Melting Arctic ice means new opportunities for biological invasions

Arctic ice is melting. You knew that already. What you perhaps didn’t know is what the melting ice means for the possibility of biological invasions into the northern latitudes. For the first time in several million years, the melting of the Arctic sea ice has connected the North Pacific and North Atlantic Oceans. That allows for the natural dispersal of species into new territories, to be sure, but more worrisome is the potential for the long-distance transport of marine organisms thanks to our commercial shipping fleets.

The first commercial cargo carrier, loaded with coal from British Columbia, transited the Northwest Passage in September of 2013. And an already large number of ships are navigating the waters of Norway and Russia through the Northeastern Passage, a 3000-mile stretch of sea also called the “northern sea route” that connects the Barents and Bering seas. As large ships traverse our planet’s oceans, they take up seawater to fill their ballast tanks, and with that seawater comes millions of tiny organisms. When those ships release their ballast, they unintentionally release those organisms into a new environment, perhaps several thousand miles from their homes. Other organisms attach themselves to ships hulls, and are later washed or scraped away, also in strange, unfamiliar places.

Invasions within the Arctic are a concern – for example, shipping that moves goods to and from the Arctic – but according to Smithsonian Environmental Research Center scientists A. Whiteman Miller and Gregory M. Ruiz, a larger problem comes from ships that will increasingly use the Arctic as short-cut, moving goods from the Pacific to the Atlantic, or vice-versa. “Trans-Arctic shipping will also change global commerce patterns significantly, connecting world ports and their biota in unprecedented ways,” they wrote this week in Nature Climate Change.

Relying upon shipping data for recent years, the researchers predict that by 2040, there could be as many as 5600 ships transiting the Arctic each year. That number could be even higher, because an Arctic passage allows a shorter route between Asia and Europe than either the Suez or Panama canals, because the Arctic route will increasingly be predictably ice free, and because opportunities will increase for the exploitation of natural resources within Arctic waters themselves (oil, natural gas, rare earth metals, and fisheries). The Arctic, they point out, will also grow as a tourist destination. All of those factors will lead to increase shipping and to the development of ports and coastal areas. Those are “activities that disturb and modify the natural environment in ways that can facilitate invasion.”

Why are Miller and Ruiz more worried about the potential for biological invasions through the Arctic route than through the Suez or Panama canals? After all, those canals have also opened up routes for invasions, connecting bodies of water that have historically been separated by thousands of miles. Indeed, the two canals have been thought responsible for many invasions, both due to natural dispersal and due to human shipping. But the Suez and Panama canals have, by stroke of luck, natural filters in place to limit the success of biological invasions. The Panama Canal includes a freshwater lake in its interior, with marine water at both ends. The exposure to freshwater kills off many of the organisms clinging to the hulls of ships as they pass through, limiting their opportunities for invasion. While the Suez Canal is entirely composed of seawater, the salinity of that water varies quite a bit. Those changing conditions also stress the organisms as they move through the water, limiting their chances for a successful invasion.

Not only do the newly opened Arctic routes lack those natural filters, but because those routes are more efficient than either the Suez or Panama canals, ships that would normally have taken those routes will increasingly opt for the newer passages. For example, a ship that must sail from Murmansk, Russia to Japan, China, or South Korea would require a 40-day voyage through the Suez Canal, but only 18-20 days through the Arctic. A voyage half as long only costs half as much.

Miller and Ruiz’s predictions are dire. “Assuming current practices by ships, we predict two outcomes: (1) a substantial increase in invasions for the Arctic, which has historically received little exposure to such human-mediated transfers; (2) a new and different opportunity for interoceanic translocations of species, especially those unable to withstand the environmental stresses imposed by the Panama and Suez corridors. In short, we predict that Arctic trade routes will result in a large wave of new invasions to cold temperate and polar regions across the North Pacific and North Atlantic oceans.”

Invasions usually bode poorly for resident, native species. While Miller and Ruiz suggest that scientists and policymakers can proactively create management plans to mitigate the potential for species invasions, their Commentary unfortunately fails to reveal just what those plans might entail. – Jason G. Goldman | 02 June 2014

Source: Miller A.W. & Ruiz G.M. (2014). Arctic shipping and marine invaders, Nature Climate Change, 4 413-416. DOI:

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