Fig. 5From: How effective are created or restored freshwater wetlands for nitrogen and phosphorus removal? A systematic reviewFunnel plots showing relations between effect sizes and standard errors for TN (left) and TP (right). An asymmetric distribution suggests the possibility of publication bias or a systematic difference between small and large studies (with large and small standard errors, respectively). In the absence of publication bias and systematic heterogeneity, 95 % of the data might be expected to lie within the green funnel-shaped delineation. The blue vertical lines indicate summary effect sizesBack to article page