INVASION OF THE CRITTERS

Although most nations agree on the danger, there's no consensus on how to stop it. Having ships swap ballast waters on the high seas, where coastal species cannot survive, would mean costly delays and added risk. Brazil's oil company, Petrobras, has concocted a promising system to allow ships to gradually empty and refill their ballast tanks along the entire voyage, although shippers are still taking stock. And maritime officials worldwide are tinkering with everything from ultraviolet rays to ozone to treat ballast water, but most of these experiments have yet to leave dry land.

Technology alone will not vanquish the bioinvaders. Any lasting solution will require cooperation among seafaring nations. An international convention to control ballast water was drafted in February, but it will not become law unless at least 30 nations sign on. With the health of the world's waterways at risk, they have little choice. Besides, the alternative stinks.

WITH TOM MASLAND, SUDIP MAZUMDAR AND LIAT RADCLIFFE

© 2004