National Wilderness Inventory
Australia: Our national stories
Australian Heritage Commission, 2003
ISBN 0 642 23561 9
4. Creating The Wilderness Database (continued)
4.3 Biophysical Naturalness
Naturalness is a difficult attribute to define and measure, making any attempt to derive values for this indicator fraught with uncertainties. Leaving aside arguments concerning the concept of naturalness and its application to Australian ecosystems, there are two issues that have to be addressed in order to obtain meaningful measures for Biophysical Naturalness.
The first is the identification of principles that will give a satisfactory account of impacts of post-European development on the environment and to design a scheme that is consistent with these principles. The second is obtaining data that enables the implementation of a suitable scheme.
The NWI has approached the first problem by assuming the degree of change sustained by an ecosystem is directly related to the intensity and duration of interference.
Using this assumption, land use records and other land data may be used as means of deriving a Biophysical Naturalness value. Australia's natural lands support many land use activities, each having its own distinctive patterns, processes, and ecological interactions. For the NWI, land use considerations are restricted to the grazing of stock and the harvesting of timber.
Variation in the consistency of suitable information for making assessments of the intensity of grazing and timber harvesting means that, as a general rule, only a relatively simple qualitative approach to rating biophysical naturalness can be supported.
Biophysical Naturalness Assessment procedures for the NWI baseline survey do not provide for the effects of many other agents which biophysically impact on the natural environment. It is certainly the case that factors such as feral animals, pest plants, and fire can, and do, exert a considerable influence over natural systems in Australia and these should be taken into account in assessing the impact of modern technological society on the Australian environment.
These factors are not included in the baseline assessment principally because of very uncertain information regarding distributions and impacts. If suitable information is available, especially in local or regional situations where particular factors are known to be of critical importance, then this information may be incorporated into the analysis.
The NWI uses two simple rating procedures. Both are descriptive and expressed in terms of a five-level hierarchy of degrees of land use intensity. The first 'arid' procedure applies to those parts of the continent where arid and semi-arid livestock grazing predominates, and where the location of permanent and semi-permanent watering points is an important factor in controlling the distribution of livestock.
This rating procedure is described in Table 4.3.
|Indicator Value||NWI Descriptor|
|5 High||Ungrazable range-type; or non-grazing tenure for at least (60)* years; or beyond limit of stock access to (semi-) permanent water.|
|4||Marginal range-type, grazing tenure within preceding (60)* years, and intermediate stock access to (semi-) permanent water.|
|3||Marginal range-type, grazing tenure within preceding (60)* years, and close stock access to (semi-) permanent water.|
|2||Grazable range-type, grazing tenure within preceding (60)* years, and intermediate stock access to (semi-) permanent water.|
|1 Low||Grazable range-type, grazing tenure within preceding (60)* years, and close stock access to (semi-) permanent water.|
|* figure subject to variation on a regional basis|
The second procedure applies to 'non-arid' areas where grazing is essentially unrestricted by the availability of water and where commercial timber harvesting, may take place. This rating procedure is described in Table 4.4.
For southern and eastern Australia the 'arid' procedure is applied beyond the general limits of clearance for dryland agriculture. For the Top End of Australia the 'arid' procedure is applied to areas south of latitude 15 degrees.
|Indicator Value||NWI Descriptor|
|5 High||Unlogged and ungrazed.|
|4||Unlogged and ungrazed for at least (60)* years; excluding clear-felled and intensively grazed areas.|
|3||Single selective logging; irregular grazing within preceding (60)* years.|
|2||Light/moderate grazing; repeated selective logging within preceding (60)* years.|
|1 Low||Clear-fell logging operations and/or intensive grazing.|
|* figure subject to variation on a regional basis|
For Cape York Peninsula, the information base was initially so poor as to prevent implementation of a Biophysical Naturalness classification scheme. Recently, however, Biophysical Naturalness estimates have been produced for this region as part of the Cape York Peninsula Land Use Study (CYPLUS). Figure 4.4 indicates the areas over which the two Biophysical Naturalness assessment procedures were applied in Australia.
A more detailed description of the Biophysical Naturalness assessment procedure applied in each state is provided in the appendices.
