Greenhouse gas emissions in natural and degraded tropical peatlands.

High water table and anoxic conditions are the major drivers of the development of tropical peatlands. However, land-use change and degradation have severely disrupted their greenhouse gas exchange dynamics. Here, we synthesized published evidence to compare methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) fluxes between natural and degraded tropical peatlands and to evaluate their associations with hydrological, climatic, and soil variables. We found that degradation significantly reduced CH4 emissions and increased N2O emissions from peatlands. CO2 emissions did not differ between natural and degraded from tropical peatlands. Water table emerged as an important factor regulating N2O emission, while CH4 and CO2 emissions were significantly correlated with pH and soil carbon-to-nitrogen (C/N) ratio. These patterns represent synthesis-level associations, rather than direct mechanistic proof, because the datasets combine diverse land-use types and management histories. Our review highlights that greater attention should be directed toward the effect of drainage, fertilizer inputs, and fire events on tropical peatlands.