Gums, birds, bugs, die-back and fire regimes

Listening to the lovely sound of the bell miner, who could have thought that it could devastate our eucalypt forests? By itself it can’t, of course. All it does is eat honey. But it is particularly fond of a sugary excretion produced by sap-sucking native insects called psyllids, which feed on gum leaves.

These insects sit on the vein of tree leaves, sucking their sap and excreting a sugary solution known as lerp. “The bell miners suck off the lerp, but leave the insect, which keeps working its way around the leaf,” says Paul Meek, executive officer of the bell miner associated dieback (BMAD) working group. In return for their sugary meal, the aggressive bell miners ward off any other bird or insects that would eat the psyllid itself.

That’s according to an article in the New Scientist (behind the paywall, but available here.)

The forest can go from looking like this (image from the New Scientist article):

Eucalypt forest with dry rainforest understory

to this (from a 2006 SMH article):

A bell miner affected forst near Merimbula

It seems that in New South Wales alone, up to 2.5 million hectares of forest could be affected, and the phenomenon is not limited to NSW.

However, according to the article:

Vic Jurskis of the Institute of Foresters of Australia says tree foliage can start looking sick before any sign of psyllids or bell miner outbreaks – or, indeed, any other obvious factor that might kill the trees. So it looks like the problem runs deeper than bell miners.

The article goes on to say:

The mystery has revived a radical old theory, proposed over 40 years ago by ecologist William Jackson of the University of Tasmania. According to one of his former students, David Bowman, an ecologist also at the University of Tasmania, Jackson presented his work to the Ecological Society of Australia in 1968. Bushfires had ripped through his home town of Hobart, Tasmania, in 1967, prompting questions over frequency of natural fires.

Jackson proposed that the number of fires sweeping through the bush dictate what type of vegetation grows there. Very frequent fires favour grassland, an intermediate number would support eucalyptus forest, while infrequent fires produce a forest of dense, shade-tolerant plants, an ecosystem dubbed the “dry rainforest” for its structural similarity to the classical tropical rainforest. So, according to Jackson’s theory, without regular bushfires, many eucalyptus forests will die out, leaving species-poor dry rainforests devoid of gums.

Moreover:

There are many reasons why gums rely on fire. In the absence of regular fires, dry rainforest species grow up beneath the eucalyptus canopy, competing with the gums for water – and winning. These species also contribute a thick litter layer that changes the soil chemistry, further stressing the gums.

The problem goes beyond eucalypts and beyond Australia. The need is to establish the optimum fire regime, not too much and not too little, for a particular species and climate. The article gives this map of Australia showing where fire regimes need to be managed to maintain forest type and biological diversity:

Ecosystems threatened by changed fire regimes

There is much to be done.


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44 responses to “Gums, birds, bugs, die-back and fire regimes”

  1. TerjeP

    What is wrong with a dry rainforest? I’m all for managed burning but if any given area can support a number of alternate ecological states then what makes one more optimal than another and who decides? I’d argue that what is optimal is a subjective aesthetic question and the notion of “pristine nature” is an illusion. For instance obsessions about old growth trees (eg 300 year old trees being somehow more important than 70 year old regrowth) has more to do with aesthetic conceit than bio diversity. We should think about such issues and we should try and define optimal for the sake of fire management but we shouldn’t get too hung up on perfectionism.

  2. TerjeP

    p.s. Look at the two pictures in the article. The stand of dead trees represents lots of hollows for birds to nest in. It also allows more sun for shrubs. Other than human aesthetics (picture 1 looks nice) who is to say which state is superior.

  3. TerjeP

    Seventy year old trees have manifold hollows. If that is all that 300 year old trees have going for them then unless lots of people look at them they seem relatively unimportant. I know that for some people such statements are akin to swearing in church but I feel that it needs to be said. Romanticism and aesthetics have their place but in public policy terms romanticism and aesthetics shouldn’t be passed off as something else. Any way the bell miner seems to be good for making manifold hollows.

  4. sg

    TerjeP, this article gives an overview in the abstract of the various benefits of biodiversity in old growth forests.

    You’ve previously shown a belief that biodiversity is just a boutique leftist concern, or irrelevant to modern bio-systems, so you’re probably not the best informed person on the topic to be criticizing these scientists’ interests in maintaining a certain type of biodiversity.

