Biodiversity and climate change: Risks to dwarf succulents in Southern Africa

Abstract

The aim of this study was to explore the effects of anthropogenic climate change on the dwarf succulent genus Conophytum (Aizoaceae) within areas recognised for their floral biodiversity, namely the Succulent Karoo, Fynbos, Desert and Nama Karoo biomes of South Africa and Namibia. Niche-based modelling was used to identify the key climatic and geological variables influencing the distribution of members of the genus Conophytum. The distribution of the genus is primarily controlled by a small number of environmental variables, notably winter and summer rainfall levels, together with geology. Assuming a zero-dispersal model, the predicted effect of both the A1B and A2 climatic emission scenarios was a severe contraction in the area satisfying the bioclimatic envelope for the genus coupled with significant range dislocation. Reductions of >90% in suitable habitat for 10 of the 16 taxonomic Sections that comprise the genus and represent >80% of taxa under the A2 scenario are predicted. Under A1B the projected effects are ameliorated, but reductions of >50% of habitat can be seen in a majority of Sections. Significant projected reductions in the habitable bioclimatic envelope are very likely to increase risk of extinction of ∼80% of taxa even under a partly mitigated emissions scenario.