Fig. 2: Uncertainty and sensitivity analysis.

a Empirical distribution of r² at the continental level. b Boxplots of r² values yielded by each GM (in bold) and FAO-based dataset (centre line, median; box limits, upper and lower quartiles; whiskers, 1.5x interquartile range; points, outliers). c Sobol' indices. S_i and T_i refer respectively to Sobol' first and total order indices. S_i measures the influence of a parameter in the model output (r² in this case), while T_i measures the influence of a parameter jointly with its interactions. The bars reflect the mean value and the error bars display the 95% confidence intervals, computed with the normal method after bootstrapping (R = 1000).