Huge sections of the Great Barrier Reef, stretching across hundreds of miles, were recently found to be dead, killed last year by overheated seawater. Sections of the reef that escaped this fate have been bleached - a sign that it will soon die off.

Globally, the ocean has warmed by about 1.5 degrees Fahrenheit since the late 19th century, by a conservative calculation, and a bit more in the tropics, home to many reefs.

The Great Barrier Reef in Australia has long been one of the world’s most magnificent natural wonders, so enormous it can be seen from space, so beautiful it can move visitors to tears.

But the reef, and the profusion of sea creatures living near it, are in profound trouble.