The fourth global coral bleaching event, which started in January 2023, has been confirmed by Coral Reef Watch (CRW) and the International Coral Reef Initiative (ICRI). This event is on track to become the most severe, potentially surpassing the 2014-2017 global coral bleaching episode by over 11%, making it the most damaging coral bleaching event recorded to date. This event is an unprecedented phenomenon, being the second global coral bleaching event in the last ten years, recorded in less than half the time compared to the previous global coral bleaching event (GCBE3).

Severity and Speed of the Current Event

The January 2023 coral bleaching was the fastest and widest by area recorded in history in just 20 months. 77% of coral reefs experienced remarkably high heat stress, causing a mass bleaching event compared to the previous global coral bleaching event when 65.7% of the world’s coral reefs were exposed to heat stress.

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Impact on Coral Reef Areas

Tropical coral reefs are essential ecosystems for ocean life and vital for economies, food security, and biodiversity. Most corals have a mutually beneficial relationship with a certain type of algae, and each helps the other survive. When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel this algae.

This causes the coral to appear white as its skeleton becomes visible. The current bleaching event has been documented all over the world since early 2023 and is driven by the build-up of heat stress in our oceans. Bleaching, especially mass bleaching covering large areas of a reef or multiple reefs in a region, is the most visible and damaging impact on coral reefs worldwide. Coral can recover from bleaching events if the heat stress lessens.

However, bleaching events are becoming more common, severe, and longer lasting due to ocean warming from accelerated climate change. This gives coral little time to recover between heat stress events.

NOAA (National Oceanic and Atmospheric Administration) is monitoring the widespread and severe heat stress that is driving the coral bleaching witnessed around the world. The data records that bleaching-level heat stress has affected 99.9% of coral reef areas in the Atlantic Ocean, addressing how mass coral bleaching has been affecting over 74 countries across the Atlantic, Pacific, and Indian Oceans since February 2023.

Confirmed high heat stress-induced coral bleaching is found in Palau, Guam, Israel, and continued high heat stress in the Caribbean and South China Sea. Moreover, some areas within the Caribbean are experiencing a second year of extreme heat stress. There are documented high mortality rates (50-93%) of corals in the Huatulco region of Oaxaca, Mexico.

From a historical perspective, all severe coral bleaching events have been accompanied by strong El Niño events. El Niño-Southern Oscillation (ENSO) plays a critical role in global coral bleaching events, with the fourth global coral bleaching event being no exception, increasing during the La Niña period. Coral mortality can continue for up to 1-2 years after bleaching as stressed corals become more susceptible to illness.

Also Read: Why Are Coral Reefs Dying?

In Conclusion

There is no doubt that the number one threat to Coral reefs is climate change. For centuries, corals have been able to heal themselves. What’s happening with the intensity of climate change impacts? They’re so severe and so frequent that there is no longer a window of recovery, so an event occurs that wipes out half the coral reefs.

It’s too much for the ecosystem’s inherent resilience to repair itself. What we’re seeing on coral reefs right now is a wake-up call and a cry for help, as oceans are not able to continue to absorb all these pressures. They need the pressures reduced, but they also need us to dive in and restore these ecosystems back to their former glory. We need to uncover the signs to help them adapt to future conditions of climate change.

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