Reconstructing the spread of invasive alien plants on privately-owned land in the Cape Floristic Region: Vergelegen Wine Estate as a case study

Abstract

Invasive alien plants (IAPs) are a major threat to biodiversity in South Africa’s Cape Floristic Region (CFR). Activities like agricultural development, the establishment of forestry plantations and urbanization change environments and provide opportunities for IAPs to spread. We examine the factors that have contributed to plant invasions on a privately-owned farm in the CFR. The objectives of the study were: (1) to determine what land-use changes took place that could have influenced the spread of IAPs; and (2) to document the patterns of spread of IAPs. Aerial photographs from 1938, 1966, 1977, 1989 and 2004 were used to determine the types and rates of land-use change over time. Key land-use changes involved agriculture, commercial plantations, urban development and the spread of IAPs. The spatial analysis identified the main drivers of change. Agricultural development was the main land-use change driver and affected 40% of the study area by 1977. Areas occupied by IAPs increased with land-use change from 8% cover in 1938 to 40% in 2004, and then declined to 15% in 2013 following the initiation of control operations in 2004. The study illustrated a clear link between human activities, changes in land-use and the spread and proliferation of IAPs.

Keywords:

• Biological invasions
• fynbos
• invasive species
• land-use change
• tree invasions

Acknowledgements

We are grateful to Vergelegen Wine Estate for supporting this research. Prof Timm Hoffman provided helpful advice on the use of transition matrices. DMR and BWvW acknowledge funding from the DST-NRF Centre of Excellence for Invasion Biology and the National Research Foundation (grant 85417 to DMR and grant 87550 to BWvW).