A study involving scientists from the United States and Australia compared 18th century British nautical charts with current satellite data to uncover some surprising facts about how the coral reefs in the Florida Keys have developed over the past two centuries.

"We found that some reefs had completely disappeared," said Professor John Pandolfi, from The University of Queensland (UQ).

The study, which included research from UQ and the Australian Research Council Centre of Excellence in Coral Reef Studies, was published recently in the Science Advances journal.

It was led by Professor Loren McClenachan, Assistant Professor at Colby College, in Waterville, Maine, USA. She added that more than half of the coral reef habitat mapped in the 1770s was no longer there. In fact, almost 90 percent of the coral had been lost in some areas, particularly those near land.

For this study, the loss of coral reef habitats was measured across a large geographic area. This is in contrast to most other studies that focused on the loss of living coral from smaller sections of the reef.

Professor Pandolfi said they discovered that coral reefs had previously existed in areas that are not presently classified as reef habitat. "When you add this to the 75 per cent loss of living coral in the Keys at that finer scale, the magnitude of change is much greater than anyone thought,” he said.