A long-term natural experiment hints at how species disperse

THAT SPECIESAAAS might spread overseas by hitching lifts on floating vegetation is an idea going back to Charles Darwin. It is a plausible thought, but hard to test. A test of sorts has, however, been made possible by the tsunami that struck the Pacific coast of Japan in 2011, in the wake of a submarine earthquake.The incursion and regression of this tsunami dragged with it millions of pieces of debris, many of them buoyant. After a year or so some of the debris started arriving on the coast of North America—and it is arriving still. James Carlton, of Williams College, Connecticut, and his colleagues have been studying the living creatures on board pieces of it, and Dr Carlton gave a round-up of what they have so far found to an audience at the meeting in Washington.