Can Trees Cause Salinity? Asks Ian Mott

Regular commentator at this blog Ian Mott sent me the following email:

Hello Jen,

We have all grown accustomed to the notion that it is the removal of trees from the landscape that causes salinity. But recent research from the Argentine Pampas indicates that the addition of trees to a natural grassland can also increase the salinity of groundwater flow systems (GFS).

This could have major implications for the management of salinity in the Murray Darling Basin, particularly in rangeland areas where major thickening events have taken place or where existing small clusters of forest have expanded onto grassland ecosystems.

The study, by Esteban G. Jobbagy and Robert B. Jackson, published in Global Change Biology compared 20 paired plots of forest and grassland and found a significant increase in groundwater salinity under the forested plots. “Afforested plots (10-100 ha in size) showed 4-19-fold increases in groundwater salinity on silty upland soils but less than twofold increases on clay loess soils and sand dunes.”

While this study has been limited to planted forest plots on previously grassland ecosystems, the same causal factors are at play whenever forest vegetation expands on grassland. And it logically follows that the same causal factors will be at play when, for example, a 10% canopy woodland thickens to become a 60% canopy forest.

Jobbagy & Jackson have concluded that “Soil cores and vertical electrical soundings indicated that …salts accumulated close to the water table and suggested that salinization resulted from the exclusion of fresh groundwater solutes by tree roots.”

To which the average farmer would say, “Well, they would do that, wouldn’t they”.

The extensive, 1400 plus, rangeland sample plots done by Bill Burrows confirm that more than 60 million hectares of rangeland in Queensland is subject to thickening at an average rate of circa 0.25m2 increase in basal area per hectare. There is a further estimated 30 million hectares in NSW. And there are also numerous landholder reports of properties that had only 3,000 ha of Gidgee in the early 1900’s but have in the order of 50,000 ha today as a result of major encroachment onto grassland.

And this poses an interesting question for the publicly funded anti-salinity industry and the policy arms that have focussed so much public attention on the removal of trees as salinity causal agent. If the lowering of a water table by excess bore irrigation can be widely recognised as a causal factor in increasingly brackish ground water resources, why has it taken so long to recognise that a similar lowering of a water table by the addition of trees can produce the same result?

It certainly invites the question, is there any similar research conducted here in Australia?

Clearly, the political exploitation of salinity appears to be sinking deeper and deeper into murkier water.

Ian Mott

47 Responses to Can Trees Cause Salinity? Asks Ian Mott

  1. detribe February 15, 2006 at 11:31 pm #

    Its a really interesting paper Motty, with good comments in the discussion section about Australia. Just when I though I understood what is going on with salinisation, you throw a spanner in the works. Drat—the real world ‘s like that though.

  2. rog February 16, 2006 at 5:03 am #

    I dont think that tree removal “causes salinity”, the salinity was always there, it is just that it has moved to a more visible location.

  3. Taz February 16, 2006 at 5:54 am #

    An item in the Canberra Times today that refers to Nature, “Greenhouse gas causes floods as plants become less thirsty” Paris. It’s hardly about salinity or Ian’s post but it adds to our knowledge of trees and their take up of ground water.

  4. detribe February 16, 2006 at 8:09 am #

    Some quotes from the Nature comments on the paper:
    Global change: The water cycle freshens up
    Damon Matthews

    Rivers are delivering increasing amounts of fresh water to the ocean. The cause seems to be the influence that higher concentrations of atmospheric carbon dioxide are having on water use by plants.

    Measurements of stream flow around the world have documented an increase in the amount of water that runs off the continents and returns to the ocean1. This trend has been occurring since the beginning of the century, yet changes in precipitation over land do not sufficiently account for this increase. On page 835 of this issue, Gedney et al.2 identify an important contributor to increasing global runoff — decreased evaporation resulting from the influence of elevated atmospheric carbon dioxide on plant physiology

    The balance between precipitation (P) and evaporation (E) over land determines the surface runoff (R), which returns water from the continents to the oceans. Plant photosynthesis plays an integral role in the global water cycle, by mediating the transfer of water from the land surface to the atmosphere. Elevated CO2 can lead to closure of leaf stomata, which reduces leaf water loss and thereby decreases overall continental evaporation. Gedney et al.2 show that this process, initiated by increased atmospheric CO2, can account for the increases in surface runoff observed over the past century.

    Using a technique known as ‘optimal fingerprinting’ (also known as ‘detection and attribution’), Gedney et al.2 show that this direct effect of elevated CO2 on plant transpiration is the dominant contributor to observed increases in continental runoff. Optimal fingerprinting is simply a statistical regression in which a model simulation is compared with observations to isolate which processes in the model are consistent with the observed data. If a model simulation is consistent with observations, the process that drives the model trend is said to be ‘detected’ in the observations; if the observed trend is also inconsistent with other plausible explanations, then the trend can be ‘attributed’ to a specific cause.

