Fires are still burning out of control across much of the Australian High Country. Yet we are already well into the blame game, where some people and groups are blaming environmental activists and/ or The Greens party for ‘stopping’ fuel reduction burning and hence making the fires worse. While this is not true, this resonates with certain anti green and conservative demographics (check here for an alternative view of the conversation).
There is no doubt that fuel reduction burning has a role to play in how we manage forests and other landscapes. The problem is that it is often seen as a ‘one size fits all’ tool that will reduce fire intensity in all environments. But in reality, it works well in some ecosystems and is counter productive in others. This is a subtlety that is lost on the ‘fuel reduction is the answer’ boosters.
The argument that we need to increase fuel reduction burns in snow gum and true alpine environments is already caught up in the broader land management debate, and will continue in the coming months. So it’s worth taking a good look at what science says about the value of fuel reduction in our high mountain areas.
Snow gums are the quintessential alpine tree of the mainland, generally growing at elevations between 1,300 and 1,800 metres asl. Wildfire has devastated large swathes of snow gum habitat in the last few decades, with significant fires in the Victorian High Country in 1998, 2002/3, 2006/7 and 2013. Over 90% of the Victorian distribution of snow gums has been burned at least once since 2003. Each of the large fires of the last 15 years has overlapped to some extent, leaving thousands of hectares of snow gums burned by wildfire twice, and sometimes three times.
Much of Kosciuszko National Park was burnt in 2003.
‘Fire has always followed fire’
Early European occupation of the mountains was based on the widespread use of fire to clear land. This broad acre approach to burning was at odds with First Nations careful, localised use of fire. As noted by Philip Zylstra (Centre for Sustainable Ecosystem Solutions, University of Wollongong):
‘British graziers … cleared country using fire. The Snowgums tell the story: a seven-fold increase in fire scars when the invasion came’.
This use of fire has continued today, but does it reduce the flammability of the mountains? Philip points out that fuel reduction only brings a short reprieve:
‘Recently, I looked at every fire mapped across these mountains for nearly 60 years, and I found one thing in common from the foothills to the peaks: fire has always followed fire. For a couple of years, it brought quiet, then the undergrowth made the forests up to eight times more likely to re-burn for the next couple of decades until it self-thinned. So why did anyone burn it if this was the result?’
Keeping fire out may be the solution in snow gum forests
One significant piece of research that should inform our understanding about fire on snow gum forests looked at the impacts of fires on Lake Mountain and the Buffalo Plateau. The report How snow gum forests and sub-alpine peatlands recover after fire was written by Fiona Coates, Philip Cullen, Heidi Zimmer, James Shannon. They used the long unburnt Baw Baw Plateau as an example of what these systems could be like in the absence of fire events.
They found that:
- Even areas that have been subjected to hot and very destructive wildfire, such as on the Lake Mountain plateau during the 2009 Black Saturday fires, can be expected to recover – provided we can keep fires out of these systems. However, this will take time. For instance they suggest it will take the forests at Lake Mountain at least 70 years to return to pre-fire structure. No specific management needs to be undertaken to aid this process beyond excluding fires
- The researchers repeatedly note that there are serious doubts about the value of fuel reduction burning in these forests. They note that low intensity fires negatively impact on tree resprouting ability
- Repeated fires change the character of snow gum forests, creating a multi stemmed forest of shorter trees. That is, forests get denser, with more of a ‘Mallee’ aspect to how the trees grow. They call this ‘potentially irreversible degradation of stand structure’, which has already happened to the extent that old growth snow gum forests are now rare. They note that the traditional open forest structure of snow gum forests will not be able to develop if there are repeated fires, as the result over time will be that forests will become dominated by lots of small stemmed trees rather than a ‘traditional’, open snow gum forest
- Repeated fires can also inhibit the ability of trees to store carbon above the ground.
