Kiritimati's corals are dying

Kiritimati is one of the world’s largest coral islands, located near the centre of the Pacific Ocean and part of the island nation of Kiribati (formerly the Gilbert Islands). It is also one of the Line Islands, which is one of the world’s longest island chains. The name Kiritimati is a re-spelling of Christmas, which was the name given to the island by Captain James Cook when he landed there on Christmas Eve in 1777, although he was not the first European to discover it.

Despite being created from coral, the phenomenon known as coral bleaching threatens the future of the island in terms of its ecology and economy. It has been estimated that 95% of its coral reefs may die within the next few years, and it could take decades for them to recover, if they ever do. A recent survey has shown that 80% of the giant table-top corals around the island are already dead and another 15% are dying.

The problem is that rapid increases in water temperature cause the tiny algae that nourish coral and give it its colour to be expelled, leaving behind ghostly white skeletons that are subject to disease and erosion. The algae are at the base of the food chain of a coral reef, so without them there are no fish, which are unable to escape to other islands because of Kiritimati’s remoteness. Without the fish, there is no livelihood for the human population of the island.

At the heart of the problem is the El Nino phenomenon, which is a periodic shifting of warm water within the Pacific Ocean that has worldwide consequences for weather patterns. El Nino events have been known about for centuries and can be expected every three to seven years, but their intensity has been increasing in recent decades, with global warming being a prime suspect. The warming of the ocean around Kiritimati, for example, has been measured at around 3.5⁰ C.

Short-term rises in water temperature can lead to the temporary bleaching of coral, from which a relatively rapid recovery can be expected as things return to normal in non-El Nino years. However, it is expected that future El Ninos will be more intense and more frequent, which means that coral reefs will find it very hard to recover.

Coral bleaching is a worldwide phenomenon, with the Caribbean being another region that has suffered badly. However, the problem at Kiritimati is particularly bad and few scientists are optimistic about its prospects if ocean temperatures continue to rise, as seems likely given current trends.

© John Welford