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Trees are killing our Koalas

Posted: Mon May 07, 2012 11:34 am
by RestoreAustralia
The following is a paper I, Mike Holt of Buderim, wrote after many discussions with Harry Chambers, an old-time farmer out in western QLD at Mangallala. He is great thinker, basing his many 'outside the box' ideas on his own many years experiences. I hope the following will get you thinking differently about the drive to plant as many trees as possible. As you will read, planting trees in the wrong place can destroy the ecology just as much as chopping them down.....
Every time we interfere with nature we create more problems than we solve.
And yet we never seem to learn from our mistakes.

With the terrible floods that have been afflicting Australia lately, many people have offered theories about what might really be causing such widespread flooding.

It is obvious that today’s land management policies have not been effective. Instead, they have created conditions ripe for flooding. There are a few factors at work here, but by far the most important one is the tree planting and preservation policy.

For the past century or so perceived wisdom has said that if you plant trees along the banks of rivers they will prevent erosion and silting. But as we have seen, this is not the case.

Ecologists have also been telling us for years to plant more trees to combat the greenhouse effect. That sounds very reasonable. After all, trees take in carbon dioxide and exhale oxygen. So, obviously the ‘experts’ reasoned the more trees we plant the better.

Trees also help generate rain. It has been accepted as gospel for years that the more trees we grow the more water we will have.

Successive governments since the early 20th Century have accepted these ideas because so many ‘experts’ have said this is so.

As a result we have seen a long term policy of planting thousands…millions of trees along our watercourses.

But the ‘experts’ have led us up the wrong path again today, just as they did when they told governments to import prickly pear and cane toads in the past.

By planting too many trees along our waterways we are actually creating the wrong environment for a healthy watercourse. And the more trees we plant the less sustenance is available for our native animals, like the koala and possum.

Sounds strange? Not when you understand what is really happening.

What causes flooding?

We all know that water needs to flow downhill. If it can’t find a channel to flow down it will break over the banks of the watercourse where it normally runs and flood the surrounding countryside.

Next time you watch a news helicopter on TV flying over a flooded water course, look carefully at the waterscape below. It is very easy to see where the watercourse usually runs because it will be lined with trees.

We have had a huge volume of rain falling lately, so if planting more trees was supposed to reduce flooding, why are we seeing such devastating floods instead?

Today, even if farmers need to clear the land to increase production they are not allowed to cut down trees on their own property without getting council permission first. Yet our farmers are the custodians and nurturers of the land we all rely on. They are our best judges of what is best for the land to keep it healthy – not politicians and tree-hugging greenies.

Any gardener will tell you that thinning out and pruning encourages better growth. All plants need plenty of sunlight and water to grow well. When plants or trees are crowded together they become stunted as they compete for access to sunlight and for moisture from the ground.

So what happens when we don’t thin out the river bank trees?

Trees need huge amounts of water. A large tree can transpire about 600 gallons of water a day up to its leaves. That is enough to supply at least four average households with ample water for all their needs for a day.

But the more trees there are the less water there is available for each one.

As trees suck up these large quantities of water they create a ‘vacuum’ between the trees and the watercourse. Debris such as leaves, sand, soil, and twigs get sucked down into the waterway, silting it up.

When the next rain comes along the buildup of water cannot find a deep channel to flow down. Where it meets a blockage it is forced to spread out, causing floods like the ones we are seeing now.

If we want to help the water flow and at the same time reduce flooding we must have a policy that allows our best land managers to do what needs to be done.

We need much more research into water and land management. Some of the best people to talk to are those who work on the land, not politicians, especially the Greenies. Our policymakers should be talking to the farmers and other people who depend on the land for their livelihood. They are the people with the most to lose if they can no longer farm their land effectively. And as they live on the land and are able to observe how nature behaves they can also see what the best way to manage their land is.

So, to manage our water resources properly all we have to do is allow them to make logical decisions about their land, and this includes allowing them to decide if or when they need to thin out the trees on their land.

