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The Economic Consequences of Alien Plant Invasions: Examples of Impacts and Approaches to Sustainable Management in South Africa

  • B.W. van Wilgen
  • D.M. Richardson
  • D.C. Le Maitre
  • C. Marais
  • D. Magadlela
Article

Abstract

The invasion of natural ecosystems by alien plants is a serious environmental problem that threatens the sustainable use of benefits derived from such ecosytems. Most past studies in this field have focussed on the history, ecology and management of invasive alien species, and little work has been done on the economic aspects and consequences of invasions. This paper reviews what is known of the economic consequences of alien plant invasions in South Africa. These economic arguments have been used to successfully launch the largest environmental management programme in Africa.

Ten million hectares of South Africa has been invaded by 180 alien species, but their impacts are not fully understood, although they are undoubtedly significant. The indications are that the total costs of these impacts are substantial. Selected studies show that invasions have reduced the value of fynbos ecosystems by over US$ 11.75 billion; that the total cost of invasion would be about US$ 3.2 billion on the Agulhas Plain alone; that the net present cost of invasion by black wattles amounts to US$ 1.4 billion; that invasions by red water fern have cost US$ 58 million; and that the cost to clear the alien plant invasions in South Africa is around US$ 1.2 billion. These few examples indicate that the economic consequences of invasions are huge.

One of the unique aspects of invasive plant control programmes in South Africa has been the ability to leverage further benefits (mainly through employment) for the expensive control programmes from the government's poverty relief budget. This has made it possible to allocate substantial funding to a programme that would otherwise have struggled to obtain significant support. Biological control of invasive species also offers considerable benefits, but is often the subject of debate. We believe that, at least in the case of many invasive alien plant species in South Africa, biological control offers one of the best, and most cost-effective, interventions for addressing the problem.

biodiversity biological control cost-benefit analyses forestry social benefits water resources weeds 

