A Ghost Town Under the Sea

The Great Barrier Reef is one of the most iconic natural phenomena on the planet, as well as the world's largest coral reef. At more than 1400 miles long, it was visible from space and home to thousands of species of sea life. But that was in its prime. Today, the Great Barrier Reef is a shadow of its former self--so much so that some would argue that has reached a point of no return, where no amount of conservation effort will ever be able to fully restore it.
The reasons for the reef's decline is due to a variety of factors. Certainly water pollution and the overfishing of local sea life have played their parts, but the biggest factor by far is the increase of water temperatures due to global warming. Corals, such as those that make up the reef, cannot tolerate such drastic shifts in temperature. This is because most corals live mutualistically with algae, which feed on sunlight and in doing so provide nutrients to the coral. If the temperature is too high, the algae die, leaving the coral "bleached" and starving to death. As of the most recent survey, more than 50% of the coral in the Great Barrier Reef is completely dead, and 93% of the coral shows at least some signs of "bleaching." Small pockets of healthy coral do remain, but they are unlikely to last for much longer, especially if temperatures continue to rise.
The result of all this is essentially an underwater ghost town: the dead, pale husks of the coral remain attached to the seabed, but most of the other animals that once depended on this for food and shelter no longer live there.
Is it too late to save the Great Barrier Reef? That depends on who you ask and what you mean by "save". Since the Great Barrier Reef is a vast, complex ecosystem and not a single species, there is no single point at which it goes extinct, and no one in-situ conservation plan that works for every component. However, we do have a good idea of what the issues plaguing it are, and if we change our lives to reflect that and cut down on global warming, the Great Barrier Reef may yet rebound.

                                              
The coral on the left in this picture is healthy. The coral on the right has had all of its algae die, and has become "bleached".