    Gedney et al. investigated four plausible contributors to observed increases in runoff: climate change leading to changes in temperature and precipitation; land-use change and consequent changes in vegetation cover; so-called ‘solar dimming’, resulting from an increasingly hazy atmosphere; and the direct effect of CO2 on plant transpiration. The effects of each of these on surface runoff were simulated using a sophisticated land-surface and vegetation model, and the results of the model were compared with historical observations of continental runoff. The authors’ analysis shows that model-simulated runoff trends are consistent with the observed trend only when the direct effect of CO2 on transpiration is included in the simulation. So they attribute increases in continental runoff over the past century to the physiological effect of elevated atmospheric CO2.

    Nature 439, 793-794 (16 February 2006)

  5. Phil February 16, 2006 at 9:16 am #

    Detribe – may I ask what rivers – where is was this research done?

  6. Thinksy February 16, 2006 at 9:56 am #

    Ian do you have the full article to share or you did access the abstract only?

  7. Ian Mott February 16, 2006 at 10:50 am #

    The issue of carbon fertilisation and greater water use efficiency has some very interesting implications for the rate of water cycling but it also has implications in respect of vegetation growth potential.

    If a woodland in a pre-industrial landscape has a long term average rainfall of 500mm and a ‘normal’ canopy cover of, say, 10% then any increase in water use efficiency by the trees and grasses in that landscape will produce a number of outcomes; (please add more if you can)
    1 soil moisture will be retained for a longer period after each rainfall event,
    2 this extended soil moisture will enable extended microbial activity and thereby increase the fertility of the soils,
    3 this combination of water and fertility improvements will produce an increase in the underlying growth potential of the site which will be exhibited by increased growth of existing trees, increased survival of seedlings (thickening) and increased fodder and weed growth,
    4 Over time the canopy cover of existing trees will increase and new trees will augment the canopy in a way that will cancel the improvement in pasture growth and lead to a reduction in stock carrying capacity.
    5 The Co2 fertilisation and water utility effects will only produce an increase in runoff in circumstances where the modified soil moisture deficit is less than the next rainfall volume. This may be the case for early season falls in the tropics but will not apply to end of wet season falls as they are usually followed by an extended dry period that can completely deplete the moisture profile.
    6 It may produce increased runoff in more temperate locations but it may also mask the effects of structural shifts in rainfall volumes.
    7 Enhanced water utility and soil fertility will improve the nutritional inputs of leaf, bud, sap and bark based food chains. For example, the duration of supply, nutritional value and volume of green shoots will improve the health and disease resistance of Koalas. It will produce smaller territories and reduce the risks associated with transit in search of, or between, food resources.
    8 Over time a new vegetation equilibrium will be established but this may not be consistent with existing ground water flow equilibriums.
    9 If the pastured portion of the ecosystem is subject to continual or periodic removal, the only long term consequence will be an even greater site occupancy of non-grazed vegetation, ie, trees will exceed the new equilibrium level.
    10 This excess of trees, over and above the new carbon based equilibrium, will capture a greater depth of soil moisture profile and contribute to ground water salinity in the manner described by Jobbagy and Jackson above.

    So what does it all mean?

    The need to control thickening is both an economic and environmental imperative.

    The character and scale of both ‘positive and negative’, ‘natural’ responses to climatic variation is much greater than those produced by collective ‘on-farm’ attempts to address them. That is, the increased runoff and recharge from land clearing, mostly of regrowth and thickening, is only a fraction of the decrease in runoff and recharge from the thickening itself.

    And the smiling god of irony will note that a significant contributor to regional salinity problems, to the extent that they actually pose a problem at all, are the excessively concentrated, and hence unmanageable, carbon emissions of the metropolitan majority, not the farmers who have worn the blame to date.

    But it has yet to be determined whether the Co2 from fine mosaic firestick burning, delivered in situ to enable maximum re-use by the forests and woodlands, produced localised atmospheric Co2 levels well in excess of global means.

  8. Ian Mott February 16, 2006 at 10:56 am #

    I wonder if Gedney et al assumed that land use change was solely veg clearing or whether regrowth and thickening was included as well?

  9. Ian Mott February 16, 2006 at 10:59 am #

    Thinksy, no, they wanted me to pay for the whole article. Can someone with a budget allocation get us a copy?

  10. detribe February 16, 2006 at 11:31 am #

    If you write to me privately about the paper I may be able to repond contructively to your needs


  11. Davey Gam Esq. February 16, 2006 at 11:59 am #

    Detribe et al.,
    Vairy interesting, but did the Nature study on increased runoff consider the increase in bitumen & concrete due to highways, suburbs, cities etc? I remember walking through the rainy streets of Brussels, with a professor explaining how laying bitumen over old cobblestones had increased runoff significantly, flooding people’s wine cellars (Mon Dieu!).
    Also, what about large irrigation schemes, or even thousands of suburban sprinklers?

  12. detribe February 16, 2006 at 1:53 pm #

    The paper is a serious empirical contribution. It came out this morning. Ive ganced through it- I was too busy reading Motties citation which is great too to deal fully with a new one. I have very modest knowledge of (but great interest in) natural vegetation and thickening issues. I know a little more about agriculture. I suggest we all go away and read the paper carefully and think about its implications. We can all learn from the methane tree-farts affair and think before we leap.

