Bridging boundaries: Six years of community engagement with biological control implementation and monitoring of water hyacinth on Hartbeespoort Dam, South Africa

Water hyacinth has been present on Hartbeespoort Dam since the 1960s. Historical weed management consisted of herbicide and mechanical/manual removal. However, due to funding constraints, biological control was implemented as a cost-effective and environmentally friendly alternative. The impoundment receives excessive phosphorus and nitrogen due to its location downstream from densely populated cities, which includes one of the capital cities of South Africa, Pretoria. Considering that Hartbeespoort Dam is in a temperate region, with cool winters, we embarked on an augmentative biological control approach. To increase our biological control efforts, we had to bridge the research-implementation gap. We fostered a community of practice, by creating a space for the affected community to actively participate in the programme. This would give us the opportunity to share scientific knowledge to affected stakeholders, gauge the public perception, and align potential goals. Social media, in-person meetings and training sessions were used to engage with the public. To increase the availability of the water hyacinth biological control agent, Megamelus scutellaris, community members (i.e. private stakeholders) were offered the opportunity to manage satellite rearing stations. Between 2018 and 2023, nearly half a million Megamelus scutellaris individuals, sourced from both the Centre for Biological Control’s mass-rearing facility and satellite rearing stations around Hartbeespoort Dam, have been released into the dam. Water hyacinth cover on the dam drastically declined every year following a build-up of Megamelus scutellaris. Over the course of the programme, private stakeholders that were actively involved grew from two (2018) to 16 (2023). Analysing the participation of private stakeholders using a framework that looks at the level of value gained from our interactions, two partners reached a value chain phase that led to an expansion of biological control implementation. Longer-term private stakeholders generated increased interest for biological control implementation in their community, which resulted in recruitment of new private stakeholders. We also evaluated the knowledge of the affected community in 2023 through an online questionnaire. Out of 132 respondents, 51 % had knowledge of what biological control entails, with 56 % acknowledging that biological control has had a positive impact on the management of water hyacinth. Bridging the research-implementation boundary has strengthened biological control efforts, enabling a more sustainable approach to the management of water hyacinth on Hartbeespoort Dam. However, continued community engagement is necessary to increase the public’s knowledge about the practice of biological control.