The correct answer to this open question is the following.
Tidal barrages can have negative environmental impacts for the following reasons.
Tidal barrage uses big and noisy turbines. If animals swim through the turbines, they risk their life. The silt deposits that are created by this barrages can block the sunlight and affect the life of plants. Tidal barrages change the movement of water into estuaries affecting fishes reproduction. Tidal barrages change the movement of water into estuaries affecting fishes reproduction. This technology is very expensive.