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References

  1. Avis, A.M.: 1989, 'A review of coastal dune stabilization in the Cape Province of South Africa', Landscape and Urban Planning 18, 55–68.Google Scholar
  2. Baars, J-R. andNeser, S.: 1999, 'Past and present initiatives on the biological control of Lantana camara (Verbenaceae) in South Africa', African Entomology Memoir 1, 21–33.Google Scholar
  3. Breytenbach, G.J.: 1986, 'Impacts of alien organisms on terrestrial communities with emphasis on communities of the south-western Cape' in I.A.W. Macdonald,F.J. Kruger andA.A. Ferrar (eds.), The ecology and management of biological invasions in southern Africa, Cape Town, Oxford University Press, pp. 229–238.Google Scholar
  4. Breytenbach, G.J.: 1989, 'Alien control: Can we afford to slash and burn hakea in fynbos ecosystems?', South African Forestry Journal 151, 6–16.Google Scholar
  5. Bromilow, C.: 1995, Problem plants of South Africa. Pretoria, Briza Publications.Google Scholar
  6. Brown, C.J. andGubb, A.A.: 1986, 'Invasive alien organisms in the Namib Desert, Upper Karoo and the arid and semi-arid savannas of western southern Africa' in I.A.W. Macdonald,F.J. Kruger andA.A. Ferrar (eds.), The ecology and management of biological invasions in southern Africa, Cape Town, Oxford University Press, pp. 93–108.Google Scholar
  7. Brutsch, M.O. andZimmermann, H.G.: 1993, 'The prickly pear (Opuntia ficus-indica [Cactaceae]) in South Africa: Utilization of the naturalized weed, and of the cultivated plants', Economic Botany 47, 154–162.Google Scholar
  8. Cellier, S.: 1994, 'Are all trees green? The forest industry replies', Africa Environment and Wildlife 2(1), 79–85.Google Scholar
  9. Chapin, F.S. III,Reynolds, H.L.,D'Antonio, C.M. andEckhart, V.M.: 1996, 'The functional role of species in terrestrial ecosystems', in B. Walker andW. Steffen (eds.), Global change and terrestrial ecosystems, Cambridge University Press, pp. 403–428.Google Scholar
  10. Cilliers, C.J.: 1999, 'Biological control of parrot's feather, Myriophyllum aquaticum (Vell.) Verd. (Haloragaceae), in South Africa', African Entomology Memoir 1, 113–118.Google Scholar
  11. Cole, N.S.,Lombard, A.T.,Cowling, R.M.,Euston-Brown, D.,Richardson, D.M. andHeijnis, C.E.: 2000, Framework for a conservation plan for the Agulhas Plain, Cape Floristic Region, South Africa, Institute for Plant Conservation, University of Cape Town.Google Scholar
  12. Cowling, R.M.,Pressey, R.L.,Lombard, A.T.,Heijnis, C.E.,Richardson, D.M. andCole, N.: 1999, Framework for a conservation plan for the Cape Floristic Region, Institute for Plant Conservation, University of Cape Town.Google Scholar
  13. Cowling, R.M. andHilton-Taylor, C.: 1994, 'Patterns of plant diversity and endemism in southern Africa: an overview', in B.J. Huntley (ed.), Botanical diversity in southern Africa, Pretoria, National Botanical Institute, pp 31–52.Google Scholar
  14. Department ofWater Affairs and Forestry: 1997, TheWorking forWater Programme 1996/97 Annual Report, Department of Water Affairs and Forestry, Pretoria.Google Scholar
  15. De Wit, M., Crookes, D. and van Wilgen, B.W.: 'Conflicts of interest in environmental management: Estimating the costs and benefits of black wattle (Acacia mearnsii) in South Africa', Biological Invasions, (in press).Google Scholar
  16. Dukes, J.S. and Mooney, H.A: 'Biological invaders disrupt ecosystem processes in western North America.', in G.A. Bradshaw, H.A. Mooney and P. Alaback, P. (eds.), Disruptions and variability in ecosystem processes and patterns, New York, Springer-Verlag, (in press).Google Scholar
  17. Dye, P.: 1996, 'Climate, forest and streamflow relationships in South African afforested catchments', Commonwealth Forestry Review 75, 31–38.Google Scholar
  18. Eckert, J.B.,Liebenberg, G.F. andTroskie, D.P.: 1997, The Macroeconomics of Western Cape Agriculture: Analysis With A Social Accounting Matrix, Department of Agriculture of the Western Cape, Cape Town.Google Scholar
  19. Euston-Brown, D.: 2000, 'The influence of vegetation type and fire severity on catchment stability after fire: a case study from the Cape Peninsula, South Africa', Working forWater Programme, Department ofWater Affairs and Forestry, Cape Town.Google Scholar
  20. Fraser, M.W.: 1990, 'Foods of Redwinged Starlings and the potential for avian dispersal of Acacia cyclops at the Cape of Good Hope Nature Reserve', South African Journal of Ecology 1, 73–76.Google Scholar
  21. Geldenhuys, C.J.,le Roux, P.J. andCooper, K.H.: 1986, 'Alien invasions in indigenous evergreen forest'. in I.A.W. Macdonald,F.J. Kruger andA.A. Ferrar (eds.), The ecology and management of biological invasions in southern Africa, Cape Town, Oxford University Press, pp. 119–131.Google Scholar
