Abstract
Risk assessment tools for non-native species can avert ecological and economic harm when they inform regulatory or voluntary management actions that seek to reduce the probability of introducing high-risk species. The Laurentian Great Lakes region contains many aquatic invasive plants, non-native species whose introduction causes economic or environmental harm or harm to human health. Additionally, new species continue to arrive, including through trade (e.g., aquarium, water garden). Currently, each Great Lakes jurisdiction manages a separate risk assessment program, leading to a regional situation with diverse assessment methods and large discrepancies in assessed and regulated species. Because the Great Lakes ecosystem crosses state and national borders, each jurisdiction will be best protected when all jurisdictions prevent the import of potentially harmful species. We have modified an existing risk assessment tool for use across the Great Lakes Basin to assess the invasion risks posed by aquatic plants. The tool comprises 38 questions, with points associated with each response that are summed to give a total score. We assessed all known established aquatic plant species in the Great Lakes (n=40) and found this score to be positively correlated with invasiveness, allowing thresholds to be identified that distinguish between invasive and non-invasive species with 84% to 90% accuracy. Assessing species proposed for introduction with this tool, and using these thresholds to determine acceptable risk, could reduce the number of future invasions. If widely adopted, this risk assessment tool would enable a common suite of species to be regulated and thus a more effective approach to reducing the risk of future invasions. Regional risk assessment approaches should reduce the threat of invasive species where environmental and climate conditions are relatively consistent across jurisdictional boundaries.
Highlights
The occurrence of problematic pest organisms is an increasing global phenomenon, adversely affecting a range of ecological and socio-economic values in terrestrial and aquatic environments (Ruiz et al 1997)
Most approaches to marine pest control rely on diver removal and physical or chemical treatments (Hewitt et al 2005), which may have limited efficacy, or are labour-intensive and impractical to apply at broad spatial scales (Piola et al 2009)
A recent study showed that high density inoculation of sea anemones prevented the settlement and accumulation of problematic biofouling, with space pre-emption considered one of the key controlling mechanisms (Atalah et al 2013a)
Summary
The occurrence of problematic pest organisms is an increasing global phenomenon, adversely affecting a range of ecological and socio-economic values in terrestrial and aquatic environments (Ruiz et al 1997). Human activities such as vessel movements, aquaculture, and fishing represent significant pathways for the spread and introduction of pests into new areas, with invasion rates being recorded at unprecedented levels (Mack et al 2000). Marine artificial structures, such as marinas, wharfs, ports and marine farms provide extensive novel habitats that enable many sessile organisms to proliferate, and provide stepping-stones for the spread of many pests (Ruiz et al 2009). There is a need for costefficient and acceptable alternatives
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