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Myrtle Wilt
and Logging Practices Impacts on Cool Temperate Rainforest in the
Otways
February 2001
- Explanation of Myrtle Wilt
- Impact of logging
- DNRE actions with regard to Myrtle Wilt
- Reasons For Rainforest Protection
- Rainforest and the Flora and Fauna Guarantee
Act
- Regional Forest Agreement
- Explanation of Myrtle Wilt
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.
- 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.
- 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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