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Methane emissions from wetlands: biogeochemical, microbial, and modeling perspectives from local to global scales

2012; Wiley; Volume: 19; Issue: 5 Linguagem: Inglês

10.1111/gcb.12131

1365-2486

Scott D. Bridgham, Hinsby Cadillo‐Quiroz, Jason K. Keller, Qianlai Zhuang,

Methane Hydrates and Related Phenomena

Abstract Understanding the dynamics of methane ( CH 4 ) emissions is of paramount importance because CH 4 has 25 times the global warming potential of carbon dioxide ( CO 2 ) and is currently the second most important anthropogenic greenhouse gas. Wetlands are the single largest natural CH 4 source with median emissions from published studies of 164 Tg yr −1 , which is about a third of total global emissions. We provide a perspective on important new frontiers in obtaining a better understanding of CH 4 dynamics in natural systems, with a focus on wetlands. One of the most exciting recent developments in this field is the attempt to integrate the different methodologies and spatial scales of biogeochemistry, molecular microbiology, and modeling, and thus this is a major focus of this review. Our specific objectives are to provide an up‐to‐date synthesis of estimates of global CH 4 emissions from wetlands and other freshwater aquatic ecosystems, briefly summarize major biogeophysical controls over CH 4 emissions from wetlands, suggest new frontiers in CH 4 biogeochemistry, examine relationships between methanogen community structure and CH 4 dynamics in situ , and to review the current generation of CH 4 models. We highlight throughout some of the most pressing issues concerning global change and feedbacks on CH 4 emissions from natural ecosystems. Major uncertainties in estimating current and future CH 4 emissions from natural ecosystems include the following: (i) A number of important controls over CH 4 production, consumption, and transport have not been, or are inadequately, incorporated into existing CH 4 biogeochemistry models. (ii) Significant errors in regional and global emission estimates are derived from large spatial‐scale extrapolations from highly heterogeneous and often poorly mapped wetland complexes. (iii) The limited number of observations of CH 4 fluxes and their associated environmental variables loosely constrains the parameterization of process‐based biogeochemistry models.