Severn barrage - environmental godsend or catastrophe?
A tidal barrage in the Severn estuary could meet almost 5% of the UK's energy needs but environmental NGOs are concerned that the cost to habitats could be too high.
The mighty Severn, with one of the largest tidal ranges of any river on Earth, features large in the report.
And while the SDC bends over backwards to stress that a barrage should not be built without meeting the strictest environmental criteria, pressure groups from Greenpeace to the RSPB argue that a large number of smaller, less intrusive schemes would be more effective and less damaging than a flagship barrage.
The SDC argues that, were a barrage to be built, public ownership and leadership is essential to ensure the public get a fair share of the reward rather than lining the pockets of a developer.
While its contribution to UK energy generation could be significant, says the SDC, the barrage must not be allowed to divert Government attention from the much wider action needed on climate change.
The fact that a barrage would damage habitat is undisputed and EU law would require Government to take action to replace what is lost.
A habitat creation scheme on this scale would be unprecedented in the UK.
SDC chairman Jonathon Porritt said: "The enormous potential for a Severn barrage to help reduce our carbon emissions and improve energy security needs to be balanced against the impact on the estuary's unique habitat, as well as its communities and businesses.
"This is why we believe that any development must be publicly-led as a project and publicly-owned as an asset, in order to ensure that the Government takes full responsibility for taking a sustainable, long-term approach."
"The Sustainable Development Commission is issuing a challenge to Government to embrace a new way of managing this major project," said Porritt. "We are excited about the contribution a Severn Barrage could make to a more sustainable future, but not at any cost.
"It is vitally important that all parts of Government - including the Welsh Assembly Government and the South West Regional Development Agency - are actively involved in the project, to ensure that work is fully integrated into regional economic and development plans."
The report also looks at the potential for emerging tidal technologies in the UK.
A statement from the SDC said: "Tidal stream technologies present exciting opportunities for low carbon energy production, and the report cites potentially huge rewards in terms of export potential from developing this technology.
"The commission concludes that Government should 'stay the course' to make tidal stream technology a viable proposition, whilst putting in place a robust regulatory framework and supporting the research required to understand potential environmental impacts.
On tidal lagoons, it added: "there are few direct conflicts between tidal barrages and tidal lagoons, with the exception of claims made for large scale lagoon development in the Severn Estuary.
"Although there is little authoritative evidence available on tidal lagoon technology, which proposes using hydropower turbines in an offshore impoundment, lagoons could potentially be developed in a number of shallow coastal areas with sufficient tidal range.
"The commission would like to see the Government investigating their long-term potential by funding a demonstration project. This would allow a full evaluation of the costs and the potential environmental impacts."
The thought of a barrage across the Severn has ruffled feathers at the RSPB, which fears the loss of valuable wetland habitats.
"Europe's most dynamic estuary will be destroyed by the construction of a barrage across the Severn while other less striking measures would cost less and could do more to cut carbon emissions," said a spokesperson for the NGO.
The RSPB argues that the barrage should be built as a last resort, only once other options for renewable energy generation have been exhausted.
It also flags up the significant amount of GHG emissions the construction of such a major piece of infrastructure would entail.
Dr Mark Avery, the RSPB's conservation director, said: "Tackling climate change is hugely important but this can be done without destroying irreplaceable national treasures like the Severn estuary.
"We should be harnessing the power of the Severn but there are better ways of doing this than by hauling ten miles of concrete into the estuary.
"The government should be aiming to help, not destroy, wildlife and that applies to proposals for green energy schemes just as much as new supermarkets or housing estates."
Replacing lost habitat would be a mammoth task, he argued.
"It took eleven years to replace 110 hectares of mudflats destroyed at Lappel Bank on the Medway, when the Government last broke European law," said Dr Avery.
"Damage on the Severn would be ten, twenty or thirty times as great. Other land is being lost to sea level rise so replicating Severn habitats would be enormously difficult."
Greenpeace has also given proposals for a Severn barrage a frosty reception, saying offshore wind is a more sensible solution to the UK's energy needs.
John Sauven, executive director of the pressure group said: "Tidal power can provide the UK with a tremendous amount of energy along with other marine renewables like wave power.
"And, importantly, it can do so without creating dangerous climate change emissions or nuclear waste. The Severn barrage could be a huge resource of carbon free energy, but the jury's still out on the best way to reap the tidal power of the river without having huge environmental impacts on wading birds.
"Offshore wind, as a cheaper option, should also be much higher up the government's priority list. The UK has about 40% of Europe's wind resource which could be harnessed to meet our demand for energy."
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