Introduction

Abstract

After human urban and agricultural activities, fire is the most ubiquitous terrestrial disturbance. From Arctic tundra and boreal forests to tropical grasslands and savanna, fire annually consumes enormous quantities of plant biomass (see end papers). In the tropics alone, it has been estimated that 2700–6800 million tonnes of plant carbon is burnt annually, mostly in savanna fires or in shifting agriculture (Crutzen and Andreae, 1990). Terrestrial vegetation has been swept by fire since at least Mesozoic times. Since the mid-Tertiary, the lethal combination of grasses and fire helped create open plains and initiate the great radiation of grazing mammals. Hominids first mastered fire over a million years ago (Brain and Sillen, 1988), setting in motion a great wave of environmental transformation which continues today. In Australia, the vegetation of the continent was transformed first by Aboriginal firestick farming and then by the burning practices of European settlers (Singh et al., 1981; Kershaw, 1986; Pyne, 1991). In North America, fire set by the first human settlers expanded the prairies and ate into woodlands and forests (Pyne, 1982; Axelrod, 1985). In Africa, evergreen forests shrank and grasslands and savanna expanded. People, fire and vegetation continue to interact in modern landscapes.