Thinning trees will encourage grasses to grow. These grasses bind the earth and prevent debris from sliding down into the water. A watercourse with only a few trees along it will deepen with each flood as larger volumes of water flow down the channel. Any blockages, such as trees and rocks that might fall into the channel will be swept away. The more water flowing through the channel the deeper it will get and the healthier the water system becomes.

The flash flood in Toowoomba and the subsequent destruction further down in the Lockyer Valley and Brisbane occurred because the water was dammed up behind debris in the waterways – the result of poor riparian land management. Eventually, the water built up to such a huge volume that when it broke free of the blockages a swathe of destruction resulted that devastated thousands of lives and businesses.

These floods come in cycles. This is not the first time that the Lockyer Valley and Brisbane have been dangerously flooded. It will not be the last. But we can mitigate the effects of the next one by taking sensible steps. I have spoken to the people tasked with restoring the river to health and I was impressed with the work they are doing. They are clearing the trees away from the banks and allowing the natural native grasses to grow.

We have already seen that building a dam didn’t work. When the water levels reached high levels the flood gates were opened at Wivenhoe. But the people responsible for that decision have admitted that they didn’t know when they should have made that decision. In the event, the decision came too late to be any use. The runoff water rushed downstream from the dam and built up water levels in the Brisbane River just before the floodwaters arrived from further up in the mountains. The already bloated rivers could not cope. That water had to go somewhere. We all know now where it went.

Building levees is not the answer either. Imagine a condom filled with water squeezed between two rulers. The more you constrict that condom, the higher it rises. The same thing happens when we build levees. The water level rises above the ground level and when a levee bursts its banks it quickly rushes out to flood the surrounding countryside.

We obviously need to think this through carefully and come up with viable solutions that will help us mitigate the effects of heavy rains.

Before we examine solutions, let’s see why planting too many trees is also affecting our wildlife, even when there are no floods.

We are not the only ones

Koalas depend on eucalyptus trees for sustenance. Ecological advisors have been telling us for years that increasing the number of trees will provide more habitats for koalas.

Despite this, we are seeing a worrying decline in koala numbers.

Now, imagine you are a koala sitting up in one of those trees along a creek. Koalas depend on getting their moisture from the tree leaves they chew on. But as the water in our watercourses dries up the overcrowded trees cannot supply enough moisture in their leaves to sustain the koalas.

Eventually, the koalas are forced to come out of the trees and drink from whatever water is left in the silted up rivers, creeks and billabongs. This water is full of organisms and pollutants that cause Chlamydia, and degardia – a deadly form of dysentery – and other diseases. Our koalas have no immunity to them and so they sicken and die.

When the koalas were getting their moisture from the leaves they were chewing on up in the trees they thrived. The trees filtered out all the pollutants. But as we have encouraged more trees to grow and compete for diminishing water supplies we have actually been killing our koalas and other wildlife by forcing them down out of the trees to drink.


Before we take the advice of the Greenies and ‘armchair ecologists’ we must be sure that they have really done their homework. Making a statement that sounds logical is not enough today. In some cases we have seen politicians make statements that are definitely not logical. Despite this they expect us to swallow their advice anyway.

A good case in point was the recent claim by Senator Brown, former leader of The Greens party, who tried to blame the floods on the mining companies. And then he went on to justify this by saying that because the floods were the fault of the mining companies should pay for the cleanup.

This sort of wooly thinking does no one any good. If people like this who do not even understand the problem are in positions of power where they can influence decisions, it’s no wonder we have a problem!

Thousands of people, our livestock, and our native wildlife all badly affected by the floods are proof that we need resource managers who to understand how nature works. We don’t need airy-fairy theories from people with good intentions or crackpot ideologies. We need solid scientific inquiry, and solutions that will work.

