Economic evaluation of chemical and biological control methods on four aquatic weeds in South Africa

Maluleke, Mary

Title: Economic evaluation of chemical and biological control methods on four aquatic weeds in South Africa
Creator: Maluleke, Mary
ThesisAdvisor: Fraser, G (Gavin)
ThesisAdvisor: Hill, M P
Subject: Invasive plants -- Biological control -- Economic aspects -- South Africa
Subject: Introduced organisms -- Biological control -- Economic aspects -- South Africa
Subject: Aquatic weeds -- Biological control -- Economic aspects -- South Africa
Subject: Aquatic weeds -- Control -- Economic aspects -- South Africa
Subject: Aquatic resources -- Management
Subject: Cost effectiveness
Subject: Net present value
Subject: Herbicides -- Cost effectiveness
Subject: Working for Water Programme
Subject: Water conservation -- South Africa
Date: 2020
Type: Thesis
Type: Masters
Type: MCom
Identifier: http://hdl.handle.net/10962/145953
Identifier: vital:38481
Description: Invasive alien plants (IAPs) of various kinds pose a threat to ecosystems, biodiversity, conservation and overall economy. In a world experiencing exponential increase in IAPs – this issue has become endemic, especially for developing countries such as South Africa. South Africa is a water scarce country and IAPs increase water stress. Thus, South Africa must invest in a more realistic, environmentally and economically inclusive policy outlook on the management of IAPs including aquatic weeds. This is especially urgent when considering the changing global climate, which is predicted to further reduce the quantity and quality of potable water. The Working for Water Programme (WfW) in South Africa aimed at addressing the issue of IAPs in a way that protects the environment as well as produces maximum return to society through poverty alleviation. As such, the aquatic weeds management strategy put in place for four of South Africa’s aquatic weeds Pista stratiotes, Salvinia molesta, Azolla filiculoides and Myriophyllum aquaticum - should be one that is cost-effective, efficient and sustainable; yielding the best possible return on investment. Since these four weeds are already under complete biological control, in the absence of biological agents, the WfW programme would have used herbicides to control these weeds. As such, this thesis conducted a retrospective analysis of the relative herbicide cost-saving associated with the use of biological control. To do this, due to existing limitations, E. crassipes was used as a surrogate weed and its herbicide control costs were used as proxy for the herbicide control cost estimates of the four selected weeds; with reasonable conversion factors applied to cater for the biological difference of the five weeds. Using the cost benefit analysis (CBA) framework, the net present cost (NPC) of each control method was calculated to which the relative cost-saving was considered to represent the avoided cost of using biological control instead of chemical control on these weeds. The avoided cost was used as the main benefit component when deriving the relative benefit cost ratios (BCR). Two scenarios were used, one assuming no follow-up requirement and the other assuming one follow-up requirement for chemical control. Using an 8% discount rate, the study found that the estimated cost of the biological control method on all four aquatic weeds was about R7,843,205 while for chemical control the estimated costs would have costed R149,580,142, R268,264,838 and R881,711,738 for application by means of a boat, bakkie and knapsack. Chemical control cost estimates would have increased to about R164,538,052, R295,216,120 and R1,008,761,000 for boat, bakkie and knapsack approach respectively when including a possible follow-up programme. These would have led to positive BCRs of 90.24:1, 164.97:1 and 557.99:1 across the three chemical control approaches without a follow-up (with BCR of about 99.67:1, 182.00:1 and 631.56:1 for the boat, bakkie and knapsack approach respectively with the accepted follow-up programme). When running a sensitivity test with varying discount rates of 5% and 10%, these results remained robust. As such, failing to reject the dominant hypothesis in literature, the main conclusion of the study is that biological control is indeed the more cost-effective management option compared to chemical control with respect to herbicide cost-saving. Further, biological control is most-likely to produce more environmental cost-saving and water-saving over chemical control. The study recommends the continued use of the biological control investment on the four aquatic weeds under study as well as on emerging aquatic weeds such as Iris pseudacorus, Nymphaea mexicana and Sagittaria platyphylla in South Africa.
Format: 155 pages, pdf
Publisher: Rhodes University, Faculty of Commerce, Economics and Economic History
Language: English
Rights: Maluleke, Mary

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