Methane emissions partially offset carbon sink function in global wetlands: An analysis based on global data.

Area of Science:

• Environmental Science
• Climate Change Research
• Ecosystem Carbon Cycling

Background:

• Wetlands are significant atmospheric carbon dioxide (CO2) sinks.
• Anaerobic conditions in wetlands lead to methane (CH4) emissions.
• The impact of CH4 emissions on the net carbon balance of global wetlands is not fully understood.

Purpose of the Study:

• To conduct a global data analysis on the offset of net ecosystem exchange of CO2 (NEE) by CH4 emissions in various wetland ecosystems.
• To quantify the contribution of CH4 emissions to the overall greenhouse gas balance of wetlands.
• To assess the long-term carbon sink potential of wetlands considering both CO2 uptake and CH4 release.

Main Methods:

• Collected simultaneous measurements of NEE and CH4 flux from diverse global wetlands (inland and coastal).
• Calculated CO2-equivalent flux (CO2-eq flux) using 100-year and 20-year global warming potentials for CH4.
• Analyzed the net greenhouse gas balance across different wetland types.

Main Results:

• All studied wetland types acted as atmospheric CO2 sinks, with varying NEE values (e.g., mangroves: -2011.0 g CO2·m-2·a-1).
• CH4 emissions partially offset CO2 uptake, ranging from 14.0% to 64.9% (100-year scale) and up to 192.0% (20-year scale) across wetland types.
• Some mangroves, peatlands, and non-peatland wetlands became net CO2-equivalent sources on a 20-year scale, but remained net carbon sinks over 100 years.

Conclusions:

• Wetlands are crucial atmospheric carbon sinks, even when accounting for methane emissions over longer timescales.
• Understanding and mitigating CH4 emissions from wetlands is vital for maintaining their carbon sink function and combating climate warming.
• Effective management strategies are needed to preserve the climate regulation role of wetland ecosystems.