Many large coral reefs around the world are fading due to rising sea temperatures in the fourth global bleaching event, and satellites are tracking the carnage.

The second devastating event in the last decade affected more than half of the world’s coral reefs in the Pacific, Indian and Atlantic oceans. This may be the worst bleaching ever on Australia’s famous Great Barrier Reef, according to the US National Oceanic and Atmospheric Administration and the International Coral Reef Initiative, which confirmed the bleaching on Monday (April 11).

Coral bleaching occurs when corals are exposed to stress and wash out symbiotic algae called zooxanthellae. These algae live inside corals and are critical to their survival; Without zooxanthellae, corals would not only lose their color but also face the risk of starvation and disease. Corals, which are actually animals and give life to millions of people, begin to die if the waters they live in remain at high temperatures.

“As the world’s oceans continue to warm, coral bleaching is becoming more frequent and severe,” said Derek Manzello. expression From April 15th. Coral die-offs “harm people who depend on coral reefs for their livelihood.”

Satellites regularly collect data on ocean temperatures, water quality and coral color changes from vantage points in Earth orbit, helping scientists identify reefs at risk.

The data they beamed back to Earth helped create the Allen Coral Atlas, the world’s first real-time coral bleaching monitoring tool, launching in 2021. The tool creates a mosaic of coral reefs around the world based on images of the Earth’s surface taken by two European Sentinel 2 satellites and a spacecraft belonging to San Francisco-based Planet. Planet operates several satellites, including the 150 shoebox-sized Dove cubic satellite.