Australia: Great Barrier Reef massively damaged

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18.05.2022 14:42
Kategorie: News

More than 90 percent of corals in greatest danger

The Great Barrier Reef off the northeast coast of Australia is the largest contiguous collection of more than 2,900 individual coral reefs on earth. The UNESCO World Heritage Site is nearly 2300 kilometers long and covers an area roughly the size of Germany. The world's largest coral reef is also a tourist magnet. Every year, almost two million visitors want to discover the fascinating underwater world of the Great Barrier Reef.

Gallery 1 here

High temperatures despite "La Nina"

The ongoing heat wave in Australia has damaged more than 90 percent of the Great Barrier Reef's corals, according to a government report. "Climate change is advancing, and the reef is already facing the consequences," the report said last week. Of the 719 reefs surveyed, 654 - or 91 percent - showed some degree of coral bleaching, according to the report.

The heat wave has been ongoing since December. It is the first time since temperature measurements were taken that the reef was affected by bleaching during a "La Nina" weather period, when lower temperatures are normally expected.

The global climate phenomenon, counterpart to El Niño, began last fall and is currently ongoing. "Normally, La Niña brings rain and cooler temperatures to the Great Barrier Reef, providing much-needed relief from hot summer conditions," explains Kathy Townsend, a marine biologist at the University of the Sunshine Coast in Queensland state. However, while Queensland and New South Wales did indeed get plenty of rain, the cooler conditions failed to arrive; a death blow to many coral colonies that would be in dire need of temperature relief.

Although bleached corals are still alive and moderately affected sections of reef may be recovering, "heavily bleached corals have higher mortality rates," the report said. Coral bleaching is a phenomenon that occurs when corals are stressed and shed the colorful algae that live within them.

Bad forecast for the world's natural heritage site

Coral bleaching off the east coast of Australia made headlines around the world for the repeated time last year. Bleaching is the term used to describe a fading of the colorful stony corals: When water temperatures are too high, the cnidarians repel the algae that provide the coloration, with which they otherwise live in a community for mutual benefit. Without these zooxanthellae, they cannot survive in the long term and die off if the algae do not reestablish themselves within a few weeks or months.

Since 1995, the Great Barrier Reef in Australia has lost more than half of its corals permanently. The reason is the climate crisis and the associated warming of the oceans. At the beginning of last year, coral researchers already summed up "It's five to twelve from a research perspective."

One of the reasons for the advancing process is believed to be that water temperatures were up to four degrees higher than usual. Corals are cnidarians that live in a mutually beneficial community with algae. "It's the first time we've had bleaching on the Great Barrier Reef over a two-year period," the director of the 345,000-square-kilometer marine park, David Wachenfeld, said most recently.

The Australian authority in charge of the Great Barrier Reef Marine Park downgraded the long-term outlook for the reef from "poor" to "very poor" back in 2019. The situation has worsened significantly since then.