Shifting sands: mining the seabed for sand and gravel for use in construction is a major industry in the UK. But while the official line from the government and the mining industry is that damage is inconsequential, environmental groups are voicing concerns about the impact on sea defences, fish stocks and fragile coastal habitats. Mark Rowe dives into the increasingly fractious debate.
Concrete, an alien might reasonably conclude, is as indispensable to life on Earth as oxygen and water. In the UK alone, our annual demand for aggregates, which are a vital ingredient for the production of concrete, adds up to 272 million tonnes, the equivalent of four tonnes per person. To meet this mind-boggling demand, the construction industry turns to three sources of aggregate: land quarries; secondary, or recycled aggregate; and, increasingly, the offshore sand and gravel resources that lie beneath our seas.
Last year, 24.8 million tonnes of coarse gravel and fine sand were removed from the seabed off England and Wales, providing around 17 per cent of the sand and gravel needs of the two nations, and six per cent of Britain's total primary aggregate needs.
Although the annual turnover of the marine aggregate industry is a modest 250million [pounds sterling], the scale of demand--augmented by huge projects such as the Thames Gateway development and the London Olympics--is causing disquiet among environmentalists, who argue that understanding the impacts of extracting aggregates is vital if our marine environment is to be protected from long-term or irreversible damage.
Marinet, a marine arm of Friends of the Earth (FOE), argues that aggregate dredging imperils sensitive coastal habitats such as salt marshes, sand dune systems and sand cliffs, and even inland habitats that are vulnerable to coastal erosion. 'Sandbanks are major players in the wave regime', says Marinet's Stephen Eades.' The height of the sandbank can determine the height and strength of waves. The wave regime starts far out to sea, and sandbanks acts as a buffer. If the sandbanks are disappearing, then the wave regime intensifies and erosion around the coast becomes greater.'
Critics say the erosion and emaciation of sandbanks off the Norfolk and Suffolk coasts are linked to dredging, and that the industry is wasteful in its approach. According to Mariner, just over half of the dredged material is rejected because it's silt or the wrong size. Of the 24.8 million tonnes landed last year, 13.4 million tonnes was landed in UK ports and went on to supply the construction industry. A further 4.2 million tonnes was placed on the shoreline to replenish holiday beaches damaged by erosion--often, says Marinet, caused by dredging--and 6.7 million tonnes was taken to Dutch and Belgian North Sea ports. 'This is an astonishing practice,' says Eades. 'The Netherlands and Belgium don't allow the commercial exploitation of the offshore seabed for aggregate materials within 25 kilometres of their shoreline, so why should the UK?'
But despite FoE's concerns, the environmental impacts of dredging remain uncertain. 'We don't really know quite what's going to happen; says Jolyon Chesworth, conservation manager of the South East Marine Programme for the Wildlife Trusts. 'One of our biggest issues is recovery. Sandy environments appear to recover within three to four years--because they are mobile and dynamic--but in the gravel environments, the pits and furrows left by the dredgers can remain for 20 years or even be permanent.'
The long-term impact is evident at Formby on Merseyside, where dredging 100 years ago has led to an incremental loss of 400 metres of coastline. During the early 20th century, new'training walls'--barriers to create a deeper channel for larger ships moving along the Mersey - were dredged up. While natural sand movement north of Formby continued, this was no longer replenished from the south. According to Andrew Brockbank, property manager for the National Trust, which owns 220 hectares of Formby, four metres of coastline are reclaimed by the sea there each year. 'Formby Point was once truly a point--now it's more flattened,' he says.
The sand dunes of Merseyside's Sefton Coast are the fourth largest in the British Isles and are part of a wider Site of Special Scientific Interest and a Special Area of Conservation, a nationally important habitat for the natterjack toad and sand lizards, which live in the edge of the dune system. 'As the land is ever more squeezed, we continue to lose more of the area and its diversity; says Brockbank. 'If it continues, it will have a significant impact on infrastructure.'
Back in the Southeast, the coastal waters are made up of 90 per cent gravel and sand. Much of this comes from recent deposits, but there are also other, deeper deposits, laid down by the movement of ancient river systems. 'The gravel features have been there since the last ice age,' says Chesworth. 'They haven't really changed in 12,000 years, so these are complex biotopes with a lot of biological diversity.'
The sand habitats host a range of both mobile and burrowing organisms. Here you will find worms, molluscs, crabs, rays and sand eels, which make the sand banks so attractive for fish such as bass. The gravel habitats, meanwhile, are home to corals, sponges, bryozoans and anemones.
One of the most spectacular, but hidden, wildlife displays in the UK takes place here: five-armed brittlestars, sometimes numbering in the tens of thousands, link arms as they float in the water. A close relative of the starfish, these creatures filter organic matter from the water to feed on. In order to avoid being carried away by currents, they link their highly flexible, snake-like arms with their neighbours.
For its part, the British Marine Aggregates Producers Association (BMAPA), which represents more than 90 per cent of the marine aggregates industry, points out that its activities, which dredge an area of 141 square kilometres each year, impinge on 0.016 per cent of the UK's overall continental shelf and is only 12 per cent of the area it's licensed to dredge. According to BMAPA, this amounts to approximately 50 medium-sized land-based quarries.
And it has supporters in the environmental movement. 'The industry is generally well regulated', says Kate Tanner, marine policy officer for the Royal Society for the Protection of Birds. However, she does caution that dredging has the potential to disturb feeding grounds for hard-pressed seabirds such as kittiwakes and fulmars.
