A modelling project has examined how best to configure landscape change at catchment scale for the effective conservation of biodiversity, using native vegetation as the building blocks for exploring different management scenarios. The catchment analysis tool (CAT), which simulates water–soil–plant interactions at a land management scale, was used for the modelling exercise. Information from the scientific literature, which is largely based on habitat requirements of mammals and birds, was used to develop the following set of rules to model changes to landscapes (400 ha blocks). - Rule 1: Increase the size of the largest remnant to achieve one remnant >40 ha for each 400 ha grid cell in the 400 ha landscape units that does not have a remnant >40 ha.
- Rule 2: Link each remnant >40 ha with riparian or roadside vegetation or other remnant 40 ha, whichever is closest, with 40 m wide strip of vegetation.
- Rule 3: Increase the size of the largest remnant(s) closest to a first or second order stream to achieve two remnants >10 ha within each 400 ha grid cell in the 400 ha landscape units that do not have two remnants >10 ha.
- Rule 4: Link all remnants >10 ha with riparian or roadside vegetation, or remnants > 40 ha, whichever is closest, with 40 m wide strip of vegetation.
- Rule 5: Create a 50 m buffer both sides of all first and second order streams.
- Rule 6: Create a 40 m buffer both sides of secondary and tertiary roads, terminating buffers within 1 km of major roads.
The mapped data layers of existing vegetation, roads and streams were used as a basis for creating vegetation in areas of each landscape within a catchment, using a geographic information system. An example of the potential output from the model is provided in Figure 18. The modelling of the rules resulted in a change of landscapes within the catchment, particularly in agriculture-dominated regions, from highly fragmented with few large remnants to highly connected landscapes with large remnants. Figure 18: A small section of modelled catchment showing existing vegetation (black) and the ‘vegetation’ added by eachof the six rules (shades of grey).
Source: Wilson JA, Lowe KW, Showers C, Ebert S (2002) Using Spatial Modelling to Plan for the Conservation of Biodiversity within the Goulburn-Broken Catchment, Victoria. In ‘Land-use change – YES – But will biodiversity be OK?’ Attwood, Victoria. (Eds. J Crosthwaite, Q Farmer-Bowers and C Hollier). Department of Sustainability and Environment
This project was considered useful in identifying gaps in knowledge about how best to revegetate landscapes to conserve the majority of species. The large scale of the project resulted in a vision for how future planning for the catchment might occur. It is intended as a tool for discussion and assessment for planning land use change, along with other considerations. Users of such modelling tools need to be aware of the limitations of the data and modelling approaches being used, which are well documented by the project authors. An Ecosystem Services Project has also used a set of decision-making rules to model different vegetation scenarios as a surrogate for biodiversity conservation planning. Eighteen decision rules were created based on catchment objectives, ecological theory and design principles adopted for the Heartlands project. The rules are used to create a pattern of vegetation options that would enhance biodiversity outcomes in the sub-catchment. Each of these decision rules was weighted (multiplied by an index of priority) to reflect the relative influence of each rule on the desired vegetation pattern. The weighting process requires both expert and community opinion to fully embrace the range of views about how vegetation enhancement should be achieved. In all, 11 mapped options for future native vegetation enhancement were generated as well as the map of current vegetation pattern. A 15 per cent target is commonly used in catchment management documents and also for State priority-setting (Figure 19). The modelling suggested that an increase from the current level of 8 per cent vegetation in the sub-catchment to a 15 per cent target produces only small increases in ecosystem services as indicated by habitat configuration scores, carbon storage, shelter, shade, stream sediment load, sheet and rill erosion control, deep drainage control and control of soil acidity. At a 40 per cent target the landscape has become relatively well connected (Figure 20). These sorts of analyses can be used to explore potential thresholds in ecosystem responses, although our understanding about many of the processes involved and how they interact is still quite limited. Figure 19: Modelled 15 per cent target for native vegetation enhancement.
Source: Abel N, Cork S, Gorddard R, Langridge J, Langston A, Plant R, Proctor W, Ryan P, Shelton D, Walker B, Yialeloglou (2003) ‘Natural Values:Exploring options for enhancing ecosystem services in the Goulburn-Broken Catchment.’ CSIRO Sustainable Ecosystems, Canberra, ACT. p.89
Figure 20: Modelled 40 per cent target for native vegetation enhancement.
