Dr Bradley Opdyke from ANU met today with AIMS coral reef scientists to discuss the fate of the Great Barrier Reef under changing global climate conditions.

Opdyke outlined a range of geological and chemical evidence to suggest that coral reefs will not form and grow in a greenhouse-affected world because the coral's ability to form skeletons will be degraded by carbonate changes in the ocean. That change may come about within 100 years and coral reefs may change dramatically.

AIMS scientists, Dr David Barnes and Dr Janice Lough, argue that the ocean's buffering capacity is sufficient to prevent the disruption to coral growth, and that corals are not showing ill effects. They point out that instead of a 6-14% decline in calcification over the past 100 years predicted by the Opdyke group, their results show that calcification has increased by about 4%. Clearly this scientific debate must be pursued as a high priority.

The geological evidence shows that during the past 60 million years naturally high levels of CO2 have occurred when the world was considerably warmer. During these periods the world did not have reefs as we see them today. Tropical coral reefs formed only after the world cooled and Antarctica formed massive ice sheets.

Under the enhanced greenhouse effect the world is warming because of heat-trapping gases in our lower atmosphere produced by post-industrial society. The scientific community is presently debating the effect that this warming will have on coral reefs, but many argue that the environment of corals will shift to a point where major 'bleaching' events will become more common, and the water chemistry will change in a way that makes coral skeleton formation increasingly slow. Opdyke argues that within 100 years it may become impossible for corals to build and maintain reefs.

However, the scientific debate has been widened by Barnes and Lough who suggest that the ocean chemistry is more complex than portrayed above. They argue that the ocean can buffer the changes in acidity, and any changes in coral growth will be positive and driven more by temperature changes than by carbonate changes. The temperature changes may well, however, affect the frequency of future coral bleaching events and should not be dismissed as unimportant.

There is no doubt more to come. The debate is important and will become part of the wider global climate change debate.