Evidence for climate-induced range shift in Brachystegia (miombo) woodland

  • Brenden Pienaar School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
  • Dave I. Thompson 1. South African Environmental Observation Network, Phalaborwa, South Africa 2. School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa
  • Barend F.N Erasmus School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa * Current address: Global Change and Sustainability Research Institute, University of the Witwatersrand, Johannesburg, South Africa
  • Trevor R. Hill School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Pietermaritzburg, South Africa
  • Ed T.F. Witkowsk School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
Keywords: Brachystegia spiciformis, climate change, ecological niche model, MaxEnt, refugia

Abstract

Brachystegia spiciformis Benth. is the dominant component of miombo, the sub-tropical woodlands which cover 2.7 million km2 of south-central Africa and which is coincident with the largest regional centre of endemism in Africa. However, pollen records from the genus Brachystegia suggest that miombo has experienced rapid range retraction (~450 km) from its southernmost distributional limit over the past 6000 years. This abrupt biological response created an isolated (by ~200 km) and incomparable relict at the trailing population edge in northeast South Africa. These changes in miombo population dynamics may have been triggered by minor natural shifts in temperature and moisture regimes. If so, B. spiciformis is likely to be especially responsive to present and future anthropogenic climate change. This rare situation offers a unique opportunity to investigate climatic determinants of range shift at the trailing edge of a savannah species. A niche modelling approach was used to produce present-day and select future B. spiciformis woodland ecological niche models. In keeping with recent historical range shifts, further ecological niche retraction of between 30.6% and 47.3% of the continuous miombo woodland in Zimbabwe and southern Mozambique is predicted by 2050. Persistence of the existing relict under future climate change is plausible, but range expansion to fragmented refugia in northeast South Africa is unlikely. As Brachystegia woodland and associated biota form crucial socio-economic and biodiversity components of savannas in southern Africa, their predicted further range retraction is of concern.

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Published
2015-07-27