School of Biological and Behavioural Sciences, Queen Mary University of London, London, E1 4NS, UK.
Sustainable Agriculture Sciences, Rothamsted Research, North Wyke, Okehampton, Devon, EX20 2SB, UK.
Nat Commun. 2022 Jul 1;13(1):3810. doi: 10.1038/s41467-022-31559-y.
Headwater streams are natural sources of methane but are suffering severe anthropogenic disturbance, particularly land use change and climate warming. The widespread intensification of agriculture since the 1940s has increased the export of fine sediments from land to streams, but systematic assessment of their effects on stream methane is lacking. Here we show that excess fine sediment delivery is widespread in UK streams (n = 236) and, set against a pre-1940s baseline, has markedly increased streambed organic matter (23 to 100 g m), amplified streambed methane production and ultimately tripled methane emissions (0.2 to 0.7 mmol CH m d, n = 29). While streambed methane production responds strongly to organic matter, we estimate the effect of the approximate 0.7 °C of warming since the 1940s to be comparatively modest. By separating natural from human enhanced methane emissions we highlight how catchment management targeting the delivery of excess fine sediment could mitigate stream methane emissions by some 70%.
源头溪流是甲烷的自然来源，但正遭受严重的人为干扰，特别是土地利用变化和气候变暖。自 20 世纪 40 年代以来，农业的广泛集约化增加了从陆地向溪流输送的细沉积物，但对其对溪流甲烷影响的系统评估却缺乏。在这里，我们表明，英国溪流中普遍存在过量的细沉积物输送（n=236），与 1940 年代以前的基线相比，明显增加了河床有机质（23 至 100 克/平方米），放大了河床甲烷的产生，最终使甲烷排放量增加了两倍（0.2 至 0.7mmol CH m d，n=29）。虽然河床甲烷的产生对有机质有很强的响应，但我们估计，自 20 世纪 40 年代以来，大约 0.7°C 的变暖影响相对较小。通过将自然和人为增强的甲烷排放分开，我们强调了集水区管理针对过量细沉积物输送的目标，可将溪流甲烷排放量减少约 70%。