    What is clear from this and the recent methane incident, I would suggest, is that accurate modeling of a complex global ecosystem has substantial uncertainties in it, and that those who think computer models are the bees knees on global warming should be very modest about their claims.

    That said, Motty seems to know a few things, its his thread this time, so I’ll shut up.

  13. Ian Mott February 16, 2006 at 2:18 pm #

    I knew a few things once, gosh it hurt.

    I agree on the “the salinity was always there, it is just that it has moved to a more visible location”, Roq.

    “Methane tree-farts” sounds like a good name for an ageing jug band.

  14. Phil February 16, 2006 at 2:20 pm #

    It would be a tree belch not a fart. Popular misconception.

  15. rog February 16, 2006 at 3:44 pm #

    Have to be careful what you say about the Thanes, they could be easily offended;

  16. Boxer February 16, 2006 at 11:13 pm #

    The good thing about salinity is that whatever your perspective, you can always find some information from somewhere around the planet to support your point of view.

    From within the “publicly funded anti-salinity industry” I have read this explanation that may (or may not) apply to your situation Ian.

    Stream salinity is a function of the amount of water entering the stream AND the amount of salt also entering the stream. If a predominantly grassed catchment becomes dominated by deep-rooted vegetation (e.g. by excluding fire or grazing) then the rate at which water yield decreases may be greater than the rate at which salt yield decreases, so the concentration of salt in the stream may increase. In such a situation, it may be preferable to maintain the grassland nature of the catchment so that the salt entering the stream is diluted by the maximum amount of water.

    If the catchment was naturally timbered or dominated by woody heathland, then removal of the deep-rooted vegetation often increases the amount of salt entering the stream by such a large amount that the simultaneous increase in stream flow is not enough to dilute the very large increase in salt flow. So we see examples of streams that were fresh become more saline than the ocean. Perhaps this does not occur in your part of the country, but it most certainly does in mine.

    This is a topic dominated, in the hydrological sense, by variability and local conditions. I grant you that if a part of Australia that does not have a salinity problem comes under the influence of a political situation dominated by concern about salinity, that is a failing of national politics. It is the broad-brush application of a policy derived from another part of the country. This is not good, to the power of “n”, where “n” is larger than 10.

    But, if you argue that the lack of a salinity problem in your part of the country means I don’t have a problem with my once fresh creek becoming saline, then that is just the same problem of national broad-brush politics in reverse. No matter how much you don’t have a salinity problem, I still do have a salinity problem.

    The real problem is our inability to think nationally about problems that occur locally. It’s like trying to apply the principles of rainforest management to the management of the Great Sandy Desert. You may be a victim of this shortcoming, but I don’t understand why you want to perpetuate this political silliness by trying to force the argument about salinity back to the other extreme. Can we make the pendulum stop in the middle?

  17. Phil February 16, 2006 at 11:40 pm #

    Phone-a-friend says once again appears to be a good strategy of throwing many forms of salinity-related issues into one banner. We do have examples of changes in groundwater salinity related to a change in vegetation (work by Glen Walker, Peter Thorburn and other on floodplains of the Murray – salinity tolerance mechanisms of Ironbox have developed to cope with these variations over time).

    The key issues/parameters are:
    1. Shallow groundwater systems which interact with vegetation systems and/or capillary fringe generated through evaporative demand often fluctuate in quality over time as the balance occurs between concentration from evaporative demand (water removed and salt remains) and dilution from rainfall/recharge. This is obviously more distinct in systems which have low yield and transmissivity ( a bit like boiling water in a kettle – roughly the same solute but depending on the volume of water the concentration varies). Also would require a system which is strongly driven by near-surface interactions.

    2. You do not see large fluctuations in regional groundwater system as the tend to have longer response times in terms of both quality and volume.

    3. I would imagine the Pampas scenario could be explained by processes similar to my comment 1, whereby the replacement of grasses by trees reduces the dilution effect of rainfall/recharge as a larger proportion of water is removed from the system by transpiration. Need to explore the balance between deep drainage (climate – soil – plant interaction) and aquifer properties (transmissivity, quality). You would expect less change in shallow groundwater salinity under a sandy soil as your impact of change from grass to trees is proportionally less in a highly permeable system.

    Bottom line is that need to distinguish groundwater salinity (which can be influenced by saltwater intrusion, groundwater extraction, mobilisation of stored soil salt stores) from rising groundwater salinity issues (discharge of salts into rivers or bringing salts into soil root zone where they are concentrated through evapotranspiration – commonly known as dryland or irrigation salinity dependent on the driver).

  18. rog February 17, 2006 at 5:42 am #

    RIRDC take the view that trees are crops and that saline can be managed by judicous placement of crops.

  19. Taz February 17, 2006 at 8:05 am #

    Ian: On thickening I make this plea; let every one make their own observations and draw their own conclusion. Forget science, ignore its remoteness and get close to your own dirt. Join me and use a camera somewhere every day. Choose any typical area that is close.

