Human fires and wildfires on Sydney sandstones: History informs management

Abstract

There is a concept in fire ecology that some natural (pre-European) fire regimes were dominated by infrequent high intensity fires ignited by lightning. In Australia, some ecologists extend this to most or all ecosystems across the landscape. They regard contemporary human burning or prescribed burning as an unnatural disturbance that threatens biodiversity. Their particular concern is the potential extinction of slow maturing obligate seeders by frequent fire. However, a completely different picture emerges from study of Australia's ecological history and prehistory. There is ample evidence that Australian vegetation was shaped by thousands of years of frequent mild burning by Aborigines. Infrequent, high intensity lightning fires affected only small areas of wet forests in refuges that were physically protected from mild fires. We present a case study of ecosystems on the Sydney sandstones to demonstrate that a regime of infrequent high intensity wildfires since European settlement has caused structural changes and reduced spatial diversity. This has put many fire dependent plants at a competitive disadvantage and increased their susceptibility to disease.We argue that biodiversity, ecosystem health, and fire safety are threatened by lack of frequent mild fire. Ecological theory should build on ecological history. Australia is fortunate in having comprehensive historical records of Aboriginal burning against which paleoecological data can be calibrated. We emphasize the importance of using historical information to interpret ecological studies and inform fire management.