Introduction

Throughout last year, extremely destructive fires raged throughout Australia and the Western United States. Great monetary and human resources have been diverted to fighting these fires, but to lead to a more sustainable future there must be an emphasis on fire prevention instead. This is especially crucial in areas currently suffering from intense and frequent fires, as climate change will only continue to worsen the consequences. To develop the best fire management strategies, Indigenous Knowledge (IK) should be considered. By living off the land for centuries, Indigenous peoples were able to pass down knowledge about their environments to each subsequent generation. This IK contains strategies as to how to best maintain sustainable fire regimes that they have developed over centuries. In order to demonstrate this, two case studies will be presented: one of the Martu in Western Australia, and one of the Native Americans in the Southwestern United States. The fire regimes of the two groups will be explored using a historical ecology framework, showing how both construct niches through burning, which increases which increases biodiversity and the productivity of the land. While it is clear through these case studies that fire thus can be beneficial when applied appropriately, fire suppression still remains the customary practice in modern culture and IK is often ignored. This is explored using a political ecology framework, which looks at the social, economic, and political issues that still exist when attempting to implement IK. Furthermore, it is also important to discuss how IK and prescribed burning cannot be applied to every situation, but management must be adaptive to location and current climate change. Overall, this paper argues that IK must be consulted for adaptive fire management to be effective and sustainable. 

 

Background on Fire Regimes

Natural fires have existed for at least 400 million years, shaping biomes and affecting plant and animal evolution (Bowman et al. 2011). The majority of these fires are started by lightning, which require dehydrated or dry vegetation that burns at 325ºC (Scott 2000). If lightning strikes this vegetation, it will heat it above this threshold and ignite. From here, oxygen is needed for the fire to continue. While natural fires do continue today, human-set or anthropogenic fires emerged at least by the last Ice Age during the Middle Pleistocene, affecting the environment around them in a dynamic way. To best understand the relationship between humans and their environment in regard to fire use, historical ecology can be used as a framework. To reconstruct historic fire regimes, palaeoecological proxies and historic sources are used, such as: remote sensing, tree rings, micro- and macro-charcoal, isotope chemicals, and written sources. As shown in Figure 1, each of these sources have differing benefits depending on the timescale and location of study. For example, looking one thousand years ago, using tree rings would be appropriate to reconstruct a local fire regime, but micro-charcoal would be better suited for regional fire regimes. Natural and human fires are distinguished from one another by looking for a change in fire activity over space or time that is not predicted by the climate-fuel-fire relationship. For example, if it is known that a particular location in a point of time was warm and dry, but there was very little vegetation and fuel there would be an expected low prevalence of fires in the area. If the reconstructed fire regime instead shows a high prevalence of fires, this does not align with predictions and suggests human alteration of the fire regime. For a fire to be determined as anthropogenic, the change in fire regime must be accounted for by coinciding with a temporal or spatial change in human history – whether this be changes in demography, humans arriving in the area, development of new technology, etc. These data sets are synthesized to demonstrate the relative dominance of natural vs. anthropogenic fire over time. In the last 2000 years, charcoal analysis demonstrates that human fire activity had a more dominant effect on the environment than natural fires, as global charcoal levels changed primarily based on human burning of forests in the Americas, Europe, and Australia. Especially with the last 300 years of industrialization, human fires undoubtedly are a driving force in altering the environment with the burning of forests and fossil fuels (Bowman et al. 2011). 

Figure 1: Summary of historical sources and palaeoecological proxies for reconstructing historic fire regimes (Bowman et al. 2011).

Once anthropogenic fire is introduced, it can be used as a tool for niche construction and managing land over periods of time. Fire depends on three vital ingredients: oxygen, heat, and fuel (Bowman et al. 2011). Humans can alter different aspects of these ingredients, resulting in different fire regimes. As shown in Figure 2, the effect of these changes can be visualized in triangular schematic models called pyric phases. This model illustrates how changes to the three ingredients of fire can create new fire regimes. This transition from one regime to another is called a pyric transition. The main way in which humans can alter the fire regime is by altering fire intensity. Fire intensity is a measure of the amount of heat (measured in Watts) released per meter of the fire front. Low to moderate fires have an intensity of less than 3000 kW/m, whereas high intensity fires are any values above 3000 kW/m (Alexander and Cruz 2018). As this value is calculated from the heat of combustion, amount of fuel consumed, and rate of fire spread, the alteration of fuel and heat by humans alters the fire intensity.

Figure 2: Visual representation of pyric phases, demonstrating how changing oxygen, fuel and/or heat can lead to a pyric transition (Bowman et al. 2011).

The ecosystem in which humans burn becomes adapted to the new anthropogenic fire regimes. This leads to co-evolution, which alters the prevalence and distribution of plant and animal species in the area. This is done as a form of intensification, which can be defined as the increasing of resource productivity and efficacy (Bird et al. 2016). Disturbances such as fire or predation may at first appear to have negative consequences on an ecosystem, when in reality they can intensify short- and long-term returns. The collective impacts of fire regimes are encompassed by Bowman and Legge’s interpretation of Martin and Sapsis’ term “pyrodiversity”, looking especially at food webs and biodiversity (Bowman and Legge 2016). In terms of food webs, fire affects all trophic levels differently and allows for dynamic interactions as fire regimes are changed. For example, the sudden introduction of high intensity fires can affect predation practices. Burning reduces the amount of vegetation available as a primary food source, and thus larger mammals will begin to hunt more small/medium sized mammals. The use of fire for intensification and niche construction also affects biodiversity, which is the variety of species in a particular ecosystem. With the same example, the presence of high intensity fires decreases biodiversity as diverse plant mosaics are burnt off and the numbers of small/medium mammals decline (Bowman and Legge 2016). Low intensity burning patterns, on the other hand, have been found to lead to a heterogeneous mosaic of vegetation, supporting a wider diversity of species (Bird et al. 2016). Since each species has an important role to play, maintaining biodiversity is crucial for a stable, healthy ecosystem. Throughout the following two case studies, niche construction and intensification will be used as a way to assess and understand the effects of different fire management techniques.

 

Martu in Western Australia

Human foraging has been an important practice for at least 36,000 years in Australia. Many Aboriginal foragers were forcibly relocated by the government in the 1950s-1970s out of the desert to missions and reserves, but in the 1980s some groups returned (Bird et al. 2013). The Martu are a group of Aboriginal peoples that returned to the deserts in 1984 after a 20-year absence, with the main communities today being a part of a 13.6-hectare determination in Western Australia (Kanyirninpa Jukurrpa n.d.). Once arriving back on their land, the Martu re-established their traditional burning practices for the purpose of hunting. Because the desert does not easily provide many resources for the Martu, they must intensify their land in some way to support their population. They utilize a low-intensity mosaic patch burning technique that serves to effectively burn off hummock grass to aid in tracking small animals. Prey is “hunted with fire in the winter and tracked in recently burned ground in the summer” (Bird et al. 2016). Since burns are completed during the winter and dry season, these fires are much cooler and easier to control. While the fires are contained by natural barriers such as trails or desert areas where there is no fuel, the Martu continue to carefully monitor the low flames and are prepared to extinguish them. This technique of burning leads to a finer-grained successional mosaic, with each patch in a different stage of regrowth, as seen in Figure 3 and 4 (Bird et al. 2013).

Figure 3: Land in Western Australia without controlled burning where lightning fires have cleared the land (Gattuso 2020)