Global hot spots of biological invasions: evaluating options for ballast–water management

John M. Drake, David M. Lodge

Abstract

Biological invasions from ballast water are a severe environmental threat and exceedingly costly to society. We identify global hot spots of invasion based on worldwide patterns of ship traffic. We then estimate the rate of port–to–port invasion using gravity models for spatial interactions, and we identify bottlenecks to the regional exchange of species using the Ford–Fulkerson algorithm for network flows. Finally, using stochastic simulations of different strategies for controlling ballast–water introductions, we find that reducing the per–ship–visit chance of causing invasion is more effective in reducing the rate of biotic homogenization than eliminating key ports that are the epicentres for global spread.