Fig. 6: Spillover frequency at different effect sizes.
From: Protected area management has significant spillover effects on vegetation
Numbers of protected areas with non-zero positive spillover effects (increases in any vegetation type relative to the counterfactual) of different sizes at different distance bands from their boundaries. Shading indicates 95% confidence intervals for each curve. The red vertical lines indicate the values of 0.2, 0.8 and 1.4 that have been proposed55 as suitable values to distinguish between small, medium, large and very large effects, respectively. Noting that the residual standard error for these curves (uncertainty on the x axis) is 0.52, the number of protected areas that show a large spillover effect (effect size >0.8) decreases rapidly from the 0–5 km band, but even for the 45–50 km band, the number of protected areas that are estimated to exhibit spillovers is close to 20%. This figure provides, to my knowledge, the first large-sample estimate of distance-related decay in the magnitude of spillover effects, and thus of the magnitude of potential spillover benefits that might be expected from an average Australian protected area.
