Biogeochemical Processes In Marshlands: A Comprehensive Review Of Their Role In Mitigating Methane And Carbon Dioxide Emissions

Abstract

Marshlands play a crucial role in global carbon cycling, acting as significant carbon sinks while also contributing to methane emissions through complex biogeochemical processes. This systematic review examines the mechanisms regulating carbon sequestration and greenhouse gas fluxes in marshland ecosystems by synthesizing findings from 320 peer-reviewed studies, collectively encompassing 5,860 citations. The study follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to ensure a rigorous, transparent, and comprehensive evaluation of existing literature. Key focus areas include microbial methane production and oxidation, the influence of hydrological regimes on carbon fluxes, the impact of nutrient dynamics on decomposition rates, and the role of anthropogenic activities such as agricultural expansion, urbanization, and climate change in altering marshland carbon balance. Findings indicate that 84% of reviewed studies confirm the ability of marshlands to sequester carbon efficiently due to slow organic matter decomposition under anaerobic conditions, with coastal wetlands exhibiting higher sequestration rates due to sulfate-mediated methane suppression. However, 190 studies emphasize the regulatory role of water table fluctuations, showing that prolonged flooding enhances methane emissions by 30% to 80%, whereas seasonal drying phases increase carbon dioxide emissions through aerobic decomposition. The review also highlights that nitrogen and phosphorus enrichment accelerate microbial activity, altering methane fluxes, while rising temperatures and shifting precipitation patterns amplify methane emissions, particularly in tropical wetland ecosystems. Furthermore, 207 studies document significant carbon losses due to land use changes, with agricultural conversion and wetland drainage exposing organic carbon to oxidation. Importantly, the review identifies wetland restoration as a viable mitigation strategy, with 128 studies demonstrating that rewetting degraded marshlands restores up to 90% of their original carbon sequestration capacity. Overall, this study provides a comprehensive synthesis of marshland carbon dynamics, offering valuable insights for policymakers, researchers, and conservationists in developing sustainable management strategies to balance wetland conservation with climate change mitigation.