And whilst the living tree was poisoned in 2006 with glyphosate for reasons that remain unknown, despite arborists’ efforts to save it, the tree was declared dead in October that year. Although its death was a loss felt across the region, the tree’s journey from decline to preservation and eventual reconstruction has become a remarkable example of heritage conservation and local scientific expertise.

For more than a century, the Tree of Knowledge served as a gathering point for unionists and workers. For many Australians, it was more than a tree; it was part of the nation’s identity.

The challenge was how to honour the tree and ensure future generations understood both its significance and the science behind its preservation.

Scientists from the wood protection team at the Queensland Department of Primary Industries’ state-of-the-art forestry research facility in Salisbury, Brisbane, led the effort.

In 2007, the tree was carefully dismantled at its original site, with every branch meticulously marked to allow accurate reconstruction. The branches and main trunk were then loaded onto a bed of sand and transported to Salisbury in Brisbane. There, they were installed over a large, covered, purpose-built tank fitted with an irrigation system before a preservative solution was sprayed regularly over the timber to keep it damp throughout the treatment process.

A boron-based preservative supplied by Koppers Performance Chemicals was used to impregnate the wood. The treatment, supported by regular testing, continued for more than a year to ensure full penetration.

And as the boron diffused into the timber, it provided protection against insect and termite attack. Because the reconstructed tree would be housed under cover, additional decay protection was not required.

In 2009, the preserved Tree of Knowledge returned to Barcaldine.

But simply reinstalling the trunk was not enough; it needed long-term protection from the elements. A roofed structure was built above it, and a canopy of 8000 hanging slats made from recycled spotted gum was suspended 18 metres above the ground. These slats mimic the form of the original canopy, creating the illusion of a leafy ghost gum from a distance while revealing the preserved remains up close.

And whilst the boron protects the timber from insects and termites, it is not fixed in the wood and can leach out under wet conditions. The covered installation shields the trunk from rain and direct sunlight while allowing airflow.

At night, lighting transforms the structure, making the tree’s “ghost” visible across the flat plains surrounding Barcaldine.

Whilst the full Tree of Knowledge is no longer alive, it has been preserved as a monument that has a different kind of immortality. It stands as a quiet reminder of the birth of a movement, sheltered beneath its timber canopy in the town where its story began.

Hazard Class H3 is designed for preserved timber that is exposed to the weather but is out of ground contact and can readily dry out after wetting events. Think decking, fence rails and palings, cladding, and balusters — situations where the wood gets wet but airflow quickly dries it.

But what happens when the right treatment meets bad detailing?

An important part of H3-level protection is that the wood can dry out. The preservative systems specified in the Standard will protect wood if it gets wet. However, they won’t work if the wood isn’t allowed to dry out, staying wet (damp) for long periods.

Timber that remains consistently damp, even if it’s out of ground contact, becomes a different environment entirely. It provides the right conditions for rot or fungi to thrive, leading to decay. This is the condition where H3 is not H3.

In the real world, common design mistakes can convert an H3 application into a harsher, quasi-H4 environment. The issue is almost always poor moisture management, stopping airflow and drainage. Some examples I have seen:

• The Ledger-Flashing Trap: A common failure point is where a deck ledger board (H3) is fixed to a house wall. If the flashing, house wrap, or sealant is incorrectly installed, water gets trapped between the ledger and the wall sheathing. The timber cannot dry out, leading to decay, not just in the deck structure, but often the wooden house components as well.
• The End-Grain Water Sink: Timber balusters, handrails or deck posts in saddles or rails (H3) that are capped or contained in an impermeable material (like a metal or plastic cap or even paint) without an air gap, often trapping moisture at the vulnerable end grain. Painted joints can create a problem. This turns the top of the post or a housed joint into a long-term water reservoir, accelerating decay.
• The Planter Box and Balcony Barrier: H3 timber used for external planter boxes or in balcony construction where it directly contacts soil, potting mix, or is permanently encased by waterproofing membranes on all sides is almost guaranteed to fail prematurely. These are H4 (in-ground) applications, and H3 is simply inadequate. OK, a planter box is not really detailing, but you get the idea!
• Timber decks exposed to the ground and often poorly ventilated create a persistent humid environment, turning a H3 application into an H4 situation.

For any timber member that stays damp for long periods where the drying-out process is significantly impeded, the required Hazard Class should be H4. H4 treatments use higher concentrations and deeper penetration of preservative to provide the necessary protection for the more aggressive decay environment.

The Conclusion: Design Matters Most

The treatment standard can’t specify all the exposure conditions to which timber may be exposed. The design and detailing of where timber is used is important. A H3 level of protection is not a magical shield, and a H3 preserved wood performance specification is based on an expected environment.

