It is customary to imagine that alien invaders will arrive from space, but Jamaica is at serious risk of an incursion of alien invaders from the sea.

Shipping is vital to Jamaica's economic sustainability as an island state with more than 90 per cent of all commodities imported and exported from the country arriving by sea. Each year, approximately 4,000 calls are made to various seaports in Jamaica where bulk cargo and containerised goods are loaded or discharged. These ships also carry tons of ballast water which may contain unwanted stowaways in the form of harmful aquatic species and pathogens.

Ballast water is used to control the stability of a ship to ensure its safe operation when it is empty or partially loaded. Prior to the construction of steel ships, wooden ships were used to carry cargo and stones and other debris were used as ballast. The Harbours Act, 1874 reflected this practice by making the removal of stones from Kingston Harbour a criminal offence. Seawater has replaced stones as the source of ballast and currently three to four billion tons of ballast water are being transferred each year.

When a ship arrives at a port to load cargo, it is not unlikely that it would have discharged its ballast water just prior to entering the port. This ballast water may contain invasive aquatic species which would have been pumped into the ship's tank at the last port of call and transferred to the waters at the port of loading during the deballasting operations.

In the United States, US$5 billion is spent annually to control the damage caused by the Zebra Mussel in the Great Lakes while the American Comb Jellyfish has caused the collapse of the fishing industry in Iran.

Poisoning

Invasive aquatic species have also been known to cause shellfish poisoning and death in humans. Of note, the non-native Asian Green Mussel has been identified in Kingston Harbour where it was found to compete with native sedentary species for food and space, especially on wharf pilings, seagrass beds and mangrove prop roots.

The International Maritime Organisation (IMO), the United Nations agency tasked with the regulation of safe and environ-mentally sustainable shipping, has responded to the threat posed by invasive aquatic species carried in ballast water. In 2004, the IMO adopted the international convention for the control and management of ships' ballast water and sediments (BWM convention). The BWM convention provides for a number of measures to be taken by flag states and coastal states alike and Jamaica is currently taking steps to facilitate its accession to the convention.

The Maritime Authority, which administers the Jamaica Ship Registry, is taking steps to ensure that internationally trading Jamaican ships will be in compliance with the BWM convention and is preparing the drafting instructions for legislation to incorporate the provisions of the convention into Jamaican law.

A multi-agency Ballast Water Management National Task Force has been established to address Jamaica's coastal state rights and obligations under the convention, and the task force will guide the implementation of the convention when it comes into force for Jamaica.

Betrand Smith is director of legal affairs at the Maritime Authority of Jamaica. He is also a member of the International Biodiversity Day Committee.