The Fire Planet

Fire challenges the hegemony of paleoecology, biogeography and ecology that climate and soils are sufficient to explain the origin and distribution of plant species. Just like the fire triangle of oxygen-fuel-ignition controls fire occurrence, there is a need for a climate-soils-fire triangle to explain the distribution and assembly of past and present plant communities. Plant functional types are an integrated response to these three factors and past failure to recognize this has greatly inhibited conceptual models of plant distribution that are only now evident in obstacles to modeling global vegetation distribution with climate and soils alone. The venue for this meeting is in one of the most fire-prone landscapes in the world, yet paleobotanical studies of plant origins in this region have almost entirely excluded fire as a relevant factor. That view, however, is challenged by an increasing body of literature that indicates the Earth System was primed for a world of fire that began the instant land plant emergence provided biomass fuel. The fossil record shows the earliest land plant communities experienced wildfires, and throughout the Paleozoic and Mesozoic eras fire was a widespread ecosystem process and mirrored contemporary fire regimes. Today many plant traits are adaptive in fire prone landscapes yet it is uncertain to what extent these represent adaptations vs exaptations evolved in response to other environmental drivers. Distinguishing between the two may never be possible, however, this limitation is by no means unique to fire and applies to most plant traits. Although fire molded the Earth System long before humans, since their emergence as a dominant force they have played a profound role molding contemporary landscapes through alterations in natural fire regimes. As human populations have expanded, their actions have come to dominate some ecosystems and change natural fire processes in diverse ways that threaten the sustainability of some landscapes.