Scientists who completed the longest-ever coral reef survey, spanning almost a century, have found some habitats in Australia’s Great Barrier Reef have “vanished completely”—and man-made climate change is partly to blame.
The 55 acres of reef surrounding the Low Isles on the northern Great Barrier Reef has seen major changes since 1928, and are unlikely to return to their original state, according to the authors of the study published in the journal Nature Communications.
To conduct the study, researchers at Bar-Ilan University and Interuniversity Institute for Marine Sciences in Israel and the University of Queensland in Australia looked at data collected 91 years ago during an expedition by the Great Barrier Reef Committee and the Royal Society of London. This trip saw a diving helmet used for the first time at the coral cay to the north-east of Port Douglas, Queensland.
The pioneering team also created a map of the island based on aerial photography, which the authors of the latest study used to examine how the coral reef communities have changed over time. The researchers also looked back on research in the area conducted in 1954, as well as carrying out their own in 2004, 2015 and 2019.
By examining 13 sites in the Low Isles, the team found “a long-term systematic decline” in the richness of coral and invertebrates at the Low Isles. The number of species of coral in every one had fallen, from a total of 40 to 21. Also, as coral coverage has thinned and the organisms become less structurally complex, invertebrates who rely on them have become less diverse, too.
These inshore reefs are threatened by a range of factors, from global warming to localized man-made problems such as flooding, which sends nutrients and sediments into the water. But cyclones, including one in 1999, have had the biggest effect on the reefs, and for the longest period of time, the scientists found. Coral communities still haven’t recovered from the ravages of cyclones that hit five decades ago.
Over the past nine decades the sea level in this area his risen by 7.9 inches, which may cause reef drowning, the authors warned. The sea surface temperature has meanwhile spiked by around 0.7 C, and coral reefs have been hit by mass bleaching.
Branching corals that inhabit the reef are, for instance, vulnerable to changes such as shifts in temperature. Repeated floods, as well as bleaching and marine heatwaves, could, therefore, explain the extinction of many of these species in the area.
The work comes as coral reefs are “under rapid decline, putting the food and livelihoods of hundreds of millions of dependent people at risk,” the authors warned. As such, scientists are trying to understand how coral reefs can cope and recover from a combination of natural disturbances, as well as manmade problems on a local and global scale.
Co-author Professor Maoz Fine, who studies the resilience of reefs and corals at Israel’s Bar Ilan University, told Newsweek that as detailed records only exist for the Low Isles, it is not clear if the findings are representative of other inshore reefs, said Fine, “although we are pretty sure this is the case.”
Fine said he was shocked to find some habitats and coral communities have not only changed, but vanished completely since 1928.
The coral expert said the study highlights the extent to which reefs can shift from a healthy to a poor state, and how important it is to minimize localized problems when these organisms must also contend with the effects of climate change to survive.
“There is climate change that affects all reefs,” he said. “The combined effect of global and local disturbances presents inshore reefs with big threats to their survival.”
Fine told Newsweek he was inspired to look back and examine long-term changes on reefs after reading the 1928 expedition reports.
Addressing what can be done to protect reefs, Fine argued: “We need a culture change to a less ‘carbon-hungry’ society. We have to convince policy makers to adhere to the Paris agreement and do utmost to stabilize our mean temperature below 1.5 C above pre-industrial temp if we are to manage our natural resources and benefit from the many ecological services that coral reefs provide us with.”
“We should also minimize land-based local disturbances and the effect of the growing coastal population on the ocean,” he added.
