Forest plot of meta-analysis of effect sizes (raw mean difference) comparing dissolved organic carbon (DOC) concentration in drained versus undrained peatlands. The dashed line represents no effect. Size of boxes represents the weight of the study in the analysis. Horizontal lines represent 95% confidence intervals. Positive effect sizes indicate greater concentration in drained peatlands than undrained controls. The position of the centre of the diamond represents the overall summary effect (a weighted average) and its horizontal extent represents the positive and negative 95% confidence intervals.