Kina Barrens or Urchin Barrens in the Hauraki Gulf. Kina Barren areas are where an over population of Sea Urchins / Kina have mowed down the seaweed and kelp forests, leaving barren bare rocky bottoms, reducing the biodiversity. The over population is caused by reduction in predators like crayfish, snapper, red moki etc from over fishing pressure. This is why large marine reserves are really important to try and restore the balance. For more info, here's an interview on Radio New Zealand. https://www.rnz.co.nz/audio/player?audio_id=201872063

And another piece; https://www.scoop.co.nz/stories/SC1412/S00052/international-science-paper-reveals-collapse-of-kelp-beds.htm