In our age, coral reefs are the canary in the coal mine. Tim Radford writes:
Forty years ago, the world’s coral reefs faced a known risk: every 25 or 30 years, ocean temperatures would rise to intolerable levels.
Corals would minimise the risk of death by everting the algae with which they lived in symbiotic partnership: that is, the reef animals would avoid death by getting rid of the algae, deliberately weakening themselves.
This response is known as bleaching, and it can have a catastrophic effect on other life on the reef. In the Pacific such episodes were sometimes linked to cycles of ocean warming known as an El Niño event.
By 2018 the odds had altered. Coral reefs now face this hazard every six years. That is, in four decades of global warming and climate change, the risks have multiplied fivefold.
We still have not got used to the fact that climate change sets up a series of geometrical progressions. The longer we refuse to do something about it, the faster catastrophe approaches. Consider the following study from James Cook University:
Before the 1980s, mass bleaching of corals was unheard of, even during strong El Niño conditions, but now repeated bouts of regional-scale bleaching and mass mortality of corals has become the new normal around the world as temperatures continue to rise,” said Terry Hughes, who directs Australia’s Centre of Excellence for Coral Reef Studies at James Cook University.
He and colleagues report in the journal Science that they analysed data from bleaching events at 100 locations around the planet between 1980 and 2016. Bleaching events are a fact of life for corals: these little creatures tend to live best in temperatures near the upper limit of their tolerance levels, and respond to extreme events by rejecting the algae that normally provide the nutrients they need.
But as global air temperatures have increased, in response to profligate burning of fossil fuels that increase greenhouse gas levels in the atmosphere, so have sea temperatures. And Professor Hughes and his team report that in the last two years more than a third of all bleaching events have been “severe,” extending over hundreds of kilometres.
Disaster is no longer inching its way toward us. It's galloping our way. And we close our eyes.
Image: Green Left Weekly