A few weeks ago I dived the Great Barrier Reef, near Port Douglas. It was one of the saddest days of my life. I am haunted by what I've seen. And infuriated.

I had come with hope, for some recovery at least from the largest coral bleaching event on record. But what I found was worse than I could have imagined. The Great Barrier Reef is losing its adjective.

Most of the reef's usually vibrant staghorn and plate corals are covered with an ugly green slime. Even some of the massive stony corals – the hardiest of all – are scarred with the tell-tale white of bleaching. The reef's diverse and stunning fish population are starving.

A green turtle passes by. As the dead reef breaks down, its habitat will be eroded to rubble. And climate change is affecting the species in other ways. Rising seas have massively degraded its most important nesting site – Raine Island in the northern Great Barrier Reef. Those same rising waters caused, around 2011, the first mammal extinction brought about directly by climate change, when the entire habitat of the Bramble Key melomys (a native rodent unique to the Great Barrier Reef) was destroyed by saltwater intrusion.