Biological Invasions

, Volume 12, Issue 12, pp 4113–4124 | Cite as

An economic assessment of the contribution of biological control to the management of invasive alien plants and to the protection of ecosystem services in South Africa

  • Willem J. de Lange
  • Brian W. van WilgenEmail author
Original Paper


This study is a first attempt at a holistic economic evaluation of South African endeavours to manage invasive alien plants using biological control. Our focus was on the delivery of ecosystem services from habitats that are invaded by groups of weeds, rather than by each individual weed species. We established the net present value of the weed biological control efforts, and derived benefit:cost ratios by comparing this value (a cost) to the estimated value of ecosystem services protected by weed biological control. We identified four major functional groupings of invading alien plants, and assessed their impact on water resources, grazing and biodiversity. We estimated the area that remained free of invasions due to all historic control efforts in South Africa, and the proportion that remained free of invasion as a result of biological control (which was initiated in 1913). The estimated value of potential ecosystem services amounted to 152 billion South African rands (ZAR—presently, about US$ 19.7 billion) annually. Although an estimated ZAR 6.5 billion was lost every year due to invading alien plants, this would have amounted to an estimated additional ZAR 41.7 billion had no control been carried out, and 5–75% of this protection was due to biological control. The benefit:cost ratios ranged from 50:1 for invasive sub-tropical shrubs to 3,726:1 for invasive Australian trees. Benefit:cost ratios remained positive and our conclusion, that biological control has brought about a considerable level of protection of ecosystem services, remains robust even when our estimates of the economic impacts of key variables (i.e. sensitivity analyses of indeterminate variables) were substantially reduced.


Benefit-cost analysis Invasive alien plants Water resources Grazing Biodiversity 



We thank Cliff Moran and John Hoffmann for suggesting that individual weed species be combined into functional groupings for these analyses, and we thank the numerous experts who assisted with the estimations of the relative contribution of biological control. The Plant Protection Research Institute, the University of Cape Town and Rhodes University allowed us access to records that led to the costing of research. This work was funded by the South African Working for Water programme of the Department of Water and Environmental Affairs.


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Centre for Invasion BiologyCSIR Natural Resources and the EnvironmentStellenboschSouth Africa

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