Journal of Global Ecology and Environment

Water hyacinth is simultaneously an invasive ecosystem engineer, a symptom of catchment degradation and a potential source of recoverable biomass. These overlapping roles complicate assessments that equate plant presence with ecological damage or visible clearance with restoration. This critical narrative review examines the mechanisms, context dependence and management implications of water hyacinth invasion across freshwater lakes, reservoirs, wetlands and slow-flowing channels. Targeted scholarly searching and citation tracing identified research published through 31 July 2026, with evidence appraised according to study design, environmental comparability, outcome measurement and duration. The synthesis connects invasion ecology, water quality, biodiversity, human exposure, biological control and biomass processing rather than ranking interventions solely by short-term plant suppression. The most consistent evidence concerns shading, oxygen depletion under extensive persistent mats, obstruction of water-dependent activities and changes in habitat composition. Nutrient concentrations, fish assemblages, disease-transmission potential and greenhouse-gas fluxes show more conditional responses. Contradictory findings frequently reflect differences in hydrological exchange, reference habitat, plant rooting, decomposition and measurement scale. Physical removal can rapidly restore access and export nutrients, but recurrence remains likely where propagules and favourable growth conditions persist. Biological control can provide substantial suppression, including in nutrient-rich reservoirs, although agent establishment, seasonal population recovery and sustained delivery determine performance. Herbicides and microbial products require formulation-specific assessment and cannot be judged safe from plant mortality or basic water chemistry alone. Biomass utilisation offers complementary disposal and resource-recovery pathways, but laboratory yields do not establish commercial viability, contaminant safety or landscape-scale control. A defensible management strategy separates immediate hazard reduction, sustained suppression and ecological recovery, linking each objective to appropriate monitoring. Priorities include replicated long-term intervention studies, whole-system nutrient and greenhouse-gas accounting, independent economic evaluation and participatory assessment of who benefits from control. Durable management depends on matching interventions to ecological processes and institutional capacity rather than treating water hyacinth as either an unqualified menace or an inherently sustainable resource.