Urchins can be highly destructive to kelp forests. They are also a delicacy for sushi-lovers.
The first recorded modern artificial reef came from Japan 500 years ago, where rubble and rocks were used to grow kelp. 180 years ago, logs were placed in coastal waters around South Carolina as fish aggregation devices. Today artificial reefs can be found throughout the world, very often placed - if not created - to fill a specific purpose.