Atmospheric methane is a potent greenhouse gas that plays a major role in controlling the Earth’s climate. The causes of the renewed increase of methane concentration since 2007 are uncertain given the multiple sources and complex biogeochemistry. Here, we present a metadata analysis of methane fluxes from all major natural, impacted and human-made aquatic ecosystems. Our revised bottom-up global aquatic methane emissions combine diffusive, ebullitive and/or plant-mediated fluxes from 15 aquatic ecosystems. We emphasize the high variability of methane fluxes within and between aquatic ecosystems and a positively skewed distribution of empirical data, making global estimates sensitive to statistical assumptions and sampling design. We find aquatic ecosystems contribute (median) 41% or (mean) 53% of total global methane emissions from anthropogenic and natural sources. We show that methane emissions increase from natural to impacted aquatic ecosystems and from coastal to freshwater ecosystems. We argue that aquatic emissions will probably increase due to urbanization, eutrophication and positive climate feedbacks and suggest changes in land-use management as potential mitigation strategies to reduce aquatic methane emissions.

大气甲烷是一种强效温室气体，在控制地球气候方面发挥着重要作用。鉴于多来源和复杂的生物地球化学，自 2007 年以来甲烷浓度重新增加的原因尚不确定。在这里，我们对来自所有主要自然、受影响和人造水生生态系统的甲烷通量进行了元数据分析。我们修订后的自下而上的全球水生甲烷排放结合了来自 15 个水生生态系统的扩散、沸腾和/或植物介导的通量。我们强调水生生态系统内和水生生态系统之间甲烷通量的高度可变性以及经验数据的正偏分布，使全球估计对统计假设和抽样设计敏感。我们发现水生生态系统贡献了（中位数）41% 或（平均）53% 的全球人为和自然来源的甲烷排放量。我们表明，甲烷排放量从自然到受影响的水生生态系统以及从沿海到淡水生态系统的增加。我们认为，由于城市化、富营养化和积极的气候反馈，水生排放可能会增加，并建议改变土地利用管理作为减少水生甲烷排放的潜在缓解策略。