The Islands of Ireland: Tarbert morphed onto the mainland

Tarbert Island.

Geography is often the defining factor for the destiny of an island. Those islands that lie close to the shore have often been snapped up by interests on the mainland and their morphology changed to something completely different. 

Exhibit A: Haulbowline, in Cork Harbour was transformed into a naval base. Exhibit B: the adjacent Corkbeg Island, with its fin de siècle hotel, was converted into an oil refinery base.