Biodiversity and Conservation

, Volume 16, Issue 1, pp 245–258 | Cite as

Conservation planning with irreplaceability: does the method matter?

  • J. Carwardine
  • W. A. Rochester
  • K. S. Richardson
  • K. J. Williams
  • R. L. Pressey
  • H. P. Possingham
Original Paper


A number of systematic conservation planning tools are available to aid in making land use decisions. Given the increasing worldwide use and application of reserve design tools, including measures of site irreplaceability, it is essential that methodological differences and their potential effect on conservation planning outcomes are understood. We compared the irreplaceability of sites for protecting ecosystems within the Brigalow Belt Bioregion, Queensland, Australia, using two alternative reserve system design tools, Marxan and C-Plan. We set Marxan to generate multiple reserve systems that met targets with minimal area; the first scenario ignored spatial objectives, while the second selected compact groups of areas. Marxan calculates the irreplaceability of each site as the proportion of solutions in which it occurs for each of these set scenarios. In contrast, C-Plan uses a statistical estimate of irreplaceability as the likelihood that each site is needed in all combinations of sites that satisfy the targets. We found that sites containing rare ecosystems are almost always irreplaceable regardless of the method. Importantly, Marxan and C-Plan gave similar outcomes when spatial objectives were ignored. Marxan with a compactness objective defined twice as much area as irreplaceable, including many sites with relatively common ecosystems. However, targets for all ecosystems were met using a similar amount of area in C-Plan and Marxan, even with compactness. The importance of differences in the outcomes of using the two methods will depend on the question being addressed; in general, the use of two or more complementary tools is beneficial.


Biodiversity Conservation Planning C-Plan Irreplaceability Marxan Reserve compactness 


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This study was funded by a Queensland Environmental Protection Agency Research Grant and Hugh Possingham’s ARC Discovery Grant (2002), and the data were provided by the Queensland Herbarium. The following people also deserve thanks for helpful discussions and assistance: Ian Ball, Jeremy Thompson, Mal Ridges, Matt Watts, Emily Nicholson and Romola Stewart.


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Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  • J. Carwardine
    • 1
  • W. A. Rochester
    • 2
  • K. S. Richardson
    • 3
  • K. J. Williams
    • 4
  • R. L. Pressey
    • 1
  • H. P. Possingham
    • 5
  1. 1.The Ecology Centre, School of Integrative BiologyThe University of QueenslandSt LuciaAustralia
  2. 2.CSIRO Marine ResearchClevelandAustralia
  3. 3.Department of GeographyMcGill University805 Sherbrooke St. WCanada
  4. 4.CSIRO Sustainable Ecosystems, Level 3, Queensland Bioscience PrecinctSt LuciaAustralia
  5. 5.The Ecology Centre, School of Integrative Biology and Department of MathematicsThe University of QueenslandSt LuciaAustralia

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