How does wave energy impact the environment?

Good... waves bring nutrients and food to shore on a regular basis, exposing different ecosystems which are neither suited for water or land but both. There are numerous bird species that live on small sea animals washed ashore. In shallow areas, waves can create sand bars that protect the mainland or even form islands for people. Waves also transfer massive amounts of oxygen into water, that aquatic animal life uses. Waves also increase the absorption of CO2 from air to water.

Bad... erosion. Waves erode beaches and ocean cliffs, witness the reshaping of the coasts.