In the aftermath of the Roe8 debacle, the topics of weeding, replanting and revegetation of the cleared bushland to restore its natural flora created vigorous discussion.
This is an article I had previously written about regeneration of our local WA bush, and I have added some links for more information. It’s important to revisit the experience of those actively involved in the past, to tap into their practical knowledge.
In particular, dealing with “dieback” in the area cleared in preparation for Roe8, and up to date information on how devastating it is, means the revegetation process is crucial. It requires proper supervision, understanding and care, and “dieback” is already a major concern if access to the cleared area is not secured. (Footnote 4)
Revegetation: Pull It or Plant It?
In 1971, the sisters Joan and Eileen Bradley put forward the idea that controlled weeding without replanting is the best way to regenerate natural bushland, because it gives the existing seed bank a better opportunity to germinate with less competition.
In her book “Bring Back the Bush,” Joan says “native seeds and spores are already in the ground and the natural environment favours the plants that have evolved in it. The balance is tipped back towards regeneration. Keep it that way, by always working where the strongest areas of bush meet the weakest weeds.” Their method was quite radical in its day, because the usual idea was to pull out the weed and replace it with a plant of choice.
The challenge of the Bradley Method
To actually leave the bush to do “its own thing” was a call to restrain from overly interfering with the environment. A raw spot in the ground – unplanted! The challenge of the Bradley Method is recognising that many times the earth is capable of awakening and able to heal its hurt, replenish its loss, to even restore its generous measure without our direct interference, once the weeds have been removed. A hard call indeed, for the inveterate planter of things native!
Rehabilitation, Restoration or Regeneration.
On the other hand, Judith Rawling (1993 Director of Urban Bushland Management Ltd) made it very clear that rehabilitation of urban bushland involves more than just weed control. It aims to restore or recreate a viable native plant community, by revegetation with plants that are indigenous to the area being restored.
In 1997, Tein McDonald presented her conclusions that natural landscapes must be given a chance to regenerate on their own before wholesale planting or seeding is undertaken. Her concept is that some kinds of natural disturbances to which the vegetation was adapted may be needed to trigger recovery.
Regeneration Management Regimes Vary
Regeneration may require a management regime such as fire, or ripping or weeding. At those times, we will be welcome for the help we bring because a stronger trigger is needed. Tein’s advice is that you need to keep prodding and poking the system to find what responds, but that you must be capable of following up whatever you do.
Since the initial acceptance of the Bradley Method of hand weeding with no planting, the term ‘bush regeneration’ has developed to be a much more pragmatic and specific approach to rehabilitating areas of degraded bushland.
Creating and maintaining landscape integrity.
We are developing a better understanding of how habitat can be redeveloped, managed and maintained. Strong feelings for great integrity in the landscape mean using plants that are truly indigenous to the local area.
We are collecting and potting up seeds, propagating tube stock, removing even native plants that are not local, replacing local plants whose seed bank is long gone. We must be prepared to accept that some areas can never be returned to their former selves.
Because of fire, flood, overgrazing, bulldozing, often it is impossible to restore an area in full. Selective regeneration with plants better suited to the changed landscape is often an acceptable alternative, rather than trying fruitlessly to restore an original habitat that is actually lost.
Revegetation: Timbertop Way, in Stoneville.
The Friends of Timbertop Way in Stoneville, (just up from Cameron Road where we visited Strawberry Hill on our tour) have found that ripping has produced excellent results for quick, strong growth among the hundreds of young trees and shrubs that have been planted in what can only be described as a gravel pit.
After only a few years, the revegetation was an outstanding success, coupled with the creation of a seasonal frog pond where the storm water collected in a clay depression, and the strategic placement of large logs and tree stumps.
Suzanna Brook Rehabilitation and Revegetation.
In 2007, a bus tour of seven or eight sections of the Suzanna Brook catchment area was both heart-breaking and exciting. Heartbreaking, when you see possum boxes invaded by bees; vandals wantonly destroying the hard work of volunteers; weeds like watsonia choking the life out of little creeks that have nothing more to do than to meander their way down the Darling Scarp to the Helena River bringing their cargo of leeches, water snails and tiny fish with them.
