Land use and environmental drivers of methane and nitrous oxide emissions in Eswatini peatlands

Abstract

Peatlands play an important role in carbon and nitrogen cycles, functioning as either sinks or sources of greenhouse gases (GHGs) depending on environmental and management conditions. While extensive research has been conducted on peatlands in northern latitudes and the tropics, there is limited knowledge of GHG flux dynamics in southern African peatlands. This study examined methane (CH4) and nitrous oxide (N2O) fluxes from two differently managed peatlands in Eswatini over 12 months using the opaque static chamber technique. The Motjane peatland, under community management, functioned as a slight net sink for CH4-C (-2.92 mg m-2 hr-1) but was a slight net source for N2O-N (0.11 µg m−2 hr−1). The Malolotja peatland, located in a nature reserve, was a slight source for N2O-N (0.26 µg m−2 hr−1) and neither a source nor a sink for CH4-C (0.06 mg m-2 hr-1). CH4-C flux was positively correlated with temperature (below-ground, surface and air), while N2O-N fluxes showed a negative relationship with rainfall. Seasonal environmental factors and land use management influenced CH4-C and N2O-N fluxes. Differences between CH4-C and N2O-N fluxes in the two peatlands were linked to variations in the degree of human disturbance, vegetation communities, climatic factors and soil properties. The findings highlight the importance of targeted intervention measures that are informed by continuous ecological monitoring. Sustainable peatland management strategies should focus on restoring indigenous vegetation and stabilising water levels to minimise CH4 and N2O emissions and enhance carbon sequestration. Future assessments of the overall GHG balance and carbon sequestration potential should consider the combined effects of all three major greenhouse gases, including CO2.