Their f'ing with ya dude. It's an uninhabited island with horses on it and the horses swim to other islands from time to time. The whole thing could wash away and the horses would be long gone before that happens. They are likely doing it to protect the inhabited island and coast behind it. Which is futile.
I'm just saying, if you photoshopped cute hats and big ol porno cocks onto the horses in that picture it might make you feel a teeny bit better.