When the tide goes out at Southend-on-Sea in Essex, a remnant of Britain’s lost sea life comes into view. The thin, olive-green strands coating the muddy shore are a seagrass meadow — a habitat that used to cover much of the country’s coast, providing shelter for juvenile fish and sucking planet-warming carbon dioxide out of the air.
“They support a huge abundance of life,” Alex Smith, a marine conservationist at Essex Wildlife Trust, said. “A seagrass meadow can support crabs, cuttlefish, seabass. But that’s if it’s healthy, which this meadow isn’t.”
The seagrass at Southend faces many pressures, from anchors dragging across it to children playing in it. But one pressure is particularly intense — this meadow is perhaps the most polluted in the country.
A 2018 study of 11 seagrass meadows around Britain found that this one had the highest levels of an isotope called nitrogen-15, more than twice the national average. Nitrogen-15 comes from sewage and agricultural manure.
While the meadow is buffeted by the polluted water flowing out of the Thames, there are also several sources of pollution closer by. Private water pipes misconnected to storm drains are sending sewage directly from homes in Southend out to sea, walkers are letting the tide clean up after their dogs, and about half a mile along the beach from the meadow is a sewer storm overflow owned by Anglian Water that spilled for 60 hours in 2022, the most recent year for which data is available. Further west on Canvey Island is another that spilled for 210 hours, and in the middle of the Thames estuary is another that spilled for 280.
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Along with manure and fertiliser washing off farmland, sewage pipes such as these have filled the water around Southend with too much nitrogen. Lime-green algae, which takes in nitrogen faster than seagrass, has thrived in these conditions, blooming and depriving the seagrass of the light that it needs to photosynthesise. This in turn has stunted the seagrass’s growth and limited its intake of carbon dioxide.
“Algae is a natural feature of the environment but it’s being supercharged by the amount of nutrients in the water” Smith said. “It can suffocate the seagrass.”
This isn’t just a problem in Southend. A report by the Blue Marine Foundation, Project Seagrass and Surfers Against Sewage has found that 34 per cent of the country’s seagrass meadows are in poor condition, primarily due to too much nitrogen and phosphorus flowing into the sea from polluted rivers and sewage pipes. Nationally, agriculture is responsible for 70 per cent of nitrate pollution, while sewage is responsible for 25-30 per cent.
Together with other pressures such as land reclamation and overfishing, water pollution has brought about a mass die-off of seagrass around the country. Since 1985 Britain has lost half of its seagrass meadows. Overall, the loss could be as high as 92 per cent. Up the Essex coast, the seagrass meadow in the Stour estuary has shrunk by 98 per cent since 1973.
Smith said this die-off has also been bad for the fishing industry in Essex, because “many of the fish in the North Sea start their lives in seagrass meadows”. It has also had a negative impact on the climate, because seagrass meadows are fantastically effective at storing carbon in their root systems. Worldwide, they occupy just 0.1 per cent of the seafloor, but account for as much as 18 per cent of the ocean’s total carbon dioxide absorption.
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It is still unclear quite how much carbon Britain’s seagrasses take in, but a 2018 study by researchers at University College London and King’s College London puts it at 108,000-221,000 tonnes — equivalent to the emissions of 23,000-47,000 British people. Restoring seagrass around the country could therefore make a small contribution to reaching net-zero carbon emissions.
“It’s a fantastic nature-based solution to climate change but when you realise how much of it we’ve lost it can be demoralising,” Smith said. “It can feel like you’re fighting a losing battle, but at the same time it motivates me to raise awareness about the scale of the problem.”
Last year, Essex Wildlife Trust began restoring a seagrass meadow in the Blackwater estuary, transplanting plants from a healthy meadow into areas where they might flourish. In the coming years the organisation intends to restore meadows along the Essex coast. The Blue Marine Foundation and Project Seagrass are also working to restore meadows in the Solent around Portsmouth.
In theory, the law should prevent the pollution that has damaged seagrass meadows across the country — it only permits sewage spills in “exceptional circumstances”. But in 2022, water companies discharged sewage into watercourses 300,000 times.
Similarly, the law requires farmers to take steps to stop nitrates entering water courses, but this requirement is largely unenforced. A freedom of information request by the World Wildlife Fund and ClientEarth revealed that in 2020 and 2021, the Environment Agency issued sanctions for just one in a thousand breaches of agricultural pollution regulations.
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Richard Unsworth, an associate professor at Swansea University and chief scientist at Project Seagrass, said: “Poor water quality from sewage, agriculture and poor land management is placing our ability to fight climate change with the power of the oceans in doubt.
“We need our marine habitats and biodiversity for many things and we can no longer keep undermining their health through poor water quality. We have to start enforcing legislation properly so that the polluter pays and is prosecuted when they cause environmental damage.”
Toby Perkins, the Labour shadow minister for rural affairs, said: “It’s sickening beyond belief that raw sewage is pouring into our oceans and seas, destroying nature like seagrass and damaging tourism.
“The water companies are getting away with this because the Conservative government is too spineless to stop them. Labour will put failing water companies under special measures to force them to clean up their toxic mess. We will immediately give the water regulator power to ban bonuses and make water bosses who continue to oversee law-breaking face criminal charges.”
Anglian Water is working on a sustainable drainage system in Southend that should reduce the number of sewage spills by reducing the amount of rainwater flowing into the drains. A spokesman for Anglian Water said: “As part of our next business plan from 2025 which is currently with Ofwat for approval, we’re proposing over £100 million of investment in Southend alone, to reduce storm spills buy increasing the capacity of the sewer network and our storm water storage at our water recycling centre.”
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The Times is demanding faster action to improve the country’s waterways. Find out more about the Clean It Up campaign.
