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Modelling relationships between species spatial abundance patterns and climate

Authors

  • Brian Huntley,

    Corresponding author
    1. School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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  • Res Altwegg,

    1. Birds and Environmental Change Partnership, Climate Change and BioAdaptation Division, South African National Biodiversity Institute, Kirstenbosch Research Centre, P/Bag X7, Claremont 7735, Cape Town, South Africa
    2. Animal Demography Unit, Department of Zoology, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
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  • Phoebe Barnard,

    1. Birds and Environmental Change Partnership, Climate Change and BioAdaptation Division, South African National Biodiversity Institute, Kirstenbosch Research Centre, P/Bag X7, Claremont 7735, Cape Town, South Africa
    2. Percy FitzPatrick Institute of African Ornithology, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
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  • Yvonne C. Collingham,

    1. School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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  • David G. Hole

    1. School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
    2. Science and Knowledge Division, Conservation International, 2011 Crystal Drive, Arlington, VA 22202, USA
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Brian Huntley, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK. E-mail: brian.huntley@durham.ac.uk

ABSTRACT

Aim  To move towards modelling spatial abundance patterns and to evaluate the relative impacts of climatic change upon species abundances as opposed to range extents.

Location  Southern Africa, including Lesotho, Namibia, South Africa, Swaziland and Zimbabwe.

Methods  Quantitative response surface models were fitted for 78 bird species, mostly endemic (68) or near-endemic to the region, to model relationships between species reporting rates (i.e. the proportion of checklists reporting a species for a particular grid cell), as recorded by the Southern African Bird Atlas Project, and four bioclimatic variables derived from climatic data for the period 1961–90. With caution, reporting rates can be used as a proxy for abundance. Models were used to project potential impacts of a series of projected climatic change scenarios upon species abundance patterns and range extents.

Results  Most models obtained were robust with good predictive power. Projections of potential future abundance patterns indicate that the magnitude of impacts upon a proxy for abundance are greater than those upon range extent for the majority of species (82% by 2071–2100). For most species (74%) both abundance and range extent are projected to decrease by 2100. Impacts are especially severe if species are unable to realize projected range changes; when only the area of a species' simulated present range is considered, overall abundance decreases of more than 80% are projected for 19 (24%) of species examined.

Main conclusions  Our results indicate that projected climatic changes are likely to elicit greater relative changes in species abundances than range extents. For most species examined changes were decreases, suggesting the impacts upon biodiversity are likely generally to be negative. These results also suggest that previous estimates of the proportion of species at increased risk of extinction as a result of climatic change may, in some cases, be under-estimates.

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