Impacts of savanna burning on biodiversity

Savanna burning has a long history in Australia, with Aboriginal use and management stretching back for millennia. Across northern Australia, it is a landscape-scale activity that affects vegetation and biodiversity. Many factors affect the frequency and timing of burning including land tenure (e.g. protected areas, pastoral, Indigenous land) and related management objectives (e.g. biodiversity, emissions trading, grazing, weed management, fire prevention). The various fire management aspirations for Indigenous land have been well described in the literature and continue to be the focus of discussion at annual north Australia savanna fire forums.

The impact of different fire regimes on biodiversity is of global interest and is a common aim of many savanna fire management programs. This project aimed to review the current burning regimes in northern Australia and the existing understanding of their relationship to biodiversity conservation. A secondary aim of the project was to identify pathways and opportunities for monitoring activities and future research which can help to inform how different fire regimes can benefit biodiversity.

There are some excellent published long-term systematic biodiversity surveys in the Northern Territory – particularly in Kakadu and Nitmiluk national parks – and several large-scale ongoing monitoring programs measuring different elements of biodiversity in partnership with land holders (e.g. Karrkad Kanjdji Trust). These monitoring programs will become important future studies to better understand the responses of biodiversity to different fire management practices applied across the region.

The project:

• completed a systematic desktop review of the impacts of fire on biodiversity in savanna landscapes, including compiling evidence that can inform improved long-term fire management
• convened workshops with biodiversity and fire experts to identify critical knowledge gaps, important data sources and refine the systematic review
• described current fire management regimes on different land tenure types and reviewed their differences and impact on biodiversity
• synthesised contemporary policy and management influences on savanna burning to understand recent trends and changes
• engaged Indigenous organisations to develop a robust and ethical process for capturing the diverse views and experiences of fire managers across northern savanna landscapes.

• There is a significant knowledge gap that encompasses fire and biodiversity in the diverse range of habitat and climatic types across northern Australian savanna landscapes outside the Darwin Coastal Bioregion.
• Previous research has not assessed the mechanisms that are responsible for biodiversity declines.
• Increasing understanding of savanna burning effects on biodiversity will require longitudinal studies that have a consistent experimental design over numerous years, particularly when time scales have to account for species recovery time of vertebrate fauna.
• Addressing critical knowledge gaps will depend on a coordinated and strategic approach across the fire management and research community.

By and large, the most instrumental driver of change to savanna burning regimes has been the implementation of carbon farming methodologies. Carbon farming methodologies within this zone promote the change of fire regimes from predominantly late dry-season, intense fires to lower-intensity, lower-emissions, early dry-season fires. This is achieved through the promotion of early dry-season fire which decreases fuel loads before they can build to destructive levels. Although carbon farming methodologies are a dominant driver of fire management, there are many different reasons why fire is used and these change across and within tenure types. We summarised fire historical fire regimes in major land-use types across the region to explore broad trends in fire management between sectors.

• Conservation estates: These areas are managed primarily for the protection of native biodiversity through control of invasive species (pests and weeds), habitat protection, restoration and fire management. Over the last 20 years, the peak fire season in conservation lands has remained relatively stable, occurring mostly across the beginning of the late dry-season period. Like other tenure types, fire size and area has decreased throughout this period.
• Indigenous land: Management of land on Indigenous estates has traditionally focused on managing land to care for Country and protect or restore cultural and natural resources (e.g. bush tucker). Historical disruption to Indigenous fire management led to an increase in late dry-season fuel loads resulting in increased fire frequency, size, and intensity. The development of carbon farming projects supported the reinstatement of Indigenous-led fire management and this has significantly decreased fire frequency, size and intensity with marked changes in fire seasonality with shifts towards early dry-season fire in recent times.
• Pastoral: More recently, pastoral lands have begun to adopt the savanna burning carbon methodologies as an additional source of revenue. Over the last 20 years, changes in fire size have followed the general trend for the region, decreasing in size, particularly following the implementation of the savanna burning methodologies in 2012. Fire seasonality has remained similar across these years, with a trend for more fire during the late dry season.
• Defence: On average, the Department of Defence burns 44% of its land via early dry-season burns – twice the amount of burning that occurs on Indigenous-owned land (22%). These large, non-mosaic type burns do not prioritise conservation values.
• Mining: Fire management regimes within these areas differ depending on the current state and use of the land. For example, if land is under restoration, it is managed for conservation values with early dry-season mosaic burning or weed-suppression burning, while land being actively mined will be managed for protection of assets.

The current knowledge base for biodiversity responses to fire regimes is concentrated in the Northern Territory, with Queensland and Western Australia having significantly fewer studies. Due to the vast range and variations throughout northern savanna bioregions and subregions, this limits the opportunities and appropriateness of applying NT-based knowledge to other locations.

Seeking to improve understanding of biodiversity responses also provides opportunities to capture, review and integrate other knowledge sources, such as Indigenous knowledge, into existing understanding of using fire for land management. There is also a concurrent opportunity to better describe and create metrics for how to implement specific fire regimes on-ground as well as increasing use of remote sensing technologies to aid the development metrics and improve the database on changing fuel loads across savanna landscapes.

Given the increasing development and uptake of savanna burning programs and methodologies in northern Australia and a growing interest in biodiversity, cultural and social benefits in response to a changing climate, this project reinforces the need for systematic and comparable studies into biodiversity responses to savanna burning.