The Great Barrier Reef has lost half of its coral reefs

Researchers from the ARC Center of Excellence for Coral Reef Studies, in Queensland, northeastern Australia, assessed coral populations and the size of their colonies along the Great Barrier Reef between 1995 and 2017, and found nearly all coral populations depleted, they said Tuesday.

The Great Barrier Reef, the largest coral reef in the world, covers nearly 133,000 square miles and is home to more than 1,500 species of fish, 411 species of hard corals, and dozens of other species.

“We’ve found that the number of small, medium and large corals on the Great Barrier Reef has decreased by more than 50% since the 1990s,” co-author Terry Hughes, Distinguished Professor at ARC’s Center of Excellence for Coral Reef Studies, says the current situation.

Coral reefs are essential to the health of marine ecosystems – without them, ecosystems would collapse and marine life would die.

The sizes of coral populations are also vital when it comes to corals’ ability to reproduce.

“The vibrant coral group has millions of small corals, as well as many large corals – the large mother that produces the most larvae,” said Andy Dietzel, PhD student at the Center of Excellence for Coral Reef Studies at ARC. The current situation.

“Our results show that the restoration capacity of the Great Barrier Reef – its resilience – is at risk compared to the past, because there are fewer children, and fewer adults who reproduce significantly.”

Declines in coral numbers have occurred in shallow and deep waters, experts have found, but branching and table-shaped corals – which provide habitats for fish – have been hardest hit by mass bleaching events in 2016 and 2017, triggered by record temperatures.

The report’s authors warn that climate change is increasing the frequency of “coral reef disturbances”.

William West / AFP / Getty Images

Warm ocean temperatures are the main driver of coral bleaching, when coral turns white in response to stress in extremely hot waters. Bleaching does not kill corals right away, but if temperatures remain high, the corals will eventually die, destroying the natural habitat of many species of marine life.

Tuesday’s study found sharp degradation of coral colonies in the North and Central Great Barrier Reef following mass bleaching events in 2016 and 2017.

The Great Barrier Reef has suffered from several mass bleaching events in the past five years, and experts said the southern portion of the reef is also experiencing record temperatures in the early 2020s.

“We used to think that the Great Barrier Reef is protected by its enormous size – but our results show that even the largest and relatively well-protected coral reef system in the world is increasingly threatened and in decline,” Hughes said.

The report’s authors warn that climate change is leading to an increase in the frequency of “coral reef disturbances” such as marine heat waves.

“There is no time to lose – we must drastically cut greenhouse gas emissions as quickly as possible,” the report’s authors warned in the paper published in the Proceedings of the Royal Society.

CNN’s Helen Reagan contributed to this report.