Posidonia herbarium
Native to the Mediterranean, the Posidonia seagrass meadows cover an area of more than 2 million hectares along the coasts. This underwater forest of high ecological interest is threatened by global warming and by boat anchors near the coasts. VIDEOGRAPHIC
Category
🗞
NewsTranscript
00:00 Native to the Mediterranean, the Posidonia seagrass meadows cover an area of more than
00:12 two million hectares along the coasts.
00:14 The leaves can reach up to a metre high.
00:17 They provide shelter and a place to reproduce for fish, which feed on the small invertebrates
00:21 which live there, such as worms and shrimp-like crustaceans.
00:25 The Posidonia seagrass meadows also protect the coast from erosion by breaking the swell
00:30 and forming a covering on the beaches where it accumulates in winter.
00:34 This underwater forest also absorbs carbon, which helps to reduce greenhouse gases causing
00:39 climate change.
00:40 Carbon, which is absorbed in the leaves via photosynthesis, travels to the roots and the
00:45 rhizomes, as do the sediments floating in the ocean.
00:49 The seagrass roots and sediments form a dense mattress which can become several metres thick
00:54 and hold carbon for thousands of years.
00:57 For the same amount of surface area, the seagrass meadows absorb more carbon than a tropical
01:02 rainforest.
01:04 But the Posidonia seagrass meadows are threatened by the heating of the oceans and are damaged
01:09 by boat anchors near the coast.
01:11 Scientists fear that the degradation of the seagrasses could result in the release of
01:15 the large amounts of carbon they contain into the atmosphere.
01:18 [Sound of a thunder]
01:20 [Silence]