Figure 1.

Regional differences in fire regimes can be seen along the GPP-population density axis. The frequency of occurrence of different GPP-population density driver pairs (A), and the mean burned area observed for each pair (B). Population density is log-transformed with the function ($y=\text{log10}(1+x)$). In general, fires occur at intermediate values of GPP and decrease with population density. However, the responses of burned area to population density are starkly different in different regions: In South America, burned areas are already low at low population densities, and decrease sharply to almost zero at population densities >3 persons/${\text{km}}^2$. By contrast, fires persist till very high population densities and decline only gradually with increasing population density in Africa. In Australia, burned areas are high at near-zero population densities, but decline sharply even for small population densities.