'Forever plant' faces uncertain future The green, underwater meadows of Posidonia seagrass that surround the Balearic Islands are one of the world's most powerful, natural defences against climate change. A hectare of this ancient, delicate plant can soak up 15 times more carbon dioxide every year than a similar sized piece of the Amazon rainforest. But this global treasure is now under extreme pressure from tourists, from development and ironically from climate change. Posidonia oceanica is found all over the Mediterranean but the area between Mallorca and Formentera is of special interest, having been designated a world heritage site by Unesco over 20 years ago.