The 'arid' Biophysical Naturalness procedure is applied to those parts of the continent where arid and semi-arid livestock grazing predominates and where one important factor in controlling the distribution of livestock in the landscape is the distribution of permanent and semi-permanent watering points. The rating scheme is outlined in Table 4.3.
Consistent with the three distance-based indicators, the 'arid' procedure for calculating Biophysical Naturalness values is largely automated. Thus, any variation in the quality of results across survey areas will largely relate to variation in the quality of the primary data available for use in analysis. The model makes no allowance for the influence of many important factors that contribute to biophysical disturbance in arid and semi-arid environments, particularly feral animals which are not dependent on the presence of permanent free water.
Any additional information which may be relevant to a Biophysical Naturalness assessment for a particular region (e.g. feral animals, pest plants, or fire) may be included in the assessment either by adjusting the model, or by associating this additional information with standard results from the model. For the baseline program no such modifications or adjustments were made.
A summary of the 'arid' Biophysical Naturalness process is presented below, as a sequence of four steps. Information concerning the nature and quality of the primary data used in 'arid' Biophysical Naturalness analysis can be found in Sections 3.3.4 (Environment Stratifications (rangetype)) and 3.3.5 (Land Tenure (pastoral)).
i) Primary features:
Point, line and polygon primary data are drawn from the appropriate layers of the Librarian data manager. The primary data codes and associated grouped feature coverages are detailed in Section 3.4 (Feature Codes and Grades). Water features are grouped in files according to feature type.
|Description||Grouped Primary Data Coverage|
|Permanent Water Point||PERM-PT|
|Permanent Water Line||PERM-LN|
|Permanent Water Polygon||PERM-PL|
|Range Type Classification||RANGE|
ii) Assignment of range type and tenure classifications:
The primary data coverages rangetype and past are used to assign the appropriate range type (RANGE) and tenure type (STOCK) classification to each sample point as an attribute in the 'lattice'.BIO INFO file. Table 4.6 outlines these classifications.
iii) Distance Calculation:
Euclidean distance (in metres) is calculated from each sample point to the nearest water feature in each file. The nearest distance, in each case, is assigned to each sample point as an attribute in the 'lattice'.BIO INFO file.
Descriptors relating to proximity to permanent and semi-permanent water are outlined in Table 4.7.
|Access to water||Cattle||Sheep|
|Intermediate||3 to 8 km||2 to 6 km|
|Beyond||> 8 km||> 6 km|
iv) Deriving Final Biophysical Naturalness Values:
Attributes are processed to produce a final Biophysical Naturalness value which is recorded for each sample point as an attribute in the 'lattice'.PAT INFO file. The assignment process is matched with the 'arid' Biophysical Naturalness classification scheme outlined in Table 4.3.
Areas assigned to class 1 are those that are 'close' to (semi-) permanent water, with 'grazable' range-type and 'sheep'/'cattle' tenure.
Class 2 areas are those that are 'intermediate' to (semi-) permanent water, with 'grazable' range-type and 'sheep'/'cattle' tenure.
Class 3 areas are those that are 'close' to (semi-) permanent water, with 'marginal' range-type and 'sheep'/'cattle' tenure.
Class 4 areas are those that are 'intermediate' to (semi-) permanent water, with 'marginal' range-type and 'sheep'/'cattle' tenure.
Class 5 areas are those that are 'beyond' (semi-) permanent water, with 'non-grazable' range-type and 'none' tenure.
4.3.2 'Non-Arid' Biophysical Naturalness
The 'non-arid' Biophysical Naturalness assessment procedure involves classifying natural areas according to the intensity of timber harvesting and livestock grazing activities. The rating scheme is presented in Table 4.4.
As previously noted, the scheme makes no allowance for land use activities other than grazing and timber harvesting. Neither does it take into account other factors which may be relevant to Biophysical Naturalness estimations, such as fire, weeds, and feral animals. Where additional relevant information is available this may be incorporated into the assessment either by associating this information with the model's standard results, or by incorporating this information in a revised modelling procedure.
