Many of the world's coral reefs are in a critical condition - all are under threat. In the International Year of the Reef, Kieran Mulvaney assesses the problems facing the ocean's richest ecosystems. To some, the open ocean exists as a vast wasteland, an aquatic desert largely devoid of life beyond the occasional playful dolphin or breaching whale.
Coral reefs are a different matter.
No need here for any expensive equipment to scan the tiniest water droplets or to plumb the ocean depths. As long as you're on the coast in the right parts of the world, you need nothing more than a mask and snorkel to enter the realm of the reef. And a coral reef can be host to an amazing richness of life. Indeed, reefs are home to by far the greatest abundance of species in any marine ecosystem. A recent estimate suggests that there may be about 93,000 species already described from coral reefs.