If your design creates a perpetually damp environment – wet pocket, a moisture trap, or an airflow barrier –you must treat the timber as if it were constantly exposed to the ground. When specifying and building, remember the advice:

If it can’t, step up the treatment. Ensuring adequate drainage, using spacers to promote airflow, and protecting end-grain are not just good building practices. They are essential to making sure your H3 timber actually delivers performance.

Durable timber is commonly used for house framing, decks, fences, fascias, cladding and outdoor structures (among other products). However, as the timber industry evolves and environmental concerns grow, it’s time for the public and media to adopt the more precise and beneficial term: preserved wood.

While the phrases might seem interchangeable, ‘preserved wood’ offers clearer communication about the product’s function, better reflects modern preservative treatments, and helps to dispel persistent consumer concern associated with the older term.

The word ‘treated’ often conjures an outdated image of hazardous chemicals. In the 1980s and 90s, the main chemical treatment was chromated copper arsenate or CCA. Contains arsenic, right? Arsenic is dangerous, right? Arsenic is a chemical, right? Therefore, all chemicals are dangerous, right? WRONG!

Everything, and I mean everything, is made up of chemicals. The bottled water many are fond of and the food we eat are chemicals. The central fact that everything is a chemical is a fundamental concept taught to chemistry and toxicology students and most importantly it is the dose that makes the poison. This remains is a basic principle of toxicology.

Nevertheless, even though CCA is used to protect about a third of the preserved wood currently used in Australia, people are concerned when treated wood is used in residential settings.

Today, residential wood preservatives are vastly different. Since 2003, the industry has reduced arsenic for residential use, mainly by using non-arsenic-containing ingredients such as pyrethrins (originally from flowers, so it must be OK), and copper-based systems such as alkaline copper quaternary (ACQ) and micronised copper azole (MCA).

By using the term ‘preserved wood’, we shift the focus from the chemicals being applied to the result we are after: longevity, durability, and protection. It highlights the product’s ability to resist fungal decay or rot, and insect damage – the main reasons for its use – rather than focusing on older systems, which have a fraught history.

In today’s market, the term ‘preserved wood’ serves as an umbrella term that encompasses a range of protection methods, from the classic vacuum-pressure-impregnated wood to newer alternatives. It communicates that the wood has been made to last longer than its natural state, which is the core value proposition for the consumer.

Moreover, ‘preserved’ aligns with the technical language used by major industry bodies such as the International Research Group on Wood Protection and the American Wood Protection Association (AWPA) and the Timber Preservers’ Association of Australia (TPAA).

The AWPA sets the preservation standards in the US and the TPAA is heavily involved in setting the penetration and concentration standards for wood protection chemicals in this country. Adopting this term helps to foster greater transparency between the industry, builders and the general public.

In an era where consumers demand safer, more sustainable and better-performing building materials, the language used must reflect modern reality.

Shifting from the generic, historically tainted ‘treated wood’ to the descriptive, future-focused ‘preserved wood’ is a simple yet powerful change that benefits everyone by providing greater clarity and restoring consumer confidence in a vital, long-lasting building product.

A quick AI search revealed that in 2022, South Korea spent 5.2% of its GDP on R&D compared to Australia’s 1.9%. The US spent 3.6% and Japan 3.4%. OK, AI research should be treated with a hefty dose of scepticism, but the numbers mirror those that I developed in pre-AI days (2018). In 2022, South Korea’s population was about double Australia’s, 26.3 million people.

Now I know that there are a squillion ways to massage the numbers and all sorts of justifications we can put in place, but I also know that I spent the vast majority of my working career looking for money and justifying what I reckon was meagre expenditure rather than smashing the frontiers of science.

One justification for reducing publicly funded research is that universities can do the work. This was one of the reasons given for the recent announcement that CSIRO staff numbers were being reduced.

I believe this to be a flawed argument.

Firstly, the universities themselves are struggling for funding, and secondly, universities don’t have the long-term researcher memory that publicly funded agencies have, or, in the case of wood protection research, had.

Long-term knowledge is being thrown out, or I could say, kicked out the door.

A lot of the university researchers are Master’s and PhD candidates. Don’t get me wrong, these are great kids, but they are still learning!

As a nation, we pride ourselves on ‘punching above our weight’, but it doesn’t seem to be happening when it comes to R&D spending!

Don’t get me wrong, we do alright in scientific output, but just imagine what we could achieve if resourcing R&D started approaching that of South Korea or even the US…. not in dollar value of course, but as a per cent of GDP.

It is hard to compare how much money is spent on sport in this country against the amount spent on R&D, but Google and AI searches reveal that the combined annual Federal and State Government expenditure on sport infrastructure, community facilities and sporting organisations runs into the billions of dollars.

I can’t help but conclude that, as a nation, we have an issue with priorities.

