Off the coast of Formentera, an island in the Spanish Mediterranean, lives an organism that stretches 15km from one end to the other. Posidonia oceanica, more prosaically known as seagrass, spreads by sending shoots out beneath the sediment. Entire meadows, covering several hectares, can thus be made up of a single organism. The grasses are long-lived, too. The vast meadow in Formentera is thought to have been spreading for tens or hundreds of thousands of years.
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