Long before British invasion of southeast Australia in 1788, Indigenous people managed Australia’s flammable vegetation with “cultural burning” practices. These involved frequent, low-intensity fires which led to a fine-grained vegetation mosaic comprising grassy areas and scattered trees.

World-first research confirms Australia’s forests became catastrophic fire risk after British Invasion… 

The Conversation this week reveals its research

Australia’s forests now carry far more flammable fuel than before British invasion, research by The Conversation shows, revealing the catastrophic risk created by non-Indigenous bushfire management approaches.

Contemporary approaches to forest management in Australia are based on suppression – extinguishing bushfires once they’ve started, or seeking to prevent them through hazard-reduction burning.

This differs from the approach of Indigenous Australians who’ve developed sophisticated relationships with fire over tens of thousands of years. They minimise bushfire risk through frequent low-intensity burning – in contrast to the current scenario of high-intensity fires.

Our research, provides what we believe is the first quantitative evidence that forests and woodlands across southeast Australia contained fewer shrubs and more grass before colonisation. This suggests Indigenous fire management holds the key to a safer, more sustainable future on our flammable continent.

 

Not just a climate story

Globally, climate change is causing catastrophic fire weather more often. In Australia, long-term drought and high temperatures were blamed for the Black Summer bushfires in the summer of 2019-20. This event burned 18 million hectares, an area almost twice the size of England.

The unusually high fire extent in forests prompted several important questions. Could these massive fires be explained by climate change alone? Or was the way we manage forests also affecting fire behaviour?

Recent catastrophic fires in Australia and North America prompted renewed scrutiny of how the disruption and exclusionof First Nations’ burning practices has affected forest fuel loads.

Fuel load refers to the amount of flammable organic matter in vegetation such as leaves, twigs, branches and trunks. Large fuel loads in the shrubby layers of vegetation enable flames to more easily reach tree canopies, causing intense and dangerous “crown” fires.

Long before British invasion of southeast Australia in 1788, Indigenous people managed Australia’s flammable vegetation with “cultural burning” practices. These involved frequent, low-intensity fires which led to a fine-grained vegetation mosaic comprising grassy areas and scattered trees.

Landscapes managed in this way were less prone to destructive fires.

 

“ FROM THE RESEARCH PAPER …..

Abstract

In a nutshell:

 

• Historically unprecedented fires in Australia have raised questions about fire management and changes in forest structure since British colonization
• New modeling techniques were used to assess past vegetation change from fossil pollen sequences
• Results show an increase in shrub cover in southeast Australian woodlands following colonial settlement, linked to the suppression of Indigenous burning practices
• Increased shrubbiness, in conjunction with climate change, may have exacerbated wildfires in southeast Australian forests

