Teacher background information

This elaboration provides students with the opportunity to consider the impact of human activity on the Australian continent through the fire management practices of Aboriginal and Torres Strait Islander Peoples. The flora and fauna on the surface of the Australian continent have changed over millennia as a result of human activity. Aboriginal Peoples first came to the Australian continent in the late Pleistocene and adapted to life on the unfamiliar Australian continent. While Australia’s First Peoples were adjusting to the new environment and employing scientific practices to gain information about previously unknown species of plant and animal life, the environment was also adjusting to the ecological pressures caused by the arrival of humans. The Australian environment had long adapted to the presence of fire prior to the arrival of humans. However, the arrival of humans altered these fire regimes, and ultimately Aboriginal and Torres Strait Islander Peoples developed and implemented fire management practices that purposefully changed the distribution of flora and fauna in many environmentally diverse regions of Australia. This elaboration provides students with the opportunity to consider these changes to the Earth’s surface over millennia and understand the impact of human involvement through fire-managed environmental changes.

An aspect of paleoecology, the study of past ecosystems, involves the analysis of fossil charcoal and pollen to reconstruct the vegetation and presence of fire in past landscapes. Such analyses of areas of the Australian continent provide the scientific evidence base used to postulate reasons for environmental changes and to reconstruct the Australian landscape over time. During the late Pleistocene the Australian continent was colder and drier than it is today, glaciers existed across the south east of mainland Australia and Tasmania, and sea levels were at their lowest. The large size and climatic diversity of Australia supported a wide range of vegetation. Rainforest vegetation predominated in parts of the Australian continent including the area to the east of the Great Dividing Ranges where rainfall was high and regular. Climatic variation in the late Pleistocene caused the continent to become drier; this resulted in the spread of sclerophyll vegetation to the west of the Great Dividing Range, where rainfall was lower and arid conditions prevailed.

The expansion of sclerophyll vegetation in relation to rainforest vegetation in many parts of the Australian continent, and associated increases in fossil charcoal indicating increased biomass burning, suggest that fire has been a part of the Australian landscape for more than 15 million years. Natural fire has long been a part of the Australian environment, triggered by lightning, volcanic activity or other initiators of combustion. The sclerophyll vegetation and seasonal arid conditions provided fuel that facilitated the maintenance of fire by these natural causes. Parallel increases in fossil charcoal and sclerophyll pollen suggests that the late Pleistocene fires further dried out the environment, favouring the spread of fire-adapted sclerophyll vegetation. Australian fauna has evolved along with fire. Some Australian species such as Eucalyptus spp. reproduce vegetatively after fire, re-sprouting from a dormant bud under the thick bark, while other species, such as Banksia spp., require fire, heat or smoke for seed germination.

The arrival of humans on the Australian continent more than 60,000 years ago further altered the habitat balance of ecosystems as flora and fauna adjusted to respond to the presence of human activity. Charcoal evidence in lakes and swamps in Australia suggests an increase in landscape burning approximately 40,000 years ago, coinciding with human activity. In north eastern and northern Australia charcoal records indicate an increase in landscape burning and vegetation change that may suggest evidence of Aboriginal Peoples’ fire management regimes. Frequent application of fire to the environment can result in permanent vegetation changes through alterations to the physical and chemical properties of the soil, changes to the moisture holding capacity of the soil, and an impact on species germination. Such environmental changes favour the growth of more open sclerophyll vegetation.

Fire regimes implemented by the Jirrbal Peoples in the Atherton Tablelands region of north Queensland about 45,000 years ago resulted in sustained replacement of drier rainforest vegetation with sclerophyll vegetation. The charcoal analysis of this region shows an increase in the presence of fire and an absence of significant climatic factors that could account for the change, leading researchers to interpret the vegetation change to be the result of Aboriginal fire management. Similarly, an increase in fire activity by the Gundangara and Ngunnawal Peoples of the Lake George region near Canberra, as evidenced in charcoal and pollen records, may have caused a shift from evergreen vegetation to eucalypt woodland.

Contemporary science acknowledges that vegetation changes that were the result of natural fire prior to the human occupation of Australia have been understood and utilised by Aboriginal Peoples for tens of thousands of years. There is a belief that these fire regimes were responsible for the Australian landscape that was documented at the time of early European exploration.

When Australia’s First Peoples arrived on the continent, the landscape was populated by megafauna, a group of large land animals that existed in the last 2.5 million years. In Australia, many species of megafauna became extinct approximately 46,000 years ago in the late Pleistocene. However, not all Australian megafauna is extinct; the red kangaroo, cassowary, emu and crocodiles are all species of megafauna that exist on the Australian continent today. The reason/s for the demise of many species of megafauna in Australia remains contested by scientists as research continues to investigate the cause/s of extinction. One hypothesis is that the burning of the landscape that altered the vegetation types, whether by Aboriginal Peoples or natural causes, diminished the food supply for the megafauna and led to their extinction. Other hypotheses include climate change that led to an increase in arid conditions and less surface water availability, anthropogenic pressures following the arrival of humans to the Australian continent, and various combinations of these theories.

