Harnessing the predictable power of the tides has been a dream of engineers for decades. This led to a number of proposals to build barrages across some of our most iconic and environmentally sensitive estuaries such as the Mersey and the Severn. The dream of abundant renewable energy eventually ended in the stark realisation of the massive costs both financially and in terms of their profound environmental impact.
They were a nightmare for nature.
This week a new approach to tidal power on the Severn is making the news, one which holds out the prospect of tapping the renewal energy of the tides whilst keeping the impact to our natural environment within potentially acceptable bounds.
Tidal lagoons are an interesting new idea that deserves serious consideration.
We welcome innovation – indeed the RSPB was at the forefront of stimulating new thinking while we were challenging the folly of building a barrage across the Severn estuary. . And we’ve been working with Tidal Lagoon Power to explore the opportunities and risks constructively, focussing on their proposals for Swansea Bay.
But let’s be under no illusion, each tidal lagoon installed will change the shape of the coastline, affecting the flow of water through the Bristol Channel, with knock on effects for sediment transport, habitats and flood risk. There is an urgent need for research to understand what the effects of different combinations of lagoons might be, in order to highlight, and potentially mitigate, negative environmental and social impacts. The cumulative effects of large infrastructure projects of this type can be significant and far reaching: research by the University of Liverpool demonstrated that multiple tidal barrages on the UK’s west coast had the potential to raise sea level on the east coast of Ireland by several centimeters.
Rushing to roll out a new technology at multiple sites around the coast risks failing to learn vital lessons – the crucial first step is to agree a sound monitoring programme that validates the modelling and predictions that are, currently, all we have to go by.
The biggest risk to the future of tidal lagoons is to fall victim to short term thinking driven purely by financial considerations. The impact of a new technology must be properly understood in the context of the importance of the coast environment in which they are proposed.
Some aspects of the Severn estuary environment are well known – the distribution of the birds that winter there in internationally important numbers is one example. The Severn is even more important for fish including the globally threatened Atlantic eel and Twaite shad. Disruption of coastal environments can have profound implications for flood management, the complex issues around the potential release of carbon currently locked up in the sediments of the estuary, the survival of archaeological resources and fisheries. Understanding the implications of development on fundamental ecosystem services – those benefits our environment bestow on our lives – is crucial and should not be overlooked in the short term haste to roll out a new technology.
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