Wetlands restoration and recovery of associated ecosystem services: a win-win strategy

Coastal wetlands are one of the most productive and valuable ecosystems on earth. They provide local and global populations with a wide range of ecosystem services, such as carbon storage, efficient nutrient cycling, and habitat provision for diverse species Coastal restoration emerges as a key strategy to revert their global cover decline trend and facilitate the recovery of their ecosystem services. The development of offset markets, such as carbon, could facilitate the implementation of restoration projects. These investments will require evidence of the outcomes of coastal wetlands restoration. However, there is no consensus on the definition of coastal restoration success, and how it is measured. This lack of framework hinders knowledge transmission and can lead to inaccurate estimation of restoration outcomes. This thesis first displays a literature review on indicators of coastal wetlands restoration success (Chapter 2) to outline the importance of ecosystem function indicators, closely related to restoration objectives and goals. I pinpointed nitrate reduction processes, such as denitrification, and greenhouse gas emissions as important but understudied coastal wetlands ecosystem functions. I performed a meta-analysis on denitrification and modelled this process's rates using nitrate as a predictor (Chapter 3). I set up field studies to assess the greenhouse gas emissions reduction potential for tidal restoration of coastal wetlands in the Burdekin catchment in Queensland, Australia (Chapter 4). I employed the Isotope Pairing Technique to assess the effect of tidal restoration on nitrate reduction processes in the Maroochy catchment in Queensland, Australia (Chapter 5). Finally, I developed an indicator framework to assess the outcomes of marine and estuarine habitats management interventions in Queensland (Chapter 6). The results of this thesis emphasise the importance of coastal wetlands as nitrate removal hotspots, and their potential to be included in water-quality offset schemes. I demonstrated the potential for tidal restoration to drastically reduce methane emissions from freshwater-impounded wetlands. I also outlined the necessity to investigate nitrate reduction processes, denitrification and DNRA, as their relative prevalence has important implications for the fate of nitrate in coastal ecosystems. The endorsed indicator framework will enable reliable monitoring, evaluation, and reporting of marine and estuarine management interventions and be accessible to a wide range of practitioners. The results from this thesis can facilitate the integration of coastal wetlands restoration in carbon abatement, water quality, and biodiversity offset schemes. Our results will also contribute to the efficient share of coastal restoration knowledge. This thesis provides valuable knowledge that can contribute to large-scale coastal wetlands restoration success.