Photo via runhmc via Flickr CC
Invasive species hitching rides on cargo ships has been an issue for decades, but it's been getting increasing attention as species like zebra mussels take over rivers and lakes and nudge out native species. So far, no one can decide what regulations should be in place so that the impact of shipping on an area's ecology can be minimized. But mapping shipping routes is one area where there's hope in tracking, and decreasing, the number of invasive species spreading to new areas via cargo ships. AFP reports that by using data on arrival and departure times of ships, gathered from automatic transmitters installed on 16.363 large ships from 2001 to 2007, and mapping out that data, scientists saw that the traveling habits of the types of ships were dramatically different. Journey lengths, port stays, and typical routes varied depending on if the vessel is a bulk dry carrier, container ship, or oil tanker. And that means there's likely a series of different solutions to be hammered out for different types of ships.
"For instance, a container ship may shuttle frequently around Europe, visiting Rotterdam, Hamburg and Antwerp, and around Buenos Aires, Montevideo and Santos in South America. These vessels travel fast...and spend less than two days in a port on average. In contrast, bulk dry carriers are more unpredictable, changing their routes at short notice according to the fluctuating supply and demand of the goods they carry. In the course of a year, they do few repeat trips on the same route."
Mapping the shipping networks provide new perspectives on how invasive species are moved around, and what is discovered can help scientists figure out solutions to mitigate the instances of species such as microbes, larvae, snails and shellfish hitching a ride from home to somewhere they don't belong.
Both the problem of hitch-hikers finding a ride in the ballast water, and the frequency of trips between ports giving invasive species a stronger foothold in a new area are items to be dealt with, but the mapping showed that the former is more an issue among oil tankers and dry bulk carriers and the latter is more an issue among cargo ships. Armed with these new realizations, scientists can help make more intelligent regulations that can slow the spread of invasive species.
"With 90 percent of world trade carried by sea, the global network of merchant ships provides one of the most important modes of transportation" of intrusive species, says the study, which also estimates that bioinvasion is responsible for about $120 billion in financial losses per year. Fighting off invasive species is no easy task, and yet the efforts have to be made to protect native species that aren't equipped to hold their turf against invaders.
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