We see this transformation right away. The island is a paradise, and then the boys land on it. The plane slashes a nasty burning line through the green peaceful vegetation. The burning strip hisses like a snake. The vines around the scar coil like snakes. The evil on the island is the evil that the boys brought with them. There is a lot of Garden of Eden imagery. Eden was a paradise and then Adam, Eve, and the serpent corrupted it. The island was a paradise, and then the boys arrived with their dark designs, fears, and corruptions and transformed it.