The impact of large wildfires is escalating across many parts of the globe as climatic conditions become more conducive to extreme fire weather (Nolan et al. 2020). Western North America and southeast Australia are global hotspots of catastrophic wildfires with severe economic and social consequences (Bowman et al. 2017). As human populations increase worldwide, urban expansion into forested zones and climate change are raising fire impacts to unprecedented levels (Bowman et al. 2017). Thus, the development of efficient forest management plans in accordance with past land-use history is imperative (Whitlock et al. 2018).Western North America and southeast Australia are areas where European colonization disrupted long-standing Indigenous burning practices (Guiterman et al. 2019; Fletcher et al. 2021). In North America, tree-ring evidence indicates the suppression of Indigenous fire regimes, or “cultural burning”, had major consequences for forest composition and fuel connectivity (Whitehair et al. 2018; Guiterman et al. 2019; Larson et al. 2020). Ecologically sustainable Indigenous fire management protected biodiversity and provided ecosystem services for millennia. Cessation of these practices has increased the risk of environmentally and socially destructive extreme fires (Whitehair et al. 2018). Indigenous peoples have inhabited Australia for at least 65,000 years (Clarkson et al. 2017) and oral tradition, historical, and ethnographic sources attest to sophisticated systems of land management, including skillful cultural burning (Gott 2005; Gammage 2011; Pascoe 2014). Routinely ignoring these sources, authorities in colonial and subsequent governments falsely asserted Australia as terra nullius (“nobody’s land”), thereby justifying land expropriation and discounting the wisdom of traditional ecological knowledge (Borch 2001; Steffensen 2020).Prior to British colonization in the year 1788, Australia’s flammable vegetation had been managed by Indigenous peoples primarily through the frequent ignition of small fires (Gott 2005). A consistent ecological outcome of this management was to alter the balance between herbaceous and woody biomass, limiting shrub density in understory vegetation and maintaining patchy open woodlands and savanna-like landscapes across a broad elevational range (Gott 2005; Gammage 2011). Not only did fire management increase landscape productivity and facilitate hunting practices, it was a tangible cultural connection of people to place (Jones 1969; Hallam 2014). Indigenous fire regimes created fine-scale landscape heterogeneity (Bliege Bird et al. 2016), with pyrodiverse mosaics of open woody vegetation (ie low shrub abundance) and sparsely treed plains (Bowman and Prior 2004) that were less prone to destructivehttps://esajournals.onlinelibrary.wiley.com/doi/10.1002/fee.2395 fires than current forests (Gott 2005). In contrast, colonial vegetation management implied clear-cutting and intense firing to create large-scale patches in areas deemed suitable for agricultural activities, particularly low-elevation plains, while forests in rugged terrain were left unmanaged or exploited through selective logging (Griffiths 2001).Globally, there is growing recognition that Indigenous burning practices are key to sustainable fire management (Colombaroli et al. 2019). In Australia, cultural burning is experiencing a renaissance (Steffensen 2020), yet its potential to mitigate catastrophic forest fires is still under debate (Cary et al. 2003; Russell-Smith et al. 2009). In part, this discussion stems from uncertainties concerning how British colonization affected the composition and structure of vegetation, thereby altering the core components of fire regimes (frequency, extent, and severity) (Head 1989; Bradstock et al. 2002; Enright and Thomas 2008). Accurate determination of pre-colonization baselines, along with an understanding of vegetation and fire-regime trajectories, are prerequisites for the development of sustainable fire management.

Proxies for Indigenous-managed landscapes

Science has had mixed success in uncovering evidence of cultural burning on different continents. Detailed fire-scar studies – crucial for demonstrating the prevalence of Indigenous cultural burning and the impacts of its cessation in North America (Whitehair et al. 2018; Guiterman et al. 2019; Larson et al. 2020) – cannot be replicated in southeast Australia. Detailed fire-scar histories are prevented by the poor dendroecological potential of Eucalyptusto disclose annual fire history (Brookhouse 2006), and the loss of ancient trees to logging, land-use change, and recent severe fires in southeast Australia (Cary and Banks 2000). This necessitates an alternative approach to investigating how cessation of Indigenous land management practices, due to forced removal from traditional lands and imposition of foreign fire management practices, changed the region’s forest structure.

Controls on fire in southeast Australian vegetation

On a landscape scale, fire occurrence and spread are determined by the confluence of an ignition source (humans or lightning), sufficient fuel (biomass), and suitable weather (Krawchuk et al. 2009). Ignition sources in southeast Australia have been largely anthropogenic since the arrival of Indigenous peoples (Bradstock et al. 2002). Although lightning-strike fires are still relatively rare, these have increased in recent decades as a result of climate change (Styger et al. 2018).

Biomass availability depends on long-term moisture availability and landscape management (decades to millennia), while its suitability to burn depends on short-term weather conditions (hours to months) (Bowman et al. 2009). The sclerophyll vegetation of southeast Australia characterizes one of the most fire-prone regions on Earth (Hennessy et al. 2005). In this region, fires range from infrequent and low-intensity in pasture/cropland, through medium frequency and variable intensity in dry sclerophyll forests and woodlands with limited tree mortality, to infrequent but high intensity in wet sclerophyll forests, often with substantial tree mortality (Bradstock 2010; Murphy et al. 2013).

Fire weather (hot, dry, and windy conditions) in southeast Australia is regionally controlled by interactions among the El Niño–Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Southern Annular Mode (SAM) (Hennessy et al. 2005; Harris and Lucas 2019). These inter-annual climatic modes have played major roles in modulating rainfall patterns and preconditioning vegetation to burn across southeast Australia over the past 50 years (Harris and Lucas 2019). Climatic change over the past 1000 years has been reconstructed using corals, tree rings, and speleothems (for temperature; Gergis et al. 2016), as well as a seasonal sea-salt record from Antarctica (for precipitation; Vance et al. 2015). These records show that the most substantial climatic change over the past millennium occurred in the mid- to late-20th century through increased temperature and greater frequency of megadroughts, both of which are linked to anthropogenic climate change. “

Full original research paper  is here