Coral Reef Status – The Good, the Bad, and the Truth
Coral reefs hold a special place in both our hearts and as critical ecosystems that support a staggering array of marine life. But what exactly is going on with the coral reefs on a macrolevel? Most of us receive sporadic, dire updates from mainstream news. Outside magazine famously published Obituary: Great Barrier Reef in 2016. With the subhead Climate change and ocean acidification have killed off one of the most spectacular features on the planet, it opens thus: “The Great Barrier Reef of Australia passed away in … after a long illness. It was 25 million years old.”
And yet, almost a decade later, the Great Barrier Reef is undeniably still alive—even as the Earth’s coral reefs do face very real challenges. What’s the truth? We offer two important facts in the classic “good news, bad news” format in the spirit of truth seeking. Nature’s processes are complex and in trying to understand what’s going on around us, following the facts is more important than ever.
Bad News: Coral Bleaching Event Underway
To be fair to Outside magazine’s hyperbolic obituary of the entire Great Barrier Reef, the world’s corals have been experiencing a mass bleaching event triggered by warming ocean temperatures since at least 2023. Among the prominent scientific alarm raisers is the National Oceanic and Atmospheric Administration (NOAA) that has issued several statements with data that include heat maps and all-new alert levels for coral mortality.
From a February 2024 NOAA statement: “Last year’s record-breaking ocean heat content led to several extreme marine heat waves across the world’s oceans, including in the eastern tropical Pacific and the wider Caribbean. The intensity and duration of this heat stress caused entire coral reefs to bleach, with some experiencing widespread death, in Florida and throughout the Caribbean. In the aftermath of this unprecedented coral bleaching and heat stress, the scientists at NOAA’s Coral Reef Watch released an update to their satellite-based coral bleaching monitoring maps to include new risk categories.”
Why does heat matter so much and what’s coral bleaching? Basically, when corals become stressed they expel the symbiotic zooxanthellae algae that they host in their tissue. This algae expulsion turns the coral completely white and while technically still alive it is in a very fragile, sickly state prone to mortality. Essentially starving, the longer the coral is bleached the more likely it is to actually die for good, leaving behind its white skeletal structure. The causes of coral stresses that triggers bleaching is varied, ranging from temperature, light, nutrients, disease, overgrazing, and more. Basically, bleaching is a last-ditch effort from coral to survive life threatening changes in their environment, a sort of hibernation.
The observed globe-spanning oceanic heat wave that began in 2023 appears to be triggering mass bleaching across tropical oceans. According to the International Coral Reef Initiative, the bleaching may be affecting 84% of the world’s reefs—however one should take this estimate from a single source that is an international advocacy group as a data point and not the definitive analysis.
But not all corals are of the tropical shallow water reef variety that we think of when we picture coral—some less charismatic “turbid corals” are adapted to life in brackish mangrove lagoon environments. Coral scientists from multiple institutions including the University of Technology Sydney and the Natural History Museum of London are studying these corals with renewed interest because these corals are specialized to live in warm and acidic “stressful” conditions that would bleach other types of corals. Perhaps studying these stress-and heat-resistant corals will provide insights to help the overall situation.
It is also worth remembering that there are cold water, deepwater corals as well. According to the Smithsonian, scientists have discovered approximately as many cold water, deepwater corals as tropical shallow water corals—and the potential to discover more in those difficult to study inky depths promise many more discoveries in the years ahead. These corals are likely less impacted by these heat waves.
Good News: New Satellite Data, Far More Coral than Realized
On the good news front, a global coral reef mapping effort powered by our latest satellite technology shows that there is more coral reef surface area on our blue planet than previously thought. The discovery of thousands more square miles of shallow water tropical coral reefs is cause for celebration, adding some welcome degree of resilience to our conservation estimates.
This new information was brought to us thanks to a 2024 paper published in the journal Cell Reports Sustainability that uses European Space Agency Sentinel-2 satellite data to map the world’s corals. This effort is part of a wider project known as the Allen Coral Atlas, a coral reef mapping and monitoring effort powered by Arizona State University. Dr. Mitchell Lyons, lead author of the University of Queensland, is quoted by the Natural History Museum of London as saying, “This is the first accurate description of the distribution and composition of the world’s coral reefs, with clear and consistent terminology.”
Among the epiphanies of this study is that there are 64,000 km2 (24,710 mi2) more shallow coral reef than thought, bringing the total to 348,000 km2 (134,363 mi2). The new estimated area of coral in total is about the size of South Carolina, underscoring that while there may be more shallow water tropical coral reef than originally thought, it’s still a very rare ecosystem comprising of less than .1% of the Earth. An important detail to note is that the paper also states about 80,000 km2 (30,888 mi2) is coral habitat—actually area of confirmed coral growth. The remainder of the mapped shallow coral reef area are parts of larger coral complexes or could support corals but may be home to other ecosystems like seagrass beds. The paper reports 95% confidence on its numbers.
Another revelation is that Indonesia is officially home to the most coral, dethroning Australia as the coral capital. The Philippines, Cuba, and Papua New Guinea sequentially follow as the top five coral rich waters.
The Takeaway
On one hand, we have a global oceanic heat wave threatening many of our tropical shallow water coral reefs. Inevitably, scientists and others will debate on the cause of this marine heat wave and whether or not it’s a result of manmade climate change. Regardless of the source, the damage to corals worldwide is real. Coral reefs are an essential part of a unique underwater ecosystem that forms habitat for countless creatures. The biodiversity in the reef environment including spectacularly colored organisms has been captivating humans since we first peered beneath the waves.
On the other, thanks to new satellite powered mapping, we can confirm there are more tropical shallow water coral reefs than previously thought—a positive development by any measure. Perhaps, rather than oscillating between the narrative extremes of writing obituaries for the Great Barrier Reef and dismissing a record marine heatwave as inconsequential, we ought to adhere to the timeless foundation of both science and journalism: follow the data and the story, don’t lead. Our fascination with corals and tropical creatures will likely keep us focused on this issue and drive our better understanding of our oceans and planet.
