Before sacrificing an island, you could always see if there’s somewhere that needs a harbour or the like. This has been considered before, e.g. https://en.wiki

Before sacrificing an island, you could always see if there’s somewhere that needs a harbour or the like. This has been considered before, e.g. https://en.wikipedia.org/wiki/Project_Chariot https://en.wikipedia.org/wiki/Project_Chariot