Piers, groins, or other structures aren’t allowed. Sea walls are only built in limited areas where the coast is exposed reef. And the sewage outfall is taken by a pipe very far beyond where people fish. The island isn’t overpopulated.
The article, written by Patrick Nunn, a Geography professor, is here https://theconversation.com/rise-and-fall-social-collapse-linked-to-sea-level-in-the-pacific-56268
My post from 2014, "Drowning Islands", is here if you wish to read a counterpoint to Nunn's article.