Projected effects of the Panama Canal expansion on shipping traffic and biological invasions

AimThe Panama Canal expansion, scheduled for completion in 2015, is expected to have major effects on commercial shipping and port operations throughout the world, with potential consequences for the transfer and establishment of non-indigenous species that remain largely unexplored. We developed a series of scenario-based models to examine how shipping traffic patterns may change after expansion and consider possible implications for species transfers and invasion dynamics in the USA. LocationCoastal USA, excluding Alaska and Hawaii MethodsUsing a Monte Carlo simulation approach, we predicted changes in discharged ballast water, wetted surface area of ship hulls and frequency of ship arrivals modelled under scenarios that are based on (1) current shipping patterns from the western Pacific Rim to the USA, (2) estimates of fleet expansion and (3) diversion of traffic away from the US West Coast through the Panama Canal. ResultsDuring the 5-year period following canal expansion (2015-2019), our models estimated that the Gulf and East coasts would receive 78% and 99% median increases in total ballast discharge and 172% and 182% increases in total wetted surface area, respectively. For the West Coast, our models estimated 9.6% median decreases in both total ballast discharge and wetted surface area. We further predict that many ports in the Gulf and East coasts will receive up to three times the current number of arrivals and increased ballast water discharge, from this region after expansion. Main conclusionsOur scenario-based analysis provides a first estimate for increases in frequency, magnitude and spatial distribution of exposure that the Gulf and East coasts will experience due to ships and ballast arriving from the western Pacific, following the canal expansion. If organisms transported via ballast water or ship hulls are able to survive transit of the canal, the predictions suggest increased likelihood of introduction along these coasts by species originating in the western Pacific.