Biologists are equally worried about the threat from invasive species attached to the debris. How big a threat remains to be seen. They fear that foreign species that arrive on our shores — crabs, barnacles, starfish, snails and plants — could establish a foothold and crowd out native creatures and plants.
There's precedent for the concerns: The European green crab wrecked the soft-shell clam industry in New England and Nova Scotia in the 1950s. Zebra and quagga mussels clog water intake pipes, filtration and electric power plants across the Midwest to the tune of $1 billion in annual cleanup costs.
Shipworms, small-shelled clams that burrow into wood, established themselves in San Francisco Bay. They bore into piers, docks and boats and cause $200 million in yearly damage.