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Otway Ranges Environment Network
     

Myrtle Wilt and Logging Practices Impacts on Cool Temperate Rainforest in the Otways

February 2001

  1. Explanation of Myrtle Wilt
  2. Impact of logging
  3. DNRE actions with regard to Myrtle Wilt
  4. Reasons For Rainforest Protection
  5. Rainforest and the Flora and Fauna Guarantee Act
  6. Regional Forest Agreement
  1. Explanation of Myrtle Wilt
  2. Myrtle Wilt is a disease which causes Myrtle beech trees to die. Beech trees are the primary canopy species for Cool Temperate Rainforest. Although a naturally occurring phenomenon, the presence of Myrtle Wilt is increased by human disturbance, notably logging.

    Myrtle Wilt occurs when a fungus (Chalara australia) enters a beech tree (Nothofagus cunninghamii) through an exposed flesh wound, which are naturally caused when tree limbs are broken off during a storm. The fungus grows into the tree and chokes the flow of sap to the tree crown, killing the tree. It can take up to three years from the time of infection for the tree to die.

    As the sapwood dries out in the tree, pin hope borer beetles (Platypus subgranous) bore into the wood and lay eggs. Larvae bore through the tree. When the larvae pupate, they drill their way out the tree and fly off into the forest to find another dying tree infected by fungus. It is likely that dust (frass) produced by the boring beetle becomes airborne and help spread the fungus spores throughout the forest to infect more myrtle beech trees.

  3. Impact of logging

Scientific studies in Tasmania have demonstrated that the use of heavy machinery to build roads and clearfell forest is causing an increase in the wounding of Myrtle Beech.

A report about the scientific basis of current and proposed protection measures of rainforest in Victoria describes the relationship between Myrtle Wilt and mechanical/human disturbance of forests:

"Because the disease is a wound pathogen, and because forest harvesting and roading activities result in many otherwise insubstantial wounds to trees, it reasonable to suggest that there should exist a causal relationship between (particularly) mechanical disturbance activities and disease frequency, either within or among rainforest stands. In Victoria, road construction, harvesting in mixed forest stands, and windthrow in buffers have the potential to elevate background wounding rate.

"Wounding and infection are natural processes, particularly in mixed forests and ecotonal communities with eucalypt overstoreys where branch fall must cause wounds. Cameron and Turner suggest that background inoculation rates are sensitive to human disturbance because fungal spores are wind spread. Thus if the wounding rate throughout the landscape increases, the amount of inoculum in the environment will increase throughout the landscape from a series of local point infections, resulting in an accelerated infection rate. This scenario is not unreasonable, and deserves the attention of a specific research project."

The implications of this research indicate the effects logging in State forest can cause localised infection that can elevate the probability of infection across the whole Otway landscape due to the air dispersal nature of the myrtle wilt fungus.

This has implications for rainforest in the Otway National Park. The Cool Temperate Rainforest at Maits Rest in the Otway National Park has significant economic value to the local tourism industry as it receives hundreds of thousands of domestic and international tourists every year who drive along the Great Ocean Road. Tourism Victoria has stated the Great Ocean Road is worth one Billion dollars a year in tourism expenditure

 3. DNRE actions with regard to Myrtle Wilt

Section 8.4.3 of the Otway Forest Management Plan (OFMP) 1992 acknowledges Myrtle Wilt as a problem in Otway Cool Temperate rainforest. The OFMP gives high priority to:

"Investigate the extent, rate of spread and floristic impact of Myrtle Wilt."

In March 1994, the Cameron and Turner report was draft form, with the research and analysis completed. By early 1996, nearly two years later, the report was still in draft form and unavailable to the public.

Conservationists and local residents had been alerted the Myrtle Wilt was at epidemic levels in the Otways. In January 1996 efforts were made to obtain the report through Freedom of Information (FOI). DNRE refused the FOI request on the grounds that the report was not in the public interest.

Local conservationists and the Wilderness Society with assistance from the Environmental Defenders Office (EDO) took the matter to the Administrative Appeals Tribunal. With the threat of further adverse publicity, the DNRE released the final report. The DNRE gave a copy of the finalised report to conservationists on the day of a hearing at the Administrative Appeals Tribunal (2 August 1996).

