Ballast water management
Ships taking ballast water on board in one part of the world and discharging it in another may thereby cause ecological harm through the introduction of marine species in a non-native environment where they can prove to be invasive. Problems of this kind were first recognized in the early twentieth century but came to prominence only as they increased in significance with growth in world trade in the 1970s. It has been estimated that in modern times between 3 and 10 billion tonnes of ballast water are transferred globally each year.
The IMO’s work on a mandatory instrument in this field led to the adoption on 13 February 2004 of the International Convention for the Control and Management of Ships’ Ballast Water and Sediments. The BWM Convention provides for its entry into force 12 months after ratification by 30 states, representing at least 35 per cent of the world merchant shipping tonnage, but these conditions have not yet been satisfied and the Convention is therefore not yet in force.