Beijing, March 3 (Zhongxin Net) -- Does global warming affect the function of greenhouse gas "sinks" (referred to as carbon sinks) in wetlands? What is the impact? The research team of the Institute of Atmospheric Physics of the Chinese Academy of Sciences (CAS) using experimental data from more than 21 wetland sites in the past 30 years has found that wetlands are currently "sinks" of greenhouse gases, and with global warming, the greenhouse gas "sink" function of wetlands will be greatly weakened.

This study on the important impacts of global climate change was jointly completed by Bao Tao, a postdoctoral fellow at the East Asian Regional Climate and Environment Key Laboratory of the Institute of Atmospheric Sciences of the Chinese Academy of Sciences, and co-supervisors Professor Jia Gensuo and researcher Xu Xiyan, and the resulting paper was published in the international professional academic journal Nature Climate Change in the early morning of March 3, Beijing time. They studied the response of three greenhouse gas emissions, carbon dioxide, methane and nitrous oxide, to warming by integrating simulated data from anthropogenic warming conducted at 21 independent natural wetland sites between 1990 and 2022.

Based on data crawler technology and inverse variance random-effects model meta-analysis method, the research team found that wetlands are currently "sinks" of greenhouse gases, and if the global warming range is 1.5-2°C, the greenhouse gas "sink" function of wetlands is weakened by more than half (about 57%), that is, even if the Paris Agreement global average temperature increase is controlled within 2°C compared with the pre-industrial period, and efforts to limit the temperature increase to 1.5°C can be achieved. The role of wetlands in mitigating climate change will continue to diminish significantly.

At large spatial scales, the differences in the dominant plant functional groups of wetlands can well explain the uncertainty of greenhouse gas source and sink changes in wetlands in different warming simulation experiments. After warming, the net uptake of carbon dioxide increased in wetlands where vascular plants such as shrubs and grasses predominated. In wetlands where cryptoflowering plants such as moss and lichen predominate, net CO2 emissions have increased significantly. Warming contributed to net wetland methane emissions regardless of wetland dominant plant functional groups, as methanogensis were more sensitive to changes in soil temperature than low-affinity methane oxidizing bacteria.

At the same time, this study quantifies the response of wetland nitrous oxide emissions to warming. Although wetland nitrous oxide emission fluxes are low, climate warming significantly enhances the net emission of nitrous oxide from wetlands where grasses (about 27%) predominate. Considering that the greenhouse effect of nitrous oxide on a centennial scale is 298 times that of carbon dioxide, even a small increase in nitrous oxide emissions may make a non-negligible contribution to global warming. The study also found that in permafrost wetlands where vascular plants predominate, warming contributes more significantly to net emissions of methane and nitrous oxide, resulting in a positive feedback effect on warming.

According to the research team, the sixth climate change assessment report of the Intergovernmental Panel on Climate Change (IPCC) specifically pointed out that one of the main sources of uncertainty in the spatial estimation of future carbon emissions under the temperature control goals of the Paris Agreement is the uncertainty of the response of greenhouse gas emissions from ecosystems such as wetlands to climate change. This study reveals the characteristics of the response of wetland greenhouse gas emissions to warming and the main sources of uncertainty, and also provides new insights for the simulation study of wetland-climate feedback mechanism.

Wetlands cover 6% of the Earth's surface but store one-third of the world's soil organic carbon. Wetland vegetation converts atmospheric carbon dioxide into organic carbon through photosynthesis, which accumulates in wetland soils. In addition, the anaerobic environment of wetlands makes the decomposition of organic carbon slower, so wetlands are the natural ecosystems with the fastest rate of carbon accumulation. There is growing evidence that climate warming is significantly altering the structure and function of wetland ecosystems. Whether climate warming will stimulate wetlands to release more greenhouse gases is one of the key issues that need to be solved urgently in global change research. (End)