Exciting when a small dugite slithered between our feet towards the water opposite the Parkerville Tavern while we listened to tiny frogs revelling among the logs and stones some of our group had put into place before winter, to help with riverbed reconstruction of habitat.
The Power of Seeds
Diana Corbyn, Lecturer in Conservation and Land Management at Challenge TAFE, enthralled us with her presentation on the power of seeds, at The Hub in Mundaring, in July 2007. Her simple illustrations and easy language helped us appreciate their variety from the simple to the complex and the wonders of plant reproduction.
From the fleshy fruits we love to eat to those with their hard, seed bearing cases (like Banksia) that we scarcely regard as “fruit”, Diana demonstrated how a seed is “a baby plant with a raincoat, a sandwich, and a very small drink of water”.
It was fascinating to gently peel away the outside skin of a broad bean (its “raincoat”) and split it into two. You could clearly see the radicle that develops into the primary root and the cotyledon, which will develop with the plumule to bear the first leaves. Their power to grow is awesome when you regard them at such close quarters.
She showed us spores that drift on the wind; cones which let their seeds fly free like little helicopters when they sense smoke from a fire is sufficiently cool for the seeds to be safely released; seedpods that forcibly eject their genetic code in the natural process of reproduction.
If you have read Hey Dude! Who Moved My Gumnuts? you will know how much her presentation moved me. It led to writing much of that book.
Seed Collection vs Salvaging Seeds.
There is a world of difference between collecting seeds and salvaging them.
Diana held us spellbound while we learnt the difference between collecting seed (with the right license and not more than 20% from any plant) and salvaging seed, with permission for all seed to be collected if an area is to be cleared.
Eastern Hills (Mundaring Shire) has excellent structures and achieves outstanding outcomes from volunteers for bush and wetlands rehabilitation in Australia, and the local schoolchildren are a regular part of those volunteer groups.
Teaching them to understand their local biodiversity also means ensuring they have the highest regard for protecting the bush against the spread of dieback. Preventing dieback is everyone’s responsibility. We can all do something to help reduce the spread of this devastating plant disease.
The Tuart Forest National Park
On the way down to Busselton, my grandson and I took the tourist route through the Ludlow block — which has had a lot of attention from the conservation lobby. The look of the Australian bush can be scrubby a lot of the time and often doesn’t seem to be very inspiring.
We actually missed the best part of the forest. Why? Because we were driving and we did not know what we were looking for! Early records of the State’s history described the tuart forest as being “a beautiful open forest in which visibility was clear for half a mile in any direction”.
Of course if you didn’t know that, you think a forest and expect only vegetation that is almost impossible to traverse. So sadly we were not impressed and probably other people feel the same.
(Footnote 2) The short forest extends several kilometres across the one row crossroads towards Bunbury. This is the only natural stand of these rare giants of the forest left in the world. You need to have a picnic, to walk along the forest trails and soak up the peaceful setting.
Wetlands of International Importance
There is also a bird hide in the wetlands near one up which are listed as “wetlands of International importance”. They offer views of prolific bird life and my grandson, Aiden, got a bird watching book as a late birthday present.
In fact, the Tuart Forest is a shadow of its original self, and it’s only the small amount now preserved within the Tuart Forest National Park which allows us to see this magnificent native tree.
Endangered Western Ringtail Possum.
The Tuart Forest National Park protects WA’s largest remaining wild population of the endangered Western ring tailed possum. (Footnote 1) This is mainly because old Tuart trees contain many hollows, while the dense secondary story of peppermint vegetation supplies their major source of food.
The forest is also home to the densest population of brushtail possums ever recorded in the State. Other residents include the brush-tailed phascogale, bush rat, kangaroo, quenda (also known as the southern brown bandicoot), at least 11 species of birds of prey and nocturnal birds.
The Western ring tailed possum is now critically endangered, with the loss of major habitat around Busselton. Many of the native peppermint trees on which they feed have been cleared.
The Western Australian peppermint tree (Agonis flexuose) is related to the paperbark, unique to the south west corner of Western Australia, and has been used all around our local metropolitan area and parts of the world as a street tree. Yet, our own native ring tailed possums who rely upon it for food are been forced towards extinction.
