Scientists from the Institute of Urban Environment, Chinese Academy of Sciences, have determined elevated carbon dioxide concentration (e[CO2]) increased paddy methane (CH4) emissions but did not affect wetland CH4 emissions.
Understanding and quantifying the impact of e[CO2] on CH4 globally is important for effectively assessing and mitigating climate warming. Paddies and wetlands are the two important sources of CH4 emissions. Yet, a quantitative synthetic investigation of the effects of e[CO2] on CH4 emissions from paddies and wetlands on a global scale has not been conducted.
A meta-analysis was conducted using 488 observation cases from 40 studies to assess the long-term effects of e[CO2] (ambient [CO2] + 53-400 μmol mol-1) on CH4 emissions from paddies and wetlands and to identify the relevant key drivers. Notably, scientists found e[CO2] effects on paddy CH4 emissions were positively related to that on belowground biomass, methanogens. However, these factors under e[CO2] resulted in no significant change in CH4 emissions from wetlands. In addition, tillering number of rice and water table levels affected e[CO2]-induced CH4 emissions in paddies and wetlands, respectively.
On a global scale, CH4 emissions changed from an increase (+0.13 and + 0.86 Pg CO2-eq yr-1) under short-term e[CO2] into a decrease and no changes (-0.22 and + 0.03 Pg CO2-eq yr-1) under long-term e[CO2] in paddies and wetlands, respectively. This indicated that e[CO2]-induced CH4 emissions from paddies and wetlands changed over time. Although the results need to be confirmed in long-term field experiments, these findings suggest that e[CO2]-induced CH4 emissions from paddies and wetlands may be smaller than previously thought.
Scientists not only shed light on the different stimulative responses of CH4 emissions to e[CO2] from paddy and wetland ecosystems but also suggest that estimates of e [CO2]-induced CH4 emissions from global paddies and wetlands need to account for long-term changes in various regions. These results are of great significance for proposing effective emission reduction measures to cope with severe global climate change.
The study was published in Environmental Research entitled "Comparing the variations and influencing factors of CH4 emissions from paddies and wetlands under CO2 enrichment: A data synthesis in the last three decades ".
This work was supported by the National Key Research and Development Program of China and Ningbo Municipal Science and Technology Bureau.
Effects of elevated CO2 on CH4 emissions from paddies and wetlands
Page: https://doi.org/10.1016/j.envres.2023.115842
Contact: YAO Huaiying
Institute of Urban Environment, Chinese Academy of Sciences
E-mail: hyyao@iue.ac.cn
