ALL AT SEA - The New Wild: Why Invasive Species will be Natures Salvation - page 29

flip-flops. (On remote Ascension Island, Boy Scouts regularly collect flip-flops from the South Atlant-
ic shoreline and enjoy trying to establish their origin.) Floating plastic is virtually indestructible and so
has a longer range than most vegetation. We hear from time to time about how it chokes, smothers, and
starves unsuspecting turtles, albatrosses, and even whales. But plastic detritus also carries hitchhikers
and even victuals for their journey. A water bottle might supply fresh water; a food container could yield
scraps of sustenance.
David Barnes, a zoologist at the British Antarctic Survey, scavenged remote shorelines from
Spitzbergen in the Arctic to Signy Island off Antarctica, and from Galapagos in the Pacific to Ascension
in the Atlantic. He found that more than half the debris was of human origin, and much of it was inhab-
ited by worms, ants, barnacles, larvae, and even hardy insects. The density was highest in the Southern
Ocean, probably because there are fewer shores for the debris to beach. With a year-round circumpo-
lar current, the detritus just keeps on going around. 14 Barnes says that “the vast amounts of waterborne
debris is almost certainly drastically changing opportunities for many marine organisms to travel and
thus for exotic invaders to spread.” 15
Beachings can be spectacular. On June 5, 2012, waves tossed onto the beach of Newport, Oregon,
a sixty-foot-long piece of jetty. It had crossed the Pacific from Japan, where it had been cut loose by
the tsunami fifteen months before. It was a journey of at least five thousand miles and possibly a great
deal more. On Newport's beach, demolition teams quickly arrived to break up the wooden structure and
dispose of it, for fear that Japanese species were ready to hop ashore and colonize. As they worked,
scientists found ninety species of hitchhiker that had either survived the entire journey or joined en
route. These included an edible Japanese seaweed called wakame that is on the IUCN's list of one hun-
dred worst alien species, a starfish called the Northern Pacific seastar, and several mussels, crabs, and
worms. 16
If humans had not been around to police the arrival, any of those species might have become Amer-
icans. While the jetty is a human artifact, a tree trunk or other large piece of organic debris could
have made the same journey and carried the same passengers. The event showed how easy—and over
millions of years how frequent—such journeys must be. If the Pacific can be crossed so easily, then
nowhere is too remote to be visited by aliens.
One can imagine that a similar kind of journey might have resulted in a land crab making it to As-
cension Island. Before humans showed up there, Ascension's ferns and seabirds were ruled by its largest
terrestrial animal, a land crab ( Johngarthia lagostoma ) found nowhere else. Tens of thousands of the
crabs burrow into the island's central mountain and go on long expeditions down to the shore to re-
produce. But given that the island is some seven hundred miles from the nearest speck of land, it is a
mystery how the crab got there. It never goes to sea, beyond dipping its claws into the waves while
depositing larvae. It most likely arrived when larvae of some land crab from Africa or South America
accidentally rode on some floating vegetation. After that, it evolved to what we see today. 17
What doesn't travel by sea may fly. Many birds migrate around the globe, following the seasons.
Birds that spend part of the year in Britain may winter in South Africa or summer in Siberia. There are
flight lines across the Atlantic, from Australia to Japan, from North to South America, and in the case
of the Arctic tern, from the Arctic to Antarctica. And birds make mistakes. While I was on Ascension
Island, there were reports that one of the “endemic” Ascension frigatebirds had shown up in the Scottish
Hebrides. Perhaps it was similar faulty navigation that resulted in many birds from the Pacific region
making it to Hawaii over millions of years, where they found rich pickings and stuck around, evolving
into new species. Without such random migrations, many more places around the world would be life-
less.