The Bushfire Crisis: Implications for Australia’s Unique Alpine Flora and Fauna

Alpine-Wetland-Complex Photo by James Camac

The bushfire crisis in Australia has dominated news headlines these past few weeks, affecting cities, towns and rural areas including the unique Australian alpine environment. This has prompted many to question what implications these fires have for these alpine ecosystems, but also the complex interactions with human dimensions and management options in a changing climate in mountain social-ecological systems.

 

The following article was written by University of Melbourne Postdoctoral Research Fellow James Camac and originally posted by James as a Twitter thread, in which he shares some key perspectives. 


The ongoing catastrophic fires burning across Australia have sparked immense national and international interest for its impacts on both human lives as well as our environment. As of 9 January, 2020, bushfires across Australia have burnt more than 18,626,000 hectares of land and are expected to kill more than 1 billion native animals.

Alpine ecosystems, which occupy less than 0.04% of Australia’s land mass, are also being burnt by these fires. This has prompted many to question whether these alpine ecosystems can recover, and whether we should reintroduce grazing to mitigate future risk of such fires. Below, I outline what we know about the recovery of Australian alpine ecosystems post-fire and what longer-term threats will be. 

Post-fire recovery of Australian alpine ecosystems

First, fire in the Australian alps is more common than what most people think. Dendrochronological evidence indicates that large fires have occurred in the Australian Alps every 50—100 years over the past 400 years. Parts of the Australian Alps were recently burnt in 2003 and 2006. In both cases, the area burnt spanned many ecosystems from the foothills forests, montane tall open forests, subalpine forests, and woodlands. Significant proportions of treeless alpine ecosystems, such as alpine heathlands, herbfields, grasslands and peatlands, were also burnt.  

Australian Bushfire 1Fire burning through alpine heathland. Photo by Dr Henrik Wahren.

We also know that some vegetation types are much more flammable than others. In the high elevation treeless zone, heathland is substantially more flammable than grasslands, to such an extent that the 2003 alpine fires burnt 87% of closed heathland on the Bogong High Plains, while only 13% of the grasslands burnt.

Scientific studies following the 2003 fires have shown that most of the vegetation within the snow gum treeline, as well as above it, has a strong capacity to recover, with many plant species either resprouting or germinating by seed within months post-fire.  In most cases, floristic composition, and in some cases vegetation structure, can reach pre-fire levels within a decade or two, even within severely burnt sites.

Australian Bushfire 2Top Left: Extensive alpine landscape burnt by the 2003 fires; Top Right: Differential flammability between shrubs and grasses; Bottom Left: Severely burnt alpine shrub - Orities lancifolia; Bottom Right: Severely burnt Orities lancifolia resprouting post-fire. Photos by Dr Henrik Wahren.

 

While this suggests that an entire ecosystem collapse is unlikely to occur from a single large fire, some fire-sensitive plant communities can be devastated by fire. One such alpine example is the coniferous heath – Podocarpus lawrencei. This slow-growing shrub provides vital habitat and a food source for the critically endangered mountain pygmy possum.

Like the lower elevation mountain ash forest, when these coniferous heaths are burnt, it re-establishes by seed which then may take a century or more before it becomes large enough to act as viable pygmy possum habitat. Worse still, if these coniferous heaths are burnt again before becoming reproductively mature, they could be lost forever. 

Australian Bushfire 3Podocarpus lawrencei 14 years of post-fire recovery following the 2003 fires. Photo by Dr Phil Zylstra.

 

Similarly, if alpine sphagnum wetlands and bogs are severely burnt – the primary habitat for the critically endangered Corroboree frog – recovery will take decades and, in some cases, may not happen at all.

Alpine Wetland ComplexAlpine wetland complex. Photo by James Camac.

 

What we don't know much about is how the dominant alpine fauna (invertebrates) will be impacted by fire, whether their populations can recover, and over what timescales. These fauna are the dominant herbivore in the Australian Alps and are critical to multiple ecosystem services ranging from pollination through to decomposition of plant litter. 

In many cases, Australian alpine invertebrates have very limited dispersal capabilities. While this can result in significant genetic divergences among insect populations over short distances, it also means they are unlikely to outrun fire. My own guess is that invertebrate responses in the Australian Alps will mostly be driven by how their habitat is impacted by fire and how quickly it can recover. 

