A new report has revealed a 32 per cent decline in coral cover of the outer reef slope communities in the far northern and northern Great Barrier Reef from 2014 to 2016.
Lead author of the report and UQ Global Change Institute’s (GCI) Dr Manuel Gonzalez-Rivero said the coral loss was due to unusually warm sea temperatures in 2015 and 2016, and to a lesser extent two strong cyclones in the region.
“Reefs in some of the most pristine and healthy regions of the Great Barrier Reef were severely impacted and even without considering further disturbances, will take decades to recover. Unfortunately, under the current coral bleaching observations, further coral loss is expected within the area of impact,” he said.
“Between 2012 and 2014, the loss in coral cover was restricted to sites affected by tropical cyclone Ita, with the highest and most widespread loss in coral cover occurring after the impact of tropical cyclone Nathan in 2014, and the coral bleaching event between 2015 and 2016.”
UQ Researchers from the GCI, in collaboration with the Department of Environment and Energy, undertook a large-scale survey in October 2016 to document the effect of these cumulative impacts on the outer reef slope communities at ~10 m depth in the far northern and northern Great Barrier Reef.
The 2016 data was compared to data GCI collected at the same locations and depths in 2012 and 2014 as part of the XL Catlin Seaview Survey – a total of ~100 km of reef was surveyed per survey year.
Coral species susceptible to cyclones and bleaching were the most affected, however given the strength and cumulative nature of these events, mortality was observed across a range of coral reef species, including stress-tolerant and slow growing corals.
The results confirm data collected by a number of other groups, including the National Coral Bleaching Task Force, Australian Institute of Marine Science, and the Great Barrier Reef Marine Park Authority and the Australian Research Council Centre of Excellence for Coral Reef Studies.
Chief Scientist and GCI Director Professor Ove Hoegh-Guldberg said adherence to the Paris Climate Agreement, to hold the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels average global surface, is therefore crucial to ensure the long-term sustainability of the Great Barrier Reef and coral reefs worldwide.