  22. Hall, A.V.: 1987, 'Threatened plants in the fynbos and karoo biomes', Biological Conservation 40, 29–52.Google Scholar
  23. Harding, G.B. andBate, G.C.: 1991, 'The occurrence of invasive Prosopis species in the north-western Cape, South Africa', South African Journal of Science 87, 188–192.Google Scholar
  24. Henderson L.: 1991, 'Alien invasive Salix spp. (willows) in the Grassland Biome of South Africa', South African Forestry Journal 157, 91–95.Google Scholar
  25. Henderson, L.: 1998, 'South African plant invaders atlas (SAPIA)', Applied Plant Sciences 12, 31.Google Scholar
  26. Henderson, L.: 1999, 'The southern African Plant Invaders Atlas (SAPIA) and its contribution to biological weed control', African Entomology Memoir 1, 159–163.Google Scholar
  27. Heydenrych, B.: 1999, 'An investigation of land-use practices on the Agulhas Plain (South Africa), with emphasis on socio-economic and conservation issues', M.Sc. dissertation, University of Cape Town.Google Scholar
  28. Higgins, S.I.,Azorin, E.J.,Cowling, R.M. andMorris, M.J.: 1997a, 'A dynamic ecological-economic model as a tool for conflict resolution in an invasive alien, biological control and native-plant scenario', Ecological Economics 22, 141–154.Google Scholar
  29. Higgins, S.I.,Turpie, J.K.,Costanza, R.,Cowling, R.M.,Le Maitre, D.C.,Marais, C. andMidgley, G.F.: 1997b, 'An ecological economic simulation model of mountain fynbos ecosystems: Dynamics, valuation and management', Ecological Economics 22, 155–169.Google Scholar
  30. Higgins, S.I.,Richardson, D.M.,Cowling, R.M. andTrinder-Smith, T.H.: 1999, 'Predicting the landscapescale distribution of alien plants and their threat to plant diversity', Conservation Biology 13, 303–313.Google Scholar
  31. Hill, M.P. andCilliers, C.J.: 1999, 'A review of the arthropod natural enemies, and factors that influence their efficacy, in the biological control of water hyacinth, Eichhornia crassipes (Mart.) Solms-Laubach (Ponterderiaceae), in South Africa', African Entomology Memoir 1, 103–112.Google Scholar
  32. Hoffmann, J.H. andMoran, C.M.: 1988, 'The invasive weed, Sesbania punicea in South Africa and prospects for its biological control', South African Journal of Science 84, 740–742.Google Scholar
  33. Hoffman, M.T.,Todd, S.,Ntshona, Z. andTurner, S.: 1999, Land degradation in South Africa, National Botanical Institute, Kirstenbosch, South Africa.Google Scholar
  34. Holmes, P.M. andCowling, R.M.: 1997a, 'The effects of invasion by Acacia saligna on the guild structure and regeneration capabilities of South African fynbos shrublands', Journal of Applied Ecology 34, 317–332.Google Scholar
  35. Holmes, P.M. andCowling, R.M.: 1997b, 'Diversity, composition and guild structure relationships between soil-stored seed banks and mature vegetation in alien plant-invaded South African fynbos shrublands', Plant Ecology 133, 107–122.Google Scholar
  36. Hosking, S.G. andDu Preez, M.: 1999, 'A cost-benefit analysis of removing alien trees in the Tsitsikamma mountain catchment', South African Journal of Science 95, 442–448.Google Scholar
  37. Johannesmeier, M.F.: 1985, Beeplants of the South-Western Cape. Department of Agriculture, Pretoria, 59 pp.Google Scholar
  38. Johns, M.: 1993, 'Are all trees green? The spotlight on forestry', Africa Environment andWildlife 1(3), 77–85.Google Scholar
  39. Kaiser, J.: 1999, 'Stemming the tide of invasive species', Science 285, 1836–1841.Google Scholar
  40. Knight, R.S. andMacdonald, I.A.W.: 1991, 'Acacias and korhaans: an artificially assembled seed dispersal system', South African Journal of Botany 57, 220–225.Google Scholar
  41. Kruger, F.J.,Reid, P.,Mayet, M.,Alberts, W.,Goldammer, G.J. andTolhurst, K.: 2000, A review of the veld fires in theWestern Cape during 15 to 25 January 2000, Department ofWater Affairs and Forestry, Pretoria.Google Scholar
  42. Le Maitre, D.C.,Versfeld, D.B. andChapman, R.A.: 2000, 'The impact of invading alien plants on surface water resources in South Africa: A preliminary assessment', Water SA 26, 397–408.Google Scholar
  43. Le Maitre, D.C.,van Wilgen, B.W.,Chapman, R.A. andMcKelly, D.H.: 1996, 'Invasive plants and water resources in the western Cape Province, South Africa: modelling the consequences of a lack of management', Journal of Applied Ecology 33, 161–172.Google Scholar
  44. Le Maitre, D.C., vanWilgen, B.W., Gelderblom, C.M., Bailey, C., Chapman, R.A. and Nel, J.: 'Invasive alien trees and water resources in South Africa: Case studies of the costs and benefits of management', Forest Ecology and Management, (in press).Google Scholar
