Environmental water management and H5 bird flu in waterbirds: context and scenarios for decision-making

Abstract The impact of animal viruses has dramatically increased over the last decade globally, exemplified by the disruption caused by the recent panzootic of high pathogenicity avian influenza (HPAI) H5N1 clade 2.3.4.4b (H5 bird flu), which has caused the deaths of millions of wild birds and mammals, as well as domestic animals such as poultry. Wild waterbirds play a role in the spread of H5 bird flu and suffer mass mortality from this virus. They are central to virus risk, given they undertake long-distance movements and often aggregate densely to breed, forage and roost. In many regulated river systems, wetlands and waterbirds can be influenced by managed ‘environmental water’, which is used to maintain habitats and support ecological processes such as waterbird breeding. However, the same water management levers that aim to support ecological processes may also influence host and environmental factors that can affect virus transmission and spread. Here, we explore potential virus incursion and outbreak scenarios relevant to decision-making about environmental water, including differences in outbreak location, timing, spread pathways and severity. We describe potential management levers and decisions, ranging from maintaining or increasing planned watering to altering, reducing or ceasing watering where disease risks outweigh ecological benefits. Overall, decision-making must balance ecological objectives, disease mitigation, operational feasibility and risks to threatened species and ecosystems. Improved understanding of relationships between water management, waterbird movements and disease dynamics will be essential to support predictive modelling and guide environmental water management under emerging virus threats.