Abstract

Keywords

Introduction

Land evaluation can assist government, industry and individuals in rational decision-making about agricultural land use. The most commonly used systems of land evaluation are land capability and land suitability assessments. Land capability assessments conducted in Victoria are based on the USDA method (Klingebeil and Montgomery, 1961), while land suitability assessment is generally based on the FAO framework (FAO, 1976). These methods have been used for:

• linking the survey of basic land resources to land use planning
• quantifying the degree of land degradation risk present and providing a baseline that can be used to assess changes in the landscape over time
• allowing modern methods of information processing, such as Geographic Information Systems (GIS), to be employed in land use planning

Despite the land evaluation and planning tools currently available, severe land degradation is widespread in Victoria and increasing in area, affecting agricultural productivity and farm viability (Office of the Commissioner for the Environment, 1991; DNRE et al., 1997). Agricultural systems in their current form in Victoria are generally not sustainable. Although traditional land evaluation methods are useful for the initial assessment of the feasibility or suitability of proposed agricultural land use, further development of land evaluation techniques is required to effectively assess the sustainability of proposed and current land use and more specifically, land management practices.

There is a need for stronger linkages between regional land use planning and on farm land management. Greater attention needs to be given to how sustainable land management decisions can be made. This will require inclusion into any assessment of sustainability, the perspective of both regional planners (ie. Catchment Management Authorities) and land managers (ie. farmers and developers), from a regional scale to the farm scale. Farmers and land users remain the ultimate land management decision-makers. They require information describing those management options that are most appropriate for the resource they have.

The inception of Catchment Condition Reporting by the Department of Natural Resources and Environment, Victoria, has provided the opportunity to develop a framework for assessing land use sustainability. Catchment Condition Reporting arose in response to legislation under the Catchment and Land Protection Act, 1994, Government of Victoria, which states that the condition of the state’s land and water resources must be reported on. Indicators of catchment health are the tools that will be used to assess the condition of the land and water resources.

The Land Use Impact Assessment framework (LUIA) and methodology satisfies the catchment condition reporting requirements, one output being the Land Use Impact Index (LUII) and offers the potential as a more refined tool for assessing and amending land management practices at any scale (paddock, catchment, region, State). The framework builds on the foundations laid by traditional methods of land evaluation and provides a method for measuring the mismatch between agricultural land management and land capability.

The framework represents a method for identifying priorities for future land use planning efforts and a tool for determining spatially explicit best management practice options. This paper describes the application of the framework to the cropping areas of Victoria using the Land Use Impact Model (LUIM), an expert system designed specifically for this purpose. Various applications of the framework including scenario modelling and its application as a Land Use Impact Index (LUII) are also discussed.

The Land Use Impact Assessment Framework (LUIA)

The LUIA Framework (Figure 1) outlines a process for identifying the relationships between the inherent degradation susceptibilities of the landscape, such as water erosion and salinisation, and individual management practices. It is designed to function as a dynamic system that brings together relevant models and databases to produce spatially and temporally explicit information identifying areas that are currently being managed unsustainably.

The objectives of the LUIA Framework are to:

• identify the inherent risk of land and water degradation and the induced or accelerated degradation risk associated with existing or proposed land management practices
• provide a robust and spatially explicit performance indicator for land management across Victoria

A key outcome for the LUIA Framework is a change in focus from capability/suitability ratings as the only outcome of land evaluation, to one that incorporates measures of sustainability. The increased emphasis on quantitative data and interpretation methods, GIS and dynamic modelling techniques are also important.

Figure 1: Land use impact assessment framework (LUIA)

(Shaded boxes represent modelled outputs)

The importance of including economic and social considerations into any measure of sustainability has been widely recognised (Smith and McDonald, 1998). Figure 2 illustrates where the LUIA Framework is designed to sit in relation to the “triple bottom line” approach to sustainability. Currently the LUIA Framework encompasses only the biophysical component. The framework can be developed to incorporate economic and social components to achieve more robust options for sustainable land use and land management decision making.

Figure 2: Strategic sustainability assessment framework

Prior to assessing land use sustainability, the feasibility of the land use for a particular area must be established by looking at the major unchangeable biophysical features of an area. This step considers any prohibitive soil, climate, landform, vegetation or water factors, as well as any legislative and planning restrictions on a land use. It is also desirable that social and economic factors be taken into account at this stage. Land uses that are found to be unfeasible for an area are not considered further.

• Soil, landform, water, climate & vegetation attributes
• Inherent environmental susceptibility ratings
• Land management practices

Environmental susceptibility ratings are developed for individual map units using soil, land form and climate data. Whether or not land use mapping is required will be dependent upon the objectives of the study. If the aim is to assess current land use sustainability, then mapping of current land use and land management practices will be required. If the aim is to assess future land management scenarios then land use mapping is not critical.

The Land Use Impact Model

The Land Use Impact Model (LUIM) is a software program designed to implement the LUIA Framework. It is an expert system that uses data defining land management practices, environmental susceptibilities and their relationships. The objectives of the LUIM are to assist natural resource managers in the:

• identification of appropriate management practices for managing agricultural land
• estimation of the land degradation risks associated with agricultural land management, and
• evaluation of current and potential land management practices in terms of environmental performance

The model can be broken into four main components.

