The coral reefs along the Yucatan are in bad shape, and have degraded significantly over the past decade. I have spoken with lots of local people (including naturalists) about this, and none of them mentioned anything about climate. They blame snorkelers, pollution and most of all sunscreen oils from snorkelers who swarm the reefs.
It is sad hearing about how vibrant the reefs here used to be, and seeing how much they have deteriorated.
