Predicting the spread of marine species introduced by global shipping

Abstract

The human-mediated translocation of species poses a distinct threat to nature, human health, and economy. Although existing models calculate the invasion probability of any species, frameworks for species-specific forecasts are still missing. Here, we developed a model approach using global ship movements and environmental conditions to simulate the successive global spread of marine alien species that allows predicting the identity of those species likely to arrive next in a given habitat. In a first step, we simulated the historical steppingstone spreading dynamics of 40 marine alien species and compared predicted and observed alien species ranges. With an accuracy of 77%, the model correctly predicted the presence/absence of an alien species in an ecoregion. Spreading dynamics followed a common pattern with an initial invasion of most suitable habitats worldwide and a subsequent spread into neighboring habitats. In a second step, we used the reported distribution of 97 marine algal species with a known invasion history, and six species causing harmful algal blooms, to determine the ecoregions most likely to be invaded next under climate warming. Cluster analysis revealed that species can be classified according to three characteristic spreading profiles: emerging species, high-risk species, and widespread species. For the North Sea, the model predictions could be confirmed because two of the predicted high-risk species have recently invaded the North Sea. This study highlights that even simple models considering only shipping intensities and habitat matches are able to correctly predict the identity of the next invading marine species. alien species | model predictions | species identity | marine ecoregion | climate change T he number of alien species transported by human assistance has increased rapidly during the last decades with serious consequences for native flora and fauna (1-3). These biological invasions are considered to be one of the major drivers of biodiversity changes (4-6). Once an unwanted alien species has naturalized in the new environment, it is nearly impossible to eradicate the species, and thus the mitigation of further introduction is the most efficient way of combating biological invasions (6, 7). However, a targeted monitoring and an efficient adaptive management requires knowledge about spreading dynamics of the next potential invaders and thus about the distribution of species, their invasiveness, and the likelihood of new introductions. Although all of these topics have been analyzed on their own, the potential to predict the spreading of alien species while combining these components remains to be tested.A large amount of recent introductions can be attributed to the intensified global trade and transport as many species were accidentally or deliberately translocated through the exchange of commodities or the movements of transportation means (8, 9). The amount of exchanged commodities and the intensity of global traffic have therefore been found to be a good predictor to model th...

Biological invasions and natural colonisations are different – the need for invasion science

“…The transportation of alien species by human agency across biogeographic barriers that have never historically been crossed before is essentially a daily occurrence now (Seebens et al 2016). No passerine birds of European origin had colonised New Zealand over the tens of millions of years of the archipelago's independent existence, but now there is a thriving assemblage of such species that has developed in New Zealand over the last 150 years thanks to human intervention (Duncan, Blackburn & Cassey 2006).…”

“…Invasions differ from natural colonisation in biogeographical, ecological and anthropogenic dimensions (Rejmánek 2000), and historically too little research has focussed on how species are moved around (Puth and Post 2005). This is changing, and there has been a recent focus on introduction pathways (Essl et al 2015a;Cope et al 2016;Faulkner et al 2016;Ricciardi 2016;Seebens et al 2016). Moreover, species that have arrived in a new region through human-mediated extra-range dispersal or through natural colonisation can, of course, also co-opt the same dispersal pathways once in a region.…”

Aliens on the Move: Transportation Networks and Non-native Species

“…Nevertheless, despite the range of possibilities, the movement of stowaway fauna and flora is poorly documented for terrestrial transportation systems. This is in contrast with aquatic transportation, especially maritime, for which there is a large body of research, particularly regarding the movement of species in ballast waters (Drake and Lodge 2004;Seebens et al 2016). We speculate that overland transportation of biological stowaways is likely to be less frequent than those by aquatic vehicles; however, we also suspect that the lack of studies for the terrestrial counterpart does not reflect the true contribution of this process for non-native species dispersal.…”

Tracking marine alien species by ship movements

“…The researchers note that the largest donor region to the Northeast Pacific is the Northwest Pacific, and that elevated temperatures in the former will create a better environmental match for Asian species from the latter region. Another driver of temporal variation is revealed by the finding that total invasion probability varies with the number of ecoregions occupied such that propagule pressure (spreading opportunity) to unoccupied regions increases as neighboring regions become invaded (7). Therefore, the rate of spread of an emerging species through the shipping network is expected to increase over time until the number of available suitable ecoregions begins to saturate.…”