Look at what the cargo ship dragged in

In a rare convergence of interests, the shipping industry – worried by the prospect of having to comply with standards that vary from country to country and even state to state – has also pushed for universal standards. "Ours is an international industry," says John Berge, vice president of the Pacific Merchant Shipping Association. "To suddenly be in a situation where you have to meet different standards throughout the world, it can create an untenable situation."

That situation may soon change. National ballast water discharge standards are "the No. 1 regulatory project for the Coast Guard," says Lt. Keith Donohue of the Guard's Environmental Standards Division, although he declined to specify a date beyond "very soon."

In 2004, the IMO announced its intention to provide international guidelines. And although the conventions have yet to be ratified by the 30 member nations, the mere suggestion of global regulation gave birth to a $10 billion to $15 billion industry overnight. "It just catapulted progress," says Allegra Cangelosi, a senior policy analyst at the Northeast-Midwest Institute, a nonprofit dedicated to the environmental quality of those regions.

Frustrated by what they see as lethargy at the federal level, and viewing proposed IMO standards as lax, some states have moved ahead alone. (The National Aquatic Invasive Species Act, itself an update of the 1996 National Invasive Species Act, has languished in Congress since 2003.)

Michigan enacted legislation in 2005 to require all incoming vessels to prove that either they will not discharge ballast water or that, if they do, they possess the technology to prevent the escape of aquatic organisms. The law takes effect in 2007. And in September, California Gov. Arnold Schwarzenegger signed a bill widely viewed as the country's most stringent. By 2020, ballast water discharged in California must contain no living organisms.

How that goal will be achieved is still unclear, but possible technologies run the gamut from filtration and biocides – substances that kill living organisms – to techniques with no long-term residue like ultraviolet radiation and heat treatment.

Once universal standards are in place, ballast water treatment solutions won't be difficult to develop, says Andrew Cohen, a marine biologist at the San Francisco Estuary Institute. "The basic problem is, how do you kill or remove organisms in a tank of water? And that just doesn't seem that daunting a challenge in the 21st century."

Improved shipping technology, more ships, faster voyages, and antipollution efforts over the past 100 years have contributed to the accelerating rate of exotic aquatic species appearing worldwide.

The use of seawater as ballast became widespread with the advent of steel-hulled steamships a century ago. Wooden sailing ships had used rocks, cargo, and other dry ballast to stay on an even keel.

Significantly faster, the new ships shortened the time stowaway organisms had to survive in order to arrive in – and colonize – new environs. In the 1850s, a trip from New York to San Francisco took up to three months. By the 1950s, it was weeks.

More trade has meant more ships. According to the International Maritime Organization, the number of ton-miles logged – a gross ton shipped one mile – quadrupled between 1965 and 2004. In 2004, a world trading fleet of 46,200 ships moved 6.76 billion gross tons 4 million miles.

In the same period, new canals linked previously isolated bodies of water. In 1952, the Volga-Don Canal joined the Sea of Azov and the Caspian Sea. In 1959, the St. Lawrence Seaway opened the Great Lakes to the Atlantic. The 1992 completion of Europe's Rhine-Main-Danube Canal linked the Rhine and Danube Rivers, permitting direct travel between the North and Black Seas.

Ironically, efforts to clean polluted waterways beginning in the 1980s may have helped disperse exotic species in Europe and North America. Toxic pollution levels may have served as a barrier before.

The infamous zebra mussel, which has spread throughout freshwater systems east of the Rockies over the past 18 years, is a case in point. Native to the Caspian Sea and long established in northern Europe, it colonized the Great Lakes only in the late 1980s, 30 years after the St. Lawrence Seaway opened, but just as pollution was abating.

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