While there is a reasonably good knowledge of some of the elements of biodiversity, there are numerous elements that still remain poorly surveyed or known. Forest types can be used to some extent as a surrogate for floristic diversity and unknown faunal diversity (notably invertebrates). The Commonwealth proposed the following broad criteria for the inclusion of forest types in a reserve system:
Reservation benchmarks should be varied for different forest communities according to extent, natural rarity, past depletion and the level of threat to their continued existence. As a broad benchmark, 15 per cent of the pre-1750 distribution of each forest community should be represented in the dedicated conservation reserve system. This benchmark should be varied according to the proportion of the existing distributions of forest communities in reserves and levels of depletion from past clearing.
In applying the above criterion the areas of reserved forest communities should include a range of successional stages and a range of environmental variation typical of the communities' distribution, wherever possible.
A single comprehensive forest type map is not available for eastern NSW, therefore, a number of existing forest type and vegetation mapping data sets were used or developed by modelling to provide a mapped coverage across the study areas of Section 2.2 (excluding Tumut). The vegetation surveys used included: SFNSW forest types and broad forest typing for the Northern and Central study areas, NPWS multi attribute, coastal and pre-1750 mapping for the Northern study area, CSIRO Pre-1750 mapping for the Southern study area and the Keith, Bedward and Smith vegetation mapping for the Eden study area. In order to apply the appropriate reservation targets it was necessary to determine the extent of pre-1750 forests as identified for each area (NPWS in prep; CSIRO 1995), and also the extent of clearing as determined by the Eastern Bushlands Database (NPWS 1992). Pine plantations were considered as cleared land. Where possible, forests were delineated at a scale of 1:25,000.
The current extent and pattern of distribution of forest types in NSW reflects more than 200 years of European occupation, notwithstanding the prior impacts of Aboriginal people. The Commonwealth therefore proposed that the pre-1750 forest extent be used as a reference point for calculating reserve targets for forest types (COA, 1995). The pre-1750 distribution of forest types was estimated by predictive modelling (NPWS 1995, CSIRO 1995). Data extracted from existing forest type mapping and many thousands of vegetation plots were used to derive models relating the distribution of forest types to physical environmental variables. These models were then used to develop maps of forest type distributions across unmapped areas including cleared land.
The Commonwealth broad benchmark of 15% pre-1750 reservation was adjusted for each forest type according to natural rarity, past depletion and vulnerability.
The natural rarity of forest types was assessed in relation to the predicted pre-1750 extent of forest types. Reservation targets applied in the IAP were adjusted for natural rarity by increasing targets for forest types as naturally rare and decreasing targets for more abundant types, while maintaining an overall reservation benchmark of 15%. This adjustment established targets for individual forest types from 100% for rare forest types to 10% for the most extensive forest type (see Figure 3.1). It should be noted, that after subsequent adjustments for depletion and vulnerability, the lowest percent reservation targets for individual forest types within the negotiation regions were usually higher than 10%.
Figure 3.1 The distribution of natural rarity targets for all forest types in north east NSW, with 100% reservation targets set for naturally rare forest types varying in a logarithmic manner to a 10% reservation target set for extensive forest types.
The adjustment for natural rarity was calculated using the following formula:
NR (Y)% = [(((M-A) x C) + (0.15 x A)) / A] x 100%
where:
NR = target for forest type Y after adjusting for natural rarity
A = % reservation of pre-1750 area of forest type Y
M = the mean pre-1750 predicted area of all forest types in the region, excluding non-forested types, eg heath, coastal complexes
C = a constant which determines the extent to which targets for rare types are increased and targets for abundant types decreased, according to their deviation from the mean pre-1750 area. C is calculated as follows:
C = [(0.15 - 0.10) x U] / [U - M]
where:
U = the pre-1750 area of the most extensive forest type in the region.
Past depletion was defined as the proportion of pre-1750 area of a forest type that had been cleared, including areas converted to pine plantations. Past depletion was considered indicative of a forest type's desirability for exploitation and thus vulnerability to clearing, modification and fragmentation. The adjustment for depletion applied in the IAP ensured that highly depleted forest types were assigned proportionally higher reservation targets than less depleted forest types. The depletion adjustment was set as a proportional increase to the target already adjusted for natural rarity. The past adjustment ranged linearly upwards from 0% for forest types with no depletion through to 50% of the target developed for natural rarity for types with 100% depletion.