Right now – today – we must ask our governments to re-think their policies towards land management and especially trees. The current policies are obviously not working. We need to re-think our approach towards nature and start working with her instead of trying to bulldoze her into submission. In the end, nature will do what she wants, despite our efforts.

We need a comprehensive, logical and effective land and water management policy. It’s time we allowed our farmers and others who work closely with the land to have the power to thin out trees under good management policies. Local councils should be tasked to ensure that tree management is carried out in harmony with the entire water system. And they should monitor watercourse depths and calculate how much water can safely flow down them. If they see a problem they should take logical steps to correct the problem without fighting nature.

We cannot allow a band-aid approach any more. Instead of wringing our hands after the damage has been done our governments must be proactive and ensure that everything is done to facilitate the safe flow of water.

With more effective management of our natural water resources we can substantially reduce the effects of flooding on our cities and towns. But we will never do it if our government doesn’t sit down and do an exhaustive study in conjunction with people close to the land, as well as hydrologists and other scientists who understand how nature works.

Until we do this, we will continue to suffer the floods that are still devastating large areas of Australia today.


All of these pictures were taken within a few days of each other along the Mungallala Creek just after the first big drought-breaking rains.

Harry Chambers

The silted up Mangallala Creek on the property next to Harry's place just a few days after the rain. Note the trees clogging the banks

The same creek on Harry's property taken on the same day as the picture above. The water in this section of the creek is about 12 foot deep and teeming with fish.

Re: Trees are killing our Koalas

Posted: Mon May 21, 2012 9:03 am
by matto
Are you saying all Harry did was chop down trees along the river bank and voila....?

A different, and I think an ecologically sound appraisal can be found on the thread viewtopic.php?f=12&t=863&p=3695&hilit=flood#p3695

Re: Trees are killing our Koalas

Posted: Wed Jun 06, 2012 1:25 pm
by duane
I agree with Matto....Sorry Mike but this paper is pure drivel !!!

Re: Trees are killing our Koalas

Posted: Sat Sep 08, 2012 10:05 am
by lturner
I read the article by Mike Holt and the comments by Matto and Duane. The article may not be well written as it tries to cover so many related topics and theories. Please do not disregard the waterhole evidence because of the article. Harry Chambers has returned the silted up waterholes on his Mungallala property to big, deep, permanent waterholes through his timber management program.

His techniques and theories are controversial but they have worked on his property. There are long stretches of silted up waterholes in the creek before and after his property. There are deep waterholes from one end of his property to the other. His first deep waterhole starts on his boundary where the creek enters his property. I had trouble believing his timber treatment program could have such an immediate effect but it does. When Harry explained how he believes it works, I understood how it could have this immediate effect. I will not try to explain the theory here but I am happy to discuss the theory or try to provide more details on it if people are interested.

The process does not just rely on removing trees from the watercourse but involves a holistic approach to timber management on the property. Harry has tried to return his property to pre-European timber levels. In doing so he is returning his waterholes to more like their pre-European condition and size. This is also controversial and requires a paradigm shift in thinking.

Many of these western Queensland creeks had large waterholes in the past and have only remnants of waterholes now. This process may work in many of these areas. We need to open our minds to the evidence and make this process possible on a larger scale. Only more evidence will demonstrate if there is real value in his findings over a wider area.

Re: Trees are killing our Koalas

Posted: Tue Sep 18, 2012 10:09 am
by duane
I for one would like to hear more....alpha-numeric language is subject always to mis-interpretation both by the reader and the listener.

This could be one to follow.

Re: Trees are killing our Koalas

Posted: Fri Sep 21, 2012 7:41 am
by Kilbilli farm
I would like to hear more too. I agree with tree management, ESP of eucalypts, in the RIGHT places but just can't see how further eroding our waterways could be a positive thing as that piece suggests.

