Ballast water woes

Forest and Bird, Issue 267, 1 February 1993, Page 3

Ballast water woes

NEW ZEALAND’S problems with introduced plants and animals does not end at the shoreline. Like other countries with a highly endemic flora and fauna, New Zealand’s waters are particularly at risk from the introduction of exotic marine organisms. The ballast tanks of international cargo ships are mobile aquaria, transporting organisms across the seas to be discharged in visiting ports. Unlike the problems of more visible marine environmental calamities such as oil spills, the problems of pests introduced through ballast water discharge are chronic, cumulative and irreversible. The introduced organisms have the potential to wipe out marine life, destroy shellfish industries and threaten human health. As a net exporter of bulk cargoes, this country is also a leading importer of ballast water from around the world. Since 1975 over ten new species of exotic organisms have been found in our coastal waters. These include seaweeds, crustaceans and molluscs and it is likely that most of them were introduced via ballast water. Some, including the large seaweed Undaria pinnatifida introduced from Japan, are succeeding well in

disturbed environments and may displace the natural marine flora. There are likely to be many more we don’t know about. ‘Last year MAF instituted a system of voluntary controls on overseas ballast discharge. Vessels which need to discharge ballast in New Zealand waters are now asked to exchange their initial water at sea. This is thought to remove about 90 percent of stowaway organisms. A survey over six months of 792 ships suggested that over 90 percent were complying with the new controls. However some ships’ masters were unable to give a sample of ballast water upon request and others indicated that they would not comply with the controls until they became compulsory. Australia and New Zealand have pressed the International Maritime Organisation to set up international rules on the discharge of ballast water, but to date the IMO has only established a working group to research the issue. Global warming is only likely to make matters worse. Transport by ballast will be an easy way for organisms to "test" their ability to colonise changed environments.