Thirty years ago, a ship from North America sailed up the Bosphorus channel in Istanbul and dumped ballast water containing comb jellyfish from back home. The invader went crazy, gobbled up huge amounts of plankton and triggered a catastrophic decline in marine life. At one point its biomass reached a billion tonnes. It became known as the blob that ate the black sea.
Around a decade later another ship, discharged ballast water into the coastal waters of Peru, which released a strain of cholera that contaminated shellfish. The shellfish were consumed and the disease spread, killing 12,000 across Latin America.
Cargo ships and tankers need ballast water to avoid capsizing when they are empty. Ships take sea water on board after offloading cargo and discharge the ballast when they take on a new load – often in a port thousands of miles away. These are huge quantities of water, a large ship can carry 60,000 tonnes of ballast. The world’s ballast water contains an estimated 7000 different species in the form of seeds, spores, plankton, bacteria and the eggs and larvae of larger creatures.
According to ecologists alien species are the second biggest threat to the planet’s biodiversity after habitat destruction. The global transport of ballast water is the single biggest cause of marine species spread. That’s how the European zebra mussel got into North America’s Great Lakes, where billions of dollars had to be spent to keep it from blocking irrigation channels and water pipes. That is how the toxic “red tides” spread round the globe, how Chinese mitten crabs reached Europe, how Asian kelp made it to southern Australia, and how Mediterranean mussels came to carpet the coast of South Africa.
Not all alien species cause trouble the majority are harmless. But the risk of a new zebra mussel or comb jellyfish or disease infestation is always present. So why has the problem not yet been tackled?
It is not because the technology is unavailable. More than 20 commercial ballast water treatment systems involving various combinations of filtration, irradiation, ozone, heat, electrolysis and biocides have been certified by the International Maritime Organization. Installing the treatment systems will be costly – up to $500,000 dollars per ship for the biggest vessels. But a study by the WWF suggests that the economic cost of dealing with existing invasive species from ballast water is more than three times the cost of preventing more.
In 2004 the United Nations agreed a treaty that would require ships to install kit to kill off biological stowaways in their ballast water however, 9 years on the treaty has still not been ratified by enough nations to come into force. The Ballast Water Convention requires 30 nations to ratify the treaty, which they have – but those nations must hold the registrations for 35 per cent of the world’s merchant shipping tonnage. So far the ratifiers only account for a little over 29 per cent.
Nations yet to sign include many of the “flags of convenience” nations such as Panama, the Bahamas, Malta and Cyprus, these countries offer registration to foreign shipping lines so they can benefit from low taxes and more relaxed regulations. They hold 30 per cent of the world’s merchant shipping.
However, it is not only the delaying tactics of the ‘flags of convenience’ nations that is holding up the treaty, the US, UK, Germany, Italy and Japan have also not yet ratified the convention, combined their collective tonnage would instantly trigger the treaty into force.
In the late 20th century, the owners of oil tankers responded to public outrage after a spate of massive spills by cleaning up their act. Oil spills have been reduced by more than 80 per cent since the 1980s. Isn’t it now the time to apply the same vigour to ending the release of biological time bombs into the coastal waters of the world?
Sources include New Scientist
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