National Geographic : 2005 Mar
Caulerpa seaweed A native of tropical seas, Caulerpa was found in two spots off southern California in 2000. Fearful it would choke out native plants, as it has elsewhere, scientists attacked with chlorine and close monitor ing and are now hopeful: No new populations have been spotted since 2002. CAULERPATAXIFOLIA from Africa. The rats were infected with a dangerous smallpox relative called monkeypox, which skipped to the prairie dogs and thence to their new owners. Fortunately no one died, but more than 70 people in six states were sickened before the Centers for Disease Control and Pre vention traced the source.) Next stop on Jackson's tour of Miami is Exotic Aquariums, boasting aisles of glittering exotic fishes, many of which-including the poison-spined lionfish-you can now find in U.S. waters. More damaging than any fish, says Jackson, is the aquarium strain of a tropical seaweed, Caulerpataxifolia. In 1984 a sprig of Caulerpa was dumped into the sea from Monaco's ocean ographic museum. When it was discovered, three years later, the Caulerpacolony wasn't much bigger than a bath mat. But "France and Monaco argued about how it got there," says Dan Simberloff, director of the University of Tennessee's Institute for Biological Invasions. "Then they argued over which agency was responsible for it. Then they argued over whether it would become problematic. When they finally got around to dealing with it, it was too late. Today, Caulerpacarpets 30,000 acres of the Mediterranean. If they'd just jumped in when they found it and pulled every scrap, they could have nailed it." Despite the calamity in the Mediterranean, the U.S. didn't prohibit the sale of Caulerpa until 1999. The next year, Caulerpawas found growing in the water northwest of San Diego. Authorities acted with impressive speed, isolat ing and poisoning the Caulerpapatches in a four-million-dollar strike that appears to have been successful. Tour over for the day, Jackson drives me back to his bungalow to pick up my car. On 106 NATIONAL GEOGRAPHIC * MARCH 2005 his doorstep we find a plastic tub with a frog inside and a note on the lid: "Tom, I found this in my pool. Any idea what species?" Jackson can't say offhand. The amphibian's not from Florida, but it could be from almost anywhere else in the world. Restricting the entry into the United States of alien species such as Caulerpa and zebra mussels, already known to be invasive elsewhere, would be almost automatic, one would think. The reality is more complex-and far more difficult. In most countries, unless a species is on a short blacklist of noxious weeds or inju rious wildlife, or restricted under the Conven tion on International Trade in Endangered Species, you're free to import it. (Australia and New Zealand have abandoned this presumption of innocence in favor of a more effective "clean list" of approved species; species not on the list are denied entry.) A lone fisherman dips his line into a San Francisco Bay that has lost many populations of its native aquatic species in the past 150 years. One potential culprit motors past in the background. Each ship in this busy port carries, on average, a million gallons of water in ballast tanks, for stability in open waters. (Large ships often carry 20 million gallons.) In the past, water taken up in a distant port-and whatever was in it-was released here, devastating the ecosystem. California attempts to regulate the practice, but it is still com mon here and in ports the world over.