A copy of the original draft report dated November 1994 had fallen into the hands of OREN. The draft and the July 1996 final report was compared by SG Mueck, a former botanist with the Department of Natural Resources and Environment:

"The 1994 version clearly identifies timber harvesting as a significant potential initiator of myrtle wilt. It also makes recommendations to be applied in Victoria for appropriate buffer widths to protect existing stands of Nothofagus dominated Cool Temperate Rainforest from timber harvesting and associated activities such as roading. These recommendations are based on the precautionary principle, in an attempt to minimise the potential risk of disease spread to Cool Temperate Rainforest in the vicinity of timber harvesting activities. The 1996 version has removed or altered the buffer width recommendations and statement identifying timber harvesting as a significant vector of disease in a Victorian context. With no recommendations to influence current timber harvesting practices, the threat of an accelerated spread of this disease through Cool Temperate Rainforests . remains very high."

"The recommendations for further research presented in the 1994 version . however have been deleted. It would appear, therefore, that there will be no action or research undertaken . to restrict the spread of myrtle wilt".

The likely reasoning for DNRE (Forestry Victoria) removing recommendations for further research and buffer widths is to retain the option to log near stands of Cool Temperate Rainforest. Currently buffers outlined in the Code of Forest Practices restricts logging to 40 metres from rainforest. The 1994 Cameron and Turner report recommended buffers between 250-350 metres to protect rainforest. DNRE has failed to "conserve and protect the natural forest environment" as outlined in Section 3.2 of the OFMP.

4. Reasons For Rainforest Protection

1. The Otway forests have suffered extensive logging since European settlement. Most of the forest has had some form of selective logging. The proportion of old growth forest remaining is small. Old growth myrtle beech rain forest represents a large proportion of the remaining old growth forest in the Otways. If the rainforest is altered by the myrtle wilt disease then the Otway forests will have a structure that has been almost totally altered by European influences. Future generations of Australians will be unable to experience the original physical and spiritual nature of the forest.

2. An unknown number of species are dependant on old growth cool temperate rain forest for their survival. These species, both flora and fauna have evolved over millions of years to survive within the rain forest. They could be threatened if the Myrtle wilt disease starts to alter the forest structure.

3. As trees die of myrtle wilt, they open up the canopy to allow more sunlight onto the forest floor, drying it out and making it more bush fire prone.. Rainforest species are not fire adapted. A hot fire can kill further trees, opening up the rain forest canopy further. Often after fire, the forest regenerates eucalypt species instead of rainforest species. If a fire is intense and the rainforest significantly dried out by canopy gaps, the entire patch of rain forest can be destroyed. It takes thousands of years for a burnt out rainforest to regenerate.

4. Maits Rest is a popular cool temperate rainforest walking trail in the Otway National park. Hundreds of thousands of tourists both local and international visit each year. Yet there is little warning displays informing the public about the disease and need to protect the rainforest. Information must be made available so the public can take care not to damage beech trees. The tourist industry could see valuable rainforest asset areas lost. Beech trees can already be see dying from myrtle wilt along the Maits rest walking trail.

 

  1. Rainforest and the Flora and Fauna Guarantee Act

Cool Temperate Rainforest is listed as a threatened community under the Flora and Fauna Guarantee Act 1988. No action statement has been completed for Cool temperate rainforest despite being given final recommendation for listing on the 21 May 1992

Human activity which results in artificially elevated levels of myrtle wilt within Northofagus dominated cool temperate rainforest has been nominated (nomination 453) for listing under the Flora and Fauna Guarantee Act 1988 as a threatening process. It was put forward in July 1997 and was gazette on the 22nd December 2000. An Action statement must now be done that sets out prescriptions for the protection of rainforest from human activities such as logging practices

6. Regional Forest Agreement (RFA)

The RFA totally fails to consider the myrtle wilt issue. Page 58 of the RFA Consultation Paper states the draft CAR reserve system will increase buffers to 40 metres. No mention of research is given to justify that 40 metre buffers are adequate. The updating of the Otway Forest Management Plan in 2005 is referred to in a bid to justify putting off management decisions and avoid placing production forest into buffers. The RFA failed to consider the nomination in the Flora and Fauna Guarantee Act

 

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