CHICAGO — The global shipping industry hasn't just tied together the world's nations economically, but biologically, too.
The average Great Lakes port, such as Chicago, is only an average of two degrees of separation from 80 percent of the ports in the world, from Kuala Lumpur to Amsterdam, according to new analysis of more than 2 million ship movements presented at the American Association for the Advancement of Sciences annual meeting.
The biological upshot of that logistics reality is that the evidence on which scientists have based their studies of species (stretching back to the era of Charles Darwin) is being erased.
The boundaries of previously distinct geographies with their own distinct forms of life have been blurred by invasive organisms hitching rides on shipping vessels. The world's bodies of water are getting more homogeneous, leading some biologists to refer to the current era of global biological flatness as "the homogecene."
"This phenomenon of invasions is obliterating the patterns of biogeography that Darwin and Wallace relied on in formulating their theories of evolution," said David Lodge, a biologist at the University of Notre Dame. "I don't know that they would have been able to come up with the theory of evolution in the situation we're faced with now, where biogeographical provinces are increasingly mixed up."
Invasive species have long been known to impact ecosystems by throwing natural systems out of whack, but it has been difficult to know how damaging they really are or what organisms are likely to show up in cherished environment like Lake Michigan or the Mediterranean Sea. But ecologists and economists are working to understand how global shipping works and find ways to monitor the riskiest ships.
Species move easily between aquatic habitats that are worlds apart because ships take on ballast water to stay the same weight, no matter how much freight they're carrying. So, in port A, they pump in water to get heavier, then in port B, they pick up some goods and expel that water —
along with all the organisms that they picked up back at port A. That's how scientists think the destructive and oft-pilloried Zebra mussel got into the Great Lakes.
U.S. researchers, just by dint of proximity, have exhaustively studied the greater Great Lakes region, which includes all the bodies of water stretching out to the St. Lawrence Seaway and the ocean. But they're just one subnetwork out of many across the globe.
"The Great Lakes are just one of many possible examples of leakages between shipping ports," Lodge said. "They have been and remain a continuing laboratory for scientific and policy work."
Biologists know that the Great Lakes are filled with 57 invasive species. They are heavily-invaded, in the parlance of the scientists.
Yet the Lakes aren't particularly heavily-trafficked in the scheme of global shipping, University of Georgia ecologist John Drake found.
"We must either conclude that the Great Lakes are especially vulnerable or there are a lot more invasions going on out there in the rest of the world," Drake said.
In fact, of the Great Lakes' 200 ports, only six are in the top 3,000
in the world and only Montreal is a major node on the global shipping network. It turns out, though, that the network within the system is very integrated and dense. Once an invader gets to Montreal, it's very easy for it to travel to the rest of the ports in the system, like a virus spreading through a college dorm.
Even if the tight integration between Great Lakes ports makes them vulnerable to invasion, Drake said it's likely that just by studying the Lakes in greater detail, we've found more invaders. In other shipping ports around the world, Drake said scientists would likely find far more invasive species than they know exist today.
While there's no clear answer to stopping these unintentional species transfers — nobody wants global shipping to stop
— Drake and his colleagues are trying to develop systems to mitigate the risk of organisms hitchhiking on all those ships carrying Playstations and Porsches. They're looking at ways to flag risky vessels, the ones traveling from one area to a place that's environmentally similar.
From there, Lodge said, special water-treatment tech could be used to sterilize the ballast water.
Image: Courtesy of John Drake.
See Also:
- Fire-Ant Invasions Are Ecological Karma
- Bacterial Imbalance May Explain Honeybee Apocalypse
- One-Organism Ecosystem Discovered in African Gold Mine
- Social Networks Move Into Meatspace with "RFID Ecosystem"
- The Natural Pine-Beetle Ecosystem Goes Off Its Rails
- Deep-Sea Ocean Animals: Crazy-Looking and Imperiled
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