Forests In Landscape Trap

Intact Mountain Ash

The December edition of Australasian Science, now on the shelves, contains what may be the most important article I have written (subscriber only alas). I’m very keen to bring it some attention.

Professor David Lindenmayer (ANU) is already recognised as Australia’s leading expert on temperate forests. The paper he authored in the Proceedings of the National Academy of Sciences may well take that status global. Exciting, yes, but unfortunately his conclusions are, in his own words, “Very, very sad.”

Temperate forests can be divided into two sorts, there are those that are fire tolerant, and those that are not. Fire tolerant ecosystems contain many plants that thrive on fire – indeed many depend on it to regenerate. Although big fires will kill individual plants, the species are well adapted to bounce back, and many have seeds that only germinate after fire. (There’s some interesting work in WA on the mechanism for this, which is quite complex, using a combination of chemicals in smoke and increased light penetration into soil as the trigger.)

Since fire tolerant species benefit from fires it is not surprising that they tend to burn easily. On the other hand those species that are not well adapted to fire tend to resist it, forming natural fire breaks.

Given the horrors of the 2009 bushfires, and the forthcoming increase in temperatures, it is very important for Victoria to promote the survival of fire resistant ecosystems. Unfortunately, that is not what we are doing.

It has been known for a long time that modern logging techniques, in which the waste left after the big trees have been removed is firebombed to get a regeneration burn, promotes the colonization of the logged area with fire tolerant species, rather than fire resistant ones. In fact this is part of the reason the techniques are used – the tolerant species include those with more valuable wood. This makes the logged area more vulnerable to future bushfires.

Despite this, the myth persists that environmentalists are responsible for big fires, in part from the perception that if we remove lots of flammable material in a logging operation less will be left to burn thereafter. This may be true in the short term but, unless you want to concrete over the land on which the logging took place, within a few years something will have grown back, and that something is likely to burn more easily than what was there before.

This is not new, but what was not known was the overall impact of logging operations. Did a patchwork of recently logged areas, mixed with older pockets enhance or reduce fires? After being challenged by a logger who claimed the Black Saturday fires were a result of too little logging Lindenmayer set out to investigate.

In collaboration with leading forest ecologists around the world he discovered that Victoria’s mountain ash forests are now in a “landscape trap”. So many former coupes have become highly fireprone, that when a fire gets into the forests it becomes very hot as it burns through these parcels, gaining enough energy to destroy even untouched pockets within the forests. Even large, hard to burn trees succumb. These are replaced by more fire-tolerant species, and within a few years the area burns again, offering no chance for fire-resistance to reestablish itself.

The combination of logging and recent fires has created a tipping point where, Lindenmayer says, “The whole landscape is at risk of being consumed by mega fires.”

Lindenmayer explains “The core process underlying the landscape trap is a positive feedback loop between fire frequency and severity and a reduction in forest age at the stand and landscape levels caused by logging.”

The same process has been confirmed in tropical forests, and amounts to one of the main reasons for the decline of the Amazon Rainforest. However, it was only when Lindenmayer teamed up with international colleagues that it was revealed that many temperate forests worldwide are either in the same situation, or at risk of becoming so.

Just 1.2% of pre-European settlement mountain ash survives. Unless we get a dramatic reduction in both logging and fire, it will soon all be gone. What is more, if areas that have already been damaged experience fire too soon afterwards they can lose the forest species entirely, becoming dominated by wattle scrub. Highly flammable wattle scrub.

Ecologically the disaster here is obvious, but there are further problems. Lindenmayer has previously shown that Victoria’s intact forests are the densest carbon stores on Earth. The replacements store very little carbon indeed. Moreover, the tall forests are part of a feedback system with clouds as they pass over the ranges, increasing rainfall that provides Melbourne’s water supply. Where the forests are lost we also lose runoff. Finally, for those with homes in the area, the choice is between bushfires that slow as they encounter huge, hard to burn trees, and those that race through damaged ecosystems at astonishing speed, gaining energy as they go.

