The Severn estuary could become the site of a giant tidal barrage, generating huge amounts of clean energy but obliterating vulnerable wildlife habitats (Image: Kevin Allen / Alamy) You can’t generate vast amounts of green energy without large-scale engineering projects (Image: Toby Smith / Construction Photography)

YOU can understand the frustration on both sides. Environmentalists worldwide are clamouring for bold action to end the burning of fossil fuels and plug the world into renewables. Politicians throw their weight behind a $14 billion scheme that would replace the equivalent of eight coal-fired power stations with tidal power. What do they get for their pains? Green outrage.

“This massively damaging proposal cannot be justified,” said Graham Wynne, chief of the UK’s normally staid Royal Society for the Protection of Birds (RSPB). Friends of the Earth said it was “not the answer”. What is going on here? Have greens lost the plot? Has environmentalism been hijacked by big construction companies? Or do we simply have to learn that even environmental energy comes at an environmental cost?

The project causing all the controversy is the Severn barrage on the west coast of Britain, but similar stories are playing out across the world. As greens gradually win the argument for switching to renewable energy, they are finding that they don’t always like the look of the new world they are creating.

The problem is one of scale. Bigness is often an issue for greens, many of whom grew up reading one of the movement’s key texts: E. F. Schumacher’s Small Is Beautiful. They liked biofuel while it was about recycling cooking fat, but …