Managing alien stowaways.

Ballast water is of crucial importance to the safe operation of ships by reducing hull stress, maintaining stability and improving propulsion and maneuvrability. However, ships' ballast water may also contain alien marine organisms which establish themselves in the host environment, threatening the survival of many native species and creating a public health hazard in surrounding communities. According to the International Maritime Organization (IMO), "the spread of invasive species is now recognized as one of the greatest threats to the ecological and the economic well-being of the planet".

Global recognition of the problem was slow to develop, but eventually led to the 2004 Ballast Water Management Convention (BWMC), which entered into force in 2017. Currently there are 81 BWMC signatory countries comprising over 80percent of the world's...