There’s some hopeful news for Australia’s Great Barrier Reef, long a victim of rising ocean temperatures and widespread bleaching. Last week, a monitoring group reported the highest amount of coral cover seen in 36 years, at least on two-thirds of the reef.
The northern and central reef is showing signs of recovery, while the southern part is still losing ground to outbreaks of crown-of-thorns starfish, according to an Australian Institute of Marine Science report. While these starfish are naturally occurring in the Indo-Pacific region, when their populations get out of balance they can devastate coral.
Mass bleaching events have hit the reef every year for a while, with underwater heat waves in 2016 and 2017 being especially damaging.
“Every summer the reef is at risk of temperature stress, bleaching and potentially mortality and our understanding of how the ecosystem responds to that is still developing,” said AIMS CEO Paul Hardisty in a media release. In 36 years of monitoring the Great Barrier Reef, scientists had never seen bleaching events happen so close together. “The 2020 and 2022 bleaching events, while extensive, didn’t reach the intensity of the 2016 and 2017 events and, as a result, we have seen less mortality. These latest results demonstrate the reef can still recover in periods free of intense disturbances.”
Hard coral cover increased in the reef’s northern region from 27% in 2021 to 36% this year. The central region went from 27% covered in 2021 to 33% in 2022.
Coral bleaching happens when the coral is under stress by changes in light, nutrients, temperature or other conditions. The coral expels the symbiotic algae that lives in its tissues, making it lose all color. This doesn’t mean the coral is dead, but it’s vulnerable and at risk of dying. And while the recent report contains some good news, scientists said these gains in coral cover could easily be reversed — especially as ocean temperatures continue to rise.
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