves, saltmarshes, and seagrasses in Victoria is approximately AUD120.9 billion per year. Considering the management scenarios included in this study, our analysis showed that levee removal plus managed retreat had the highest cost at AUD7.6 billion; however, it also provided the highest net benefit of AUD134.8 trillion after 50 years, with a 5 % discount rate. In contrast, fencing was the cheapest management action to restore mangroves and saltmarshes, delivering more than AUD140 billion after 50 years. While our results demonstrate a large return on investment if coastal wetlands are restored at large scale, the implementation of small-scale projects is still a major challenge. However, this study demonstrates that an environmental economic accounting framework combined with a scenario analysis is a powerful approach to guide the decision-making process, providing critical information on the estimated return-on-investment from restoration of mangroves and saltmarshes, with encouraging implications of the impacts of actions at local scales.