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Global Warming Speeds Movement of Invasive Species


This is the sound of walruses in the Arctic.

What are they talking about?  I have no idea.  But I doubt they are debating the existence of climate change.  Rapidly melting sea ice in the Arctic left a pod of 35,000 walruses stranded on a rocky beach in Alaska earlier this month.

The mass stranding -- photographed by scientists (in the picture above) and distributed by the media around the world -- was highly unusual, and a stressful development for walruses, which need sea ice to rest on.

But it was hardly the only change unfolding in the Arctic.   The disappearance of sea ice has connected the North Pacific and North Atlantic oceans for the first time in millions of years.  This opening up of a Northwest Passage for ship traffic over the top of Canada is likely to be a game-changer not only for global commerce, but also for the spread of invasive species carried by ships, according to Whitman Miller, a research scientist at the Smithsonian Environmental Research Center in Edgewater, Maryland.

“What we are finding is that, with global warming, there are now several months a year when these waters in polar regions are navigable by commercial vessels," Miller said.  "Just last year, in September, the first commercial vessel ever to pass through the northwest passage did so.  And ironically, or maybe not ironically, the ship was carrying British Columbian coal to Finland.”

In other words, the same industry that is causing the melting of the Arctic – the extraction of coal and other fossil fuels – is now benefitting from the damage. 

A sea route for ships over the top of Russia is also now free of ice for several months a year.  Last year, 71 ships travelled the northern sea route over Siberia.  And in a recent paper published in the journal Nature Climate Change, Miller and Smithsonian colleague Gregory Ruiz predict that this Artic sea travel will soon grow to thousands of ships per year. Many of the ships will be exploiting a rush for oil and natural gas in the Arctic.

In the ballast tanks of ships moving from the Pacific to the Atlantic will ride more hitchhiking marine creatures that will likely invade places like the Chesapeake Bay, Miller said.

"These ships are taking on whole cocktails, because they are taking on entire planktonic communities," Miller said. "And those plankton could be plankton that are always plankton (like algae). Or it could be plankton that is the larval stage of an animal that gets much much bigger, like a jellyfish or a blue catfish.”

Invasive species from the Pacific have already caused trouble in the Chesapeake Bay.  For example, an Asian parasite called MSX believed to have been carried to the Chesapeake in ship ballast water in the 1950s killed large numbers of the Bay’s oysters in following decades.  

In the past, the Panama Canal served as a kind of a filter for some invasive species trying to hitch-hike on ships from the Pacific to the Atlantic or vice-versa.  This is because the canal flows through a freshwater lake, meaning that organisms that live in salt water were often killed by the shock of fresh water.  But there is no such filter for ships passing over the top of the Arctic, and many marine life forms can survive the chilly trip by becoming dormant.

There is a relatively simple solution to this problem, however, Miller said.  Countries around the world should start requiring ships to install on-board systems that use ultra-violet light, screens, or chemicals to catch and kill all stow-away forms of life.

“I honestly believe that this is a problem we can engineer our way out of," Miller said.    

Of course, reducing the movement of exotic species inside ships won’t save the walruses, who will likely be contending with all kinds of new visitors –  oil and gas drillers, maybe even tourists drawn to the warming arctic.

Perhaps that is why they sound so grumpy.

(To read Miller's article, "Arctic Shipping and Marine Invaders," visit: http://www.nature.com/nclimate/journal/v4/n6/full/nclimate2244.html)