Over the last few decades ecologists have come up with the concept of Resilience, which has proven to have considerable significance for other complex systems, such as the Internet. A system with great resilience can survive even enormous shocks, such as those produced by tropical cyclones. However, when the resilience is reduced, through repeated minor damage, exposure to such a blow can flip it into another state, from which it cannot recover without the input of significant energy.

The lasting legacy of Victoria’s mountain ash forests may be to become the text-book example of destroyed resilience, just as the importation of the rabbit into Australia has become the exemplar of the damage that can be done by an introduced species lacking natural controls.

A remarkable feature of this research has been the mass media response. Being a monthly, we almost always get to stories after other media outlets have picked over them. Some catch on like wildfire in a logged forest, while others have not been covered at all prior to my article. This one is different. The Canberra Times wrote two huge articles on it – one full page, and the ABC has also given it quite a bit of attention. Other outlets ignored the story entirely. This is particularly depressing because the work is of such public significance that Lindenmayer paid, out of his own pocket, for it to be made public access, despite publication in a journal that normally requires subscription. (The media coverage has however, been enough that Lindenmayer has received hate mail for his research).

Credit for both photos to David Blair.


About Stephen Luntz

I am a science journalist, specialising in Australian and New Zealand research across all fields of science. My book, Forensics, Fossils and Fruitbats: A Field Guide to Australian Scientists is out now through CSIRO Publishing. I am also a professional returning officer for non-government organisations. I'm very politically active, but generally try to restrict this blog to scientific matters.
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10 Responses to Forests In Landscape Trap

  1. Pingback: Current logging and back burning practices increase the risk of intense forest fires | Kieran's Review

  2. My understanding is that, in addition to what you describe, eucalypt species out compete rainforest species. This means that rainforest is replaced by dry temperate forest when large, hot fires burn. Rainforest, as its name suggests, is fire resistant but will succumb in mega fires such as that in 2009. I know that the DSE rangers were quite concerned that the remnant rainforest in the Mt Disappointment would disappear post Black Saturday. I have not heard of its fate. Thankfully, some beautiful rainforest survives in Toolangi – home to such gorgeous species as Nothofagus cunninghamii. It is, however, surrounded by heavily logged and regrowth forest so its future is by no means certain. We must learn to live with fire. Respect for our forests must be the cornerstone of fire management.

    • Yes that’s right. I didn’t write about this because I understand rainforest, wet temperate eucalypt and dry temperate eucalypts can blur into each other and its sufficiently complex I didn’t wnat to get it wrong. However, the general point is the same – the species that can stop small fires and slow large fires don’t recover after logging or a fire large enough to destroy them, leaving the ecosystem more prone to fire afterwards. In Victoria it is illegal to log rainforests, but areas with a mixture of rainforest and eucalpyts are not defined as rainforest, and consequently get logged.

  3. Fire ecologist says:

    While the idea of a ‘Landscape trap’ makes sense and has been demonstrated in other parts of the world (see ‘alternative permanent states’), there is very little evidence of the role of logging in this in Victoria. Logging is a disturbance, and it can relate in an increase in the proportion of sclerophyllous (dry / hardy) species.

    However, by weight of numbers, its impacts are miniscule in comparison to the effects of weather and climate. Any fire will result in a similar succession to logging, and the unfortunate case is that the incidence of ‘Megafires’ have been increasing with little regard to the flammability of the landscape. In 2003 and 2006, over 2,000,000 ha were burnt as a result of prolonged drought – predominantly in reserved and unlogged forest (including the Grampians and Alpine national park). Again in 2009, a single extreme weather event resulted in a large intense fire that burnt through a range of vegetation types with scant regard for fuel conditions.

    The magnitude of these weather related events indicates that climate change is the likely driver of landscape traps; the incidence of logging is so low in comparison that is more likely a distraction from the real threat.

  4. Fire ecologist, thanks for the comment. I don’t think there can be any doubt that climate change is a contributing factor to the megafires we saw in 2003 and 2009. I’m a science writer, rather than a specialist so I don’t claim expertise in the debate. If there are responses to Lindemayer in the peer reviewed literature I’ll be happy to cover them (here and in Australasian Science). If you or anyone else gets something published and I miss it (which is quite likely) I’d be grateful if you could send me a link.

