The challenges of managing invasive alien plants on private land in the Cape Floristic Region: insights from Vergelegen Wine Estate (2004–2015)

Abstract

Alien plant invasions are a major threat to biodiversity and ecosystem functioning in South Africa’s Cape Floristic Region (CFR). Large-scale government-funded management initiatives are underway to reduce the extent of invasions in this region. Among the many challenges are the huge spatial extent of the invasions and difficulties in coordinating management efforts across large areas of invaded land in private ownership. Very little information is available on the success of privately-funded alien plant control initiatives. This study investigated the effectiveness of one large project in reducing alien plant cover, the challenges faced and the costs associated with long-term clearing operations on privately-owned land in the CFR. Results for the study area (Vergelegen) show that the cover of dense invasive plant stands declined by 70% over 10 years since management operations began, but that operations cost 3.6 times more than was originally estimated (ZAR 43.6 vs 12.19 million, respectively). The challenges associated with managing invasive alien plants (IAPs) on private land are very similar to those faced on state-owned land, with the efficiency of management being constrained by multiple interacting environmental and socio-economic factors. However some success in managing IAPs can be achieved by adhering to basic principles, including careful planning with clear achievable goals in mind, a commitment to stable long-term funding and regular monitoring. Most private land owners cannot afford the substantial investment of resources that would be required to clear large stands of IAPs and to ensure that cleared areas are maintained to prevent re-invasion, and finding ways to fund this remains a challenge.

Keywords:

• biological invasions
• fynbos
• invasive species
• management
• tree invasions

ACKNOWLEDGEMENTS

We are grateful to Vergelegen Wine Estate for supporting this research. BvW and DMR acknowledge funding from the DST-NRF Centre of Excellence for Invasion Biology and the National Research Foundation (grants 85417 to DMR and 87550 to BWvW). John Wilson provided advice on statistical analyses.