Thankyou Perseus

So let’s assume in line with these stats that clearing of old-growth forests comprised about half of the total clearing figures in Qld. This still leaves an enormous extent of old-growth clearing.

You stated that the additional forest in Qld “was vast areas that had previously not been classed as forest because the canopy was less than 10% and in which the canopy had thickened to over 10%”. So it is only the fraction of thickened vegetation that has crossed this threshold that has been added to the forest total. Any grasslands that have developed a woody layer to less than 10% cover don’t count and any woodlands that already had a 10% cover don’t count either. So this statistic is really just picking out a small fraction of the total thickened vegetation. And yet this small fraction is supposed to be greater than all the clearing that occurred in the 90s!

We simply cannot tell from SLATS imagery, or any satellite imagery, or even aerial photos in most cases, when comparing pre 90s and post 90s images, whether many areas have thickened up across this threshold or not. Where we can see a significant change, we can’t assert that the thickened woody vegetation is over 10m tall and therefore within the definition of a forest. And it is impractical to get to more than a small fraction of sites on the ground, to check it out.

Then there is the ludicrous definition of a forest, as including any wooded vegetation with >10% crown cover (and >10m tall). Would you consider a Mitchell grass flat with scattered boree trees of, say 11% crown cover to be a forest? Not in a fit! It seems like a definition of convenience, designed to get the maximum change from non-forest to forest.

All of this means that the interpretation is wide open to large-scale error, and to enormous bias by those who are that way inclined

Thus, I say that many of the stats on this stuff are a million miles from Jennifer’s assertion of being “hard data”

Thanks for your comments, Jennifer. I think it is great when the author responds to the commentators. We can all learn a lot.

1. and 2. Your interpretation of Jared Diamond’s view on Australian agriculture and mine are different and I am happy to live with that. I believe that there are many properties that are not operated sustainably in Australia. I hope that efforts will be made to get them operating sustainably.

3. Please correct me if your view on the salinity in the Murray Darling is not “It’s all fixed up and there is nothing more to worry about.” That is certainly the impression that I get from your article and from your comment above.
When I read the Murray Darling Basin Commission (MDBC) website http://www.mdbc.gov.au/naturalresources/salinity/salt_interception/SaltInterceptionWorks.htm
it says the following:

“Salt interception works are large-scale groundwater pumping and drainage projects that intercept saline water flows and dispose of them, generally by evaporation. Since 1988, the States of New South Wales, Victoria and South Australia together with the Commonwealth Government have funded the construction of salt interception works that resulted in a reduction of 80 EC units at Morgan. To achieve this reduction, these salt interception works have together pumped about 55 000 megalitres of saline water from the watertables each year, resulting in about 550 000 tonnes of salt being kept out of the River Murray each year.”

These saline groundwater pumping projects have cost over $100 million and $2 million per year in energy costs alone. That is 20 million kW-hours and (assuming coal fired power), 18,000 tonnes of greenhouse gases plus all the other pollutants associated with power generation.

At least as much new groundwater pumping will be needed in the future to keep the salinity down in the Murray, and then land use solutions, such as revegetation with natives and crop rotation will have to be implemented so that groundwater pumping can be phased out. None of this will be cheap or happen quickly.

That is why I don’t think it is appropriate to imply that the salinity in the Murray is all fixed up.

Wrong Ludwig, wrong Ericc. You may not assume that 50% of Qld clearing is "old growth". It is merely woody vegetation that falls within the definition of forest. Much of it is defined as "remnant" but this term is designed to give the ill-informed observer the impression that it is old growth without actually being so. Remnant is any vegetation that is 50% of the 'normal' canopy cover, 70% of the 'normal' height, and the same composition as the original. And this has captured vast tracts of regrowth forest of comparatively recent age.

Other parts may technically fall within the definition of old growth due to a number of shade trees left in a paddock after original clearing (mostly selective ringbarking by blackfellas) and a subsequent regrowth event has supplied the canopy cover threshhold to (often wrongly) get classified as remnant. If you go to Table 6 of the above SLATS reference you will see that in 2001 some 26% of all clearing was on land that had no woody vegetation in 1990. And the reporting of "remnant vs non-remnant" clearing does not indicate what portion of the remnant clearing was actually remnant grassland clearing.

Ericc, while the MDBC would like to claim credit for reducing salinity, the real achievers were farmers themselves and nature. Put simply, one cannot have a worsening salinity problem if the water table is being lowered. And while the MDBC was busy pumping saline water from points of salt concentration at great cost, farmers were doing a much better job by pumping out the fresher water for irrigation before it got to the salt load. It paid for itself in the crops produced and the salt stayed where it was causing no harm.

But, of course, an "earth sciences" community with a vested interest in funding chose to portray even this beneficial effect as a problem caused by farmers. They were demonised for increasing salinity and aquifer depletion in the one breath.

As all ways the truth is some where in the middle.
But Jennifer let me help you rest easy you are not one of Australias elites. :-0

We need people like Jennifer and Jared they mark the road and show us the middle path.

Ericc, You keep quoting me wrong. I never said the Murray was all fixed up. I simply stated that salt levels have halved over the last 20 years. Can we agree on that one point - as a start?

The truth lay closer to Jen’s contribution. Excellent work , and keep it up.
All in small steps.