Vulnerability to clearing was considered a significant threatening process for some forest types. Forest types with extensive distributions within existing national parks, state forests and vacant crown land, were considered less vulnerable to clearing than those largely distributed on either leasehold or freehold lands. Thus, vulnerability to clearing was defined by the percentage of the remaining area of a forest type occurring on leasehold or freehold lands. The vulnerability target was also set as a proportional increase to the target, already adjusted for natural rarity. The vulnerability adjustment ranged linearly from 0% for forest types with no depletion though to 20% for types with 100% of their existing distribution on private and leasehold lands.
Figure 3.2 The natural rarity target is adjusted in a linear fashion from 0 to a maximum of 50% for past depletion and 0 to a maximum of 20% for vulnerability.
The target for each forest type already adjusted for natural rarity was further adjusted to take into account past depletion and regional vulnerability using the following formula.
FT% = NR% x (1+0.5(x%/100) + 0.2(y%/100))
Where:
FT% = Target adjusted for past depletion, regional vulnerability and natural rarity
NR% = reservation target adjusted only for natural rarity
x% = Past depletion = cleared area (ha) x 100/pre-1750 distribution (ha)
y% = Vulnerability = (freehold (ha) + leasehold (ha)) x100/ z
z = Remaining area = pre-1750 area (ha) - cleared area (ha)
The flora panels (see Section 3.5.3) checked all adjusted targets for forest types and, where absolutely necessary, made additional alterations to account for other threats not considered within these adjustments, including regional endemism and heterogeneity of forest types.
Due to the extensive clearing of some forest types and the restricted extent of some others on lands subject to the IAP, it was not possible to achieve the reservation target set for many forest types.
In the Northern study area, a small number of SFNSW forest types were split into two or more floristically distinct 'sub-types' for the purposes of the IAP. These splits were agreed to by experts from NPWS, SFNSW and independent groups and were based on a numerical analysis of floristic data from approximately 4,000 survey plots distributed throughout the study area. Even though the classification resulting from these splits are referred to as sub-types, they are intended to be given the same status as other forest types in the IAP (ie they should simply be treated as recognised forest types).
In both the Northern and Southern study areas, some forest types (including new types created as a result of the splitting just described) were further subdivided into geographical 'sub-regions'. The boundaries of these sub-regions were determined by the relevant flora panel. The aim of this sub-regionalisation was to ensure that geographical and environmental variation within forest types was adequately represented in protected and deferred areas.
Finally, where sub-regions were identified for forest types, the panels apportioned targets according to the relative area of the forest type within each sub-region and vulnerability within each sub-region.
In addition to existing mapped and modelled rainforest forest types, rainforest (at a 25 ha patch size resolution) was mapped by the broad old growth forest mapping project. In this project, rainforest was identified for the IAP as having a continuous canopy of rainforest species taller than 5 m, but less than 30% of total canopy was comprised of pyrophytic emergents (canopy species mostly requiring occasional fires for regeneration) or having less than 50% of total canopy comprised of pyrophytic emergents in a polygon classified by API as eucalypt forest and subsequently identified as old growth forest. Rainforest stands less than 25 ha in size were not generally mapped in the old growth project and thus still may require further assessment if not already identified in type maps and model outputs. Such stands will continue to be protected by prescriptions applying to harvesting plans.
Forest with 30-50% emergents that was identified through the broad old growth mapping project ( Section 3.3) as not old growth was treated as non-rainforest forest types (refer Section 3.2.3). The status of these forests will be further assessed during the CRA process.
Rainforest in negotiation area S1 was deselected as a target feature in the negotiations primarily because it was based on modelled rather than mapped data. This would have created a bias in the development of the conservation criteria. Elsewhere in the south (ie in Eden, Tumut and S2), a reservation target of 100% was established for rainforests.
To avoid problems associated with the extensive distribution of small stands of rainforest in north east NSW, the following procedures were employed: