More than 90% of the seagrass meadows that used to help the UK tackle its greenhouse gas emissions and support its fisheries have already been lost, according to a new study. Despite the grim scenario, the researchers said there are massive opportunities to restore these habitats – with efforts in place across the globe.
Seagrasses represent one of the largest global carbon sinks despite occupying only 0.1% of the ocean floor. They support biodiversity, as well as contributing to the productivity of 20% of the world’s biggest fisheries. They also increase shoreline stability, cycle nutrients, and make coastlines more affable places to live. Forests get all the great, but sea vegetation plays an equally if not greater role.
But despite this long list of ecological services, we’re not really taking care of seagrass. Coastal development and nutrient enrichment are driving worldwide declines of seagrasses, which are highly sensitive to lower water quality and light limitations to photosynthesis. Global declines only account for mapped populations, and in many countries, data is highly limited.
A group of UK researchers decided to address the information gap, assessing the remaining seagrass meadows and historical losses for a country for the first time. They found that 92% of the seagrass area was lost in the last century or two because of pollution from industry, mining, and farming – also blaming dredging and coastal development.
Almost half of the losses probably happened in the last three decades, the study found. Now there are only 8,500 hectares of seagrass meadow left and there used to be 82,000 hectares, an area as large as 115,000 football fields. Half of all mapped seagrass are now in the Scottish Highlands (20%), Devon (16.2%), and Northern Ireland (14.3%).
The researchers estimated the UK’s meadows used to store 11.5 million tons of carbon, equivalent to the annual emissions of 7.7 million cars. With their destruction, much of that carbon was added to the atmosphere. The meadows could also have sheltered 400 million fish and annually filtered pollution equivalent to the amount of urine produced by the entire population of Liverpool each year.
A UN report published last year found seagrasses have been declining globally since the 1930s, estimating that 7% of the habitat is lost every year. They are now present in 159 countries on six continents covering over 300,000 squared kilometers. Only 26% of the recorded seagrass meadows fall within marine protected areas, compared to 40% of coral reefs.
“Seagrass is the most amazing habitat that no one has ever heard of,” Green told The Guardian. “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.”
The researchers emphasize that they’re not looking to blame countries, but rather highlight the considerable opportunities to restore these habitats. Reviving them would help tackle the climate emergency and rebuild wildlife populations by protecting seagrass. Work is already being done by the WWF in West Wales, replanting seagrass, as well as in Virginia, where habitats are being restored.