    That said, my understanding is that the 2003 and 2006 fires started outside the national parks and attained a lot of energy in logged areas before it burnt in. It may well be that without this distrubance the fires would never have got hot enough to take off within the protected areas (moreover, the Alpine National Park, an area subject to grazing pressure at the time may have been unlogged, but was far from undisturbed).

  5. Pingback: Landscape Traps Gain Attention | Forensics, Fossils and Fruitbats

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  8. Ulysees Butterfly says:

    Very little evidence? Ho, ho. Pull the other one, it plays jingle bells: “Just 1.2% of pre-European settlement mountain ash survives. ” There’s your evidence. Same for other ecological forest types. All the real big water pumps are cleared out, 99% regrowth. We are talking landscape conversion done and dusted. Even at 1% logging a year (ignoring loggers always target the oldest remainders) on a 50% reduction in landcover, coming after broadscale clearing fro agriculture, at 100 years that’s 100% regrowth. And yes a 100 year old tree is regrowth compared to the 300 and 400 year old whoppers that used to be normal. Fact is loggers have been woodchipping the evidence and now normalise regrowth as the real thing for folks on their highway trek from major regional centre to centre. But some of us have seen the real thing and know what’s gone. There was even a place called Walagara Wilderness around a town called … Eden and by the 1970ies it didn’t even exist. Here’s a little colonial quote I just found from 1840 for SE NSW:

    “After I got back (from Sydney), we soon left Nangutta, we first went to Walagara (sic), near the junction of the Timbillica and the Genoa Rivers…..We soon after that shifted to Timbillica, put up two large bark huts and had to live in them awhile until I got a house up but we were quite content. The spring was coming in now. The Mrs milked the cows in a make-shift yard, so that I could keep going to get the house and a small dairy up…..after I got the house up I began to put up yards…..I was never one of the unemployed……We did most of our own work, and never went into debt, and I have stuck to the same thing all along, out of debt and danger.”

    Well not out of danger now. Walagara doesn’t exist. A Ghost of the Nation. What’s the bet those bark huts had huge slabs of bark off woolly 400 year old brown barrels Euc.fastigata and very good weather protection too no doubt.

    The Big Scrub – mostly gone too in the north east. Etc etc. Bring on the defacto plantation [read megafire] is the cry of the logger industry. Truly loggers in natural forests are reaping what they sow which is death. There is no nice way to put it. I’ve been reading about the thesis above since 1995 in different forms, and Lindenmeyer is mainstreaming it, but anyone who’s been through a majestic old forest that’s been trashed with spindly regrowth – they already know at some deep level. It’s hot dusty dry stuff where once was springy topsoil and chattering critters. It’s very sad. People who haven’t trained in ecology are lucky – it’s the best and worst of times for those who have. It won’t stop with megafires either. Tornados in capital cities on the coast will be on the list.

  9. Robert John McDonald says:

    Entomology, Mycology, Hydrology – to be a forest ecologists one has to work closely with people in these fields and others – not in Australia apparently. So after 200 hundred years of deliberate clearing and burning the differences between the various places, their fire and natural histories remain ignored. By common sense the flammability of old ash forest, for instance, must decline as they age – but for 30 or more year of spraying insecticide on coupes killing invertebrate flammable fuel reducers after they are logged, opening to forest to wind with coupes, ‘firebreaks’ and roads. This is what is making them more flammable. Resourcing rapid detection and extinguishing fires in farmland and forest will let the less flammable vegetation regrow. Clearfalling is too costly to water, makes the bush too flammable and with chemicals used kills a host of invertebrate and vertebrate species that play a key role in reducing the flammability of the bush, oecophorid caterpillars, lyrebirds etc. A solution has to guarantee local employment detection and extinguishing fires, closing and putting bends in roads and fire breaks anf full time local employment in the same whether on farmland or bushland. At the moment ew have thousands of forestry trained people burning the forests they should looking after cheered on by an equal number of botanists who are ‘addicted’ to burning for ‘plant biodiversity’ – the ‘Ice’ of Australian land management in the 21st century.

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