  45. Low, A.B. andRebelo, A.G.: 1996, Vegetation of South Africa, Lesotho and Swaziland. Department of Environmental Affairs and Tourism, Pretoria.Google Scholar
  46. Macdonald, I.A.W.: 1983, 'Alien trees, shrubs and creepers invading indigenous vegetation in the Hluhluwe-Umfolozi Game Reserve Complex in Natal', Bothalia 14, 949–959.Google Scholar
  47. Macdonald, I.A.W.: 1986, 'Range expansion in the Pied Barbet and the spread of alien tree species in southern Africa', Ostrich 57, 75–94.Google Scholar
  48. Macdonald, I.A.W.,Kruger, F.J. andFerrar, A.A.: 1986, The ecology and management of biological invasions in southern Africa, Cape Town, Oxford University Press.Google Scholar
  49. Marais, C.: 1998, An economic evaluation of invasive alien plant control programmes in the mountain catchment areas of theWestern Cape Province, South Africa, Ph.D. dissertation, University of Stellenbosch.Google Scholar
  50. Milton, S.J.: 1981, 'Litterfall of the exotic Acacias in the South Western Cape', Journal of South African Botany 47, 147–155.Google Scholar
  51. Milton, S.J., andSiefried, W.R.: 1981, 'Above-ground biomass of Australian Acacias in the Southern Cape, South Africa', Journal of South African Botany 47, 701–716.Google Scholar
  52. Milton, S.J.,Zimmermann, H.G. andHoffmann, J.H.: 1999, 'Alien plant invaders of the karoo: attributes, impacts and control, in W.R.J. Dean andS.J. Milton (eds.), The karoo-Ecological patterns and process, Cambridge, Cambridge University Press, pp. 274–287.Google Scholar
  53. Musil, C.F.: 1993, 'Effect of invasive Australian acacias on the regeneration, growth and nutrient chemistry of South African lowland fynbos', Journal of Applied Ecology 30, 361–372.Google Scholar
  54. Musil, C.F. andMidgley, G.F.: 1990, 'The relative impact of invasive Australian acacias, fire and season on the soil chemical status of a sand plain lowland fynbos community', South African Journal of Botany 56, 419–427.Google Scholar
  55. Oatley, T.B.: 1984, 'Exploitation of a new niche by the Rameron Pigeon Columba arquatrix in Natal', Proceedings of the Fifth Pan-African Ornithological Congress, Johannesburg, Southern African Ornithological Society, pp. 323–330.Google Scholar
  56. Olckers, T. andHill, M.P.: 1999, 'Biological control of weeds in South Africa (1990–1998)', African Entomology, Memoir No. 1. Google Scholar
  57. Parker, I.M.,Simberloff, D.,Lonsdale, W.M.,Goodell, K.,Wonham, M.,Kareiva, P.M.,Williamson, M.H.,Von Holle, B.,Moyle, P.B.,Byers, J.E. andGoldwasser, L.: 1999, 'Impact: toward a framework for understanding the ecological effect of invaders', Biological Invasions 1, 3–19.Google Scholar
  58. Pieterse, P.J. andBoucher, C.: 1997, 'A.C.A.C.I.A. (A Case Against Controlling Introduced Acacias)-19 years late r', South African Forestry Journal 180, 37–44.Google Scholar
  59. Prinsloo, F.W. andScott, D.F.: 1999, 'Streamflow responses to the clearing of alien trees from riparian zones at three sites in the Western Cape', South African Forestry Journal 185, 1–7.Google Scholar
  60. Richardson, D.M.: 1998, 'Forestry trees as invasive aliens', Conservation Biology 12, 18–26.Google Scholar
  61. Richardson, D.M. andVanWilgen, B.W.: 1986, 'The effects of fire in felled Hakea sericea and natural fynbos and implications for weed control in mountain catchments', South African Forestry Journal 139, 4–14.Google Scholar
  62. Richardson, D.M.,Macdonald, I.A.W.,Holmes, P.M. andCowling, R.M.: 1992, 'Plant and animal invasions', in R.M. Cowling (ed.), The ecology of fynbos, Cape Town, Oxford University Press, pp. 271–308.Google Scholar
  63. Richardson, D.M.,Macdonald, I.A.W.,Hoffmann, J.H. andHenderson, L.: 1997, 'Alien plant invasions', in R.M Cowling,D.M. Richardson, andS.M. Pierce (eds.), Vegetation of Southern Africa, Cambridge, Cambridge University Press, pp. 534–570.Google Scholar
  64. Richardson, D.M., Cambray, J.A.,Chapman, R.A.,Dean, W.R.J.,Griffiths, C.L.,Le Maitre, D.C.,Newton, D.J. andWinstanley, T.: 'Vectors and pathways of biological invasions in South Africa-Past, future and present', in G. Ruiz andJ. Carlton (eds.), Pathways of invasions: strategies for management across space and time, Washington, D.C., Island Press, (in press).Google Scholar
  65. Samways, M.J.,Caldwell, P.M. andOsborn, R.: 1996, 'Ground-living invertebrate assemblages in native, planted and invasive vegetation in South Africa', Agriculture, Ecosystems and Environment 59, 19–32.Google Scholar
