Logging elevates the level of Myrtle Wilt in Rainforest
Scientific studies in Tasmania have demonstrated that heavy machinery used to build logging roads and clearfell forest adjacent to stands of cool temperate rainforest is increasing the wounding rate of Myrtle Beech and artificially elevating levels of myrtle wilt.
Source: Kile, GA, JM Packham and HJ Elliot (1989) Myrtle
Wilt and its Possible Management in Association with Human Disturbance
of Rainforest in Tasmania. NZ Jnl Science 19:256-264
1. Photo shows the edge of logging at Ciancio
with no buffer around the rainforest (darker forest). As a result of wind
and having no buffer protection, trees (see photo 2. below) have fallen
on to a myrtle beech tree. (Arrows show fallen trees.) This has caused
branches to break. The myrtle beech tree may well die of myrtle wilt as
a result of logging too close to the rainforest. (Area logged in April
2000).
2. Wind from logged area has blown trees onto this myrtle beech at Ciancio
creek causing wounds and opportunity for myrtle wilt infection (see photo
1. above). The myrtle beech tree may well die
of myrtle wilt as a result of logging too close to the rainforest.
Above: With no buffer, myrtle beech trees have been damaged at the edge
of coupe at Ciancio creek. The damaged trees are now at high risk of infection
from myrtle wilt. It can take up to two years for the tree to die after
infection.
Myrtle Wilt is an air dispersed disease.
Research indicates that localised infection caused by logging practices can elevate the probability of infection across the whole Otway landscape due to the air dispersal nature of the Myrtle Wilt fungus. Logging practices that damage and infect a number of myrtle trees can create a localised hot spot of myrtle wilt infection. This hot spot of infection can release a large amount of fungal spores into the air thus resulting in artificially increased infection rates in remote rainforest places away from logging such as in national parks and reserves.
Artificially elevating the levels of myrtle wilt across the Otway landscape puts rainforest tourist attractions at risk.
A report by Burgman in 1995 investigated the scientific basis of current and proposed protection measures of rainforest in Victoria. It describes the relationship between Myrtle Wilt, mechanical/human disturbance of forests and the air dispersed nature of the disease:
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.
Source: Burgman MA (1995) Rainforests in Victoria - a review of the scientific basis of current and proposed protection measures. Department of Conservation and Natural Resources.
Forestry Victoria constantly try to dismiss the issue of practices logging elevating the levels of myrtle wilt across the Otway landscape. See point 7 of department discussion paper.
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Artificially elevating the levels of myrtle wilt across the Otway landscape puts rainforest tourist attractions at risk.
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