ABSTRACT

Invasive alien plants (IAPs) pose a threat to biodiversity and the economy of the countries they invade. In South Africa, the Department of Environment, Forestry and Fisheries, Natural Resources Management Programmes, previously The Working for Water Programme (WfW) is tasked with controlling IAPs in a way that protects the environment, as well as producing maximum return to society through poverty alleviation. Biological control is one of the management tools used to control IAPs in South Africa. Four aquatic weeds, Pista stratiotes, Salvinia molesta, Azolla filiculoides and Myriophyllum aquaticum, are under complete biological control in South Africa. However, in the absence of biological agents, the WfW programme would have used herbicides to control these weeds. This paper presents a retrospective analysis of the relative herbicide cost-saving associated with the use of biological control instead of chemical control. The study used cost benefit analysis (CBA) framework with an 8% discount rate. The estimated cost of the biological control on all four aquatic weeds was about R7.8 million, while the estimated cost of chemical control to achieve the same level of control varied between R150 million and R1 billion, depending on the method of application and number of follow up operations. Benefit to cost ratios varied between 90:1 and 631:1, again depending on method of application and number of follow up sprays. The results remained robust under a 5% and 10% sensitivity test and show that biological control is the most cost-effective management option for aquatic weeds in South Africa.

摘要

外来入侵植物 (IAP) 对其入侵的国家的生物多样性和经济构成威胁。在南非，环境、林业和渔业部自然资源管理计划，以前的水计划 (WfW) 的任务是以保护环境的方式控制 IAP，并通过贫困产生最大的社会回报缓解。生物控制是南非用于控制 IAP 的管理工具之一。四种水草、Pista striotes、Salviniamoleta、Azolla filiculoides和Myriophyllum Aquaticum，在南非受到完全生物控制。然而，在没有生物制剂的情况下，WfW 计划会使用除草剂来控制这些杂草。本文介绍了与使用生物防治代替化学防治相关的相对除草剂成本节约的回顾性分析。该研究使用成本效益分析 (CBA) 框架，贴现率为 8%。对所有四种水草进行生物防治的估计成本约为 780 万兰特，而达到相同防治水平的化学防治估计成本在 1.5 亿兰特到 10 亿兰特之间，具体取决于施用方法和数量。跟进操作。效益成本比在 90:1 和 631:1 之间变化，同样取决于应用方法和后续喷雾次数。