  66. Scott, D.F.: 1999, Report on an inspection of the burn site between Fish Hoek and Glencairn, Monday 10 May, 1999, Ad hoc report prepared for Gibb Africa, Cape Town.Google Scholar
  67. Scott, D.F.,Prinsloo, F.W., andLe Maitre, D.C.: 2000, The role of invasive alien vegetation in the Cape Peninsula fires of January 2000, Report ENV-S-C 2000–039, Division of Water, Environment and Forestry Technology, CSIR, Stellenbosch.Google Scholar
  68. Seydack A.H.W.: 1992, 'Fire management options in fynbos mountain catchment areas', South African Forestry Journal 161, 53–58.Google Scholar
  69. Steenkamp, H.E. andChown, S.L.: 1996, 'Influence of dense stands of an exotic tree, Prosopis glandulosa, Benson, on a savanna dung beetle (Coleoptera: Scarabaeinae) assemblage in southern Africa', Biological Conservation 78, 305–311.Google Scholar
  70. Stirton, C.M.: 1978, 'Plant invaders, beautiful but dangerous', Cape Provincial Administration, Cape Town.Google Scholar
  71. Stirton, C.H.: 1981, 'Notes on the taxonomy of Rubus in southern Africa'. Bothalia 13, 331–332.Google Scholar
  72. Stock, W.D. andAllsopp, N.: 1992, 'Functional perspectives of ecosystems', in R.M. Cowling (ed.), The ecology of fynbos; Nutrients, Fire and Diversity. Cape Town, Oxford University Press, pp. 241–259.Google Scholar
  73. Stubbings, J.A.: 1977, 'Acase against controlling introduced Acacias (A.C.A.C.I.A.)', South African Forestry Journal 102, 8–14.Google Scholar
  74. Turpie, J. andHeydenrych, B.: 2000, 'Economic consequences of alien infestation of the Cape Floral Kingdom's Fynbos vegetation', in C. Perrins,M. Williamson andS. Dalmazzone (eds.), The economics of biological invasions, Cheltenham, Edward Elgar, pp. 152–182.Google Scholar
  75. Van Wilgen, B.W. andRichardson, D.M.: 1985, 'The effects of alien shrub invasions on vegetation structure and fire behaviour in South African fynbos shrublands: A simulation study', Journal of Applied Ecology 22, 955–966.Google Scholar
  76. Van Wilgen, B.W.,Bond, W.J. andRichardson, D.M.: 1992, 'Ecosystem Management' in R.M. Cowling, (ed.), The Ecology of Fynbos; Nutrients, Fire and Diversity. Cape Town, Oxford University Press, pp. 345–371.Google Scholar
  77. Van Wilgen, B.W.,Cowling, R.M. andBurgers, C.J.: 1996, 'Valuation of ecosystem services-A case study from South African fynbos ecosystems', Bioscience 46, 184–189.Google Scholar
  78. Van Wilgen, B.W.,Little, P.R.,Chapman, R.A.,Gorgens, A.H.M.,Willems, T. andMarais, C.: 1997, 'The sustainable development of water resources: History, financial costs, and benefits of alien plant control programmes', South African Journal of Science 93, 404–411.Google Scholar
  79. Van Wilgen, B.W.,Le Maitre, D.C. andCowling, R.M.: 1998, 'Ecosystem services, efficiency, sustainability and equity: South Africa's Working for Water Programme', Trends in Ecology and Evolution 13, 378.Google Scholar
  80. Van Wilgen, B.W. andvan Wyk, E.: 1999, 'Invading alien plants in South Africa: Impacts and solutions', in D. Eldridge andD. Freudenberger (eds.), People and rangelands: Building the future, Proceedings of the VI International Rangeland Congress, Townsville, Australia, pp. 566–571.Google Scholar
  81. Van Wilgen, B.W.,van der Heyden, F.,Zimmermann, H.G.,Magadlela, D. andWillems, T.: 2000, 'Big returns from small organisms: developing a strategy for the biological control of invasive alien plants in South Africa', South African Journal of Science 96, 148–152.Google Scholar
  82. Versfeld, D.B.,Le Maitre, D.C. andChapman, R.A.: 1998, Alien Invading Plants and Water Resources in South Africa: A preliminary assessment, Report TT99/98, Water Research Commission, Pretoria.Google Scholar
  83. Yelenik, S.: 2000, Ecosystem-level feedbacks of N-fixing invasive aliens in lowland fynbos, M.Sc. dissertation, University of Cape Town.Google Scholar
  84. Whiteford, A. andMcgrath, M.: 1994, Distribution Of Income In South Africa, Human Sciences Research Council, Pretoria.Google Scholar
  85. Witkowski, E.T.F.: 1991, 'Effects of invasive alien Acacias on nutrient cycling in the coastal lowlands of the Cape Fynbos', Journal of Applied Ecology 28, 1–15.Google Scholar

Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • B.W. van Wilgen
    • 1
  • D.M. Richardson
    • 2
  • D.C. Le Maitre
    • 3
  • C. Marais
    • 4
  • D. Magadlela
    • 4
  1. 1.CSIR Division of WaterEnvironment and Forestry TechnologyStellenboschSouth Africa
  2. 2.Institute for Plant Conservation, Department of BotanyUniversity of Cape TownRondeboschSouth Africa
  3. 3.CSIR Division of WaterEnvironment and Forestry TechnologyStellenboschSouth Africa
  4. 4.Working for Water ProgrammeCape TownSouth Africa

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