- They say that ‘fire exclusion is imperative to preserve landscape quality and representation of long unburnt snow gums’
- They recommend that current ‘fire and cattle exclusion policies’ at places like Mt Buffalo and Lake Mountain be continued. They note that cattle grazing can drive the creation of multi stemmed trees, in the same way that fire tends to, again driving the forest towards a multi stemmed and immature form. Exclusion of cattle is also very important for recovery of burnt areas of peat land
- Older, more open snow gum forests are better at collecting water and ensuring regular run off, retaining soil moisture and snow accumulation.
The take home message from researchers like Philip Zylstra is clear:
- We have evidence that over time forests become less flammable
- Long unburnt snow gums are their best protection against fire. When these forests burn it is unlikely to be of a high severity
Forests exist in landscapes
When a forest burns, the fire dynamics of that forest changes, and this has a flow on effect to the surrounding landscapes. Older forests act as a break on fire spread. What is really important as climate change ramps up is that we maximise the area of older (less fire prone) forest.
This means doing everything in our power to keep fire out of the snow gum forests to allow them to move towards the old phase in their growth cycle.
Impact of fires on the upward spread of snow gums
Fires impact on mature trees and the resulting growth of seedlings may mean that snow gums start to colonise adjacent alpine vegetation.
David Turner, in his research carried out for his Masters of Environment thesis (School of BioSciences, University of Melbourne) titled Treeline physiognomy following wildfire in the Victorian Alps, Australia investigated snow gum seedling establishment above the treeline after fire.
He found that new seedling growth was greater after fire compared to locations long absent of fire. ‘Model probabilities estimate a 22% chance of seedling establishment four metres above treelines that are burnt, compared to only a 1% chance in unburnt locations’. (He does note that the number of seedlings, which was modelled to increase after fire, is controlled by the amount of litter and competition found at the site. Low levels of litter and competition facilitate maximum seedling growth).
One significant outcome regarding frequent burning showed that optimal tree ages that influence seedling establishment were found to be between 24 and 42 years of age. If climate change subsequently reduces fire frequencies to less than (for example) every 20 years, then seedling numbers may actually fall.
Repeat burn times that outpace snow gums (Eucalyptus pauciflora) reaching their optimal reproductive maturity age may subsequently have dramatic effects on the Victorian treeline.
His research suggests that the Victorian treeline physiognomy has slightly changed due to the 2003 alpine fires.
Impacts of fire on snow pack
The Australian Alps are the headwaters of most of the significant rivers of south eastern Australia. As such, they are incredibly important for their role in supplying water to downstream areas, where it is used for environmental flows, agriculture and human consumption.
Research contained in the report ‘Impact of fire on montane snowpack energy balance in Snow Gum forest stands’ by Andrew Schwartz, Hamish McGowan and Nik Callow found that bushfire affected forests have higher snowpack evaporation, which results in less runoff.
Debris shed by burned trees lowers snow albedo and increased heat emission from decaying tree stems and other organic matter.
An intact canopy cover moderates snowpack radiation.
Reduced snowpack longevity and increased melt occur in bushfire-disturbed forests.
Sadly, the fact is that climate change is making fire seasons worse. As noted by the Victorian government’s report ‘Climate Science Report 2019’,
‘There has been an increase in dangerous fire weather and the length of the fire season across southern Australia since the 1950s. Fire weather in Victoria is largely measured using the Forest Fire Danger Index (FFDI). This index estimates the fire danger on a given day based on observations of temperature, humidity, wind speed and fuel (based on factors including recent temperature and rainfall). Although considerable year-to-year variability also occurs, there is a trend in more recent decades towards a greater number of very high fire danger days in spring’.
So, regardless of how we manage forests with regards to fuel reduction treatment, we will be facing worse and longer fire seasons. It would appear that one key strategy will be to keep fire out of snow gum woodlands wherever possible, so these systems can age and become less fire prone.
