WORLDWIDE SHIP TRAFFIC UP 300 PERCENT SINCE 1992

Global shipping routes crisscross the world’s oceans in this map of shipping lanes derived from a 2008 study of the human impact on marine ecosystems. Maritime traffic along these lanes is also a major source of noise pollution, which is increasingly considered harmful to marine mammals.
Credit: Grolltech

NEW SATELLITE DATA REVEALS WHOPPING BOOST IN SHIPPING

Maritime traffic on the world’s oceans has increased four-fold over the past 20 years, likely causing more water, air and noise pollution on the open seas, according to a new study quantifying global ship traffic.

The research used satellite data to estimate the number of vessels on the ocean every year between 1992 and 2012. The number of ships traversing the oceans grew by 60 percent between 1992 and 2002. Shipping traffic grew even faster during the second decade of the study, peaking at rate of increase of 10 percent per year in 2011.

Traffic went up in every ocean during the 20 years of the study, except off the coast of Somalia, where increasing piracy has almost completely halted commercial shipping since 2006. In the Indian Ocean, where the world’s busiest shipping lanes are located, ship traffic grew by more than 300 percent over the 20-year period, according to the research.

Ships powered by fossil fuels dump oil, fuel and waste into the water and pump exhaust into the air. Shipping is also a major source of noise pollution, which is increasingly considered potentially harmful to marine mammals, said Jean Tournadre, a geophysicist at Ifremer, the French Institute for the Exploitation of the Sea in Plouzane, and the study author.

“I found it quite worrisome that the ship traffic grew so much, even in very remote regions of the world,” Tournadre said, “especially when we know that they are the major source of pollution [on the open ocean].”

International trade and the sizes of merchant fleets have both enlarged rapidly over the past two decades, explaining the steep rise in ship traffic, the study reports. The new analysis has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

Burgeoning ship traffic has increased the amount of pollution in the atmosphere, particularly above the Sri Lanka-Sumatra-China shipping lane, where the study notes a 50 percent increase in nitrogen dioxide, a common air pollutant, over the 20-year period.

Tournadre said he hopes the new study will increase scientists’ understanding of how human activities are affecting marine ecosystems and improve models of atmospheric pollution in the open ocean.

The new dataset will provide scientists with invaluable insights into the patterns of ship traffic and the traffic’s effect on the environment, said Batuhan Osmanoglu, a radar systems engineer at NASA’s Goddard Space Flight Center in Green Belt, Md., who was not involved in the study.

“The nice thing about this study is that they have a unique dataset, that maybe we’re looking at for the first time,” he said. “Whenever you have a unique dataset you can quite easily learn something new.”

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