Global rise in emerging alien species results from increased accessibility of new source pools

Abstract

Our ability to predict the identity of future invasive alien species is largely based upon knowledge of prior invasion history. Emerging alien species-those never encountered as aliens before-therefore pose a significant challenge to biosecurity interventions worldwide. Understanding their temporal trends, origins, and the drivers of their spread is pivotal to improving prevention and risk assessment tools. Here, we use a database of 45,984 first records of 16,019 established alien species to investigate the temporal dynamics of occurrences of emerging alien species worldwide. Even after many centuries of invasions the rate of emergence of new alien species is still high: One-quarter of first records during 2000-2005 were of species that had not been previously recorded anywhere as alien, though with large variation across taxa. Model results show that the high proportion of emerging alien species cannot be solely explained by increases in well-known drivers such as the amount of imported commodities from historically important source regions. Instead, these dynamics reflect the incorporation of new regions into the pool of potential alien species, likely as a consequence of expanding trade networks and environmental change. This process compensates for the depletion of the historically important source species pool through successive invasions. We estimate that 1-16% of all species on Earth, depending on the taxonomic group, qualify as potential alien species. These results suggest that there remains a high proportion of emerging alien species we have yet to encounter, with future impacts that are difficult to predict.

Invasive plants negatively impact native, but not exotic, animals

“…The consequences of introduced species to ecosystem structure and function are wide‐ranging (Levine et al, ; Strayer, Eviner, Jeschke, & Pace, ; Vilà et al, ) and continue to be an important research topic as the world becomes increasingly invaded (Guénard et al, ). The impact of invasive plants is most commonly expressed as impacts on native plants (e.g., Vila & Weiner, ) and ecological processes (e.g., nutrient cycles, Ehrenfeld, ).…”

Contrasting patterns of naturalized plant richness in the Americas: Numbers are higher in the North but expected to rise sharply in the South

“…These authors arrived at this conclusion by combining data on 60‐year trends of bilateral trade, biodiversity and climate that were used to model the global spread and future dynamics of plant species among 147 countries (Seebens et al, ). This prediction is supported by recent analyses of newly emerging naturalized species numbers over time, which show that global accumulation of naturalized species is set to continue (Seebens et al, ).…”

“…(b) Numbers recorded per year. Based on data from the Alien Species First Records database, which includes information on the first reports of species that have later become naturalized (see Seebens et al, ). Note that the plots show species that were introduced from overseas, that is, have their native ranges outside the Americas.…”

Transport pathways shape the biogeography of alien freshwater fishes in Australia

“…We examine the patterns and processes underlying this recent increase in alien fish establishment and how this has altered the biogeography of alien fishes in Australia. While our research is focused on alien fishes in Australia, recent growth in the number of alien species established in other regions of the world suggests our findings should have relevance for other regions (Capinha et al., ; Hulme, ; Seebens et al., , ).…”