Recent scientific research provided evidence that Aboriginal Australians co-existed with some extinct megafauna for at least 17,000 years and possibly up to 30,000 years. Fossil remains of the wombat-like marsupial Zygomaturus trilobus recovered from the lands of the Muthi Muthi, Nyiampaar and Barkindji Peoples of the Willandra Lakes region in far west New South Wales have been dated to 33,000 years ago, while the presence of humans in the region is dated to 50,000 years ago. Further association of megafauna and Aboriginal Peoples is evidenced by the depictions of the large marsupials in iconographic records. A painting of the large emu-like bird, Genyornis newtoni, is depicted in the caves of the Jawoyn Peoples in western Arnhem Land and a representation of a marsupial lion, Thylacoleo carnifex, is evident on the lands of the Wenamba and Gamberre Peoples in the Admiralty Gulf region of Western Australia. While recent scientific investigations associate fire with changes to both the plant and animal life on the Australian continent, the extent and significance of the impact is yet to be fully explained.

The current geological epoch, the Holocene, commenced approximately 12,000 years ago at the end of the last glacial period. At this time the climate changed, becoming wetter and warmer. Sea levels rose, inundating the coastal regions of the continent and isolating Tasmania from the mainland. Aboriginal Peoples’ records and contemporary science clearly demonstrate the longevity of the controlled and skilful application of fire to maintain the landscape. Carefully considered Aboriginal fire use is important in maintaining the function of ecosystems. Aboriginal fire regimes, including the application of frequent, low intensity fires, remove the woody understory of the landscape, prevent fuel accumulation, allow grasses and tubers to flourish, increase the productivity of important food resources such as cycads, and protect fire-sensitive vegetation. In Aboriginal fire regimes, fire is purposely applied in a mosaic pattern so that nearby unburnt areas of land can provide refuge for wildlife. This practice enhances habitat diversity.

The significance of ecosystem management through the continued fire management practices of Aboriginal Peoples is evidenced by the Dukaladjarranj Peoples of north-central Arnhem Land. The Dukaladjarranj Peoples have used fire regimes to manage the Country of which they have had unbroken custody, and this has ensured abundant and diverse plant and animal species. The scientific knowledge that underpins the continued application of long-practised fire regimes fulfils cultural obligations to the land and maintains healthy ecological distribution of native flora and fauna in the region.

European colonisation of the Australian continent resulted in changes of flora and fauna distribution caused by the suppression of Aboriginal Peoples’ fire-based agricultural practices and the clearance of vast tracts of lands for European agricultural practices. Research has shown that when long-held Aboriginal fire management practices were disrupted there were significant ecological effects. For example, the Leadbeater's possum, believed to have evolved about 20 million years ago, is now critically endangered. A wildfire that swept through the possums’ habitat in the central highlands region of Victoria caused massive population decline in an already endangered species. Wildfires can be the result of a loss of Aboriginal fire management regimes; carefully controlled fuel loads can prevent uncontrolled wildfires. Ecological changes in this region through the disruption of the necessary Aboriginal fire regimes have changed the habitat structure, reducing the availability of suitable habitats for mammals. Since European colonisation, 30 Australian land mammal species have become extinct. Although there is no single cause that can be attributed to these extinctions, the suppression or removal of Aboriginal fire regimes are thought to be a significant contributing factor.

Areas of Australia’s savanna regions provide further evidence of the impact of Aboriginal fire management practices. The lack of Aboriginal fire management has resulted in the decline of the cypress pine, an ethnobotanically important species that requires very specific fire management to sustain healthy populations. The cypress pine has long been used by the Tiwi Peoples medicinally and as an insect repellent. Fire ecologist Bowman’s evaluation of fire management in northern Australia that has affected the cypress pine led to the conclusion that “conservation of biodiversity in Northern Australia will hinge on land managers returning to fire regimes that approximate those used by Aboriginal people” (1995).

Similarly, on Saibai Island in the Torres Strait, the reinstatement of fire management practices is conducted to suit Saibai’s unique fire adapted habitats and regimes. These are carefully considered and respond directly to the unique habitat structure that exists as a result of fire regimes implemented long prior to colonisation. Saibai Elder, Mebai Warusam, has contributed to the body of knowledge for the reinstatement of effective fire regimes suitable to the vegetation of Saibai that differs from mainland Australia. Prior to colonisation, fires were purposefully set within a narrow seasonal window (September–October), were of greater intensity and covered larger areas than fires used on mainland Australia. It is now acknowledged that the habitats of Saibai are a product of this more intensive burning regime. Maintenance of these habitats, which support a diverse range of flora and fauna species, will depend on the reinstatement of burning practices that mimic those of the original fire practitioners.

This elaboration provides students with the opportunity to consider how the fire regimes of Aboriginal and Torres Strait Islander Peoples over millennia have changed the distribution of flora and fauna on the Australian continent. The Earth’s surface changes as a result of human interaction, and in Australia, fire management practices implemented by Aboriginal and Torres Strait Islander Peoples have influenced the diversity of vegetation and wildlife. Students can learn about the impact of human arrival on the Australian continent, the impact of fire (or removal of fire) on the environment for tens of thousands of years, and the resulting ecological changes. Students can also learn how current environmental fire management strategies are being informed by the long-held scientific knowledges of Australia’s first fire practitioners.