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Coral Reefs May Have Reached Their Tipping Point

A global bleaching event is underway, and some believe it is one of the main indicators that the globe has surpassed a critical climate change tipping point.
Abigail Bassett
May 8, 2024 4 min read
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As our planet continues to warm, the effects on marine ecosystems have become alarmingly evident, especially among the world's coral reefs. A little over a year ago, the world’s oceans warmed to their highest levels in modern history, surprising climate forecasters and scientists alike. The temperature variation was only a few tenths of a degree, but at the time, experts noted that the larger pattern may be the harbinger of longer-term problems for both human and aquatic life.

Recent evidence suggests that climate change has come home to roost as coral reefs around the globe experience a mass bleaching episode that has scientists deeply concerned about the immediate future of these vital ecosystems. This is the fourth global bleaching event in the last ten years.

Corals and the Health of Our Planet

According to The Grist, ocean temperatures have gone up roughly 1.5 degrees Fahrenheit since 1986, one of the first years that measurements were taken using satellites. Coral reefs are considered the "rainforests of the sea” because they are crucial to global biodiversity and host approximately 25% of all marine species in their intricate structures​.

Reefs also protect coastal areas from the full impact of ocean storms and erosion; they buffer shorelines and support fisheries and tourism industries, all of which are vital for the economies of many small island nations and coastal communities. Those communities and nations have long been the canary in the coal mine of global climate change, lobbying hard at last year’s COP28 to protect their homes from rising sea levels and climbing global temperatures. Unfortunately, as The Conversation points out, in spite of grand statements by the largest oil-producing countries, COP28 failed those island nations because final agreements were made while members of the small island nations were nowhere in the room. As of 2020, the economic value of the world's coral reefs was around $2.7 trillion annually, and an estimated 1 billion people around the world benefit from coral reefs.

The phenomenon of coral bleaching is a direct result of thermal stress caused by rising sea temperatures and climate change. Scientific research has firmly established the link between global warming and the increasing frequency and severity of coral bleaching events. As greenhouse gases trap more heat in the atmosphere, ocean temperatures rise, creating conditions that are inhospitable to the algae living within coral tissues. The world's oceans have been hotter than ever for the last year.

Notable studies, including those by the National Oceanic and Atmospheric Administration (NOAA) and the International Coral Reef Initiative, have documented the extensive damage to reefs across every major ocean, highlighting a disturbing trend that aligns with periods of heightened global temperatures​. Some scientists also believe that the latest global coral bleaching event indicates that the globe has surpassed a critical tipping point in climate change, according to The Grist.

The bleaching has severe implications for the wider health of the global ecosystem, too. In a bleaching event, when water temperatures rise, corals expel the algae (zooxanthellae) that give them color and life, turning stark white (which is where the term bleaching comes from) and compromising their survival​. As coral dies off, aquatic life loses its habitat. That, in turn, affects the natural coastal protection and economic benefits that healthy reefs provide.

A Coral Bleaching Event Like No Other Is Underway

The current global bleaching event, the fourth one of its kind, was confirmed by NOAA in mid-April. It is currently affecting reefs in over 53 countries and is the second mass event in the last ten years.

As noted by Derek Manzello, Ph.D., NOAA CRW coordinator, via NOAA’s release, “As the world’s oceans continue to warm, coral bleaching is becoming more frequent and severe,” Manzello said. “When these events are sufficiently severe or prolonged, they can cause coral mortality, which hurts the people who depend on the coral reefs for their livelihoods.”

Manzello told The New York Times that “more than 54 percent of the world’s coral area has experienced bleaching-level heat stress in the past year, and that number is increasing by about 1 percent per week.”

The current event underscores the widespread impact of these long-term climate change temperature anomalies. Research indicates that if the current rate of greenhouse gas emissions continues, we could see annual bleaching events by 2050, a scenario that would likely devastate coral populations and the ecosystems that are dependent on them.

As Tim Lenton, a professor of climate change and Earth systems at the University of Exeter in the United Kingdom, told The Grist recently, "This is one of the key living systems that we thought was closest to a tipping point. This is sort of horrible confirmation that it is."

What are Our Options to Stop or Slow Coral Bleaching?

Innovative climate tech startups and scientists are deploying new tools and techniques to stave off bleaching in response to these challenges. In places like the Florida Keys, where coral reefs play a crucial role in the local economy and environmental health, scientists and conservationists are experimenting with various techniques to mitigate the effects of high temperatures. These include relocating corals to deeper, cooler waters, using shade cloths to protect them from direct sunlight, and developing coral strains that can better withstand warmer temperatures​. Scientists are even trying to protect baby corals from predator fish using boba straws. In some places, like Australia, the repeated bleaching events have fundamentally changed the ecosystem already.

There is also a push for more robust conservation efforts and governmental and international policies that aim to reduce global greenhouse gas emissions and tackle local stressors like overfishing and pollution. The resilience of coral reefs depends significantly on the health of their environment, making comprehensive global and local actions crucial for their future.

As the situation develops, the global community faces a critical test: Can we implement effective environmental strategies that will reverse the current trends impacting our planet's coral reefs? How we collectively answer this question will not only determine the fate of these essential ecosystems but also reflect our broader commitment to preserving the natural world in the face of climate change.

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The Author

Abigail Bassett