Mountain KatydidMountain Katydid. Photo by Kate Umbers.

 

In highly flammable vegetation (e.g. snow gum woodlands & heathlands), I suspect fauna population losses are likely to be greater due to the higher fire intensity (fire line temperature) and severity (biomass consumption) relative to less flammable alpine communities (e.g. grasslands & herbfields). However, much further work is required in this space to elucidate what the actual responses are.

Public outcry for more fuel mitigation in Australian alpine national parks

 The extent and severity of current fires has recently seen significant public debate about the merits for more hazard reduction burns or the reintroduction of cattle into our alpine national parks in order to reduce risk of future fires.

In regards to our alpine zones, little can practically be done to reduce fuel loads. This is because landscape fires in the Australian alpine zone typically occur during periods of extensive drought coupled with extreme fire weather. Science has highlighted that under such weather conditions, fuel management has limited impact on the spread and severity of such fires. Moreover, due to the complex topography in these landscapes, hazard reduction burns are notoriously difficult to conduct safely. Even low intensity prescribed fire removes vegetation cover and exposes the soil to the erosive forces of frost, rain, and wind. This, coupled with climate change reducing the window of opportunity for conducting hazard reduction burns, means that this is not a feasible or effective option in this landscape.

Others have called for the reintroduction of cattle and sheep grazing within alpine national parks. This is despite significant scientific evidence conducted both within the alpine and subalpine ecosystems highlighting that such grazing does not reduce the likelihood or severity of landscape fires and may in fact actually promote fire via increasing shrub cover. More importantly, our alpine ecosystems are not adapted to hard-hooved animals, with significant increases in erosion potential, changes to floristic composition, and damage to wetlands linked to cattle grazing.

Cattle grazing alpine grassland Cattle grazing alpine grassland burnt by the 2003 fires. Photo by Dr Henrik Wahren.

 

Perhaps more simply put, grazing occurred in the Victorian alps right up to the 2003 fires yet 50% of the Victorian alpine national park was still burnt. Grazing also occurred prior to and during the previous major alpine fires of 1939, and again it didn't prevent fire spread within this landscape. So no matter how one looks at it, the evidence does not stack up for the reintroduction of cattle grazing in these landscapes.

Immediate and future threats to Australian alpine ecosystems

 The reality is, climate change via increases in drought and extreme fire weather is almost certainly going to increase the number and severity of landscape fires in Australian alpine environments.

My own scientific work suggests that this will be exacerbated in the alpine treeless zone via a positive feedback between climate, alpine shrubs and fire. Specifically, a 1°C temperature increase can result a doubling in shrub growth rates, thereby increasing fuel loads which may lead to more frequent and severe fires. Fires in turn provide the opportunity for shrubs to invade less flammable communities (e.g. grasslands) and thus make them more flammable. In fact, this idea that fire promotes more flammable vegetation has also been noted by others examining changes in flammability in the forested foothills.

Feedback loop James CamacFeedback loop between climatic warming, fire and alpine shrubs. (Camac et al. 2017, GCB). Blue = positive effects; Red = Negative impacts; Dashed lines = Possible but unlikely effects.

 

Noting that it is possible fires could become so frequent that shrubs won't be able to set seed, recent evidence I’ve accumulated suggests that shrubs are likely to set seed sooner under warmer conditions. Thus, they appear to be capable to adapt to shorter fire intervals, and may increase their range, thereby increasing the flammability of the alpine landscape.

alpine shrubAlpine shrub, Grevillea australis seed. Photo by Dr James Camac.

 

While heathland may expand under warmer conditions, wetlands and coniferous heath are likely to contract and may become locally extinct. Even the iconic snow gum may not fare well under climate change with increased susceptibility of frost and short fire intervals linked to significant mortality in an otherwise strong resprouting species.

But perhaps the greatest immediate threats to ecosystems burnt by these latest fires are ones we can perhaps control – the expansion of exotic weeds (e.g. Orange Hawkweed & Ox-eye daisy) and the increases in deer, horse, and feral pig populations. Tackling these ever-increasing threats, much like tackling emissions, will involve political will. Does the political courage exist? Only time will tell.

feral horses on Bogong High PlainsAlpine shrub, Grevillea australis seed. Photo by Dr James Camac.

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