Abstract
Globally, movements of commercial vessels can facilitate the spread of marine non-indigenous species (NIS) beyond their current biogeographic ranges. Authorities at potential destination locations employ a number of biosecurity risk assessment strategies to estimate threat levels from potential origin locations, vulnerability levels of specific destination regions, or the consequences of successful establishment of particular NIS species. Among the many factors and processes that have an influence on the probability that NIS will survive transport and establish successfully at new locations, vessel type has been identified as an important risk factor. Different vessel types have different structural and operational characteristics that affect their overall level of marine biosecurity risk. Several recent studies have examined subsets of vessel types or vessel characteristics for their ability to spread NIS. While high-quality information is available via these endeavors, it is fragmented and not readily available as an integrated resource to support biosecurity regulators or other end-users. In this study, we synthesize available empirical data on a wide range of vessel types and characteristics to develop a framework that allows systematic quantification of the relative risk of NIS transfer by common commercial vessel types. We explain our approach for constructing the framework, from selection of key risk factors for inclusion, to selection of which datasets to use for those risk factors. The framework output is a set of risk scores which denote the relative biosecurity risk of common commercial vessel types. To demonstrate a potential application of our framework, we applied the risk scores to vessel visit data for commercial ports around New Zealand and assigned a relative risk level per port based on the arrival frequencies of different vessel types. The resulting per-port risk levels matched closely with the results of a prior benchmark study that employed state-of-the-art risk modeling approaches. Our framework is based on globally relevant data, is simple to implement, and is adaptable as new empirical information arises. It can serve as a simple tool to determine the relative levels of vessel-related biosecurity risk associated with geographic shipping hubs, or it can be used as a vessel-specific “risk mask” for maritime transport models. It can be applied to any scientific or policy question that requires information on vessel type differences in relation to marine biosecurity risk.
Highlights
Over 90% of global trade is carried out by maritime shipping
To prevent or manage the harmful impacts associated with non-indigenous species (NIS), national and regional authorities at potential destination locations employ a number of biosecurity risk assessment strategies to identify the level of biosecurity threat associated with various global origin locations, identify “hotspot” areas with higher incursion probabilities nationally or regionally, or estimate the likelihood and potential consequences of introduction and establishment of particular NIS (Hewitt and Campbell, 2007; Bradie and Leung, 2015)
Out of 4,802 vessels recorded by the National Ballast Information Clearinghouse (NBIC) database to have visited the United States in 2014, 4,294 were one of the seven vessel types included in both the NBIC database and this study
Summary
Over 90% of global trade is carried out by maritime shipping. As of 2019, the global merchant fleet included 95,402 vessels (mostly tankers, bulk carriers, container and general cargo vessels) with a cargo carrying capacity of 1.97 billion deadweight tons (UNCTAD, 2019).Along with intended cargo, maritime vessels provide a means for coastal marine organisms to move to locations beyond their natural ranges (Ruiz et al, 1997), mainly in either the internal ballast water tanks or as biofouling on the submerged external surfaces of the hull (Molnar et al, 2008; Hewitt et al, 2009). To prevent or manage the harmful impacts associated with NIS, national and regional authorities at potential destination locations employ a number of biosecurity risk assessment strategies to identify the level of biosecurity threat associated with various global origin locations, identify “hotspot” areas with higher incursion probabilities nationally or regionally, or estimate the likelihood and potential consequences of introduction and establishment of particular NIS (Hewitt and Campbell, 2007; Bradie and Leung, 2015). Many factors and processes have an influence on the probability that NIS will survive transport and establish successfully at new locations, including vessel-related factors such as the structural configurations and operational characteristics of the maritime vessels providing transport, voyage-related factors that affect mortality rate during transport from origin to destination due to voyage duration and path (Verling et al, 2005; Zaiko et al, 2020), and environmental similarity between origin and destination (Keller et al, 2011). For the first step of NIS transfer, a number of previous studies, including surveys of expert opinion (Cheng et al, 2019) and analyses of empirical datasets (Kaluza et al, 2010; Clarke et al, 2017), have identified a suite of important vessel-related risk factors, which can be grouped collectively by vessel type
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