One of the biggest problems with funding research into timber durability is that you have to be in it for the long haul.

It takes time for timber to deteriorate. For example, in 1997, a trial was established to investigate the effect of preservative penetration in heartwood on the performance of preservative-treated Pinus radiata exposed externally above ground.

Resourcing was obtained to prepare and install a scientifically sound trial, and to cover inspections for up to 5 years. It may have been a little more or less. Try as he might, the researcher could not raise funding for regular assessments across the years so that we could get our heads around the rate of deterioration in the exposed pieces.

There were two trial sites, Northern NSW and Queensland. The original Queensland site was lost to a bushfire. The material from the NSW site was recently assessed and moved to the DPI facility in Nambour, north of Brisbane. Unfortunately, we could not determine the ‘rate of deterioration’ desired by engineers, architects and designers because we couldn’t get funding to carry out regular assessments. Priorities!

Just so that not all is doom and gloom, the good news is that scientists in this country are too pig-headed to give up and will continue to punch above their weight.

Update: Addressing Recent Commentary and Clarifying Research Investment

In this piece published yesterday, I could offer all sorts of excuses but I forgot to acknowledge the investment in timber durability research by Forest and Wood Products Australia (FWPA).

Specifically, FWPA provides dedicated support for timber durability research through the National Centre for Timber Durability and Design Life (NCTDDL), a commitment that has been in place since the Centre’s establishment in 2018.

This support is via a program-based funding stream provided by the industry. This initiative is I believe, the first national, centralised funding model of its kind since CSIRO’s timber durability research activities were significantly reduced in the early 2000s. The NCTDDL was purposefully established to address the need for a stable, long-term national research commitment.

The structure of this funding is strategic: the director of the NCTDDL has the discretion to allocate the program-based funds, which is for a more stable and sustained research environment compared to the traditional, often sporadic nature of project-based support.

I regret the oversight and wish to ensure the full context of current industry contributions to timber durability research is clearly understood by the reader.

Sapwood and heartwood are described in TPAA’s Technical Note 3, but an easy way to think about how a tree is built is to think of wood as a clump of drinking straws. The straws around the outside are unblocked, allowing dissolved food and water to travel up and down the stem. This is the sapwood, and in a freshly felled tree, it is full of liquid sap. The straws on the inside or the heartwood zone are blocked with resins and waxes that stop the passage of liquid.

Logs are most often cut up when they are green or full of sap, and the resulting sawn product is called ‘green-off-saw’. Because the sapwood is full of sap, green-off-saw material is extremely hard, some would say ‘impossible’ to treat properly to meet the specifications in AS1604.1. It is impossible to get a preservative solution into the cells or fluid pathways that are already full of liquid. It is like trying to pour a beer into a glass that is already full of water.

The best practice to treat green-off-saw material is to dry it before preservative treatment. This is more important with sawn pine compared to sawn hardwood.

However, by far the majority of treatment plants that treat products such as fence palings, fence rails, or landscape sleepers do not pre-dry the material. Why…… because “if I don’t treat it the bloke down the road will” and we wonder why we are losing market share to plastic and the alternate building materials. Why does one supplier condition timber before treatment and another does not?

Often, sawmillers shipping green-off-saw timber know that the material they are supplying to timber treaters will undergo a treatment process, but justify their action by saying: “we haven’t done anything wrong because we have marked it as green-off-saw.” Whilst this may be true (and legal) is it the right thing to do??

I wonder who will get to the bottom first???

Earlier this month, while responding to a query about the safety of preserved wood, I was also challenged about why the industry continues to use chemical preservatives instead of natural alternatives. This exchange illustrated the challenge of addressing scepticism and misinformation around preserved wood.

I fought back valiantly with an observation that bitumen is an unhealthy brew of cancer-inducing compounds, but that doesn’t stop the stuff from being used way more than preserved wood.

We don’t let children play on preserved (CCA) wood, but we are OK with walking barefoot on bitumen. I also pointed out that if the so-called natural preservatives were any good, they would be on the market, making producers heaps of money.

When someone holds an opinion, it feels very real to them. Even when presented with evidence, it is extremely difficult to change their mind—especially on topics such as preserved wood, where opinions are emotional and deeply held. This is a central challenge in addressing misinformation.

I was complaining to a colleague about how hard it is to change someone’s opinion when the evidence is on your side, and the response I got was, “Ahhhh!” Brandolini’s Law!!

I had to Google Brandolini’s law to see if I was being played, and I learned that in 2013 Brandolini formulated the law, also known as the Bullshit Asymmetry Principle. Brandolini’s Law states that ‘The amount of energy needed to refute Bullshit is an order of magnitude bigger than to produce it’. Put another way, it is much easier and quicker to spread nonsense, false claims, or complex theories than to gather evidence, formulate a coherent argument, and educate the public to disprove them.