  5. John D

    We tend to think of the Australia that greeted the explorers as “natural.” The reality is that much of Australia at the time was managed by the human population to an extent that it no longer is. The depopulation of most areas of Australia since then means that there has been an end to firestick farming. so the pattern now is for large areas to go through a cycle where clumps of spinnafex start to grow until they get close enough to each other to propagate a fire caused by lightening strikes. Then the cycle starts again.
    In the past firestick farming meant that the cycles were far more localized and it was easy for a wider variety of species to thrive.
    To me diversity is the feature of a healthy environment and optimal really means a diversity of fire regimes.
    The patches of bellbirds near my place do not appear to be changing the local bush but perhaps I am missing something.

  6. Paul Norton

    John D #6, it’s also worth noting that the displacement of indigenous Australians and the disruption of their culture (including firestick farming) in much of Australia has ironically made it possible for conservative politicians and various forest-user and land-user groups to make windy claims that their preferred land access regimes and land management practices replicate what the Aborigines did, because knowledge of what the Aborigines actually did has been so thoroughly erased. This has been a particular feature of the debates about fire hazard management in Victoria.

  7. TerjeP

    SG – I read the abstract for the article you linked. I’d consider paying for the full article if it seemed relevant but it does not. The author talks of old growth eucalypt forests being unique but then goes on to discuss the state of eucalypt forests. It does not appear to be an article that compares the biodiversity of an old growth forest (ie one with trees that are more than a couple of hundred years old) with regrowth eucalypt forests (ie one with trees up to say 70 years of age). So I’d does not address the point I was making.

    You’ve previously shown a belief that biodiversity is just a boutique leftist concern, or irrelevant to modern bio-systems

    That’s a fabrication invented by you so you can undertake a strawman argument. I could counter by saying you have previously called for all babies to be executed but I try to engage in discussions such as this with integrity. It would be nice if you would can the moral superiority and stick to the discussion at hand.

  8. wilful

    You people might be shocked to discover that the theory of forest succession is neither radical nor unpopular, and I can’t tell any substantive difference between standard succession models and Jackson (1968). Here’s 15100 hits on Google scholar for “Eucalyptus Forest Succession”.

    Also, ecological fire regimes, a challenge? Yes absolutely. We know far too little, though we’re putting a fair bit of money into the area, and we cannot reasonably account for all the factors that go into a fire frequency model, let alone accounting for the human factors of applying fire as a management tool. Meanwhile, climate change is completely changing the picture before we’ve even begun to colour it in!

    If you want a bit more info for SE Australia fire ecology, start here and here.

  9. wilful

    Oh TerjeP, depending on the tree of course, hollows really don’t start forming until trees are about 100 years old, and there is a significant difference in the habitat value of 300 year old forest compared to 100 year old forest. Many of our fauna are hollow dependent.

    Of course, overwhelmingly, nothing that humans do (apart form climate change and fire suppression) affects the total number of hollows in trees in a larger geographical area.

  10. Chookie

    I’ve always known the sugary solution as honeydew and the bump caused by the insect to be the lerp. Borne out by a quick google.

    The problem with understorey shrubs, Terje, is that they overshadow grasses (food for macropods), inconvenience SES, RFS and search parties, produce fuel and burn rather well — consider, for example, the way banksias *rely* on fire to propagate. Personally, I like our understorey shrubs, but open woodland is probably safer to have near your tree-change property. There are no simple answers, though: even our understorey plants vary in their preferred burn cycles, and of course crown fires cross open woodland easily anyway.

  11. Sabbra Cadabra

    Terje:

    “For instance obsessions about old growth trees (eg 300 year old trees being somehow more important than 70 year old regrowth)”

    The obsession is science based, Terje. See here for example:

    “Hollow formation is dependent on a tree’s history, its
    species and location. Generally, small hollows with
    narrow entrances suitable for small animals such as the
    brush-tailed phascogale (Phascogale tapoatafa) and the
    eastern pygmy-possum (Cercartetus nanus), take about
    100 years to form. Hollows of a medium size and
    suitable for animals such as parrots will take around
    200 years to form, and the larger and deeper hollows
    occupied by glossy black cockatoos (Calyptorhynchus
    lathami) and other larger animals such as masked owls
    (Tyto novaehollandiae) can take a lot longer
    (Mackowski 1984; Menkorst 1984; and Scotts 1991).”

    http://www.environment.nsw.gov.au/resources/nature/Factsheet5TreeHollows.pdf

    The 70 year old regrowth areas that you are fond of have no hollows, very few birds and arboreal mammals and limited diversity, density and structure in the undergrowth. The regrowth also sucks most of the water out of the soil so you end up with much less runoff, hence depriving billabongs, creeks etc of water.

