Article by Sedra Ismael
A 2019 study found that oceans had sucked up 90% of the heat gained by the planet between 1971 and 2010. Another found that it absorbed 20 sextillion joules of heat in 2020 – equivalent to two Hiroshima bombs per second. The ocean has tremendous volume and heat-storage capacity, which is why some organisms are used to temperatures being quite stable.
Coral reefs are very susceptible to climate changes, which is why so many are dying off. Coral reefs are among the world's most diversified marine ecosystems. However, they are quickly eroding as a result of human activities such as overfishing, plastic pollution, ocean acidification, and coastal expansion, causing significant coral bleaching in key reef systems such as the Great Barrier Reef.
What is coral bleaching?
Coral bleaching is a phenomenon in which coral reefs expel microscopic marine algae known as zooxanthellae that live in their tissues when under stress - such as heat, ocean acidification, or human activity - causing coral tissues to become transparent and lose their signature vibrant colors, exposing their white exoskeleton underneath. Coral bleaching does not necessarily imply that the corals have perished; rather, corals are substantially more sensitive to hunger and marine disease following bleaching, which may eventually lead to mortality.
UNESCO has warned that coral reefs in all World Heritage Sites may disappear by the end of the century if greenhouse gas emissions continue at current levels. According to the IPCC, reducing global warming to 1.5°C rather than 2°C or above will mean the difference between survival and extinction for the majority of coral ecosystems. Such a scenario would have severe consequences for the interrelated marine ecosystem: while coral covers just 0.1% of the ocean floor worldwide, 25% of marine species rely on coral for its survival. The world's seas are also the greatest carbon sinks, accumulating CO2 in algae, vegetation, and coral.
Here is a list of the world’s top 5 coral reefs currently under threat and dying.
Great Barrier Reef
The Great Barrier Reef, the world's largest and longest reef system, has seen some of the most severe consequences of coral bleaching and climate change. The most significant mass bleaching incidents happened in 2016 and 2017, killing 50% of Australia's famed reef. While significant attempts have been made to decrease coral bleaching, the rate of death has made it impossible for the reef system to recover and replenish.
Indonesia
Nearly 95% of Southeast Asia's coral reefs are currently endangered. Plastic pollution and overfishing are particularly severe in the region, and the resulting stressors and demands on reef health are similarly significant. As plastic waste accumulates, it can choke and reduce sunlight availability to the reefs. A 2017 survey on the Melinjo Islands discovered that the average coral cover had dropped to 22.2%. Scientists anticipate that if ocean acidification worsens, just 15% of coral reefs in the region would be able to support coral growth by 2050.
Pacific Ocean
El Niño, a climate phenomenon that brings rising surface waters to the central and eastern equatorial Pacific Ocean, produced the most catastrophic coral bleaching catastrophe from 2014 to 2017. During that time, it was believed that more than 70% of the world's coral reefs were damaged or destroyed. El Niño occurs every three to seven years, causing short and long-term problems for reef systems in the Pacific Ocean. These concerns range from coral bleaching frequency to the period required for reef revitalization.
Hawaii
Between 1994 and 2006, a number of Maui reef systems lost approximately 25% of their live coral, the most noteworthy example being Honolua Bay, which saw its coral cover decline from 42% to 9%. The severe reduction of coral may be traced back to human activity. However, local governments have now taken a variety of steps to revitalize and safeguard their reef systems, including prohibiting the use of sunscreens containing oxybenzone and octinoxate, which are chemicals that cause coral bleaching and other negative effects.
Caribbean
Despite being the Caribbean's biggest tourist draw, coral reefs' health has deteriorated. According to a World Resources Institute research, "nearly two-thirds of reefs in the Caribbean are threatened by human activities, while an estimated one-third are threatened by coastal development" such as building and sewage discharge. Furthermore, overfishing in the region accounts for 60 percent of the reef's health.
Not all hope is lost! Want to learn more about how to improve the resilience of coral reefs? Read this article! https://earth.org/improving-the-resilience-of-coral-reefs/
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