Regular and repeated fires kill snowgums. So if we want to see snow gum forests continue we need less fire, not more, even low intensity fuel reduction burns. According to research by Tom Fairman, Associate Professor Lauren Bennett and Dr Craig Nitschke, of the University of Melbourne:
‘We found that the lignotuber continued to re-sprout very well after one fire, but after two and three fires, the number of new sprouts significantly declined. The level of whole-tree death (that is, the stems and lignotuber dying) was fairly low following one and even two, fires; however, after three successive fires, on average half of all trees in our plots were dead. In some plots, this figure was as high as 80 per cent of all trees’. (source).
A study in the journal Austral Ecology provides the most comprehensive analysis ever performed of the fire history of forests in the Australian Alps. This is a significant piece of work because it says that unburnt forests are less fire prone than those that have been recently burnt.
This has implications for how we manage these forests and woodlands. The current widely held assumption is that by reducing fuel loads, fire reduces the flammability of most eucalypt-based forests.
The study, by Dr. Philip Zylstra of the University of Wollongong (and available here) says:
‘The study provides an evidence base for fire management in the Alps that is based on observed reality rather than theoretical concepts.
‘Throughout the period for which fires have been consistently mapped across the Australian Alps National Parks, they have been smaller and less severe in long unburnt forests’. This is consistent across the five broad forest formations that cover the Alps’ (these forest types are Tall Wet Forest, Open Forest, Subalpine Forest and Woodland, Dry Open Forest and Low, Dry Open Forest).
The study looked at fires in five key forest types in the Alps and assessed how fire frequency changed over time. To take the example of snow gum woodlands, after a fire passes through, they are unlikely to burn for 6 years after fire, then more flammable until 25 years old. However, ‘forests older than this are 2.3 times less likely to burn than younger forest’. A similar pattern can be observed in the other forest and woodland types.
Ben Keaney, in his PhD research titled Bogong Moth Aestivation Sites as an Archive for Understanding the Floral, Faunal and Indigenous History of the Northern Australian Alps noted that climate change is already impacting on the mountains, and could drive forests into a more scrubby, flammable form, and that this has implications for land management practises like fuel reduction burning:
‘Structural change of the vegetation due to human induced climate change is a real threat to sub-alpine ecology. Pryor (1939) described the possible extent of high country degradation from burning as two extremes, that is a slightly damaged forest that is more or less undisturbed, to a barren waste of eroded mountains with a sparse cover of plants. This is poignant as a prediction for the natural land managers under the effects of anthropogenic climate change, where the flammability of the forest can drive ecological change of vegetation away from a forest form into a scrub form, a point that should be taken to account in the prescription of fuel reduction burns. Predictions of the effect of climate change on the ACT include fires with higher intensities, with reduced inter- fire intervals and that are more prone to spread (Cary, 2002)’.
The take home message seems to be that if we can reduce the frequency of fire at a landscape level in these ecosystems through the juvenile ‘danger’ period when there is a lot of vigorous re-growth, they become less fire prone after a period of 14 to 28 years (depending on the forest type). This means that older forests should be left alone rather than burnt to reduce fuel load, and younger forests should be encouraged to mature rather than being treated with fire to keep them permanently in a juvenile/ more flammable stage in their growth.
Implications for fire management
What are the implications for fire fighting in the alpine country? The key message is that we need to keep fire out wherever possible. Locking in more intense fuel reduction regimes are unlikely to make snow gum forests less fire prone, for the reasons outlined above.
1/ More fire fighting resources. Most fires in the Alps start as a result of lightning strikes – that is they start small at a specific point. The aim must be to hit these fires while they are small.
This requires additional fire fighting resources at the state level to tackle these fires as soon as possible, before they grow and become difficult to contain. DELWP and Parks Victoria firefighters are well trained and equiped to fight these fires and do a great job of tackling them. But we clearly need more firefighters.
As one example of how the system gets overwhelmed: on New Years Eve 2019/20 a lightning storm passed over the Victorian Alps, starting many fires. DELWP and PV crews quickly mobilised to put these fires out before they grew, but some more remote fires were not able to be contained and subsequently grew into large blazes (such as the fire at Mt Tabletop near Mt Hotham, which eventually joined with other fires started by lightning and is now more than 42,000 hectares in size).