    This is all elementary ecology, Terje. I’m surprised by your lack of general knowledge.

  12. akn

    Without wanting to engage TerjeP in an argument on the aesthetics of forests it seems to me that democratic principles can be extended to non-human nature. That way, in acknowledging the human role in the actual manufacture of nature, the argument can be made that the preferable form of nature for a democracy is that form most suited to maintaining the greatest biodiversity in ‘natural’ (ie, unpenned) conditions.

    For further on the way that humans manufacture nature the work of Dr V. Constanza Ocampo-Raeder is informative here:

    Rainforests are considered one of last pristine or untouched ecosystems of the world. However, they have long been the home of indigenous people who have modified and left their cultural “footprint” in the forest.

  13. wilful

    Indeed, akn, ‘wilderness’ is a human construct.

  14. wilful

    Sorry, hit post too early. By human, I meant modern society.

  15. TerjeP

    Thanks Sabbra – I’ll check it out.

  16. Sabbra Cadabra

    Obviously wilderness is a human construct. There is not a square inch of the planet that hasn’t been shaped by human activity.

    It is also quite valid to question the romantic idea that indigenous Australians were an entirely benign influence on Australian ecology.

  17. akn

    Yes we can agree on the cultural history of wilderness. Even further I’d argue that it is a specific post-colonial form of nature in so far as (at my last count) the only countries that had legislatively defined ‘wilderness areas’ also had a history of dispossession of indigenous people. An aesthetic vision of ‘wild’ nature suits me better than the dominant alternative on offer which is ‘industrial nature’.

    However, before issues of aesthetics intervene I would re-assert that ‘wild’ nature apparently has a greater capacity for biodiversity and that this is the sort of nature best suited to express the intentions of democracy which must (if they are to be democratic) offer sustainable conditions for ecological survival to the greatest number of all species.

  18. Sabbra Cadabra

    “… best suited to express the intentions of democracy … ”

    Democracy is an abstract term for a form of government- it is not a person- thus it is incapable of having intentions.

    Reification: (also known as hypostatisation, concretism, or the fallacy of misplaced concreteness) is a fallacy of ambiguity, when an abstraction (abstract belief or hypothetical construct) is treated as if it were a concrete, real event, or physical entity

    I note reification is very common in crude left-wing thinking.

  19. David Irving (no relation)

    I note reification is very common in crude left-wing thinking.

    Evidence, please. I’ve found it to be extremely common in crude right-wing thinking, as a matter of fact. (The Global War on Terror spings to mind as a f’rinstance.)

  20. pablo

    Altered fire regimes have been blamed as one of the major reasons for a collapse in mammmal numbers across northern Australia. According to CSIRO monitoring, over the past 15 years Kakadu National Park has seen a 75 percent decline in small mammal numbers with species numbers falling by two thirds. Apart from fires, feral grazing and feral cats are blamed with the latter reckoned to be killing a couple of million native animals every day.
    These appalling stats are detailed by Australian Wildlife Conservancy (www.australianwildlife.org) the Perth based non-profit oufit that runs sanctuaries across Australia.
    On fires, AWC say the replacement of Aboriginal fire management by a contemporary pattern of mid-to-late dry season fires over the same savanna like country too often (1 – 3 years) is to blame. It reduces the structural and floristic complexity of vegetation, limiting key food resources and habitat, making native animals easy prey for the feral cats.
    Apart from returning to pre-European fire management techniques, AWC researchers have found that the introduction of dingoes has some range limiting effect on the cats. Some of their sancturies are fenced or on islands free of ferals and these show some success with endangered native mammals.

  21. Philomena

    [email protected] “Apart from returning to pre-European fire management technique”

    There was no such thing as this. The very notion is a category error.

  22. Salient Green

    Before the Aborigines there were diprotodons and other large creatures which kept the shrubbery down and the fire regime became necessary after they were all eaten.

