The UK has lost 90% of carbon-storing seagrass meadows

Vast carbon stores: Scientists estimate that the UK has 92% of its former seagrass meadows, a figure which is likely to continue rising. Source: Dimitris Poursanidis (via Flickr)
When you think of the sea bed you may picture sand and rocks, perhaps some seaweed or some fish - but do you think of seagrass meadows? The answer is probably no. It is not surprising, as scientists say that the UK has lost 90% of its seagrass meadows. 

By Rowenna Hoskin | Science Editor

When you think of the sea bed you may picture sand and rocks, perhaps some seaweed or some fish – but do you think of seagrass meadows? The answer is probably no. It is not surprising, as scientists say that the UK has lost 90% of its seagrass meadows. 

This decline has been labelled catastrophic by scientists, but the report published in the journal Frontiers in Plant Science, also provided readers with hope. The latest analysis shows that these flowering plants could be restored, which would in turn provide hope for the planet as these meadows would rapidly absorb carbon dioxide and provide a habitat for hundreds of millions of fish – from seahorses to cod. 

Seagrass can grow up to 2m long in clearwater that permits sunlight to pass through and they once covered the majority of sand and mudflats. 

Scientists have identified suitable habitats for seagrasses; they subsequently concluded that 92% of past meadows had been lost in the last two centuries. Pollution from industry, mining, farming, dredging and bottom trawling are considered to have caused the destruction. 

Almost half of the losses are believed to have been in the past three decades which is significantly worse than the estimated global average, according to the study. Some areas, such as Lindisfarne, Studland Bay in Dorset, parts of Devon and the Scilly Isles have managed to retain healthy meadows. However, areas such as south Wales and the Humbr and Tyne estuaries have been completely 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 at University College London (UCL), who pioneered the work. “The UK is lucky to have such a resource in our waters, and we should fight to protect it.” 

Seagrass could be revolutionary for the fight against climate change as meadows can store carbon 35 times faster than tropical rainforests and provide 40 times more habitat to marine life than bare seabeds. 

“Seagrass is the most amazing habitat that no one has ever heard of,” Green said. “If they are left undisturbed, seagrass soils will persist for thousands of years, and act as permanent carbon storage. Seagrass meadows can rebound, if allowed to, and it used to be everywhere, so there are limitless opportunities to build it back.” 

In an effort to re-establish the UK’s seagrass meadows, the Seagrass Ocean Rescue project is already planting millions of seeds on the seafloor in Dale Bay, Pembrokeshire.

Peter Jones from UCL said:  “The next decade is a crucial window of opportunity to address the inter-related crises of biodiversity loss and climate change. The restoration of seagrass meadows would be an important contribution to this. This will involve restrictions such as reduced boat anchor damage, restricting damaging fishing methods and reducing coastal pollution.” 

“Beyond their beauty, they are useful for a number of other reasons,” said Green. “They protect the shoreline from coastal erosion, by absorbing the impact of storms. One of the biggest impacts for the UK from climate change is rising sea levels and more severe storms and having these sort of buffer habitats is a lot cheaper and better environmentally than building a bunch of sea walls.”

Considering the effects carbon dioxide has on the planet and our future as a species, the harnessing of the carbon-storing power of the seagrass is imperative. Seagrass covers about 0.1% of the ocean globally at the moment, but provides 10% of it’s carbon storage. If the percentage of land covered could be increased, the carbon storing capability of the oceans would rise significantly. A 2020 UN report said that 7% of this key marine habitat was being lost worldwide each year, equivalent to a football field of seagrass vanishing every 30 minutes. Currently, we are directly destroying our chances of surviving climate change. 

UNESCO published its first global assessment of the carbon storing ecosystems in its 50 marine World Heritage sites this month. This report showed that they hosted a fifth of the global total of “blue carbon” habitats. Two of these sites in Australia have more than 2bn tonnes of CO2 locked away in their seagrass meadows, coastal mangroves and tidal marshes. 

“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 at the King Abdullah University of Science and Technology. “Protection and restoration of these ecosystems present a unique opportunity to mitigate climate change.”

The capabilities of seagrass are major, it has the potential to majorly help countries live up to their Paris Climate agreement promises. If all nations planted seagrass meadows rather than continuing to destroy them, we may actually have a chance of reaching net zero by 2050. 

Science and Technology

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