The reefs off the American Florida Keys have apparently been deteriorating for some years now. A study was done by researchers at a Florida university on why,

The reefs off the American Florida Keys have apparently been deteriorating for some years now. A study was done by researchers at a Florida university on why, with the expectation that the primary cause would be global warming. It was not. The main cause was apparently nutrient-rich runoff from south Florida agriculture and fertilized lawns. (Nutrients lead to increased growth of algae and other non-coral things, things which are not good in large quantities for coral.) And the good news is that this kind of runoff is easier to fix than global warming. My fear is that when everything can so easily (and semi-plausibly) be blamed on global warming, no one will look for other causes. ICO coral reefs, those might include runoff, but also over-fishing, over-touristing, dumping or leakage of sewage and trash and oil off boats, and even reportedly sun screen worn by those tourists. And studies like the one above will not get done, because everyone "knows" what the problem is, so the environment--the reefs, in this example--will get worse when they could get better.