A framework for testing the influence of Aboriginal burning on grassy ecosystems in lowland, mesic south–eastern Australia

Abstract

Abstract. The complex interactions among climate, soils, fire and humans in the biogeography of natural grasslands has long been debated in Australia. On the one hand, ecological models assume the primacy of climate and soils. On the other, Aboriginal burning is hypothesised to have altered the entire continent since before the last glacial maximum. The present paper develops a framework to test for the 'fingerprint' of Aboriginal burning in lowland, mesic grassy ecosystems of south-eastern Australia, using ecological theory, and the ethno-historical record. It is clear that fire-stick farming was used to promote staple roots in south-eastern Australia and, in some instances, it has been shown to influence grassland-woodland boundaries. The framework comprises the following three evidence lines: (1) archival benchmarking and palaeoecology; (2) phytoecology; and (3) ethnology and archaeology. That fire-stick farming was likely instrumental in grassland formation and maintenance must be supported by evidence that shows that 'natural' grasslands exist in climatically-edaphically unexpected places, that fine-scale patterns and dynamics are at least partly due to fire and that the fire regime has been influenced by Aboriginal burning. Application of the framework indicated that widespread Aboriginal burning for staple foods likely extended the area of temperate grasslands and influenced their structure and function.

Vegetation fires in the Anthropocene

“…The uncertainty is partially because historical records of fire activity, even for simple metrics like area burned, are short and available for only a few nations 55 . Prehistorical fire records, which are essential to understanding the fire history of infrequently burned vegetation, rely on palaeoecological proxies such as dendrochronology and analysis of sedimentary charcoal 19,[56][57][58][59][60] . These proxies, unfortunately, do not directly scale to key components of fire regimes, such as frequency or geographic extent of fires, and there are few regions, such as the western USA, with a large number of high-resolution records that extend into the prehistorical period 60,61 .…”

Soil or fire: what causes treeless sedgelands in Tasmanian wet forests?

“…In many parts of the world there remains considerable controversy as to whether savannas are the result of anthropogenic fire-activity or arise independent of human fireuse (Willis et al 2008;Bowman and Haberle 2010;McWethy et al 2010), with some authors arguing that plant and animal species diversity can be used as evidence against human agency (Bond et al 2008;Foreman 2016). In the case of Tasmanian sedgelands the diverse, and in some cases endemic, vascular (Corbett and Balmer 2007;Lawrence et al 2007) and non-vascular (Kantvilas 2007) flora and vertebrate (Driessen 2007) and invertebrate (Driessen et al 2014) fauna points to an ancient ecosystem that preceded human colonisation in the late-Pleistocene.…”

“…Environmental history narratives such as The Future Eaters, The Biggest Estate on Earth (Gammage 2011) and Dark Emu (Pascoe 2014) have ingrained in the popular imagination the idea that Aboriginal fire-use fundamentally transformed Australia. Evaluating the ecological legacy of landscape burning by indigenous people is extremely challenging (McWethy et al 2013;Foreman 2016), but is essential for understanding how current and future human-dominated fire regimes might transform vegetation distributions globally (Johnstone et al 2016) and the flow-on effects for the carbon cycle and hence anthropogenic climate change (Furley 2010).…”

Integrating charcoal morphology and stable carbon isotope analysis to identify non-grass elongate charcoal in tropical savannas

“…The relative contribution of grasses provides key information in many environments, but particularly savannas, due to potential connections between grass biomass and fire (Cheney and Sullivan 2008;Ekblom and Gillson 2010;Prior et al 2016;Leys et al 2017;Cardoso et al 2018;Wragg et al 2018). Debate is ongoing regarding the relative influence of fire caused by humans, climate, and moisture availability, along with nutrient levels and ecological disturbances, on the dominance of grasses versus trees and woody vegetation across a range of temporal and spatial scales (Hoffmann et al 2002;Murphy and Bowman 2007;Breman et al 2012;Scott et al 2012;Aleman et al 2013;Colombaroli et al 2014;Foreman 2016;Strickland et al 2016;D'Onofrio et al 2018;Feurdean and Vasiliev 2019).…”