Volume 41, Issue 7 pp. 1338-1351
Original Article

Suborbital climatic variability and centres of biological diversity in the Cape region of southern Africa

Brian Huntley

Corresponding Author

Brian Huntley

School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE UK

Correspondence: Brian Huntley, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK.

E-mail: [email protected]

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Guy F. Midgley

Guy F. Midgley

Climate Change and BioAdaptation Division, South African National Biodiversity Institute, Kirstenbosch Research Centre, P/Bag X7, Claremont, 7735 Cape Town, South Africa

School of Agricultural, Earth and Environmental Sciences, University of Kwazulu-Natal, Pietermaritzburg Campus, Pvt Bag X101, Scottsville, 3209 South Africa

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Phoebe Barnard

Phoebe Barnard

Climate Change and BioAdaptation Division, South African National Biodiversity Institute, Kirstenbosch Research Centre, P/Bag X7, Claremont, 7735 Cape Town, South Africa

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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Paul J. Valdes

Paul J. Valdes

School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS UK

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First published: 15 February 2014
Citations: 15

Abstract

Aim

To explore the magnitude and spatial patterns of last glacial stage orbitally forced climatic changes and suborbital climatic fluctuations in southern Africa, and to evaluate their potential roles in determining present biodiversity patterns.

Location

Africa south of 15° S.

Methods

Palaeoclimate scenarios for southern Africa were derived for 17 time slices using outputs from HadCM3 atmosphere–ocean general circulation model experiments, including five designed to mimic Heinrich events. Species distribution models for birds of Karoo (45) or Fynbos (31) were used to simulate species' potential past distributions. Species-richness patterns were assessed for each time slice, and minimum species richness for regional endemics of each biome determined for each grid cell. Areas of greatest ‘stability’ for endemics of each biome were identified using grid cells with greatest minimum richness.

Results

Simulated suborbital climatic fluctuations were of greater magnitude than orbitally forced changes and had anomalies of opposite sign in many areas. The principal local drivers of suborbital fluctuations were marked contrasts in South Atlantic circulation and temperature between experiments mimicking Heinrich events and those with only slow forcings. These contrasts in ocean circulation and temperature were consistent with marine sediment core evidence of changes in the South Atlantic coincident with Heinrich events in the North Atlantic. Whereas orbitally forced last glacial climates generally resulted in range expansions and increased species richness in many grid cells compared with the present, the contrasting conditions of Heinrich events resulted in much reduced ranges and species richness, especially for Karoo species. Very few grid cells remained suitable for larger numbers of endemic species of either biome under all palaeoclimate scenarios examined, but this minority of ‘stable’ grid cells correspond to present diversity centres.

Main conclusions

Suborbital climatic fluctuations during the last glacial stage were probably of considerable magnitude in southern Africa. This may account for apparent inconsistencies between regional palaeoclimate records, as well as being key to determining present biodiversity patterns.

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