    If the ACT can be used as a prime example of procrastination in high places, conclusions from our coroner’s bushfire inquiry are delayed yet again. This place has lost more ground cover than most recently. Who knew what before the 2003 fires may never be known if authorities had their way. But our regional management affects many.

    Late Wednesday we had a bit of an electrical storm. Yesterday I noticed crushed driveways were heaped up on our footpaths. Scoria and granite was everywhere, on the streets by the barrow load just after the stormwater inlet sumps had been cleaned by the mobile sludge tanker. On a large piece of bare ground by our latest complex of multi story dwellings I noticed the thatch was washed into waves of dune like heaps. Ginninderra Creek although it had stopped flowing for weeks was up and down like a yo yo. I could only tell that by the state of the reeds in daylight.

    A guy from Gundaroo said on ABC 666 his place was hit by hail the size of cricket balls that smashed all his windows. All the wild birds were dead. I bet none of it’s on the web.

    Ian: Without references let’s make another comment. About the mid sixties I went after environmental information related to our massive water diversions in the high country and their impact on other water reserves. I soon became acquainted with the idea that the high country itself was a major water reserve because of its vegetation and ground waters linked to more remote aquifers but not much science had been done on the issue then.

    By the mid seventies we had succeeded in negotiating agreements with the Victorian Government over public and private access to the high country that supposedly protected vegetation hence evening flows in the Murray and its tributaries without more irrigation storages. I recall some associates, the Brownlie’s, Bardwell, and Johnson wrote heaps then. Dick Johnson was an engineer who tackled the cattle grazing issue. Other friends tackled the recreation aspect like motor bikes, 4×4 and pine forests as a back up.

    All the above considerations come into play again with the ACT and its recovery.

  20. Ian Mott February 17, 2006 at 11:31 am #

    So Phil, you appear to be agreeing to my suggesting that the Wentworth Group were quite mistaken in their overly simplistic representations of the link between any clearing and salinity to Beattie, Carr and Kemp?

    Boxer, I can find absolutely nothing in anything I have said that could be interpreted as implying that you in WA do not have a salinity problem. If you were responding to a specific statement then can you indicate which one?

    Also, your suggestion that we should stop the pendulum in the middle looks OK at first glance but at this stage the pendulum is so far off centre that we have an obligation to let it return at full force, and with interest.

    We have had a highly corrupted policy process based on serious misrepresentation of fact that has been exploited through the improper exercise of power to acquire interests in land.

    My own brother, an absolute state of the art farmer on the Murray, was wiped out by a negligent stroke of a bureaucrats pen. He now works in a non-managerial role for a corporate show that he estimates is only 20% of the way up the learning curve. So talk about pendulums is just a little bit premature, don’t you think?

  21. Phil February 17, 2006 at 11:59 am #

    Ian I suddenly find myself speechless.

  22. Ian Mott February 17, 2006 at 2:30 pm #

    Surely not, Phil. I have the highest regard for your capacity as a seeker of truth and peacemaker. Not even a small reflection of truth and the Wentworth Group? I promise I would never use it in a class action.

  23. Boxer February 18, 2006 at 9:59 am #


    I’ll use these two quotes from your original post:
    “And this poses an interesting question for the publicly funded anti-salinity industry and the policy arms that have focussed so much public attention on the removal of trees as salinity causal agent.”
    “Clearly, the political exploitation of salinity appears to be sinking deeper and deeper into murkier water.”

    These are general points that, given that this blog is a national forum, could taken to refer to the national situation. You do not specifically direct your comments to the WA situation, but if your comments are made in a broad national context, then, WA being part of the nation, is included.

    I don’t understand your predicament very well, so I can’t comment on the validity of your arguments in relation to your situation.

    As for the pendulum of opinion about salinity, your remark about returning it at full force and with interest I take to mean some vengeance is justified. Your desire for revenge may be understandable in relation to your specific situation (again, I don’t know, you may be right, you may be wrong), but why do you want a sort of indirect revenge against people in WA? Perhaps you have a general problem with public servants, corruption, snouts in the trough and so on. But if you push the pendulum of the national debate back too far, you won’t just impact upon public servants who have no influence upon or role in your problem, you will be acting to the detriment of WA farmers. I am sure you don’t want to do that.

    If you and your family have been or are being wronged, I would rather you focused your anger on those who have done you harm. I am quite puzzled by the comment about your brother; clearly there are very different forces at play in different parts of the country.

    While the national salinity debate will continue, it is a very blunt instrument. Local variations are so large, there should not be a national action plan, but a series of state and regional plans. This is where the problem lies, in my opinion, the national policy approach is mostly about federal pollies and bureaucrats being totally opposed to delegating responsibility for action to the states. States have to pander to federal opinions in order to secure funding and if they don’t secure funding, the states can’t afford to do anything.

  24. Taz February 18, 2006 at 10:24 am #

    Well put Boxer; however Ian posted on the basis of some new science about trees and their water use, also thickening of the bush around agriculture not helping salinity in general.