Stay governments should consider increasing the number of remote area fire fighters for the next fire season.
2/ Minimise burning for asset protection. There are various human settlements in alpine areas, which need to be protected from fire, especially the ski resorts. Doing fuel reduction burning is sometimes used as a last resort before fire fronts hit. The longer term implications of this need to be considered. Fire breaks are widely used in the Alps to limit the movement of fire. Research should be carried out to determine the relative value of fuel reduction, use of fire breaks, and other asset protection work around human settlements.
3/ Consider the development of a volunteer remote area fire fighting force. The Country Fire Authority (CFA) and Rural Fire Service (RFS) do a remarkable job of protecting land and community from fire. While they are primarily responsible for fires on private land, they are often active in fighting fires on public land. But their equipment (trucks) is often too heavy for deployment to remote areas with rough tracks and they are not directly trained or resourced to work in remote areas.
Is it time to develop a new fire fighting force that is specialised in remote area fire fighting? It could be part of RFS/ CFA or be a new stand alone entity, and would work closely with public land firefighters who are already doing this work. They could be trained in the same way that PV and DELWP prepare their rappel and hover exit crews (specialist firefighting roles performed in remote locations).
There has previously been a similar group in Tasmania, called the Smoke Walkers. The Smoke Walkers were volunteers, mostly bushwalkers, who were deployed to remote areas in Tasmania’s World Heritage Areas in instances where lightning had started fires that had not yet turned into major blazes.
In light of the scale of this summer’s fires, this is an idea that needs consideration in NSW and Victoria. A proposal can be found here.
January 21, 2020 at 10:26 pm
Great article Cam
Pity we can’t get more people to re assume a nd understand the science.
January 22, 2020 at 10:57 am
Great article Cam,
I undertook research for my Masters of Environment thesis a couple of years ago to look at changes that may be taking place at alpine treelines after the 2003 and 2007 fires. The findings are unpublished, but available through The University of Melbourne, or I can supply a copy if needed.
My conclusions support many of those that you mention in your above literature analysis. One significant outcome regarding frequent burning showed optimal tree ages that influence seedling establishment were found to be between 24 and 42 years of age. If climate change subsequently reduces fire frequencies to less than (for example) every 20 years, then seedling numbers may actually fall.
Repeat burn times that outpace Eucalyptus pauciflora reaching their optimal reproductive maturity age may subsequently have dramatic effects on the Victorian treeline.
The abstract of my thesis is as follows:
Large areas of treeline in the Victorian Alps were burnt by wildfire in 2003, providing the opportunity to investigate changes to the treeline ecotone due to the effects of fire. This research builds on a previous data set collected shortly after the fire by Rumpff (2008) to investigate key questions that might indicate permanent treeline change over the medium to long term. This is assessed by evaluating Eucalyptus pauciflora subsp. niphophila seedlings for changes in elevation, changes in density, and determining key factors that drive seedling establishment at treeline ecotones. Models using data from burnt and unburnt locations were created to evaluate these questions.
Seedling establishment above the treeline was found to be greater after fire compared to locations long absent of fire. Model probabilities estimate a 22% chance of seedling establishment four metres above treelines that are burnt, compared to only a 1% chance in unburnt locations. The number of seedlings was modeled to increase after fire, however the change in density is controlled by the amount of litter and competition found at the site. Low levels of both facilitate maximum seedling counts. Finally, four factors were identified as influential to seedling establishment, with probability rates of greater than 90% predicted when litter and competition are low, tree coverage reaches 50% of the site area, and the age structure of the stand is between 24 and 42 years old.
This research suggests that the Victorian treeline physiognomy has slightly changed due to the 2003
April 20, 2020 at 11:26 am
Reblogged this on Research Centre for Applied Alpine Ecology.