Fig. 2: Comparison of the distributions of fire occurrence in the historical (pre-1880) and the contemporary (1984–2022) periods for all North American tree-ring fire-scar network (NAFSN) sites in the United States and Canada.

Analyses show the percent of NAFSN sites burned (a) and the average percent of sites burned within hexels (b) (see Fig. 1 for hexel map). For reference, 6% of NAFSN sites burned, on average, in the historical period (a; Table 2) and an average of 7% of sites burned, among hexels, in the historical period (b).