If we think about how our country used to function many years ago, silt and trees falling in the creeks rock formations etc are surely trying to help heal our waterways and allow the flood waters to nourish our pastures and disperse the finer silts that would once have fertilized the floodplains rather than the need to use artificial fertilizers. There never used to be massively eroding channels ripping through our landscape and flooding was a massively important accurance that kept our country self sustainable.

The statement that farmers best know how to manage the land is just so bad.. Farmers are bent over trying to make a dollar these days in our bastardized ag industry, and frankly the focus is on what inputs to spread over the land to get the best crop, or hold the most livestock and all the while the seed, feed and fertilizer companies take all the margins and leave the farmer with degrading land and looking ten years older! Don't get me wrong, I'm a beef breeder and I live in a hugely farmed region and I'm right behind every farmer, but how can a farmer be called a land rejuvenator with the industry as it is... We used all the natural fertility a hundred years ago, when farming was lucrative!... And it is with all those strong feelings, that we embarked on the journey, with NSF training and support as our mentor, to try to heal our piece of Australia lol.

I really would like to hear more about this theory Ian, the more knowledge the better (especially on what happens when it floods). And thank you for putting your knowledge of this theory up for discussion.

Re: Trees are killing our Koalas

Posted: Sun Sep 23, 2012 8:39 pm
by lturner
I am pleased to see some interest in this topic. What Harry Chambers has done on his Mungallala property works for him in that area. I think (and I hope) that his methods will work for many parts of that Maranoa to Warrego area and beyond. Unfortunately, people seem keen to dismiss a process if it may not work in all areas.

To understand how and why this process works requires an open mind. Please understand that most of what is written as scientific evidence about remnant vegetation and the effects of clearing timber on erosion is not correct for this type of country. I am reluctant to try to explain everything here as many readers will not be willing to make the paradigm shift in thinking to consider this process. Please keep thinking that this process works in this area even if you struggle with the detail.

Prior to European influences the country between the Maranoa and Warrego was not heavily timbered. Very few trees grew in this area and those few ancient trees are still present where clearing of young trees has not occurred. Fires kept the growth of trees to a minimum. This applies even to eucalypts which are reasonably fire tolerant. The fires were a constant part of the environment. The trees that were present were found in specific areas for specific reasons. After Kennedy passed through this area during a drought time in 1847 the area was referred to as “the desert between the Maranoa and the Warrego Rivers”. Hardly a description for the heavily timbered country we see in much of that area today.

Also understand that in these areas, clearing trees in the paddocks and from creeks does not cause erosion. The country people in these areas understand the benefits of clearing the trees but many not associated with this country often believe otherwise. I tried to attach photographs from the Mungallala area to show you what actually happens in this type of country. Unfortunately this does not seem possible. Photos are great as they are so much more convincing than words.

If I have not offended all readers I am happy to continue the explanation. I did assume a site like this would have some lateral thinkers who may consider the evidence. Please understand that Harry has one majestic waterhole after another with much clearer water than the shallow muddy holes and dry beds seen in other parts of the creek. What he has done has worked.

Harry has cleared most of the trees from his property and has cleared most of the trees from the creek. Both the paddocks and the creeks need to be cleared for Harry’s theory to work. He now has deep, permanent, waterholes that were silted up before his timber treatment.

The flooding is important to this theory and the fertility from the flooding is part of the original land process. I do not feel this is in opposition to the NFS ideas but actually complements it in many ways. My name is Lex and I am happy to continue with this theory if anyone is still interested. It would be better if I could work out how to attach photos.

Re: Trees are killing our Koalas

Posted: Sun Sep 23, 2012 9:28 pm
by duane

Google Photobucket. Upload your photos onto Photobucket.

When you have done so copy the URL of your photos.

Next click on the Img tag above and then click the URL tag, Right click on your mouse and hit paste.

Your photos should now be displayed on the forum.

Re: Trees are killing our Koalas

Posted: Tue Sep 25, 2012 7:16 am
by Kilbilli farm
Hi lex,

Thanks for sharing, please keep going.. Ide like to hear and see more.


