The dissolved organic carbon (DOC) export from land to ocean via rivers is a significant term in the global C cycle, and has been modified in many areas by human activity. DOC exports from large global rivers are fairly well quantified, but those from smaller river systems, including those draining oceanic regions, are generally under-represented in global syntheses. Given that these regions typically have high runoff and high peat cover, they may exert a disproportionate influence on the global land–ocean DOC export. Here we describe a comprehensive new assessment of the annual riverine DOC export to estuaries across the island of Great Britain (GB), which spans the latitude range 50–60° N with strong spatial gradients of topography, soils, rainfall, land use and population density. DOC yields (export per unit area) were positively related to and best predicted by rainfall, peat extent and forest cover, but relatively insensitive to population density or agricultural development. Based on an empirical relationship with land use and rainfall we estimate that the DOC export from the GB land area to the freshwater-seawater interface was 1.15 Tg C year⁻¹ in 2017. The average yield for GB rivers is 5.04 g C m⁻² year⁻¹, higher than most of the world’s major rivers, including those of the humid tropics and Arctic, supporting the conclusion that under-representation of smaller river systems draining peat-rich areas could lead to under-estimation of the global land–ocean DOC export. The main anthropogenic factor influencing the spatial distribution of GB DOC exports appears to be upland conifer plantation forestry, which is estimated to have raised the overall DOC export by 0.168 Tg C year⁻¹. This is equivalent to 15% of the estimated current rate of net CO₂ uptake by British forests. With the UK and many other countries seeking to expand plantation forest cover for climate change mitigation, this ‘leak in the ecosystem’ should be incorporated in future assessments of the CO₂ sequestration potential of forest planting strategies.

从陆地通过河流向海洋的溶解性有机碳（DOC）出口是全球碳循环中的一个重要名词，人类活动已在许多地区对其进行了修改。全球大型河流的DOC出口量得到了很好的量化，但是较小规模的河流系统（包括向海洋区域排放水的河流）的DOC出口在全球综合中通常不足。鉴于这些地区通常具有较高的径流量和较高的泥炭覆盖率，因此它们可能对全球陆海DOC出口产生不成比例的影响。在这里，我们描述了对整个不列颠岛（GB）入河口的年度河道DOC的全面评估，该评估跨越了北纬50-60°，地形，土壤，降雨，土地利用和人口的空间梯度很强密度。DOC的产量（每单位面积的出口）与降雨，泥炭覆盖范围和森林覆盖率呈正相关，并能最好地预测，但对人口密度或农业发展相对不敏感。基于与土地利用和降雨之间的经验关系，我们估计从GB土地区域到淡水-海水界面的DOC出口量为1.15 Tg C年。^-1在2017年的GB河流的平均收益率是5.04克C M ^-2 年^-1，比世界上大多数的主要河流，包括那些潮湿的热带和北极的高，支持的结论是，代表性不足的小河流泥炭丰富地区的排水系统可能导致全球陆地海洋DOC出口被低估。影响GB DOC出口空间分布的主要人为因素似乎是针叶林造林，据估计，该年DOC总体出口量增加了0.168 Tg C - ^1年。这相当于估计的当前净CO ₂速率的15％被英国森林吸收。随着英国和许多其他国家寻求扩大人工林的覆盖范围以缓解气候变化，这种“生态系统的泄漏”应纳入未来对森林种植策略的CO ₂固存潜力的评估中。