Management of urban wetlands for conservation can reduce aquatic biodiversity and increase mosquito risk

1. Global wetland loss means constructed urban wetlands are an increasingly valuable resource for conservation. However, priorities for managing urban wetlands for conservation are often seen to conflict with management to reduce potential mosquito risks. Understanding the ecological and public health consequences of wetland management practices is vital to maximise the conservation value of urban wetlands without negatively impacting public health, however are often untested. 2. We conducted a landscape-scale experiment to test the ecological impacts of an existing urban wetland management regime, in which a group of urban wetlands are drained annually to reduce the abundance of an invasive fish Gambusia holbrooki, and then refilled to provide breeding habitat for a threatened frog Litoria aurea. We collected and compared aquatic macroinvertebrates and mosquito larvae from these refilled wetlands, and adjacent undrained wetlands, as well as sampling adult mosquito populations on four occasions across summer and autumn. 3. Wetland draining had a significant effect on aquatic macroinvertebrates and larval mosquitoes. Twice as many macroinvertebrates were collected from drained wetlands compared to undrained wetlands, and almost all mosquito larvae were collected from drained wetlands. Differences in macroinvertebrate assemblages and larval mosquitoes at drained and undrained wetlands decreased over time, but total macroinvertebrate abundance and taxa richness did not. Draining did not affect adult mosquito assemblages. 4. Synthesis and applications. While conserving threatened habitats and species is imperative, our results highlight how wetland management practices can have unintended consequences for non-target species, with potentially negative effects on humans. As constructed urban wetlands become more common, so too does the need for both routine maintenance and management of threatened and invasive species. It is vital that future design and management of urban wetlands considers the impact mosquitoes might have on humans. Pre-emptive, targeted action for control of geographically-relevant nuisance-biting species or vectors of mosquito-borne pathogens would reduce negative impacts on public health and increase positive conservation outcomes associated with urban wetlands.07-Jan-2020Funding provided by: Holsworth Wildlife Research EndowmentCrossref Funder Registry ID: http://dx.doi.org/10.13039/100008190Award Number