PARK WATCH Article March 2023 |
Bushfire management in Victoria is causing biodiversity decline through significant loss of hollow-bearing trees reports Michael Feller
The Victorian Parliament’s Inquiry into ecosystem decline in Victoria, released in December 2021, makes for sobering reading. Victoria is now the most intensively settled and cleared state in Australia with over 50 per cent of native vegetation being removed since Europeans arrived.
The Victorian State of the Environment 2018 report noted that Victoria has the highest number of threatened plants, animals and insects by sub-region in Australia, with over 700 fauna and flora species and ecological communities listed as threatened under Victoria’s threatened species framework. The report suggests that between one quarter and one third of all terrestrial plants, birds, reptiles, amphibians and mammals, along with numerous invertebrates and ecological communities, are considered to be at risk of extinction.
Tree hollows are important across the globe. About 18 per cent of bird species in the world rely on hollows for nesting, with 13 per cent of those listed as threatened under International Union for Conservation of Nature (IUCN) Red List criteria.
In Australia, over 300 species of native animals need hollows for breeding, such as large forest owls and other threatened wildlife.
In some southern Australian forests, cavities that are suitable for vertebrates often require 120 to 180 years of tree growth to develop, and sometimes longer. Many of these older trees were removed when forests were converted to agriculture. State logging is removing many more. The net result is that very few hollow-bearing trees are left on the landscape. For example, it has been estimated that some 30–60 per cent of Victorian Mountain Ash forests contained old-growth containing hollow-bearing trees when Europeans first arrived; this figure is now just over one per cent.
Bushfires and forest harvesting are generally thought to be the major threats to hollow-bearing trees. The Victorian Flora and Fauna Guarantee Act lists both loss of hollow-bearing trees and inappropriate fire regimes as threatening processes. Bushfires may kill trees, causing some to collapse, but many dead trees remain standing for some time so any hollows they have can still be used by wildlife. Clearfelling removes hollow-bearing trees. If such trees are left standing within a logging coupe they have an uncertain future as they can be blown down. Unfortunately, we have no good data on hollow-bearing tree loss caused by fires and logging.
Another significant cause of loss of hollow-bearing trees is bushfire management operations conducted by Forest Fire Management Victoria (FFMV). There are three major contributing factors: fuel break creation and maintenance; creating breaks around areas to be prescribed burned; and prescribed burning
Fuel break creation and maintenance
FFMV recently embarked on a major program to build new fuel breaks and to clean up others. As Phil Ingamells wrote in the December 2021 issue of Park Watch:
The clearing of vegetation for fuel breaks has always been a bit of a hit or miss strategy for protecting the community and the environment from fire. Breaks can contain a fire in mild weather, but do nothing to stop fires in extreme weather when spotting by burning embers can reach kilometres ahead. Breaks have also been known to create wind tunnels that can drive a fire.
They do serve as a point from which to conduct remote fuel reduction burns, or back burns in the face of fire, but these operations are also under serious question.
Any trees in or near these breaks that are considered hazardous by FFMV personnel are cut down. This has included many hollow-bearing trees. As an example, on a 300 metre section of the fuel break running along the ridge between Donnellys Weir and Mt St Leonard near Healesville, six hollow-bearing trees were cut down in early 2022. These trees were all near the break but in Yarra Ranges National Park. They were up to 2.2 metres in diameter (at breast height) and were mostly living. It is deplorable that a living, hollow-bearing, old-growth tree cannot be protected in a national park.
Creating breaks around areas to be prescribed burned
To prevent fire escaping an area to be burned, breaks are cleared and any trees deemed hazardous to the people conducting the burns are cut down. Again it is FFMV personnel who decide which trees are to be cut and again many hollow-bearing trees are cut as these are more likely to be considered hazardous. If the burn is to be conducted within a national park, then it is trees within the national park that are cut.
Fire management seems to take priority over park management, which is the exact opposite of how proper land and fire management should occur. Proper fire management should always be subordinate to overall land management. In Victorian national parks and other protected areas fire management activities are conducted by FFMV but these activities should always be controlled by the overall land management objectives for the area.
The training given to those who decide which trees to cut appears questionable as many sound, living trees are cut and in one instance noted in January 2022, a living tree with an obvious animal nest in a hollow was cut down. The animals were possums, and were in the tree when it was cut down. A letter of objection to Victoria’s Office of the Conservation Regulator (OCR) got nowhere when FFMV simply told the OCR that they had done everything correctly.
A recent report from the Victorian Auditor-General’s Office concluded that the OCR has limited enforcement powers and has been unable to assess noncompliance by VicForests or effectively evaluate its timber harvesting activities. Thus, OCR’s inability to regulate FFMV seems similar to their inability to regulate VicForests. In fact, it is unclear if the OCR have any formal responsibility for regulating FFMV, and FFMV appear to be able to do whatever they want.
The most common form of fuel reduction in Victorian forests is prescribed burning. This operation is highly questionable due to the fact that it reduces forest flammability for only a few years after which flammability often increases to greater levels than before the burn, as a result of changes in understorey vegetation, so that long unburned forests are often less flammable than ones that have been recently burned.
Prescribed burning also has no impact on fire behaviour under extreme weather conditions. This was well described by Phil Ingamells in the June 2021 issue of Park Watch.
Not only is fuel reduction burning questionable from a forest flammability viewpoint, but it can also lead to a variety of undesirable biodiversity impacts, one of which being a loss of hollow-bearing trees, which are more prone to collapse during or after a burn.
Thus, a study in NSW concluded:
… low intensity prescription burns may cause levels of destruction of hollow-bearing trees that are substantial enough to warrant immediate attention from managers.
Another recent study in Victoria concluded:
… planned burns in Gippsland increase the collapse risk of HBTs [hollow-bearing trees] significantly and, by implication, are likely to cause loss of habitat for hollow-dependent fauna in areas where hollows are needed.
DEECA has a ‘Procedure for the removal, destruction or lopping of native vegetation on Crown land‘ which allows them to remove native vegetation (DEECA and Parks Victoria are already the largest clearers of native vegetation in Victoria).
They are supposed to consider important biodiversity values, such as hollow-bearing trees, and if vegetation removal is necessary then they are supposed to consider ‘counterbalancing’, i.e. offsetting, the removal. There is no indication that any counterbalancing of hollow-bearing tree loss has ever been conducted.
We don’t know exactly how many hollow-bearing trees are destroyed by FFMV but observations made by myself and others suggest that the numbers are indeed significant. They must be reigned in by any government serious about biodiversity protection.
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