    My own views are we had lots more native trees before board acre mono crop agriculture took root. Salinity is related to bad old farming practices where ever.

    We haven’t heard the end of any of it yet. Boxer is right on with the idea that it stops at the grass roots in each place.

  25. Phil February 18, 2006 at 10:56 am #

    Boxer good points.

    The position that Ian is putting (and he’ll tell me if I’m wrong) is that the salinity “scare” was used to justify legislation to halt all broadscale clearing of remnant vegetation in Qld. There as previously been a process of discussion between industry and government to limit clearing in endangered and “of concern” vegetation communities (endangered by size relative to original extent).

    If the ban was done on the basis of bogus science then industry would see it as a swiftie to placate urban greenies.

    Why to farmers clear trees – to increase grass production and profitability from growing more beef per unit area.

    The Feds also pocketed enough carbon to “pseudo” balance the Kyoto books without actually doing anything on growing transport and energy emissions. Of course given the dodgy nature of the accounting they actually pocketed heaps more area than they needed and didn’t even take the sequestration due to increases in woodland thickening. So short-changed on the carbon and short-changed on the accounting. Thanks bushies for free kick.

    Now lets argue that your regrowth isn’t regrowth.

    Anyway so a consultative process was replaced by a legislative process with little discussion on perceived dodgy science. Or too little science.

    Effects overall – limiting property development potential. Hence “property rights” mantra.

    Of course much panic clearing before the act was introduced and industry has not been above reproach either.

    Net result – sensible land management maybe set back 20 years and science in the wedge.

    And even funnier (if you have a perverted sense of humour) the grazing lands will probably be worse affected by climate change than elsewhere. Sorry bushies.

    But I think rural leadership also fell down on the job of selling a better compromise outcome too. And seeing some new ways of doing business.

    Do rural leaders actually represent their constituents? Or are they captive of the overall government process “game”.

    (Puts on his hard hat: Commence rock throwing now!)

  26. Ian Mott February 18, 2006 at 11:39 am #

    I do see your point, Boxer. But no-one ever asked us if they were pushing too hard in our direction. Furthermore, the appropriate time for anyone to complain about our pushing back is when the pushing is taking place, not before. So best you push your barrow and I’ll push mine.

    The point of mentioning my brother’s situation was that he had 45% of his water allocation taken back in a climate of hysteria based on a salinity boogy man.

    The irony of it all was that the ditch that he obtained his water was leaking, and continues to leak, more water than was ‘saved’ by cutting his allocation. A full third of all irrigation water is lost to groundwater and that means the leaks amount to 50% of the remaining allocation. But simply confiscating his water was deemed to be a cheaper solution than fixing the leaks in the ditch. And they would’t even let him intercept the leaks to make up the shortfall so they are still contributing to the salinity problem.

    And this was a guy that was so on-top of his job that he no longer needed to buy fertiliser, except the odd trace element. He had fine tuned the composition of his feed supplements to the point where all the nutrients required by his pastures were delivered via the bladders and bowels of his herd. It was zero waste and zero nutrient leakage delivered on a continuous, low doseage basis.

    And they shut him down in the name of sustainability.

  27. rog February 18, 2006 at 12:10 pm #

    Phil, farmers clear trees and laser plane so that they can use the big tillage machinery for cropping.

  28. Boxer February 18, 2006 at 12:54 pm #

    Clearing bans – another case of a policy that worked (to a point) in some parts of the country and not others. They were applied in WA in the 1980s, but that was a case of preventing further clearing of native forest and heathland. As natural grasslands are comparatively unusual over here, the stereotypical “clearing”, or conversion of woody native vegetation to annual crops and pastures, was banned to prevent the worsening of the stereotypical silent flood. The Victorian and South Aus mallee may be the most similar situation east of the Nullabor. This appears to have been applied right up the western slopes (?) through all east seaboard states into the natural grasslands and open woodlands country. Curious how influential the WA model appears to have been (still is?) on national policy.

    Is this the result of bad science or embryonic science? The complexity of the issue is mind boggling (see Passioura’s paper that Jennifer brought up for discussion earlier). I suspect the science is struggling to understand the situation and so policy formed from that science is overly simplistic.

    Adding in the carbon sequestration issue has just muddied the water. It would seem reasonable that if a farmer is prevented from maintaining what was the natural state of open woodland, and the tree component then thickens up, and this is done in the name of national carbon sequestration, then the nation should pay the farmer for that service. Any sign of that happening? There’s a Japanese power utility planting mallees in belts on farmland over here in a preliminary programme of carbon sequestration.

    So we all have our barrows to push, but in reality it seems to me that they are different types of barrows, and they can all be pushed towards sustainability and profitable farming. So how do we get policy to reflect the complexity of the real world? This seems a better approach than all of us trying to knock each others dunnies down. Like Christianity and Islam, there’s more in common here than there is in distinction.

  29. Phil February 18, 2006 at 1:32 pm #

    Dear Rog (Jen has me on the new Dr Phil politeness diet)

    I refer you to

    pages one and two

    You will note the historic pattern of clearing monitored by the Landsat satellite and on page 2 a summary that 95% of the land conversion is for pasture.

