PARK WATCH December 2020 |
Michael Feller, VNPA Council Member and Conservation Committee Co-Chair, writes of the ongoing loss of our invaluable old trees.
Old-growth forests are awe-inspiring ecosystems. They are rich in flora and fauna – some species completely depend on such forests for their existence. Their trees have more nesting hollows than younger trees, they protect soils, and can supply more water to streams than younger forests. They help forestall climate change by storing more carbon than any other terrestrial ecosystem. And like the world’s cathedrals, they offer great aesthetic and religious values to many people.
But they are disappearing, due to the direct and indirect impacts of people.
Logging and fires are the main causes of this disappearance. Logging directly destroys the forests, as do bushfires, which are being made worse by human-induced climate change and the presence of post-logging younger forests, which lead to more intense fires.
When one thinks of old-growth forests, one thinks of big trees and old trees. Victoria and Tasmania have some of the world’s biggest trees in Mountain Ash (Eucalyptus regnans), similar in stature to California’s Giant Redwood (Sequoiadendron giganteum) and Coast Redwood (Sequoia sempervirens) forests.
Our Mountain Ash trees may live for several hundred years, unlike the redwoods that can live for several thousand years. Although the trees in some North American old-growth forests may be only a thousand years or so in age, the forests themselves can be extremely old. They may not have been disturbed for over 10,000 years, since the last ice-age, as is the case with Western Redcedar (Thuja plicata) forests in central British Columbia, Canada.
In Victoria, however, it appears that all our forests, even our wettest ones, have experienced bushfires, making our remaining old-growth extremely valuable. It has been estimated that some 30–60 per cent of Victorian Mountain Ash forests were old-growth when Europeans first arrived; this figure is now just over one per cent. About 65 per cent of East Gippsland’s wet and damp old-growth forest was lost between 1995 and winter 2020.
In November 2019, the Victorian government announced that “90,000 hectares of Victoria’s remaining rare and precious old-growth forest – aged up to 600 years old – will be protected immediately.” This suggested that there would be no more logging of old-growth, but it would have to be assessed prior to logging. A critical issue, then, is how old-growth is to be recognised in the field. To address this, the Victorian Government’s Office of the Conservation Regulator (OCR) put out a draft old-growth field assessment procedure in late 2019, then a final procedure in July 2020.
But does the new assessment procedure really protect old-growth?
An old-growth forest in Victoria was defined in the 1990s as “a forest which contains significant amounts of its oldest growth stage in the upper stratum – usually senescing trees – and has been subjected to any disturbance, the effect of which is now negligible”. The assessment procedure considers that old-growth must have a minimum area of one hectare, and that regrowth trees must comprise less than 15 per cent, and senescent (old and declining) trees more than 10 per cent, of the upper stratum trees.
The procedure first determines whether a field assessment is necessary. This is done by consulting computer databases, which might indicate that no field assessment is required if a recent fire had occurred in the area. However, fires do not always burn 100 per cent of the area within their mapped boundaries, and a one hectare+ patch of remaining old-growth within a fire boundary is possible.
The field assessment then uses a forester’s method of inventorying tree wood volumes to estimate the proportion of different tree types in the upper stratum (there are no data to support this estimation method), instead of actually recording all upper canopy trees present in an area. This method can be somewhat subjective and the person conducting the assessment can determine which trees to include, biasing the results. This field assessment can be performed by VicForests or its contractors, who have not been noted for their concern for conservation.
Furthermore, the OCR has placed a one-hectare square grid across Victoria and requires the tree measurements be made at the centres of the one-hectare squares. This can easily miss substantial areas of old-growth if they are between the centres of adjacent squares.
Ecologists consider that it is not possible to come up with a generic definition of old-growth that can be applied to all forest types. A scientifically defensible and ecologically robust definition is only possible for a given forest type within a given region.
The point at which a stand no longer constitutes old-growth is subjective. Thus, old damp forests in Victoria have fewer senescent trees and more mature trees than old wet forests, due to the relative tolerance to fire of the trees in the different forests. So it is likely that old-growth damp forests and even drier ones should be considered to have a higher proportion of regrowth and less senescent trees than old-growth wet forests – contrary to the OCR’s uniform definition of old-growth.
A more serious concern about the definition is that although it will protect some individual stands of old-growth, it will not protect old-growth overall. All old-growth studies in Victoria have highlighted the need to protect the old-growth estate. This was first highlighted in 1992 during the development of Regional Forest Agreements, and it has been a consistent theme in all subsequent studies of old-growth in Victoria.
Properly protecting the old-growth estate
In a key study, Burgman stated:
“A protection system for old-growth forest that involves protection of young, mature and senescent forest may be termed the old-growth estate. [This] estate includes all forest within a given ecological vegetation type that has the potential to develop old-growth values. Probably most Australian old-growth forest stands eventually will bum and adequate protection will involve the provision of young forests to develop into old-growth forests…. the maintenance of a spectrum of regeneration stages is necessary to conserve the suite of ecological processes and species diversity that characterise old-growth forests.” [our emphasis added]
For example, two small (less than one hectare each) patches of old-growth separated by a few hundred metres of mostly mature forest which has the potential to become old-growth in the near future, with a total area more than one hectare, is clearly part of the old-growth estate. Such an area should be protected if old-growth is to be protected, but it would not be protected using the OCR assessment.
In another key study, Woodgate et al. (1994) pointed out that:
“the small suite of mappable characteristics that scientists will use over the next few years to delineate old-growth forest provide no certain measure of the many secondary characteristics (such as faunal attributes, functional process and intangible values) that may well warrant consideration as important management values.”
This is clearly the case with the OCR’s use of only upper canopy tree growth stages to define old-growth.
Another concern is that relatively large trees are characteristic of old-growth, and such trees are declining rapidly. Many large old trees occur in stands that are not considered old-growth by the definition used. The Victorian Department of Environment, Land, Water and Planning (DELWP) guidelines currently only protect trees that are more than 2.5 metres in diameter-at-breast-height (dbh). This would probably protect no significant large old tree in western Victoria, and relatively few in eastern Victoria.
Such a tree, in the case of Mountain Ash, would be over 220 years old, based on a dbh vs. age relationship – well beyond the age of 120–150 years when such trees function as old-growth trees by developing valuable hollows for wildlife. As another example of the poor protection of large trees, a survey of riparian trees along the entire length of Chum Creek, between Healesville and Toolangi, found 914 large trees with diameters greater than 90 centimetres (significant large trees according to DELWP) in approximately 80 hectares of Mountain Ash and different mixed species forests using DELWP’s EVC criteria, but only six of these (0.7 per cent) were more than 2.5 metres in diameter, qualifying for protection.
Thus, many large and old trees – the most common defining characteristic of old-growth forest – are not protected in Victoria.
Consequently, as a result of current government policies, neither old-growth trees nor old-growth forests are properly protected in Victoria. While the Victorian Government has made big announcements about old-growth, there are major flaws in old-growth assessment methods and large tree protection.
We urgently need to protect the old-growth estate, rather than creating new technical loopholes to allow its continued logging.
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