Coral of an unknown provenance.

Optimists look at the Great Barrier Reef and see it half-full of coral.

Australia’s Great Barrier Reef has lost more than half its coral cover since 1985, according to a new study published Monday. The loss has been spurred by a combination of factors including hurricanes, coral-eating starfish and coral bleaching.

The paper, in the Proceedings of the National Academy of Sciences, is the most comprehensive survey of a reef system over such a long period. The researchers from the Australian Institute of Marine Science found that reef cover fell from 28 percent to 13.8 percent over the past 27 years, with two-thirds of the decline occurring since 1998.

Pessimists are in the corner, sobbing and/or catatonic.

Hat-tip: Steve Silberman.