Figure 3. Distributions of the identified ecoregion flammability thresholds (EFTs) by biome type and ordered by median EFT. Point and line intervals under histograms represent the median equal-tailed distribution intervals of 50 and 90%. Dashed vertical lines reference EFT values (8, 10, 12, and 30%) identified as important biophysical thresholds constraining fire ignition and spread in prior research (Boer et al., 2017; Fernandes et al., 2008; Filkov et al., 2019; Flannigan et al., 2016; Nolan et al., 2016; Wotton, 2008). Vertical lines and dots on the right reflect non-significant differences in Dunn’s Z statistics for pairwise multiple comparisons: E.g., the mean rank value of EFTs for deserts and xeric shrublands is comparable to the three biome types below it. Note that boreal forests and taiga features a break in statistical significance: It is statistically significantly different from montane grasslands and savannas, but not tropical and subtropical coniferous forests.