Unlike a liar who knows that he is uttering a falsehood, Brandolini’s law is not about reporting facts – rather, it is Bullshit intended to ‘shape the beliefs and attitudes of listeners in a certain way’. The problem with good Bullshit is that it appeals to our emotions and our existing view of the world, and if these opinions align with our emotions and world view, they become very hard to dislodge.

Let’s say that someone whose opinion you are inclined to believe tells you that preserved wood will end civilisation as we know it. You get the idea! Think about the effort that we as an industry would have to expend just to refute this nonsense.

Think of the words we would have to craft in a readable, cogent way. The internet makes the problem worse as it is incredibly easy to publish a nonsensical opinion, and even though something is “published,” it could still be nonsense (or Bullshit).

Rather than go to all the effort of refuting a nonsense statement, a better approach may be to place the burden of proof on the person making the claim. An even better tactic would be to educate our product users, but that would be very expensive.

The workshop determined the need for a ‘quality mark’ and decided that TPAA work with other organisations to progress this initiative.

Twenty-six invited attendees across the industry discussed industry priorities in teams of five or six.

The workshop was facilitated by Peter Webb from Independent Verification Services, and there were note-takers in each team who reported back at the end of each topic session, as well as submitting their notes for collation and reporting back to the TPAA board.

The collated notes have been sent to workshop participants for verification, and participants will prioritise issues for consideration by the TPAA board.

Recommendations included that TPAA work on a voluntary risk-rated quality scheme, for example, testing landscape preserved timbers compared to structural products. There was also a suggestion that brands be allocated to importers rather than the originating plant overseas.

A major outcome of discussions on waste was that the industry and policymakers need to change the language from referring to the material as ‘waste’ to thinking about it as a ‘resource’.

In the modern social media and fake news world, preservative-treated timber classified as hazardous waste can potentially impact the industry seriously.

A little-known statistic is that around 70% of preserved product produced in Australia is treated to H2F (framing protected against termites) with organic active ingredients. As such, sawdust and off-cuts, if not repurposed, can be broken down through biological action (composting) or used as biomass fuel with little to no toxic gasses emitted.

The session on testing was vigorous and highlighted that TPAA has a role to play in removing or reducing ambiguity.

Methods for determining preservative penetration were discussed, as was using an alternate test or analytical zone.

During the session on testing, the impact of species, retention gradients, sapwood/heartwood and resin content was raised. The point was made that a major project is under way to examine these concerns.

Pine from all over Australia is being impregnated with copper, chrome arsenic (water borne) and tebuconazole/propiconazole (LOSP) preservative, and the results are being analysed to determine their impact on penetration.

Preservation standards need to be responsive to industry needs. Developing alternate pathways of standardisation was suggested.

Finally, managing the risks of product performance, resource (waste) management and chain of custody were reviewed, with possible ways forward identified.

The workshop results will be further reviewed by the TPAA board at its next meeting, where a decision on where to apply resources will be determined.

The contribution of all involved in the workshop is gratefully acknowledged

The gathering at the Eco-Science Precinct at Dutton Park discussed preserved wood quality, managing wastes, standards, testing and risks to the industry. Twenty-four participants from timber preservation plants, academia, preservative suppliers, and the government attended.

The workshop format was slightly different in that participants were allocated to teams of five or six people, so each team had a representative from an interest group. Each topic was discussed for 30 minutes, followed by a ‘report back’ to the workshop.

The workshop aimed to identify and define issues associated with each topic, identify (or predict) their impacts, and develop a way forward to address (not necessarily solve) the identified challenges.

All participants actively engaged in discussions, and the event was a success. Copious notes were taken, and once collated, the TPAA secretariat will report back to participants for confirmation. Once confirmed, a report will be submitted to the TPAA board for further action.

Discussions covered quality-linked activities in the treatment plant, a consideration of third-party auditing of preserved wood quality, the feasibility/desirability of sampling in the marketplace and ways to address under or over-treatment in the preservation plant.

The discussion on standards compared national standards’ role to industry standards and Codemark.

The discussions on waste were actively embraced. A strong message from the workshop was the desirability of approaching preserved wood offcuts from manufacturers and products coming out of service as a resource rather than a waste. Production wastes such as plastic wrapping and strapping were also considered.

Several participants identified the testing topic as the most interesting and worth following up on. Alternate test methodology and compliance criteria were explored during discussions.

Risks to the industry were identified, including poor public perception of preserved wood, premature failure, dwindling resources in the hardwood industry, and a lack of monitoring of preserved wood quality of imported products

Follow-up is vital for the workshop to be completely successful and TPAA will make every effort to ensure this happens.