The world renowned American oceanographer, Sylvia Earle, is convinced that our seas, and therefore our planet, are in grave peril. But how can she convince the world to take notice of a global threat which is invisible to most of us?
She spoke to Stephen Sackur at the Editorial Intelligence conference in Portmeirion, in North Wales.
You can watch the full discussion on BBC World News on Wednesday 16 March 2011 at 0430, 0930, 1530, and 2130 GMT and on BBC News Channel at 0430 and 2330.
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