Corals, the vibrant architects of the ocean, are facing a battle for survival. Often described as undersea cities, these remarkable collections of tiny animals are critical to the marine ecosystem. But their radiant colors and structural beauty are fading, a stark signal of the peril they face due to rising ocean temperatures.
The phenomenon of coral bleaching, where corals turn bone white under stress, is a precursor to potential death. Scientists attribute the latest widespread bleaching event, spanning from Panama to Australia, to surging ocean temperatures driven by climate change. This crisis threatens the very existence of coral reefs, which support a quarter of all marine life.
The Bleaching Crisis: A Global Snapshot
Recent data from the United States National Oceanic and Atmospheric Administration (NOAA) and the International Coral Reef Initiative highlight the alarming spread of bleaching. Between February 2023 and April 2024, 53 countries reported bleaching, a number that has since risen to 62.
The Great Barrier Reef, a UNESCO World Heritage site, has seen nearly 80 percent of its coral outcrops bleach, turning once vibrant ecosystems into what Leticia Carvalho of the United Nations Environment Programme (UNEP) calls “graveyards.”
But the Great Barrier Reef is not alone. Similar devastation is being reported across the Caribbean Sea, the South Atlantic, the Red Sea, the Gulf of Mexico, the Western Indian Ocean, and East Asia. This event, driven by climate change and the El Niño weather pattern, is on track to become the most widespread on record.
The Anatomy of Coral and the Threats They Face
Corals are composed of thousands of individual polyps, each a tiny, tube-shaped animal with a ring of tentacles used to catch prey. Many corals form limestone skeletons from calcium absorbed from seawater.
Their brilliant colors come from zooxanthellae, plant-like organisms that live inside the corals and provide them with food through a symbiotic relationship. When water temperatures rise, corals expel these vital zooxanthellae, leaving them vulnerable to disease and starvation.
Since early 2023, sea surface temperatures soaring have been recorded by up to 5°C in some regions. In February 2024, global sea surface temperatures hit a record high of 21°C, with the Great Barrier Reef experiencing unprecedented heat just weeks later.
The Economic and Ecological Importance of Coral Reefs
Coral reefs are not just ecological treasures; they are economic powerhouses in consideration of how they underpin coastal fisheries that support one billion people globally.
The loss of corals would be a devastating blow to biodiversity and the economies that depend on healthy reef ecosystems.
Carvalho emphasizes the grave implications of coral loss, both for marine life and human communities.
Efforts to Protect and Preserve Coral Reefs
Despite the grim outlook, there is hope. Researchers have identified pockets of resilience, known as refugia, where corals are surviving against the odds.
These areas, found off the coasts of Australia, Egypt, Indonesia, Kenya, Malaysia, Saudi Arabia, and Tanzania, benefit from cooler waters or corals with higher heat tolerance. Conservation efforts focus on protecting these refugia from pollution, over-fishing, and coastal development.
International initiatives are stepping up to safeguard coral reefs. The Global Fund for Coral Reefs aims to channel up to $3 billion in financing to protect these underwater cities.
Additionally, 45 countries have pledged to protect 125,000 square kilometers of reefs through the Coral Reef Breakthrough initiative, which expects to mobilize at least $12 billion in investments.
The Urgent Need for Climate Action
Ultimately, the survival of coral reefs hinges on a dramatic reduction in greenhouse gas emissions. The world must shift away from fossil fuels and mitigate local threats to reefs.
Even if global temperature rise is limited to the Paris Agreement’s goal of 1.5°C, up to 90 percent of reef-building corals could still die. A 2°C rise would be catastrophic, leading to the near-total loss of these ecosystems.
The Uncharted Ocean: A Beacon of Hope
Despite the challenges, the ocean remains a frontier of discovery. Only 20 percent of its depths have been explored. Recent discoveries, such as the red hydro corals found in Chile and Antarctica, highlight the ocean’s potential to surprise and inspire.
The UN Decade on Ocean Science (2021-2030) aims to fill knowledge gaps, supporting informed decisions to protect and sustainably use ocean resources.
The future of coral reefs is uncertain, but not yet sealed. Immediate and decisive action can still protect many of these spectacular ecosystems.
As Carvalho notes, “We still have time to protect many of these spectacular ecosystems if we act now and if we act decisively.” The survival of coral reefs is a race against time, one that humanity must win to preserve the rich biodiversity and economic benefits they provide.
