WASHINGTON, D.C.Britain’s Prince Charles, long a champion of rain forests and sustainable agriculture, has a new environmental cause: combatting ocean trash.

“Something must urgently be done to stem the tide of plastic entering the ocean,” he said Wednesday at a conference on ocean debris, as part of a three-day tour of Washington.

“Having taken a keen interest in the state of the world’s natural environment for longer than I care to remember, one thing that has always struck me as being very odd has been the comparatively low level of attention that has been devoted to the condition of the oceans,” said Charles, the Prince of Wales and heir to the British throne.

“It is … utterly crucial that we do a great deal