(Footnote 5) The Fardins have planted thousands of trees and are re-foresting cleared paddocks, yet only a few hundred seedlings have survived to maturity. The park’s tuarts are dying. In some
areas of the original tuart forest, here on the Swan Coastal Plain, which is the only part of the world where tuarts occur naturally, the mortality rate is 50%
Scientists have now identified the dieback species Phytophthora multivora; tuarts were thought to be resistant to the pathogen and nobody really knows why they became susceptible.
Dieback –prevention is critical.
Dieback is not a natural part of our local bush. Phytophthora cinnomomi is a root-rotting fungus that was inadvertently brought to Australia sometime in the early stages of European settlement. It spread to native forests and woodlands and it causes ‘Dieback’.
It spreads because the soil attaches to your car wheels, your horse’s hooves, your truck wheels, your four-wheel-drive wheels, your bike tyres and your shoes or when you take home plants, rocks or soil. Especially in wet weather.
So far, it has been impossible to eradicate and prevention methods have been to close parts of the jarrah forest and wash down vehicles that may have been in infected areas.
Everyone who travels in and out of dieback-infested areas must wash their cars, especially the wheels, and their shoes when they leave. This is especially important information for you, if you are a tourist. (Footnote 4)
Bringing Rocks, Plants and Soil from the Bush spreads dieback.
Don’t bring plants, rocks and soil from the bush into your garden, because you could introduce dieback and it will kill your garden plants including roses, azaleas and fruit trees. From Eneabba to Cape Arid, east of Esperance, its arrival has had catastrophic consequences for the biota of a number of ecosystems.
In small areas that are dieback-free, a chemical called phosphate that is not toxic to plants or animals can be applied to flora and vegetation by spraying or injection. This is done where there is risk of new infestation or to prevent the spread of an existing infestation.
Inhibiting or breeding resistance.
Dr. Ralf Cord-Ruwisch (Murdoch) found that some different compost processes could completely inhibit the growth of phytophthora in the laboratory. The ORT biogas/compost system (patented as DiCom®) produced a compost with very good inhibitory effect of the fungus. “There is therefore potential to create a biological dieback control agent from solid waste, as well as a renewable source of biogas,” he said. (2002)
The great hope was to breed a dieback resistant jarrah.
In the field, in the mid-eighties a resistance gene was identified when it was noticed that some jarrah trees were thriving while others around them were ravaged by dieback. More than twenty years of collaboration followed, between Murdoch University, CALM, Alcoa and ECU. This allowed Associate Professor Jen McComb (Murdoch University) and Dr Ian Bennett (Murdoch University, now at Edith Cowan University) to develop techniques to clone and propagate the highly resistant plants.
In July 2001, the dieback resistant seed orchard was planted at Manjimup.
Seeds collected from this orchard in 2006 grew into viable seedlings at Alcoa’s Marrinup Nursery. These dieback resistant seedlings were offered to local community land care groups. On July 8th, 2007 Alcoa launched this programme and at that event, visitors learnt about the history of the Dieback Resistant Jarrah.
They toured Alcoa’s Marrinup Nursery and the Dieback Resistant Jarrah seed orchard at Alcoa’s Huntly Mine and it was great fun to find out how local community land care groups can become involved in this project in the future. Fast forward seven years, to 2014.
2014: Eradicating dieback
Quoting from the ABC Radio programme in 2014, “New research, led by the Centre of Phythophthora Science and Management at Murdoch University and Alcoa Australia, has found that clearing contaminated bushland of living hosts is the only way to eradicate the disease.”
(Footnote 3) Thirty years of research, trials, monitoring, and reporting has led to new trials. The removal of all affected (infected but still living) plants offers the possibility of a successful outcome in the fight against dieback. “The pathogen has to have living hosts. You remove any living host, whether it is a resistant host or a susceptible host, for a period of time, it will die,” Professor Giles Hardy said, in an ABC interview.
Fifteen year field trials of the Dieback Resistant Jarrah seed haven’t provided the hoped for results. Helping control the spread of dieback is the responsibility of all in the community. We cannot overstate its negative impact on native vegetation.
This post and the links must reinforce the determination of the revegetation groups who want to work on Roe8, to deal with “dieback” with care and under proper supervision.