Ancient coral a global warming mystery

Ancestors of modern corals thrived during a time when temperatures and levels of carbon dioxide were higher than they are today, a researcher says.

An ancient coral reef specimen now on display at the Natural History Museum in London is at the centre of a global warming mystery spanning 160 million years.

The exhibit is proof that ancestors of modern corals somehow thrived during the Late Jurassic period when temperatures were warmer and atmospheric levels of carbon dioxide higher than they are today.

Yet global warming in the 21st century is already associated with serious damage to coral reefs caused by "bleaching".

Dr Ken Johnson, coral reefs researcher at the London museum, said: "By researching historical fossil corals like this, we can understand and predict the impact of climate change and other environmental factors on coral reefs over time.

"This 160-million-year-old specimen is an ancestor of some of the corals on our planet today, showing us that a sustainable future for coral reefs is possible because they can survive severe global environmental changes."

Early corals also managed to survive the mass extinction at the end of the Cretaceous period 65 million years ago that wiped out the dinosaurs and many other species.

If greenhouse gas emissions continue unchecked, atmospheric carbon dioxide is expected to match Late Jurassic levels by 2100 and to exceed them by 2250.

Bleaching occurs when stressful environmental conditions cause corals to expel the symbiotic algae living in their tissues, turning them white.

Corals depend for their survival on the algae, which provide them with oxygen and nutrients. When they bleach they begin to starve.

Professor Richard Twitchett, palaeoecology researcher at the Natural History Museum, said: "At the time this coral reef was alive, 160 million years ago, our planet's marine biodiversity was as high as it had ever been.

"The fact that this coral reef lived in a much warmer world shows that if we monitor and control future changes, coral reefs can remain one of the most important ecosystems on Earth."

Source AAP

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