The UK has lost more than 90% of the lush seagrass meadows that once surrounded the country, according to research.
Scientists have described the decline as catastrophic, but the latest analysis also shows where flowering plants can be restored. The resurgence of seagrass meadows would quickly absorb the carbon dioxide that drives the climate crisis and provide habitats for hundreds of millions of fish, from seahorses to cod juveniles.
Seagrass has declined worldwide, but the study, published in the journal Frontiers in Plant Science, is the first to assess a country’s remaining meadows and historical losses. Grasses grow up to 2m in length in clear water where sunlight passes. They once covered most of the sand and mudflats.
In identifying suitable seagrass habitat, the scientists concluded that 92% had been lost in the past one or two centuries. Pollution from industry, mining and agriculture, along with dredging, bottom trawling and coastal development are to blame.
Only 8,500 hectares of seagrass meadows remain, scientists say, an area similar in size to Newcastle upon Tyne. Almost half of the losses probably occurred in the last three decades, significantly worse than the estimated global average, according to the study.
Some places have maintained healthy meadows, such as Lindisfarne, Studland Bay in Dorset, parts of Devon and the Isles of Scilly. Elsewhere, however, in areas such as southern Wales and the Humber and Tyne estuaries, many have been destroyed.
“The catastrophic losses documented in this research are alarming, but offer a snapshot of the potential of this habitat if efforts are made to protect and restore seagrass meadows across the UK,” said Alix Green of University College London (UCL), who led o work. “The UK is lucky to have such a resource in our waters and we must fight to protect it.”
Seagrass flowers are pollinated by shrimp and other creatures, as well as streams of water. Meadows can store carbon 35 times faster than tropical forests and harbor up to 40 times more marine life than the bare seabed.
“Seagrass is the most amazing habitat that no one has ever heard of,” said Green. “If left undisturbed, seagrass soils will persist for thousands of years and act as a permanent carbon store. Seagrass meadows can recover, if allowed, and used to be everywhere, so there are unlimited opportunities to rebuild them. ”The Seagrass Ocean Rescue project is already planting millions of seeds on the shallow seabed in Dale Bay, Pembrokeshire.
Peter Jones, also at UCL, said: “The next decade is a crucial window of opportunity to address the interrelated crises of biodiversity loss and climate change. Restoring seagrass meadows would be an important contribution to this. This will involve restrictions, such as reducing damage to the boat’s anchor, restricting harmful fishing methods and reducing coastal pollution. “
Seagrass meadows are nurseries for many species, whose larvae and juveniles can hide and feed among the leaves. This includes dogfish, which are small sharks, and the only seahorses in the UK, as well as commercially important fish such as cod, plaice and mullet.
“In addition to their beauty, they are useful for a number of other reasons,” said Green. “They protect the coast from coastal erosion, absorbing the impact of storms. One of the biggest impacts of climate change for the UK is rising sea levels and more severe storms, and having this type of habitat is much cheaper and environmentally better than building a lot of walls ”.
Seagrass covers about 0.1% of the ocean globally, but provides 10% of its carbon storage. A 2020 UN report, however, said that 7% of that key marine habitat was being lost worldwide each year, the equivalent of a seagrass football field that disappears every 30 minutes.
Unesco published its first global assessment on Tuesday of ecosystems that store carbon in its 50 marine heritage sites. He found that they hosted a fifth of the global total of “blue carbon” habitats. Three sites in Australia have more than 2 billion tonnes of CO2 blocked in their vast seagrass meadows, coastal mangroves and tidal swamps.
“They store so much carbon that these ecosystems become sources of CO2 emissions when they are degraded or destroyed,” said the lead author, Prof Carlos Duarte, from King Abdullah University of Science and Technology. “The protection and restoration of these ecosystems represents a unique opportunity to mitigate climate change.”