Half of the Great Barrier Reef’s corals have died over the past 25 years, scientists said on Wednesday, warning that climate change is irreversibly destroying the underwater ecosystem.A study published in the Proceedings of the Royal Society Journal found an alarming rate of decline across all sizes of corals since the mid-1990s on the vast reef off Australia’s northeast coast.Larger species, such as branching and table-shaped corals, have been affected hardest – almost disappearing from the…