In 1980, after college, I joined the crew of a sailboat partway through a circumnavigation of the globe. Becalmed and roasting one day during a 21-day crossing of the western Indian Ocean, several of us dived over the side. Within a few swimming strokes, the bobbing hull seemed a toy over my shoulder as I glanced back through my diving mask. Below me, my shadow and the boat’s dwindled to the vanishing point in the two-mile-deep water. Human activity seemed nothing when set against the sea itself.
Just a few weeks later, on an uninhabited island in a remote part of the Red Sea, I was proved wrong. The shore above the tide line was covered with old light bulbs, apparently tossed from the endless parade of ships over the years.
Now scientists are building the first worldwide portrait of such dispersed human impacts on the oceans, revealing a planet-spanning mix of depleted resources, degraded ecosystems and disruptive biological blending as species are moved around the globe by accident and intent.