Many of the Caribbean's coral reefs could vanish in the next 20 years, according to a report published by the International Union for the Conservation of Nature (IUCN).
Data from more than 35,000 surveys suggests that habitats have declined by more than 50% since the 1970s.
The report's authors believe that over-fishing and disease is mainly to blame.
They say the trend could continue if nothing is done, but with protection the reefs could bounce back.
The report, which was also authored by the Global Coral Reef Monitoring Network, looked at data collected between 1970 and 2012 from 90 reef habitats and is the most comprehensive assessment of corals in this region.
The authors concluded that many reefs in the Caribbean were undergoing a dramatic transformation - changing from colourful realms, bursting with life, to barren habitats, covered in slimy algae.
They said the damage had been driven by the loss of some of the reefs' key inhabitants.