Both the 'non-arid' and 'arid' Biophysical Naturalness assessment procedures are fundamentally distinguished from other wilderness indicator assessment procedures in that they involve the calculation and assignment of categorical, rather than continuous, values to the wilderness database. However, the two Biophysical Naturalness procedures are also fundamentally distinguished from each other. Modelling techniques for implementing the 'non-arid' Biophysical Naturalness scheme are specially matched to the characteristics and completeness of the primary data that is available in particular survey areas. Because these vary from place to place, so too do the modelling procedures.
In contrast, the 'arid' modelling process is automated and standardised across all assessed areas, even though results do vary in consistency according to the availability and quality of primary data inputs. As the 'non-arid' Biophysical Naturalness assessment for the baseline NWI is based on the intensity, duration and length of occupation of grazing and timber harvesting activities, the key to success in implementing this component of the survey is the availability of adequate information regarding these land use activities.
Very little suitable information is presently available for Australia. Generally, few records exist which are of any use in describing the distribution and intensity of livestock grazing, other than at the broadest scale. In relation to logging and timber harvesting activities, detailed records commonly do exist for public lands and are held by state forestry agencies. These records are, however, often inaccessible, either for reasons of security, or because the data remain uncompiled and decentralized in regional offices. Timber harvesting records are uniformly very poor for private and leasehold lands.
Where information directly relating to these land use activities was unavailable, alternative, indirect methods for implementing the 'non-arid' assessment were employed. In some instances, where information such as vegetation type, tenure, access and slope exists, estimates of Biophysical Naturalness can be reasonably effectively modelled. Almost all 'non-arid' assessments for the baseline survey were produced by indirect means. Implementation procedures varied from area to area, and these are discussed in the appendices under state headings.
Generally, tenure provides a reasonable starting point for land use intensity estimates as this represents a set of definable legal and administrative constraints within which land use activity takes place. Because of this, and the availability of accessible data, tenure constituted one element which was common to almost all indirect assessments. The principal tenure data set used was the 1:250 000 AUSLIG public lands database, which generally provided sufficient detail for NWI baseline purposes.
Three broad tenure groups were distinguished.
1. 'No Use': Tenures where it is assumed there is no grazing or logging-related histories. This includes defence lands, vacant crown land, water supply reserves, and scientific reserves, as well as other groups.
2. 'Public': Generally reserve tenures with possible grazing or logging histories. This group includes timber and forestry reserves. Other reserve categories are included depending on circumstances.
3. 'Private': Generally private and leasehold tenures.
The classification of particular tenures into the above groups varied from state to state according to local peculiarities, tenure histories, and the proposed use of these data in the Biophysical Naturalness assessment process.
Another major controlling influence on land use activity is the capacity of the land to support productive activity. In this respect any information that describes the natural landscape, such as land systems, vegetation cover information and so on can assist in refining estimates of intensity of land use.
If additional data sets that relate to the physical landscape or human activity are available, they can also be used to progressively refine intensity of land use estimates. Of course, this indirect approach cannot be considered adequate at a local scale, and even at a regional scale can provide only the barest framework of an assessment; but it is a starting point in the absence of better information.
In certain situations, where basic data sets are patchy or incomplete, or where patterns of land use do not conform sensibly with physical and human landscape parameters, estimating 'non-arid' Biophysical Naturalness could not be implemented. It was for these reasons that Biophysical Naturalness estimates were originally not completed for Cape York Peninsula (cf. Lesslie et al, 1992).
Because of the need to devise assessment procedures accommodating local variations in primary data and land use patterns 'non-arid' Biophysical Naturalness assessments were completed quite independently from the automated processes used for the majority of wilderness analysis. Once assembled in polygon form, as Biophysical Naturalness classes, these data sets were stored for convenience permanently in the library manager as the layer bio. The library specifications of the bio layer are presented below.
|Layer Name||Cover Name||Item Name||INFO Item Definition|
|bio||bio||biophysical source||4 5 b
20 20 C
For areas where 'non-arid' Biophysical Naturalness assessments are completed, the automated wilderness analysis process interrogates the completed Biophysical Naturalness information in the bio layer, and assigns to the lattice of sampling points the appropriate Biophysical Naturalness class value.