A new report by the Global Coral Reef Monitoring Network (GCRMN) documents a loss of approximately 14% of corals globally since 2009. The “Status of Coral Reefs of the World: 2020” provides the most comprehensive analysis of global coral decline, drawing on data collected from more than 300 scientists across 73 countries over the past 40 years. 

Global coral cover is diminishing due to a persistent surge in sea surface temperatures caused by climate change. It has shrunk by over 14% between 2009 and 2018 – an area more than the size of Australia’s reefs combined – and will continue to do so as temperatures spike. Coral reefs occurring in South Asia, Australia, the Pacific, East Asia, the Western Indian Ocean, The Gulf, and Gulf of Oman took the biggest hit during the past decade. 

The Status of Coral Reefs of the World: 2020, published early this month, explores in detail the impact of climate change on coral reefs around the world. It is the largest analysis of global coral reef health to date; drawing on research aggregated from more than 300 scientists across 73 countries over 40 years. It includes over two million individual observations across 12,000 sites globally. The research is funded by the UN Environment Programme (UNEP) and is in its sixth iteration this year. 

The report highlighted large scale bleaching events as the biggest threat to coral reefs including an acute event in 1998, which alone destroyed 8% of the world’s reef systems. Corals release their colourful food producing microalgae when waters become too warm and they eventually starve to death. The long term reduction in coral cover over the past decade coincides with a consistent elevation in global sea surface temperatures. 

The analysis also found that reef algae, a common signal of stress, have increased by 20% over the past decade, in line with diminishing hard coral cover. Prior to this, there was twice as much coral to algae in reef ecosystems. The increase in reef algae is concerning as algae-dominated reefs tend to lose their architectural complexity and structural integrity to supporting high levels of marine biodiversity. 

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According to Inger Andersen, Executive Director of the UN Environment Programme (UNEP), “since 2009 we have lost more coral, worldwide, than all the living coral in Australia. We are running out of time: we can reverse losses, but we have to act now. At the upcoming climate conference in Glasgow and biodiversity conference in Kunming, decision makers have an opportunity to show leadership and save our reefs, but only if they are willing to take bold steps. We must not leave future generations to inherit a world without coral.”

On a brighter note, the report also found that most coral reefs are hardy enough to recover on their own if the environmental conditions prevail. Global cover for instance has rebounded to pre-1998 levels within a decade. Some recovery was also observed in 2019 with coral reefs regaining 2% of their cover. However, longer-term recovery would take a global commitment to climate and oceanic action. 

Dr Paul Hardisty, CEO of the Australian Institute of Marine Science adds, “This study is the most detailed analysis to date on the state of the world’s reefs, and the news is mixed. There are clearly unsettling trends toward coral loss, and we can expect these to continue as warming persists. Despite this, some reefs have shown a remarkable ability to bounce back, which offers hope for the future recovery of degraded reefs. A clear message from the study is that climate change is the biggest threat to the world’s reefs, and we must all do our part by urgently curbing global greenhouse gas emissions and mitigating local pressures.”

The UN Decade of Ocean Science for Sustainable Development and the UN Decade on Ecosystem Restoration kicks off this year. The campaigns strive to preserve the world’s coral reefs through scientific advancement and conservation efforts. Further, the 15th meeting of the Conference of the Parties (COP) to the Convention on Biological Diversity held this month and again early next year will solidify a post-2020 global biodiversity action plan for the next decade.