We in Britain are inclined to see the worst in massive state-driven projects, especially when these are promoted by governments that are undemocratic. We were right to be sceptical about the Soviet Union’s decision in the 1960s to divert rivers away from the Aral Sea, now largely a desert, and more recently about China’s Three Gorges Dam, which seems to be causing landslides, the displacement of millions of people and the extinction of the Yangtze River dolphin.

We have also scorned projects in democratic but poor countries whose governments have less than what we believe is an appropriate degree of environmental awareness. “Turkey plans to restart work on controversial dam project” ran the headline last week about the renaissance of the Ilisu hydro-electric dam on the River Tigris, which promises to displace thousands of people, destroy wildlife habitats and drown archeological treasures such as the ancient city of Hesankeyf.

So it is all the more surprising that Britain has got as far as it has in considering a scheme that takes state-funded environmental damage to a new level of absurdity: the Severn barrage. This £20 billion energy-generating monolith would, under the five options being considered by the Department of Energy and Climate Change, generate up to 5% of Britain’s energy needs. It would cut greenhouse gas emissions at a massive cost to wildlife. The 85,000 overwintering birds that use the Severn mudflats to feed would have nowhere else to go. And the returning salmon, sea trout, lamprey, twaite shad and allis shad of the rivers Severn, Wye and Usk – also protected under European law – would be chopped up by the turbines.

This scheme would not get funding any other way because it requires billions in subsidy and damages ecosystems that have international protection. It is being contemplated ostensibly because a government has decided climate change is the most important environmental issue facing the world. That may be how things turn out – or it may not. I say that not because I am a climate sceptic but because of the uncertainties involved. A case can be made that the destruction of ecosystems on land, species in the sea and human population growth are problems of equal magnitude for the human future and the health of the planet. But I don’t see the same priority being assigned to them.

Therefore the Severn barrage is a test case for a new political proposition: that it is all right to cause massive environmental damage in order to tackle other potentially catastrophic environmental problems – such as the warming and sea level rise that will come with climate change. Once this proposition is accepted, it is likely to be replicated. If the Waxman-Markey “cap-and trade” Bill clears the United States Senate, or when Europe tightens its carbon trading regime, there will be a glut of money-chasing emission reduction projects – which, paradoxically, may dump on the rest of the environment.

The danger is that projects such as the Severn barrage are seen as easy wins by politicians terrified of the consequences to their comfortable lifestyles of telling their electorates what CO2 reduction targets actually mean: turning some lights off, flying less or buying a more efficient car. Without energy efficiency, there is a danger of having a barrage in every estuary, or onshore wind farms everywhere, so our energy use can grow unchecked.

We need common acceptance for a new principle: changes that are intended to benefit the environment should be carried out in a way that goes with the grain of the environment, not against it. If we do not accept that, public policy becomes an absurdity, public consent will be lost and national assets squandered. You could call it Clover’s Law but it is actually common sense. That principle is not included in the government’s assessment framework for the Severn barrage – but it needs to be. It needs to be in planning policy, too: for we are beginning to realise that it would have made sense to build those giant wind turbines out at sea, where nobody gives a fig about them, instead of on the Essex marshes or the Solway Firth.

There is still hope that common sense may prevail. There is no doubt there is a potentially huge source of energy in the Severn estuary. The question is how to harness it in an environmentally friendly manner. One of the projects still under consideration is the concept of a tidal reef, with large and slow-moving turbines, strung between Minehead and Aberthaw. It could provide up to 1½ times the power of an environmentally destructive barrage. But its technology is less proven so it might not get built as readily as some of the more developed but damaging schemes.

Unless Ed Miliband, the energy and climate change secretary, finds a way of applying Clover’s Law when he announces the second phase of the Severn tidal power consultation later this month, the more damaging technologies will win. He needs to transform the remit into a challenge to the engineering industry. If he doesn’t, he might as well round up all the birds and the fish and feed them into the coal-fired power stations. At least that would save a few carbon emissions.

Charles Clover is author of The End of the Line, which examines overfishing around the world and is now a documentary film

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