    Fire selects in rather different ways to eaters of coarse bushes though and tends to impoverish what are already poor soils. The fire regime of the last 40,000 years or so is also blamed for some of the drying of our continent.

    Fire is rather nasty stuff really and labour intensive. It’s a bloody pity those big old marsupials tasted so good.

  23. Sabbra Cadabra

    “The fire regime of the last 40,000 years or so is also blamed for some of the drying of our continent.”

    It also:

    (a) robbed the land of nutrients, since heavy rains subsequent to burning wash ash into the rivers and finally out to sea

    (b)selected for forest types that need fire and that often increase fire intensity (eg plants with highly flammable oils) as part of a strategy to outcompete fire sensitive plant species.

    Gaia only knows how many plant species and forest types were obliterated by firestick farming.

  24. FDB

    Indeed.

    Check out the biodiversity (at face value, admittedly) in one of the little remaining pockets of myrtle beech forest in Victoria, compared with the mountain ash surrounding it, which swallows a little more territory every time a fire comes through. It’s pretty stark to look at.

  25. Sabbra Cadabra

    Well yes, but I don’t want to sound anti-Eucalypt because I’m most certainly not. Also many of our extant beasties do depend on them. Having said that, it is impossible not to note that number and diversity of native birdies on my highly modified acreage is much greater than in the nearby regrowth Box-Ironbark forest.

    Oz ecology is highly complex and the more you learn the more you know you’ll never really know enough! That’s what keeps me interested.

  26. Sabbra Cadabra

    My comment disappeared. Why?

    [No idea. WordPress sometimes has a ‘mind’ of its own ~ tigtog, moderator]

  27. Helen

    conservative politicians and various forest-user and land-user groups … make windy claims that their preferred land access regimes and land management practices replicate what the Aborigines did, because knowledge of what the Aborigines actually did has been so thoroughly erased.

    Yes. I’ll see your “Wilderness is a modern construct” and raise you a “Indigenous mosaic burning versus bulldozers, napalm, chainsaws, trail bikes, SUVs and low density housing: Well we can’t say for sure, but probably not comparable!”

  28. Philomena

    The journal of the The Royal Society of New South Wales from the mid 19th century records scientists from botanists to astronomers to geologists repeatedly raising the alarm about not the absence of “fire management” but of the broadscale tree-felling which many argued not only demonstrably reduced biodiversity but was causing climate change (their very words) including higher temperatures, increased evaporation combined with less rainfall.

  29. John D

    Just looking at the map Brian I would question what it is saying about the northern areas of the NT including Kakadu. Intense grass fires in grass that is over a meter tall are annual feature here with lightning as well as Aboriginal initiated fires being the cause. I find it hard to believe that the vegetation here is not adapted to this fire regime.
    As I said before the spinifex areas are different – the burning pattern has changed with the end of fire stick farming and the consequence has been a decline in some species.

  30. John D

    akn @19: You say:

    I would re-assert that ‘wild’ nature apparently has a greater capacity for biodiversity and that this is the sort of nature best suited to express the intentions of democracy which must (if they are to be democratic) offer sustainable conditions for ecological survival to the greatest number of all species.

    Doesn’t seem to work in spinifex country. In this case fire stick farming gave the ecological diversity that underpinned biological diversity. Without firestick farming a particular stage of the spinifex cycle would cover vast swathes of country and thus restricted the species in this swathe to species that preferred this stage. (And wiped most of them out when the big fire came.)
    The argument about the relative diversity in different ecologies is spurious. It is the mixture of the ecologies across the country that maximizes diversity. (With qualifications based on the area required for different species to avoid inbreeding.)

  31. wilful

    The journal of the The Royal Society of New South Wales from the mid 19th century records scientists from botanists to astronomers to geologists repeatedly raising the alarm about not the absence of “fire management” but of the broadscale tree-felling which many argued not only demonstrably reduced biodiversity but was causing climate change (their very words) including higher temperatures, increased evaporation combined with less rainfall.

    yes but Philomena, apart from the fact that astronomers and geologists have about as much relevant expertise as coopers and saddlers, these areas have now been under the plough for more than a century, contributing very materially to Australia’s economy. While I’m sure it would be very nice to have wandered through a pleasant pre-European woodland, the fact is all of that land clearing was done for a purpose, which benefited all of us. In a stochastic sense few of us would be likely to be here if the clearing for agriculture hadn’t happened, because Australia would have had a far smaller population. Shaking our heads over these sorts of historic acts really gets us absolutely nowhere.

