Landscape planning for biodiversity conservation in agricultural regions: A case study from the Wheatbelt of Western Australia
Biodiversity Technical Paper, No. 2
Robert J. Lambeck, CSIRO Division of Wildlife and Ecology
Commonwealth of Australia, 1999
ISBN 0 6422 1423 9
Chapter 2 - Retaining Biodiversity in Agricultural Landscapes (continued)
Conservation objectives and strategies
Approaches to managing biological diversity in agricultural landscapes will differ depending on the objectives that have been set. The two broad types of objectives that were identified – general versus strategic enhancement – rely on different types of information and result in different landscape responses. General enhancement strategies can be based on ecological principles whereas strategic approaches require a knowledge of the needs of the biota.
General enhancement strategies are unable to provide clear targets for dealing with immediate conservation problems. They aim to minimise the number of species lost or increases the abundance of species present. They are unable to specify which species will be lost or retained or which species may increase or decrease in numbers. Consequently there are no criteria for assessing success or failure apart from general changes in community structure and composition. General enhancement approaches can identify directions in which to proceed but provide no indication of the magnitude of the response required.
Strategic enhancement strategies, on the other hand, have clearly identified targets against which success can be judged. These targets will take the form of stable or increasing distributions and population sizes of individual species or groups of species. These types of objectives can also be used to develop explicit guidelines about how much of a landscape is required for meeting a specified objective.
Focal species in conservation planning
The focal species approach presented in this report provides a means to address the traditional dichotomy between single-species and landscape approaches to conservation management. While species are employed for the assessment of landscape adequacy and for guiding management strategies, the choice of species is based on their capacity to encapsulate the needs of other species in the landscape. These focal species can be used to identify the appropriate spatial and functional parameters that must be present in a landscape if it is to retain the flora and fauna that occur there. Area-limited species define the spatial attributes of each patch type, dispersal-limited species define patch configurations and connectivity characteristics, resource-limited species define the compositional attributes, and process-limited species define the management regimes that have to be implemented.
A critical feature of this approach is that it does not provide a template to apply across all landscapes but it does provide a procedure by which to determine the actions required in any given landscape. These actions are guided by the needs of a subset of the species present with recognition that the composition of this set will differ from one place to another due to both environmental differences and differences in the amount of human disturbance.
In relatively undisturbed landscapes where much of the original community composition remains intact, the focal taxa are more likely to be sedentary resource specialists that prefer patch interiors rather than edges. They are also likely to be larger vertebrates which have the greatest demands for habitat. In landscapes that have progressed further along the continuum of habitat reduction, fragmentation and degradation, many of the more demanding species may have already been lost. Smaller vertebrates, plants, or even invertebrates will have an increasing probability of being identified as the most demanding species that remain in the landscape. By applying the focal species approach it is possible to specify the attributes that are required to meet the needs of the species present in the landscape being managed regardless of where that landscape sits on the degradation continuum.
Mixed strategies in the absence of perfect knowledge
Ideally, nature conservation planning would always be based on an understanding of the needs of the biota in the landscape to be managed. However, it will probably never be the case that a complete understanding will be acquired for any one location, let alone for a whole region. It will therefore always be necessary to combine strategic procedures, such as the focal species approach, with general principles when the critical information is not available and cannot be acquired within the time-frame or budget of the management plan. It is essential to recognise, however, that the greater the reliance on general principles the less certain will be the conservation outcome.
Spatial scales for conservation planning
The solution generated using the focal species approach was surprisingly efficient with a small but strategic increase in the amount of habitat creating an additional 60 habitat patches that would be large enough to support the most habitat-demanding species. It is improbable that such an efficient solution could be developed by using general principles alone although this assertion remains to be tested. While the approach required a relatively small increase in the total area under native vegetation to produce an adequate landscape, it did not resolve the issue of landscape viability. The solution will meet the immediate habitat needs of the species in the catchment but in its current form the procedure cannot identify the area over which the solution must be extended before sufficient numbers of individuals of rarer species are included for the landscape to also become a viable one. Landscape viability is more likely to be achieved if assessment and planning is conducted at a bioregional scale. However, in order to ascertain the appropriate scale for achieving particular conservation outcomes it will be necessary to determine whether a landscape that can ensure population viability for focal species can also provide the requirements to support viable populations of all other species.
It is also critical to determine whether a solution developed at a larger spatial scale, such as a bioregion, will reduce the effort required per unit area to meet a specified conservation objective. For example, an attempt to provide landscape viability as well as adequacy in the Wallatin Catchment would probably require revegetation of the majority of the catchment and even then will not guarantee the persistence of sparsely distributed species. Such a strategy would obviously jeopardise the economic viability of the catchment. However, if conservation planning and action was conducted at a regional scale the land-holders would only have to contribute to the solution rather than achieve it on their own. This would require a much smaller proportion of their catchment to be allocated to nature conservation in order to meet the conservation objective. These questions of landscape viability and the effect of scale on conservation effort need to be explored in the context of a larger regional planning initiative.
In this section
- 2.1 Biodiversity: the variety of life
- 2.2 Biotic impoverishment: the impact of agriculture
- 2.3 Protecting biological diversity: the need for clear objectives
- 2.4 General enhancement
- 2.5 Strategic enhancement: using focal species to define landscape
- 2.6 Reintroductions
- 2.7 Mixed strategies in the face of partial knowledge
- 2.8 Design and management recommendations for Wallatin Creek
- 2.9 Priorities for implementation
- 2.10 Guidelines for implementation
- 2.11 Moving the goal posts: the consequences of implementation
- 2.12 Transportability of solutions
- 2.13 The role of science and data adequacy
- 2.14 Summary
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