Australian landscape burning: a continental and evolutionary perspective

Australia has long been the most fire prone continent on Earth with a dominant biota not only tolerant of recurrent fires but also highly fire-adapted. The evolutionary driver of this syndrome appears to be the conjunction of the drying-out of the continent some 15 M years BP and the predictable ignition source provided by the convection storms that herald the onset of the Australian summer monsoon. Aboriginal people played an important part in the making of flammable Australia as we now know it, but they did not trigger the relentless fire cycle; rather, over some 40-70 ka they learnt to harness the naturally-occurring fires to their economic advantage. This has been described as fire-stick farming, but given the central importance of fires for hunting perhaps a more apt description may be fire-stick ranching. While it is possible that fire-drives contributed to the extinction of the Pleistocene megafauna, a byproduct of the skilful burning of landscapes at the height of the ice-age aridity may have been the conservation of many fire sensitive habitats. Despite being tolerant of frequent burning many Australian ecosystems have been severely affected by the breakdown of Aboriginal fire management following European settlement. Thus, it appears that over an extraordinarily long time period Aboriginal landscape burning created a brittle landscape ecology. The transition from traditional Aboriginal to European fire management is a major ecological and evolutionary event that, while being different in character, is of the same significance as the Pleistocene colonization of Australia by the ancestors of Aboriginal people. Altered fire regimes in tracts of native vegetation have contributed to decline in the abundance and range contraction of many plant and animal species, especially small mammals and granivorous birds, in some case to the point of their extinction. In many landscapes, changes to fire regime are compounded by the introduction of exotic plants and animals and land uses that restrict the active use of fire. The great challenge for settler Australians was to learn how to sustainably manage a flammable land by slowing the rate of change and creating new ecological equilibria. Understanding past and present Aboriginal fire usage is a key step in this adaptive process.