Biological control and biomass valorization of an invasive aquatic plant: Insights and practices from stakeholders managing the species in Portugal

Water hyacinth ( Pontederia crassipes ) is one of the most problematic aquatic invasive species in the world, including in Portugal. It causes significant ecological and economic impacts requiring measures to manage it and mitigate damage to water bodies. The BioComp_3.0 project aims to enhance the effective management of the species by aligning with circular economy principles and promoting sustainable solutions. It focuses on mitigating the impacts of massive biomass accumulation through composting, making it suitable for use in farming. This study analyses the perceptions and management practices of entities responsible for controlling water hyacinth, with a focus on monitoring, biological control, and biomass valorisation. Through a survey targeting management entities, we identified key challenges, including gaps in data collection, a limited understanding of biological control, and concerns about the risks associated with composting water hyacinth biomass. Over 60% of respondents confirmed the presence of the species in their intervention areas, yet many were unable to quantify its spread. Most entities rely on mechanical and manual removal methods, while lacking awareness and revealing uncertainty about effectiveness of biological control. Biomass composting is seen as a potential solution but concerns about species dispersal and economic dependency exist. Despite these challenges, 42.3% of entities are interested in joining a collaborative management network, suggesting opportunities for the crucial coordinated actions that is needed. The study highlights the need for integrated management strategies, including improved monitoring technologies, awareness campaigns on biological control, and strict protocols for biomass valorisation in order to promote responsible and scientifically informed management practices.