    Given that most land clearing occurs in Qld as every other State has knocked down any trees already in the way of agriculture or pastoralism I beg to differ with your assessment of clearing for cropping.
    There may some clearing for cropping but is relatively a smaller number.

    If you study the detail of the above report of study other reports on the site you will find comprehensive detail on land conversion information. The story has been the same for over a fifteen years.

    I like big tractors too. I think I like green more than red though.

    Of course there is a story that real blokes like “recreational tillage” as it gives them an opportunity to sit in airconditioning, astride a powerful machine, sipping a cool lager, possibly with the stereo on, or having a blokey chat on th CB, on GPS auto-pilot, while escaping the nagging wife and pesky children. But we would not tell a sexist story like that here.

    I thank you again for your post.

    Yours sincerely


  30. Phil February 18, 2006 at 1:46 pm #

    Boxer – the woodland thickening is a bit complex. It gets to Jen’s dreaded discussion on what’s anthropogenic – so for Kyoto type carbon accounting – woodland thickening is assumed to have been going on anyway – lack of fire – from fire control and overgrazing – SO – only the increase in thickening over the base rate is allowed !! Thickening on thickening !! Argh – give up. Too hard.

    For land clearing reductions to be counted it has to be “Kyoto” forest which has a height definition etc. Not just anything counts.

    Similarly forestry is only counted if its new forestry – not part of an existing rotation.

    You can argue – but they’re essentially trying to only give credit for “new” activities that humans undertake. Not reward for business as usual.

    Most of this is lost on farmers who see it as some sort of swiftie.

    (And Australia is really the only country into this aspect – to “pseudo” comply with Kyoto. IMHO of course)

    Anyway by not engaging rural Australia on carbon sequestration properly and paying market prices for carbon, the nation has missed on a goldmine opportunity to sequester vast amounts of carbon in our rangelands and realise a profit from it (from perhaps Japan, Europeans and US). This profit could have been used to fund ecological outcomes requested by urban types. A win-win. Brickbats to all !

    Meanwhile back at the salinity !

  31. Taz February 18, 2006 at 5:05 pm #

    There is a long history of attack on our hapless trees. There is a museum piece of engineering, a thumping great tractor that clumped along on wooden shoes like posts. This pioneering monster was used to pull scrub around our southern flats for years, about the same time dust storms used to choke Melbourne.

    In my study I keep a battered copy, “Glimpses of Australia” V2, 1897. On page 229 is a good photo of Black Swan Lagoon near Warwick QLD, “one of the richest bits of country in the world”. It is sparsely treed but I am suspicious it was heavily cleared by then. I wonder how that block fairs today in global fertility stakes.

    On page 233 is the Torrens Weir, it looks rough country. ‘ “In the early days of Adelaide the Torrens was BIG river but as the settlement extended and forest was cleared away, the river dwindled down until it became a small stream meandering along the bottom of a big depression”.

    On page 234 is the Ovens River – “Germantown” but the description is remarkable in that it connects half of Victoria on the river’s way from the Alps to somewhere south of Geelong. The photo however shows a pretty stretch of river flats between the hills as a very woody place.

    From the “Meat Works” near Grafton p251 to “A Bush Workman’s Home” Gippsland p268, we can clearly see that the country was wooded every where. P 268 in particular gives a glimpse of original bush on the far side of a fresh farm and a vast area of ringbarked timber on the near side.

  32. rog February 18, 2006 at 5:30 pm #

    You really are a total tool Phil.

    *There may some clearing for cropping but is relatively a smaller number*

    In your inexpert opinion of course.

    From the ABS (not GreenLeft Weekly);


    Knowing how much clearing is occurring is problematic, and these figures, from the Australian Greenhouse Office, are uncertain estimates. The most reliable figures are provided by government research agencies using satellite imagery, but data collected in this way are not available for every State over the past ten years. The accuracy of estimates is expected to improve over time.

    The figures used include information about land that has been cleared for the first time as well as land that has been re-cleared. They do not distinguish between the kinds of vegetation that has been cleared – for example, whether it formed part of a healthy or a degraded ecosystem. Thus the figures cannot be used to measure the net or quality-adjusted change in vegetation cover. Both clearance and re-clearance of native vegetation have environmental impacts.

  33. Phil February 18, 2006 at 5:43 pm #

    Taz – I think it depends where you are in Australia. Certainly the coastal strip is heavily cleared in parts. SE Qld about 50%. Most of NSW wheat belt is obviously cleared. I guess Ian could inform on the Big Scrub between Grafton & Brisbane.

    But we have areas where the reverse has occurred too – woody infestation or thickening up – Pilliga Scrub, Cobar woody weeds patch, SW Qld Mulga forests, central Qld eucalypts.

    Actually cities are very interesting – South Brisbane is now a sea of concrete, asphalt and houses – on the city side there is a freeway – compare with this description.

  34. Phil February 18, 2006 at 6:04 pm #

    Dear Rog – I think you ought not be calling myself a penis as you are most incorrect and the term is not polite anyway. You are most incorrect to write your post. I am surprised as I thought you were quite knowledgeable in Australian natural resources issues.

