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

Abstract

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, such as nuisance biting and pathogen transmission. Understanding the ecological consequences of wetland management practices is vital to maximize the conservation value of urban wetlands without negatively impacting public health; however, management practices are often untested. 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, the plague minnow Gambusia holbrooki, and then refilled to provide breeding habitat for a threatened frog, the green and golden bell 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. 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. Synthesis and applications. While conserving threatened habitats and species is vitally important, our results highlight how wetland management practices can unintentionally impact non‐target species, and potentially public health. As constructed urban wetlands become more common, so too does the need for routine maintenance and management of threatened and invasive species. It is essential that future design and management of urban wetlands considers the impact mosquitoes might have on humans. Pre‐emptive action to control geographically relevant vectors of mosquito‐borne pathogens and nuisance biting species would reduce human exposure to mosquitoes and associated negative impacts, and increase positive conservation outcomes associated with urban wetlands.

Little pig, little pig, let me come in: The influence of landscape structure and La Niña climatic anomalies on the emergence of Japanese encephalitis virus in Australian piggeries in 2022

“…Importantly, the greatest risk was not associated with pristine riparian systems, but rather with riparian systems that share landscapes with agricultural land, thus highlighting the importance of habitat fragmentation and emergent anthropogenic ecotones to risk. There may be a suppressive influence on mosquito abundance in areas of higher diversity of potential mosquito predators, which are likely to be greater in less disturbed landscapes[65,66]. As expected, landscape patches receiving more upland surface water accumulation were at higher risk of JEV outbreaks, which fits with the findings of riparian proximity since these systems generally receive the highest surges of runoff following rainfall and indicates that landscapes prone to flooding may require enhanced monitoring for JEV to improve current surveillance systems.…”

Nature’s disvalues: what are they and why do they matter?

“…detriments associated with the preservation of wetlands, such as providing breeding grounds for diseasespreading mosquitoes [22] (i.e. instrumental disvalue) or infringing upon local communities' relationships to landscapes that are meaningful for them or constitutive of their individual and collective identity [14] (i.e.…”

Vegetation structure drives mosquito community composition in UK’s largest managed lowland wetland

“…Within the UK, for example, government policies and payment schemes to landowners encourage the creation, restoration and management of existing wetlands to increase biodiversity and foster local and regional flood resilience programs [ 22 – 24 ]. Water is a requirement for mosquito breeding, and thus there is an urgent need to understand how policy-driven changes in wetlands impact mosquito communities, as well as their interactions with animal and human hosts, and how this trades off with disease transmission risk [ 21 , 38 , 49 , 51 ].…”

“…Altering wetland water levels during the mosquito breeding seasons, including complete drying of water bodies, can lead to desiccation of mosquito larvae and prove an adequate control method, but these strategies can negatively impact other aquatic flora and fauna of wetlands [ 67 ]. In Australia, draining and re-filling of urban wetlands to manage an invasive fish species led to increased abundance of mosquito species compared with undrained urban wetlands [ 38 ]. In some contexts, integrated management for biodiversity and reduced public health risks and nuisance biting from mosquitoes has been possible.…”