A tidal power barrage across the Severn estuary - a project that would create new construction jobs - would increase biodiversity and boost water quality.
This is the conclusion of the journal Proceedings of the ICE (Institute of Civil Engineers) - Maritime Engineering, which analysed previously unknown data on the ecological impact of the La Rance's tidal barrage in Brittany, which is 42-years-old.
It was revealed that flora and fauna surrounding the 750-metre barrage "is far richer and more abundant" when compared to nearby areas, while in some places it has nearly doubled.
The water quality has remained "unimpaired".
These positive effects, the report authors say, will be mirrored following the completion of a barrage between Cardiff and Weston-super-Mare.
"There can be few major civil engineering projects in the world whose construction would induce such an increase [in biodiversity] but this is unavoidable," the report argued.
"Equally unavoidable, the 'Severn Effect' would drastically improve water quality."
Plans to dam or construct a barrage across the Severn esturary have existed since the 19th century.