Fig. 2: Causal strength of global change drivers on macroinvertebrate community abundance and species richness.

The cross-map skill, ρ, of the CCM at the maximum time series length represents causal strength, shown as boxplots to present values across sites. Cross-mapping significance was determined by comparing ρ with the maximum time series length as well as convergence (difference between ρ at the maximum and minimum time series lengths) between original and surrogate time series data. The P value was estimated for each site as the number of surrogates showing a higher ρ with the maximum time series length, as well as a higher convergence, divided by the total number of surrogates. The meta-significance was then calculated using harmonic mean P values. Negative values of ρ indicate no predictive ability; observed values are shown without truncation to display the full range of cross-map performance. See Supplementary Table 4 for the additional statistics in the CCM. SOI southern oscillation index, SST sea surface temperature, SS suspended solids, Chl-a chlorophyll a content, OM organic matter content, mud mud content, CCM convergent cross-mapping. Sample sizes differed among drivers (SOI, SST, SS: n = 14 sites; Chl-a and OM: n = 11 sites; mud: n = 9 sites); comparisons among drivers were therefore conducted using the subset of sites with complete data for all drivers (n = 9). There were no significant differences in the causal strengths of the drivers on community abundance and species richness (paired Wilcoxon tests, two-sided; P > 0.05). Boxplots show the median (center line), interquartile range (box), and whiskers extending to the most extreme values within 1.5 times the interquartile range; points represent observed causal strengths for individual sites.