Beyond catchment considerations in the conservation of lotic biodiversity

Authors

  • M. J. Wishart,

    Corresponding author
    1. Freshwater Research Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
    2. CRC Freshwater Ecology, Australian School of Environmental Studies, Griffith University, Nathan 4111, Australia
    Current affiliation:
    1. Projectos e Estudos Impacto Ambiental, 968 Mártires da Machaca Av. Maputo, Mozambique
    • Freshwater Research Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
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  • B. R. Davies

    1. Freshwater Research Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, South Africa
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Abstract

  • 1.The history of river conservation has largely focused on preservation of the physical and structural properties of lotic ecosystems in an attempt to ensure safe and potable water supplies for human consumption. Such strategies are increasingly being implemented at the catchment or basin scale.
  • 2.Although these reflect positive developments in the conceptualization of conservation issues pertaining to lotic systems and provide the logical economic, sociological and/or political units for management, we question whether they represent the appropriate scale for the protection of lotic biodiversity and biological processes. We argue that this requires considerations that extend beyond the protection of physical habitat to ensure protection of population processes.
  • 3.Although many species can be successfully conserved using the catchment as the basic management unit, many others cannot. We review evidence from genetic studies of aquatic populations to examine movement in relation to catchments, recognizing that organisms with poor dispersal characteristics during their life cycles exhibit a high degree of genetic structure, whilst organisms with robust dispersal characteristics typically exhibit a homogeneous genetic structure.
  • 4.Species with poor dispersal characteristics are more easily conserved at the catchment level, whereas those with high dispersal characteristics can only be safely conserved at bio-regional supra-catchment levels.
  • 5.Modern technological advances aimed at redistributing water from areas with perceived surpluses to those with perceived deficits (inter-basin water transfers), demonstrated to transfer organisms between historically isolated catchments, pose a potential threat to the conservation of biodiversity by mixing genetically distinct populations and hence altering evolutionary processes and pathways.
  • 6.If our arguments hold, then it appears that conservation authorities need to reappraise the current dominant paradigm of the catchment as the basic unit for conservation and management, and incorporate broader, strategic landscape planning in water resource management.

Copyright © 2003 John Wiley & Sons, Ltd.

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