Component 1 – Identifying and rating environmental susceptibilities

Environmental susceptibilities include those that affect land productivity or environmental integrity, and lead to on-site or off-site impacts. To quantify these susceptibilities, it is necessary to identify land attributes that can be used to measure their severity across the landscape. This is similar to the way land suitability analysis uses land attributes to map the spatial distribution of limitations to agricultural land use.

Once land attributes have been identified, land attribute class groups can be used in a five class system, to quantify the severity of each susceptibility on each land unit or land type. Susceptibility ratings determine both primary and secondary susceptibilities for each land unit. Within the LUIM, primary susceptibilities are defined as those with a rating of moderate (3), strong (4) or severe (5). Secondary susceptibilities are defined as those with a rating of low (2). Susceptibilities with a rating of one are negligible.

Component 2 - Identifying land management options

In order to identify potential land degradation risks and also best management practices, it is necessary to identify the land management options available to land users. These options can be identified through interviews with local land managers and resource management professionals, or through the use of agricultural census data. Land management options may consist of currently used or available land management practices, or new and emerging practices.

Component 3 - Rating the relationships between land management and susceptibilities

Once land management options have been identified, their relationship to environmental susceptibilities must be defined so that best practices, if they exist, can be identified and land degradation risk assessed. In the LUIM, relationships are based on expert knowledge of the nature and strength of the relationship between susceptibilities and land management practices, and the reversibility of any land degradation that may result from susceptibilities. These are termed Relationship/Reversibility (R / R) ratings.

The model uses three types of relationships. These are Beneficial Relationships (B), Adverse Relationships (A), and Neutral Relationships (N). Beneficial and Adverse relationships are further broken into Strong (S), Moderate (M) and Weak (W).

Susceptibilities are split into two categories. These are Reversible (R) and Irreversible (I). Reversible susceptibilities are further split into Reversible in the Short-term (S), Reversible in the Medium-term (M) and Reversible in the Long-term (L). Reversibility is essentially a measure of risk. The model aims to minimise land degradation risk by identify those land management practices that are likely to lead to long-term or irreversible damage and highlight those practices that are likely to avoid this.

Component 4 – Practice classification and land management recommendation

Once relationships and reversibilities have been specified, the LUIM uses this information to rate the favourability of each land management practice for use on each land unit, using a practice classification system similar to Table 1. Favourable land management practices prevent, reduce, or reverse the development of a primary susceptibility on a particular land unit (beneficial relationship). Practices that accelerate the development of a primary susceptibility (adverse relationships) on a particular land unit are unfavourable for the management of that land unit.

Table 1: Example practice classification system.

Relationship/Reversibility Rating	Practice Classification
N	Neutral practice
SB/I, MB/I, SB/RL	Essential practice
SB/RS, MB/RS, WB/RS, SB/RM, MB/RM, WB/RM, MB/RL, WB/RL, WB/I	Favourable practice
SA/RS, MA/RS, WA/RS	Conditional practice
MA/RL, WA/RL, SA/RM, MA/RM, WA/RM, WA/I	Unfavourable practice
SA/RL, SA/I, MA/I	Prohibitive practice

The results of practice classification can be used to provide land management recommendations and identify best land management practices. Best practices are identified for each land unit by eliminating those management practices that are unfavourable or prohibitive for one or more of the primary susceptibilities on that land unit. Also land degradation risk can be determined and mapped by identifying primary susceptibilities that are related to unfavourable practice.

Application of the Land Use Impact Framework

The LUIA framework was applied to broad acre cropping zones within Victoria. The results will be used for the LUII, as well as by strategic planners to highlight priority areas within Victoria needing more detailed analysis. Broad acre cropping was the land use chosen to test the model primarily because of the availability of land management practice information.

Land use/land management practices

Originally the broad acre cropping area was defined by combining the 1:250,000 land use coverage held in the NRE Corporate Library with the Bureau of Rural Sciences land use layer. However, this method was rejected in favour of using the 1997 ABS farm census data to define the cropping area (Figure 3). This was achieved by identifying those parishes in which specific cropping practices covered greater than 5% of the total parish area. These statistics were then be mapped to provide a spatial representation of cropping intensity per parish. This methodology was thought to provide a more transparent and accurate indicator of where broad acre cropping is occurring in Victoria.

Figure 3: Major broad acre cropping areas of Victoria.

For each of the parishes included in the cropping area, management practices recorded in the 1997 farm census were identified and represented spatially (Table 2). Only those practices representing more than 5% of a parish were assigned to that parish. Accompanying maps providing the percent application per parish enable the user of the results to identify those parishes that have significant adoption of specific management practices.

It is recognised that there are several inherent difficulties in utilising the ABS farm census data. Some of these problems are related to inconsistent reporting by farmers and poor farmer response to some questions. Using one year’s census data to spatially define the cropping area and distribution of specific management practices is problematic. The major concern is that this method captures only what is reported in that year by the farmer. However, this problem can be managed by repeating the process over a period of years to gain a long term view of practices being adopted.

