The 'underwater bushfire' cooking Australia's reefs
Australia is grappling with an "underwater bushfire" that is causing devastation to the country's world-famous coral reefs, with scientists warning that the reef-building corals are experiencing their worst bleaching event ever.
The devastation is caused by a combination of climate change and a prolonged marine heatwave, which has led to the highest global sea surface temperatures since measurements began.
The heat is causing corals to expel the microscopic algae called zooxanthellae that give them their vibrant colors, which can lead to coral bleaching and death.
The Australian Institute of Marine Science's Peter Doherty says the phenomenon is causing more damage to Australia's reefs than any other event in the past century.
"We have never seen bleaching like this, and we have never seen temperatures like this, and the heatwaves just keep coming," said Doherty.
In 2016, corals were affected by bleaching in the northern Great Barrier Reef, but this is the first time it has spread further south, affecting corals off the coast of Sydney.
The bleaching is caused by a heatwave that has been afflicting much of the world for the past three months, causing hundreds of deaths and unprecedented high temperatures in normally temperate regions.
The effects of bleaching can be reversed if the heat stress dissipates and corals have a chance to recover, but if it continues, it can cause them to die.
The damage to the country's reefs could be devastating, as they provide habitat to many species of marine life and are a major draw for tourists.
Doherty called for urgent action to reduce carbon emissions, saying, "We need to get emissions down, we need to do it now, and we need to do it quickly."
The effects of climate change are evident in the rising sea levels, increased frequency and intensity of extreme weather events, and degradation of marine ecosystems.
