A little more focused than the original, but it sort of feels like a setup that doesn't go anywhere. The main anomalous property of the island is that any plant matter brought to it dies and withers rapidly - the wall should be in some way linked to that, because as is it seems like they're two completely unrelated phenomena. We're told there's something written on the wall, but we don't know what it means. We're told there used to be a settlement on the island, but we know nothing about who lived there, how long they were there, why/how they left, etc.
Also, how is there a permanent base on the island if all vegetable matter decays rapidly once it comes ashore? Are they eating nothing but red meat and salt 24 hours a day, or are we airlifting in food five-six times a day? They wouldn't even be able to have a pepper shaker in the mess, since black pepper is plant-based and so it would rot, let alone any starch or sugar-based products. Might be best to keep the permanent staff on a ship anchored just outside the death zone.