Table 2: Management practices

Cultivation Type	Fallow Management	Stubble Management
Conventional Tillage Minimum Tillage No Tillage apart from sowing	Pasture Topping Chemical Fallow Cultivation Fallow	Stubble Burnt Stubble Grazed Stubble Incorporated Stubble Direct Drilled Stubble Mulched

Inherent environmental susceptibilities

The inherent environmental susceptibility coverage was obtained using the 1:250,000 land systems coverage of Victoria maintained by the Centre for Land Protection Research. Five susceptibilities were available in this coverage. These are listed in Table 3 with the land attributes used to rate each. This list will be added to over time as other susceptibilities are mapped consistently state-wide (eg. biodiversity and salinity).

Table 3: Environmental susceptibilities and attributes used to rate them.

Attribute	Water Logging	Water Erosion	Soil Structure Decline	Mass Movement	Wind Erosion
Climate	4	4		4	4
Landform	4	4		4	4
Lithology		4		4
Subsoil pH
Soil Depth		4		4
Surface Soil Consistency			4
Soil Drainage	4			4
Clay Content	4		4		4
Organic Matter
Surface Soil Texture	4	4	4		4

Rule set development

Results

Example1: Total area at risk from current broad acre cropping practices

Figure 4: Total area at risk of accelerated land and water degradation for broad acre cropping zones in Victoria (Spatial distribution of management practices based on 1997 ABS Farm Census).

Example Two: Areas where Conventional Tillage is an appropriate and inappropriate management option

Figure 5: Accelerated land and water degradation risk for areas under conventional tillage (Spatial distribution of management practices based on 1997 ABS Farm Census).

Example Three: Areas where no tillage (apart from sowing) is an appropriate and inappropriate management option

Once an analysis of current practice has been completed, further scenario modelling can be undertaken to guide future directions for the minimisation of identified land degradation risk.

Figure 6: Land and water degradation risk for areas under no tillage apart from sowing (Spatial distribution of management practices based on 1997 ABS Farm Census).

Conclusions

The Land Use Impact Assessment (LUIA) Framework has been designed to provide information to land managers regarding the sustainable management of the land resource – that is, appropriate practice, poor practice and degradation risk. Regional planners, catchment managers and farmers can use this methodology to make environmentally sustainable land management decisions - regional planners at the policy level, and farmers in their management of the land at the paddock scale. The LUIA Framework also provides a process for the collection of data for the Land Use Impact Index, which will be used in Victoria as a measure of the change over time in the area of land at risk of accelerated land degradation.

The LUIA Framework is designed to fill the information gap left by traditional land evaluation methods used in Victoria and indeed Australia. Land capability and suitability assessment methodologies were not designed to provide detailed land management information, but generalised recommendations regarding the ability of the land to sustain a particular land use. The LUIA Framework takes these land evaluation techniques to the next level by providing the information land managers need to select the best land management practices for the resources they have. Hence, while land capability and suitability assessments are still needed to assess the feasibility of land use, methods like the LUIA Framework are needed to determine the most sustainable land management practices within these land uses.

The Land Use Impact Model (LUIM) is an expert system developed specifically for the application of the LUIA Framework. The strengths of the LUIM are:

• Flexibility – the LUIM can be applied to a range of land management issues.
• Data requirements – the LUIM has minimal data requirements and these data are readily available.
• Transportable – the LUIM is easily calibrated and can be applied to new areas and data sets quickly
• Transparent – all components of the LUIM are visible to the user and can be interrogated, avoiding the “black box” method.
• Understandable – the LUIM outputs can be understood by non-experts and presented in a visual manner (eg. maps).

The strengths of LUIM have made it ideal for the development of a Land Use Impact Index (LUII). It can be applied quickly at a Statewide scale and to multiple data sets for time series analysis.

Future directions for the development of the LUIA Framework and the LUIM will focus on:

• Data improvement – improving the availability of data at scales relevant to land managers.
• Knowledge improvement – improving knowledge on the relationships between land management practice and environmental susceptibilities.
• Quantification – integrating quantitative and qualitative models in the analysis of land management.
• Multi-disciplinary approach – more explicit inclusion of economic and social factors in the analysis of land management.
• Cumulative impact – including the spatial relationship of land units in the analysis of land management.

References

DNRE, VCLPC and EPA (1997) Know Your Catchments, Victoria 1997: An Assessment of Catchment Condition Using Interim Indicators. Department of Natural Resources and Environment, Victoria.

FAO (1976). A framework for land evaluation. FAO Soils Bulletin No. 32. FAO, Rome.

Klingebeil, A. A. and Montgomery, P. H. (1961). Land capability classification. Agriculture Handbook 210. United States Department of Agriculture. United States Government Printing Office, Washington D. C.

Office of the Commissioner for the Environment (1991). 1991 State of the Environment Report: Agriculture and Victoria’s Environment. Government of Victoria.

Smith, C. S. and McDonald, G. T. (1998) Assessing the sustainability of agriculture at the planning stage. Journal of Environmental Management, 52, 15-37.