Greenhouse gas emissions from wetlands versus other land use

Global greenhouse gas (GHG) emissions have increased alarmingly fuelling climate change. Fossil fuel burning and land-use change are the main contributors to global GHG emissions, and their reductions are required to reduce global GHGs. Protection and conservation of coastal wetlands and agriculture management are the two main sectors that can provide the land-use based climate mitigation, with the potential to be reduced by 35-50%. Therefore, projects and policies involving coastal wetland protection and restoration are being encouraged globally important GHG mitigation approaches. However, the success of all mitigation approaches largely depends upon evidence-based knowledge about the types of mitigation actions, their feasibility, and potential co-benefits. This dissertation consists of six chapters that centre on exploring the magnitude of the GHG emissions due to coastal wetland loss and a potential solution through wetlands restoration on unused agricultural lands. Chapter 2 is a literature review to identify knowledge gaps regarding GHG fluxes from wetlands and other land uses. I synthetised 153 articles and found that GHG fluxes were mainly reported from temperate marshes while GHG fluxes from sub/tropical wetlands were underrepresented. Overall, 48% of the studied wetlands were marshes converted for cropping and grazing, while mangroves were mainly converted to aquaculture. I found that sugarcane fields in tropical Australia, had very high N2O emissions, suggesting that their conversion to wetlands may present a GHG mitigation opportunity. Finally, I found GHG fluxes in tropical ponded pastures, which were potentially very high, were not reported yet, calling to fill in this critical knowledge gap in Australia. In Chapter 3, I explored the soil greenhouse gas (GHG) fluxes from tropical coastal wetlands and their converted agricultural lands. I measured gaseous fluxes throughout two years between 2018 and 2020, considering seasonal differences. The GHG emissions were lowest from coastal wetlands and ...