Population, cropland area, and livestock density were important factors constraining landscape patterns of burning, yet the sign and magnitude of the spatial correlation coefficient between these variables and burned area varied across biomes and along gradients of tree cover (
Fig. 4). All three indicators had negative spatial correlations with burned area in savannas and grasslands. Although these three variables had similar global structure, we found that the distribution of agricultural activity clearly modified burned area beyond population alone. For example, widespread agricultural waste burning in large parts of Asia generated a strong positive correlation between cropland and burned area. Similarly, livestock density and burned area were negatively correlated in the Brazilian Cerrado, as livestock may directly suppress fire activity by reducing fuel loads or altering fire management decisions. In tropical forests, population density and cropland were positively correlated with the spatial pattern of burned area, as humans have introduced fires for deforestation and agricultural management (
7,
27). In boreal forests, we found a stronger positive relationship between population and burned area in Eurasia than North America, consistent with past work documenting high levels of human-driven fire activity in Russia (
30). Trends in agricultural production and fire activity were also consistent at the national scale. The largest relative declines in GFED4s burned area occurred in countries with the largest increases in agricultural extent and production value (fig. S11).