    The Qld satellite data are definitive – highly ground truthed and 95% accurate. NSW numbers have been small in comparison for a long time. Other states very small.

    ABS are farmer surveys and I don’t read Greenleft Weekly. ABS for example had one million hectares for a Queensland figure actually below half that number. About as good as their Agricultural census. Both ABS and the AGO are not expert in these matters. The AGO are uncertain as they do any ground-truthing out of the ACT.

    Regrowth clearing is included and can be estimated. But clearing for cropping is still small.

    Woody vegetation can have a phenological description of basal area, foliage cover or crown canopy. Or the analysis will be qualified down to a detection level. Of corse MODIS imagery using angular instead of spectral patterns and microwave imagery may give us information to detection differences in vegetation structure which will identify regrowth more clearly.

    Have a look at any state of environment report, state survey and convince me that the NSW number is higher or even high !

    Where are the vast new areas of cotton or wheat production?

    And just so we don’t get silly – we are talking the last 10-15 years – not since settlement.

    You may ahve found yourself in a large cleared paddock and felt it was quite large but Queensland like the universe is much larger.

    Ask Ian’s opinion?

    I hope you don’t see my correction of your refutation as offensive.

    Best wishes


  35. Philiplex February 18, 2006 at 6:13 pm #

    Dear Roger

    I also refer you to this more useful earlier national survey for a national perspective.


    I do suggest you be most circumspect in use of ABS and AGO data.



  36. rog February 18, 2006 at 9:11 pm #

    yep, you cant believe what any of these government employees say;

  37. Phillip Done February 18, 2006 at 10:08 pm #

    Dear Roger

    I think you may have posted this in the wrong place. I know it wouldn’t be a diversion so I assume it’s an slight error.



  38. Taz February 18, 2006 at 10:45 pm #

    Phil: With no stretch of the imagination a few of us can challenge this new age dependence on science, the policies and the attitudes from other well established sources such as art in relating to change, in particular mans impact on this continent over the last say 150 years. But perhaps our greatest problem today is the people who depend on their rhetoric for solutions. By that I am simply offering to share visual impressions built over decades. This is how I model most dilemmas.

    Notice I don’t usually refer to other people’s web pages either in our discussions. That said lets move on.

    Trees and landscapes can be studied in many ways, none the least is photography but other art will do too. Early English land lords brought their views with them literally and their concept of rural exploitation applied all over this country. Pioneers extended their influence deep into our hinterland and that is what I look for in all our early records. But the records also remain in old trees and that is your best clue to what was.

    There is another aspect. As one team struggled to put a model of our entire radio communications system into a computer and associate every aspect with some legal jargon about interference and compliance, I was still studying all the contour maps and wondering how the aborigines got on with their smoke signals way outback, I mean before us and our processes of understanding. We do kid ourselves at times.

    BTW vegetation in all its forms affects radio propagation over long distances. So does water and salt. QLD’s old DRCS was a particular interest as we extended the boundaries of other services

  39. Phil February 18, 2006 at 11:08 pm #

    Taz – I would interested to hear your experiences with radio and vegetation etc.

    In terms of visual effects in art depicting Australia – Russel Drysdale is interesting – how earlier pictures with happier days, greener grass and blue skies become barren, red dusty skies, desolate and isolated. e.g. Dead Bullock, Desolation, Red Landscape, The Crucifixion and alone as Woman in the Landscape.

    His exposure to the 40s droughts I guess.

    Also in the Jill Ker Conway’s book “The Road from Coorain”

  40. Taz February 18, 2006 at 11:26 pm #

    Thanks Phil; I knew a lad who helped build some of the info systems behind our RFA agreements, 20/20 vision etc. Zeroing in on some old haunts it gets a bit complex. Bet that’s why he moved on! I used to say he was just another tree counter.

  41. rog February 19, 2006 at 5:11 am #


    earlier art was essentially Romantic as was the era and hardly representative.

  42. Taz February 19, 2006 at 4:03 pm #

    hardly representative of what rog?

  43. Ian Mott February 20, 2006 at 10:47 am #

    Slip away for some vitamin F(farm) and indulge in the perfect massage by waterfall and look what you guys do. I accept the pictures, Taz but they are self selected by the artist. They have anecdotal value the same as James Cooks reports that, when the smoke cleared, one could see 2 or 3 miles inland through the woodlands at Botany Bay and earlier along the coast at Woollongong.
    Ditto the original description of Melbourne as a very wide open paddock with few trees.

    So the whole picture is muddied by the fact that the first removal of trees in those open landscapes would have had only limited impact on run-off and groundwater flow systems because grass was already the dominant vegetation.

    It has often been said that over grazing has caused the subsequent thickening of trees but this is a rather loaded value statement. Any reduction in the leaf area of grass will reduce the pasture’s capacity to transpire and tend to favour the species that have not been eaten.

