A $1 million project to restore seagrass off the Adelaide coast is about to begin as part of an effort to stop seabed erosion and support the marine environment.

South Australian Environment Minister Davie Speirs said about one third or 6000 hectares of seagrass off the Adelaide coast has been lost over the past 50 years and that seagrass is an important buffer for the ocean's wave and current energy that helps prevent erosion of nearshore areas

The project is set to re-establish seagrass meadows between suburban Glenelg and Semaphore.