Re: Trees are killing our Koalas

Posted: Wed Sep 26, 2012 9:35 pm
by lturner
The first 4 photos just show what is normal in this type of country when trees are left on the creeks. Please note this is the opposite of what everyone is told.





Where Harry has removed the trees the erosion is greatly reduced. Tree clearing here does not lead to great erosion. These photos are not just of selected areas. This is representative of what happens. The healing process is continuing in these areas.




Harry said the area in the photo above was more eroded than the first 4 photos before he removed the trees from this creek area. The main Mungallala creek is in the background. This area still has some repairing to do. This is a long process.


The removal of trees leads to lots of protective ground cover. This is a good deep waterhole. The evidence of the value of removing the trees is overwhelming. It is hard to believe people who see this evidence cannot accept that the current ideas of clearing trees and getting erosion just does not apply to these areas.

Hopefully the photos are of interest and I will continue with the theory of waterhole development on my next post.


Re: Trees are killing our Koalas

Posted: Thu Oct 04, 2012 7:45 pm
by Kilbilli farm
Thanks for posting those photos. So your saying essentially that the photos in pictures one and two are similar to what the areas in the latter photos looked like prior to the tree removal!? That is an amazing difference!

I look forward to your next post.

Re: Trees are killing our Koalas

Posted: Sun Oct 07, 2012 2:48 pm
by lturner
To return the waterholes in this type of country to more like their pre-European size, the countryside needs to be also returned to more like its pre-European condition. This is not wanton destruction of the habitat but it is very different to all that is being promoted about timber control at present.

The early explorers did not battle through constant thick scrub in exploring these areas and the early settlers relied on permanent waterholes that disappeared after settlement. Early accounts from these areas describe semi-open grassland country in most areas.

The introduction of livestock has long been blamed for the silting of the waterholes. Certainly overgrazing to an extreme degree would not have helped but Harry has evidence that suggests that it is the massive increase in tree cover that had a much greater effect.

Aboriginal fires kept the trees under control and killed most regrowth in most of the areas. A mosaic fire pattern throughout the year should have prevented the extreme fire events that could devastate large areas in hot, dry summers of the past. Much of our wildlife is not adapted to survive very severe fire events.

Like many graziers in this, and other areas, Harry has cleared most of the timber from the paddocks. This does not lead to erosion or salinity increases in these areas. Clearing the trees reduces erosion particularly in the creek areas as shown in the photos of a previous post. Clearing the trees and scrubs leads to more grass growth in this rainfall limited environment. More grass holds the soil together, protects the soil, and protects and provides food for wildlife and domestic animals. The graziers benefit as they can run more animals on their country and have a more sustainable property. All these graziers do not spend the large amounts of money required to control the timber growth with the aim of ending up with an eroded property. They all know that the advice is wrong for most of these areas. They want grass for their cattle and clearing the trees provides this grass. It is the grass that protects the soil in these dryer areas.

Harry went one step further. He removed the trees from the creek banks as well. This is now an illegal action but Harry has the evidence that maybe it should not be illegal. Maybe it should be promoted. Twenty to thirty years after removing the trees from the creek bank he has hugely reduced creek erosion and has found that large waterholes have returned.

Google maps is a great tool. I heard of Harry’s waterholes before I visited the property in August this year. I used google maps to find the property. It was not too hard to find as the paddocks had been cleared and there was very little timber along the Mungallala creek. Google maps for that area was, and still is, out of date with the images taken in the dry years. This only highlighted the fact that there was no other water in waterholes visible along the Mungallala creek. The waterholes on Harry’s place were reduced in size but were still permanent at the end of that recent dry time.