    And lets face it, what is the difference between a pasture that has been eaten bare and a pasture that has been burnt bare? Both produce bare ground but the dark ash will produce earlier soil warming and greater soil microbial activity. Both produce a marked temporary reduction in transpiration capacity and therefore produce similar effects in retaining soil moisture for longer so that more of the next rainfall event goes to runoff or recharge.

    And given that only 2% of our land area is cultivated, we can conclude that the area, scale and duration of exposed mineral soil today is only a fraction of the historical firestick farming level. So how can we describe modern farming as unsustainable when a greater level of soil exposure maintained a modified ecosystem for 50,000 years?

    And this is where Drysdale and his wide brown land come in. In part, it was more artistically cool to “discover” the worst views of the landscape and represent them. The best views were already being seen as sacharine and twee.

    But the other part was that the scale of the best and worst views became larger and more visible to the outside observer like Drysdale. And unlike their country cousins, the urban art viewer was more inclined to take a single representation of a dynamic system as “the” single truth rather than a snapshot of part of a cycle.

    But the overall truth? Bob Carter’s coral cores at the moth of Queenslands largest river, the Burdekin, indicate that the worst silt flows took place before any significant clearing had taken place while the lowest silt flows took place during the WWII drought years when the river didn’t flow at all. Bob could explain much better than I.

    And the ocean floor mud cores at the mouth of the Murray would also have some interesting things to say about the current state of the Murray Darling basin. But I guess that is why they haven’t been funded yet.

    In a nutshell, we have no chance of finding workable solutions to any environmental problems untill we can trace the detailed path that has led us to this point.

    By the stringent prescriptions against over grazing, for example, we may be departing from an historical level of firestick mosaiced bare earth that is reducing stream flows, reducing aquifer recharge, increasing the spread of wildfire and thereby increasing the size of other areas of bare earth that produce increases in stream flows and recharge in those other areas.

    We cannot define a duty of care for either public or private tenure until we know the original state, the historical range of variation and the relationships it involved. And only then can we deal with the historical changes and only then can we define a regulatory fromework based on the character, scale and intensity of MATERIAL CHANGES in those attributes.

    This bullshit that makes a guy with 3,000,000 trees guilty of an offence for cutting one 2 metre sapling (that is likely to coppice anyway) must stop because it is scientifically, legally and morally bankrupt.

  44. Phil February 20, 2006 at 12:48 pm #

    For cripes sake. A cold waterfall shower and Ian’s gone hyper. (hope you didn’t use soap !)

    Drysdale painted what he saw when he checked out the 40s droughts. He didn’t write a letter to Nature nor do a report. Checks out well with the land condition reports of the time.

    Very detailed CSIRO work show shows cows are much worse than tanks in the Burdekin (3-5x the sediment). Note I haven’t enetred into what it does nor say that there have not been big pulses in the past.

    And why does vegetation thicken – pls don’t say climate – you know it’s fire. Why do we have less fires (a) they’re not lit as it’s perceived to be risky if no followup rain (b) they’re put out – firebreaks and fence-lines (c) not enough grass fuel !!

    And if it’s so bad – why have land values gone up?

  45. Ian Mott February 20, 2006 at 2:58 pm #

    Hmm, why the ducks? in 300 words or less. That was a cold waterfall massage, Phil, the best you can get without stiletto heels (so they say).

    Hard to pin down on the cause of thickening. The fire creates the seed bed for germination and also reduces competition for soil moisture when the seedlings need it most. And this is the same outcome produced by over grazing. Both create the circumstances for increased seedling growth.

    But it seems to be the following fire that used to burn off the successful saplings and the absence of that following fire that enables the thickening process to become an established part of the landscape. And of course, the follow up overgrazing event will only remove some of the successful saplings, not all.

    But the interesting thing about pasture cover and water yield is that the improved yield from a shift from full pasture to bare soil is usually even greater than the yield improvement from a shift btween forest to pasture.

    I am not certain what research has been done by the CRC for catchment hydrology on this (and no time to look now). But the ever trusty DNRM Water Fact Sheet W24 suggests some generalised indications that at Warwick (660mm RF);
    1 heavily timbered land will yield 0.04 MgL/ha,
    2 natural grassland will yield 0.13 MgL/ha, while
    3 bare ground will yield 0.47 MgL/ha.

    And this suggests that if we really want to get our heads around catchment yields and sustainability issues then we need to assess past yields from fire mosaics, pasture depletion (bearing in mind that most pastures will be depleted at the end of a dry season) tree clearing, regrowth and thickening and crop water use.

    And after we have done that we can start to get a handle on salinity changes etc with a view to managing catchments. In part, that could include even increased clearing to restore yields from parts of the catchment that have undergone yield depletion effects. And it could include increased ground water irrigation to lower water tables that have risen for other reasons.

  46. rog February 21, 2006 at 4:27 pm #

    The early artists used softer tones and light and the bush was more luxuriant – more like a European jungle with muscular darkish skinned Europeans.

    Eg George Pitt Morrison, Conrad Martens, Capt Arthur Phillip

  47. 123 May 3, 2006 at 5:32 pm #

    u ppl need a life

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