BMAPA has just published its first annual sustainable development report, which, says chairman Kevin Seaman, 'recognises the weight that is now being attached to carbon and the need to demonstrate that we understand our own footprint and are doing what we can to reduce it'.
Unsurprisingly, BMAPA robustly defends its environmental record, pointing out, for example, that the Netherlands allows unlicensed dredging beyond the 25-kilometre limit, which isn't permitted in UK waters. 'The argument that we shouldn't take anything from the seabed is a simplistic one', says spokesman Mark Russell. 'lt fails to take into account the science-led process that leads to dredging being permitted. We can't get away from the fact that we are extracting a primary resource need. There will be an impact, but we have to make sure the impact is understood and minimised.
'This isn't an industry with a 50-year horizon', he continues. 'In terms of the volumes of resources out there, they are enormous, we're looking at hundreds of years'
Marinet, however, puts a different interpretation on the area that's extracted. 'lt's true that 0.016 per cent of something may not sound very much, but the oceans are a vast, vast place, so this actually represents a colossal area,' says Eades. 'lt's also very concentrated in a few spots.'
LACK OF PROTECTION
Historically, aggregate dredging has focused on the east coast of the UK, where demand, driven by the Southeast, has been greatest; 47 per cent of all marine dredged aggregate is taken from the East Anglian coastline. But dredging companies are extending their reach to the eastern English Channel, the south coast, around the Isle of Wight and beyond to Wales, where a series of dredging applications are in place for the Bristol Channel and Severn Estuary. Ministers from the Welsh Assembly are studying an application from United Marine Dredging and Hanson Aggregates Marine to dredge a million tonnes a year for ten years at an area known as North Bristol Deep.
After protests from organisations that included the Countryside Council for Wales and Natural England, a Severn Estuary Aggregates Working Group was created to assess the dredging proposals, with its findings expected to be published around the time that Geographical went to press. 'The potential cumulative and combination effects on a sensitive shoreline, and in or close to actual or proposed European-designated sites, were identified as needing further work,' says a spokesman for the Welsh Assembly. 'The study will determine whether or not the environmental concerns have been addressed satisfactorily.'
Extraordinarily, our gravel beds and sandbanks have no statutory protection. The Crown Estate owns about 99 per cent of the seabed out to 12 nautical miles (22 kilometres) and the rights to non-energy minerals out to 200 nautical miles (370 kilometres). Legislation introduced last May established a scheme to regulate marine aggregate activities and laid out the requirement for environmental impact assessments, but Marinet has criticised the way in which licences are issued by the Marine and Fisheries Agency, an executive arm of the Department for the Environment, Food and Rural Affairs, and questions the independence of the environmental impact assessments. 'There is no democratic process,' says Eades. 'The government department is the sole arbiter. You have very limited opportunities to make a submission'
Even the EU Habitats Directive fails to cover sandbanks to the depth at which they are usually dredged industrially. 'We don't have any laws to protect these areas, so it isn't possible to designate them as protected areas,' says Chesworth. 'The only way we ca n protect them is to try to work with the industry, government and licensing authorities. From our point of view, that isn't really adequate--we need proper legislation.'
This state of affairs makes Marinet's Stephen Eades uncomfortable. 'Something like two thirds of all species on our planet are in the sea,' he says. 'It's a largely unexplored area and our knowledge of it is fractional. As we are only just learning, the sea plays a fundamental role in regulating our climate and landscapes. Messing around with it is foolhardy. We are at risk of destroying things we never knew were there.'
Areas licensed for aggregate extraction in UK waters
1,167 square kilometres of the UK's seabed have been licensed for aggregate extraction
141 square kilometres of the seabed were dredged in 2006
0.016% of the UK continental shelf was dredged in 2006
24.8 million tonnes of aggregates were landed last year
WHAT'S AT RISK ...
Closely related to starfish, common brittlestars often link arms to avoid drifting away
The great scallop (or king scallop) is fished by dredging in UK waters
The common cuttlefish is among the world's most intelligent invertebrates
The common hermit crab is actually more closely related to lobsters than it is to true crabs
The dahlia anemone can have up to 160 tentacles, which it uses to catch shrimps and small fish
The masked crab burrows into the sand to feed on so-called infaunal invertebrates
How marines aggregates form
20,000 years ago, sea levels were around 100 metres lower, so today's sea bed was exposed as dry land
8,000 years ago, sea levels rose with the end of the last ice age, submerging old river valleys filled with sand and gravel deposits
Today, sea levels are even higher, and the sea's action has turned the submerged sediments into clean, well-sorted deposits
A few broken and fragmented brick walls, mantled with ivy, turf and lichens, are testament to what is probably the most extreme consequence of offshore dredging in the UK. The crumbling stacks are all that remain of the village of Hallsands, near Kingsbridge, which was washed away by a ferocious storm off the South Devon coast on 26 January 1917.
The village's fate was sealed 21 years earlier, when, in order to feed the demand for concrete at the expanding Keyham naval dockyard near Plymouth, permission was granted to dredge shingle along the coast. Despite protests, inquiries and occasional attempts to rebuild the lost shoreline, the level of the beach beside Hallsands fell by more than four metres. The storm waters of 1917 finally overwhelmed the village. Although no lives were lost, all but one house was dismantled by the elements.
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|Title Annotation:||Marine aggregates|
|Comment:||Shifting sands: mining the seabed for sand and gravel for use in construction is a major industry in the UK.|
|Date:||Mar 1, 2008|
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