Harry’s theory of waterhole development relies on removing most of the trees in the paddocks and most of the trees along the watercourses. In the timbered paddocks in these areas, the soil becomes quite hard between the trees. Removing or killing the trees allows more grass to grow. It is mainly this grass that slows the water flow across the paddocks. Slowing the water allows more water to enter the soil and the aquifers. Sometimes the action of ‘pulling’ the trees out of the ground also helps with preventing the water just running off the paddocks. Large numbers of trees in the paddocks would utilise this water and greatly reduce the water flow in the aquifers. Harry’s waterhole theory (like the NSF theory) relies on an increased supply of water in the aquifers.

The theory depends on a simple process. If water within the soil flows through a sandy substrate (as in an aquifer), it will loosen up the soil. If pressure is trying to pull or push water into a substrate, the substrate will pack hard. Eucalypts along the creek banks use lots of water. The action of the roots drawing water from the waterholes tends to pack the soil because of this pressure of the water flowing into the soil. Floods in the creek over this packed soil of the creek beds only deposit sand as the pressure is directed out of the waterhole.

If most of the trees are removed from along creek bank then the flow of the aquifers into the waterholes will loosen the soil along the creek as the pressure is flowing into the creek. A flood of water along the creek at this time will easily carry away the loosened soil and sand and deepen and widen the waterhole.

This is a very simplified version of the theory. There is much more to the theory that includes what happens in floods, how the ends of the waterholes develop and why the ends of the waterholes are not boggy. I hope I have done it justice in this simplified form. I am reluctant to post the theory as some people may feel it is not correct. Even if the theory needs modification, the facts remain. Harry has removed the trees from his paddocks and from the creek banks and large, beautiful, permanent waterholes have developed. The evidence is there.

The return of the waterholes in this country is a delight to behold. To know the waterholes can be returned so simply is incredible. The benefits to wildlife are many and some are unexpected. One of the unexpected benefits is that there are very few carp in the waterholes. It seems as the mud and silt are removed, the carp cannot monopolise the waterholes. Native fish dominate.

There are so many advantages. Unfortunately, clearing the timber in the paddocks has been difficult, clearing the creek beds is now illegal, waterhole development takes decades, and waterholes do not greatly increase productivity for the graziers. Bores etc can provide water for stock (and some wildlife) so why would the graziers risk prosecution to clear the banks and restore the waterholes? Research is needed and legislation needs to be changed. Please note that Harry has many other theories on why clearing most of the trees will benefit the wildlife.

Re: Trees are killing our Koalas

Posted: Sat Nov 03, 2012 10:20 am
by duane
Hi Lex
This is a really interesting post.

At first reading, I called it a load of drivel, or words to that effect.

Now I would like to retract that statement and say I was wrong to make that public statement.

This story has much to warrant attention especially the planting and removal of Eucalyptus spp., near waterways. Landcare have embraced riparian plantings of gums whilst Aboriginal people knew that they had a negative impact on stream health.

Lex....It's good that you have followed up on Mike's original post and clarified a number of points.

I will be watching this post with great interest.

Re: Trees are killing our Koalas

Posted: Tue Nov 06, 2012 8:09 pm
by matto
This is an interesting development to the thread. Thanks for the persistence and clarifications.

Its hard for me to imagine how Australia out west, but Im sure there would have been many pockets of diverse environments.

Here in the photos, I can see that the trees hampered the development of grasses underneath and along the banks, and without this coverage you can see that water has become erosive. To the point the soils even look sodic.

Peter says that grasses do the best job in dispersing overflowing water so that it doesn't concentrate and become erosive.

This might have lead to a feedback loop that while the banks became more eroded, water became increasingly concentrated in the incised channels, and water tables dropped. Without the chance for it to irrigate the floodplain, trees managed to tap into the aquifer while grasses struggled to compete in the arid environment.

I worked with a farmer out Mundubbera who was complaining that he couldn't chop down trees, even though his early settling family had described the land as being much less wooded. He believed it was because the animals targetted the grasses, allowing the trees to take over. Now its legislated that he cannot remove the trees without planning permission, but it isn't a natural environment now but one induced by mans management of the land.

Keep it up!