    As for modern day land clearing, well in Victoria the only remaining strong pressure is on threatened grasslands being swallowed by Melbourne, and isolated farm trees. Beyond that, large scale land clearing stopped in 1989.

  32. akn

    John D: I appreciate your point that the mix of ecologies across country that guarantees diversity. That seems logical to me. My point was not to advocate for a particular technos of land and fire management but to advance an argument for maximum biodiversity grounded in the political spirit of democracy.

    That spirit is apparently not shared by Sabbra Cadabra who accuses me of reification when I suggest that there is such a thing as a spirit to political institutions. In so doing Sabbra Cadabra must also reject the possibility of a national spirit derived from the history, culture and institutions of a country over time. Sabbra Cadabra, in denying the possibility of a zeitgeist specific to a place and peope effectively throws out history, national history and all representations of such in literature, art, music, dance and so on. Ridiculous, really.

  33. FDB

    “The argument about the relative diversity in different ecologies is spurious.”

    What argument? I made an observation. And it was one which fits perfectly well with:

    “It is the mixture of the ecologies across the country that maximizes diversity.”

    i.e. if fire can be clearly observed as the current cause of net biodiversity loss is some areas, with the mechanism of loss being change from one form of ecosystem to another, then that’s a bad thing, right?

    And it’s pretty reasonable to assume this mechanism is to blame for at least some previous loss of non-eucalypt ecologies, right?

    Not highly controversial, I’d have thought.

  34. FDB

    Of course, the argument you thought I was making, that some ecosystems (read: rare ones and very biodiverse ones) deserve special attention, is far from ‘spurious’ in any case.

  35. John D

    Any change in fire or land management is going to create winners and losers as well as the odd unintended outcome. It is also worth noting that ecologies are often aggressive and will try and create conditions that support their expansion. One of the points made in the black Saturday discussions was that frequent burn-off favored species that supported the stronger fires that favored them ahead of species that were less able to withstand and support fire.
    FDB @26: The case you quote of the myrtle pocket being taken over by the more aggressive ash ecology is an example of what I am talking about.

  36. TerjeP

    On the basis of the link provided by Sabbra I’d like to retract the following statement.

    For instance obsessions about old growth trees (eg 300 year old trees being somehow more important than 70 year old regrowth) has more to do with aesthetic conceit than bio diversity.

    I accept that in the case of old growth versus young growth the argument isn’t purely aesthetic.

  37. FDB

    JohnD – I think what we have here is a clear case of me ‘reading for disagreement’. Apologies – it’s pretty clear we’re more or less of a mind on this topic.

    Terje – well played. A dash of humility does wonders for one’s credibility every now and again.

  38. Sabbra Cadabra

    Thank you Terje. The age of chivalry ain’t dead.

  39. John D

    Thanks FDB. It is a complex subject that needs science to help decide to what extent human action is desirable.
    Pablo @22: Hadn’t realized the extent to which the decline in Aboriginal fire management was having at Kakadu. I suspect that the timing rather than the frequency may be the critical thing with Aborigines traditionally lighting cooler fires early during the dry season to improve travel and stimulate green shoots to attract grazers.

  40. OldSkeptic

    We know, but never will do, how to manage fire.

    Simply copy, well documented and studied, low level constant burns as done by the Aborigines.

    Chance zero. The daft (but loud) part of the greens oppose it, Govts won’t spend the money. The bureaucrats won’t do it.

    True story, big fires a few years ago around Bright (in Vic). At one point it was surrounded on 3 sides by fire fronts. The CFA was doing it’s best but a lot was in National forests, under the wonderful hands of the DSE.

    I talked to a guy who had a bunch of bulldozers ready to cut firebreaks … but the DSE wouldn’t let him. Because .. again you can’t make this stuff up .. the blades were too big.

    Heck, I’ve been watching for 27 years the Murray die, no one did anything about it. So what hope is there for some other solution to fire management?

  41. FDB

    well documented and studied, low level constant burns as done by the Aborigines.”

    They are not at all well documented or studied – at least not in areas where major forest fires are likely to occur (i.e. areas other than the far north).