Methane emissions from wetland ecosystems form a key component of the global CH4 cycle. However, the relative contribution of wetland ecosystems to both contemporary and palaeo global atmospheric CH4 concentrations remains highly debated. Despite vegetation being a primary transport pathway, the role of vegetation in transporting CH4 emissions to the atmosphere is often neglected when estimating methane emissions from wetlands. Chapter 2 describes the introduction of dynamic vegetation into a process-based peatland GHG emissions model. Heatwaves and droughts have led to substantial impacts on wetlands, and detrimental impacts have persisted for years beyond the events themselves. Despite the growing body of knowledge on extreme-events, their effects on carbon-rich systems have not been extensively explored. Chapter 3 addresses this gap by delving into the impacts of extreme temperatures, heavy precipitation, and prolonged dry spells on CH4 emissions from wetland systems. Whilst, boreal and temperate sites tend to respond similarly, the changing frequency of extreme-events varies between these two regions. Widespread peatland establishment in the northern hemisphere high latitudes led to rapid increases in atmospheric CH4 concentrations during the Pleistocene-Holocene transition. In the present day, wetlands submerged during the Pleistocene-Holocene transition can act as dangerous CH4 emission sources. Chapter 4 estimates the GHG budget of peatlands that lie submerged beneath the North Sea. These insights shine light onto the compounding and inter relating processes that contribute to wetland CH4 fluxes, near-term, and longterm climate change. Future research into the quantification of wetland methane emissions can benefit from better articulating the bounds and limitations of spatial and temporal processes in the formulations of research questions, methods, and conclusions.
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