Source: Abel N, Cork S, Gorddard R, Langridge J, Langston A, Plant R, Proctor W, Ryan P, Shelton D, Walker B, Yialeloglou (2003) ‘Natural Values: Exploring options for enhancing ecosystem services in the Goulburn-Broken Catchment.’ CSIRO Sustainable Ecosystems, Canberra, ACT. p.89
Living Landscapes is an approach that links science and community through a simple framework for learning, planning, doing and reviewing, and is described in Landscape Planning for Biodiversity Conservation in Agricultural Regions. It focuses on working with land managers to integrate nature conservation into the agricultural landscape, with the primary aim of protecting the remaining (native) biodiversity within economically viable and sustainable land-use systems. Native vegetation is one of the key assets and management tools used in the planning process. Drawing on local scientific research, a number of awareness-raising activities and tools can be developed that aim to help farmers to: - identify biodiversity assets within their catchment or region;
- identify the threats to those assets; and
- incorporate actions into their farm and catchment plans to manage the threats.
The approach addresses some of the social, understanding, communication and information issues that deter landscape-scale adoption of biodiversity conservation values and actions. It provides opportunities for land managers to learn about their local ecology, through their own experience and the eyes of others, and then to apply ‘new’ knowledge at the local level whilst contributing to landscape-scale outcomes. This approach requires a relatively high level of resource contribution and technical expertise to gain the long-term change being sought. For example, it includes scientific assessment of biodiversity values by the ‘focal species’ approach, usually bird species. The high level of resources required and technical expertise required for this approach suggests that it may not be applicable to all areas but could be best suited in areas of high priority, due either to exceptional biodiversity values or substantial threatening processes. An assessment of regional priorities will provide this investment direction. Another framework, Managing Natural Biodiversity in the WA Wheatbelt has recently been published. This links operational management of biodiversity with a philosophy of management. While developed for an environment where the remaining natural habitats are often highly fragmented, many ideas and processes can be applied elsewhere. The framework includes four elements: 1. an aspirational goal and broad management strategies that guide
operational management; 2. a description of the biodiversity assets that must be managed to achieve the aspirational goal; 3.a description of threats to goal achievement, and a process for using threats to rank management strategies and identify priority sites for action; and 4. monitoring and evaluation methods that effectively link goals, on-ground outputs and outcomes. An approach to ranking landscapes for biodiversity conservation in the wheatbelt, which is described in the Appendix, uses native vegetation as a surrogate for biodiversity. A minimum set of criteria was used to identify landscapes with a reasonable probability of retaining viable populations of all extant native species within a landscape. These criteria included the size of landscape (100-300 km2), the percentage habitat in a landscape
(a minimum of 30–40 per cent) and the distribution of habitat in landscapes (clumping).
| | | | Action: 4.19 |
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| | Consider the frameworks for native vegetation and biodiversity conservation developed in south-west WA as models to link management goals and on-ground outputs and outcomes. | | | COST |  | | | TIME |  | | | COMPLEXITY |  | | | | |
The Biodiversity Benefits Index (BBI) is a prototype toolkit designed to assess the biodiversity benefits likely to result from a change in land use. The toolkit aims to capture the requirements of a broad range of native flora and fauna rather than the specific requirements of individual (rare or threatened) species. The BBI is designed to achieve three goals: - Score the current biodiversity value of a site;
- Estimate the magnitude and direction of change to biodiversity value resulting from land use change; and
- Incorporate these current and potential values into a Biodiversity Benefits Index.
In this context, biodiversity ‘value’ is defined as the degree to which the site, which may or may not have native vegetation present, contributes to biodiversity conservation at the bioregional scale. The BBI is based on three surrogate measures of biodiversity: vegetation condition, conservation significance and landscape context. To help estimate the biodiversity value of a site in a regional context, measures of conservation significance and landscape context are used. Conservation significance measures the amount of each element of biodiversity (using vegetation type as a surrogate) currently in the landscape compared with a designated time before agricultural development. The regional component of the ‘Landscape Context’ accounts for 10 per cent of the value of this score. It uses regional planning documents as a guide to prioritising sites such as regional corridors for biodiversity conservation. The attributes measured for each of these surrogates are combined to derive a single ‘metric’ for a site – the BBI. Many of these attributes make intuitive ecological sense, but not all have been empirically tested. |
