Fire puts asunder what photosynthesis hath joined together. The alchemy of fire can be described physically as a biochemical reaction requiring the simultaneous presence of fuel, heat, and oxygen. Pyrogeography is a multidimensional subfield of geography concerned with the study of the complex space-time interactions between fire and people. Humans have always been the keepers of the flame; thus, pyrogeography is, true to its geographic roots, integrative—spanning the physical, biological, and social sciences. It is an exemplary coupling of natural and human systems.

The fireshed—the pyrogeography equivalent of the watershed—consists of four variables: fuel, weather, topography, and people. Fuel refers to combustible biomass. Weather describes precipitation, temperature, and relative humidity variations that control ignition probability. Topography determines the position of fuels on the fireshed. This aspect ...