AAAS

Bad news. In warmer seas of the future, the marine life that grows on ships' hulls will grow faster and make thicker layers.

A Warming World Could Add Billions to Shipping Costs

Sid is a freelance science journalist.

WASHINGTON, D.C.—Climate change already stands to wreak huge financial damage by inundating coastal cities and harming human health. Now, researchers have added a surprising victim to the toll: ships. In a session here today at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW), a scientist said that climate change will stimulate the growth of barnacles and other ship-clinging creatures, potentially adding billions to the cost of worldwide shipping.

As anyone with a boat knows, many sorts of marine life can attach themselves to a hull below the waterline. On a large ship, the weight of such hitchhikers—everything from algae to barnacles to small colonies of coral—can weigh as much as 10 tons, says marine ecologist Susan Williams of the University of California, Davis, Bodega Marine Laboratory in Bodega Bay. The costs of these hull-fouling stowaways are substantial: According to one study, the U.S. shipping industry spends more than $36 billion each year in added fuel costs to overcome the drag induced by clinging marine life or for anti-fouling paint that prevents that life from hitching a ride in the first place. And that figure doesn’t include the cost to regularly scrape a hull smooth, which costs approximately $4.50 for every square foot of hull surface.

In the future, those costs could rise substantially, says Williams. In lab tests for which seawater was warmed 3.5°C above today’s average—a scenario that represents water temperatures expected in the year 2100—organisms in a typical community of hull-clinging creatures grew twice as fast as they do under today’s conditions. They not only grow more quickly in the warmer water but also grew to form thicker layers.

As a result, maintenance will likely be required more often in the future, boosting operational costs even further. In fact, recent warming may already have increased the need for routine hull scraping, says Williams. Ten years ago, boat owners in the marina where she lives typically scraped their boats only once every 3 months. Now, she notes, they need to perform such maintenance on a monthly basis.

See our complete coverage of the 2011 AAAS annual meeting in Washington, D.C.

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