NOAA - 4th Global Mass Coral Bleaching Since 1990s Now Underway, HItting Reefs In 53 Countries

The Great Barrier Reef just experienced its worst summer on record, and the US-based National Oceanic and Atmospheric Administration (NOAA) announced last month that the world is undergoing a rare global mass coral bleaching event — the fourth since the late 1990s — impacting at least 53 countries. The corals are casualties of surging global temperatures which have smashed historical records in the past year — caused mainly by fossil fuels driving up carbon emissions and accelerated by the El Niño weather pattern, which heats ocean temperatures in this part of the world.

CNN witnessed bleaching on the Great Barrier Reef in mid-February, on five different reefs spanning the northern and southern parts of the 2,300-kilometer (1,400-mile) ecosystem. “What is happening now in our oceans is like wildfires underwater,” said Kate Quigley, principal research scientist at Australia’s Minderoo Foundation. “We’re going to have so much warming that we’re going to get to a tipping point, and we won’t be able to come back from that.”

Bleaching occurs when marine heatwaves put corals under stress, causing them to expel algae from their tissue, draining their colour. Corals can recover from bleaching if the temperatures return to normal, but they will perish if the water stays warmer than usual. “It’s a die-off,” said Professor Ove Hoegh-Guldberg, a climate scientist at the University of Queensland in Australia and chief scientist at The Great Barrier Reef Foundation. “The temperatures got so warm, they’re off the charts … they never occurred before at this sort of level.”

The destruction of marine ecosystems would deliver an effective death sentence for around a quarter of all species that depend on reefs for survival — and threaten an estimated billion people who rely on reef fish for their food and livelihoods. Reefs also provide vital protection for coastlines, reducing the impact of floods, cyclones and sea level rise. “Humanity is being threatened at a rate by which I’m not sure we really understand,” Hoegh-Guldberg said.

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https://www.ctvnews.ca/climate-and-environment/like-wildfires-underwater-worst-summer-on-record-for-great-barrier-reef-as-coral-die-off-sweeps-planet-1.6940563