Marine bioinvasion in the network of global shipping connections
Transportation networks play a crucial role in human mobility, the exchange of goods, and the spread of invasive species. Here, we use information about the itineraries of 29,493 cargo ships during the year 2007 to construct a network of shipping connections between ports worldwide. We combine the shipping network with port environmental conditions and biogeography to develop a model for marine bioinvasion. The model allows to identify high risk invasion routes, hot spots of bioinvasion, and major source regions from which bioinvasion is likely to occur. Using the model, we classify coastal ecoregions according to their total invasion risk and the diversity of their invasion sources. Our model predictions agree with observations in the field and reveal a pattern of maximal invasion risk at intermediate geographic distances. Our findings suggest that network-based invasion models faciliate the development of targeted mitigation strategies.