What was done
The authors assessed the extent of decline in coral cover across the Caribbean via a meta-analysis of data obtained from a total of 263 sites described in 65 scientific studies.

What was learned
The authors report "a massive region-wide decline of corals across the entire Caribbean basin, with the average hard coral cover on reefs being reduced by 80%, from about 50% to 10% cover, in three decades."  However, they also report that "the rate of coral loss has slowed in the past decade compared to the 1980s."

What it means
The authors say "there is no convincing evidence yet that global stressors (e.g. temperature-induced bleaching and reduced rates of carbonation via enhanced levels of atmospheric CO2) are responsible for the overall pattern of these recent coral declines."  Instead, they lay the blame at the feet of "local factors originating both naturally (e.g. disease, storms, temperature stress, predation) and anthropogenically (e.g. over-fishing, sedimentation, eutrophication, habitat destruction)," which they say "are occurring at Caribbean-wide scales."