Coral crisis: Mass bleaching signals urgent call for climate action
Already, 84 per cent of coral reefs are affected by bleaching. Scientists warn that the extinction of these organisms will have serious consequences for biodiversity. Their disappearance might impact the ocean's ability to absorb CO₂, thereby accelerating climate change.
Coral reefs are already over 84 per cent affected by bleaching, a phenomenon caused by thermal stress. This record level is attributable to human activity and could lead to the mass extinction of these crucial ecosystems on Earth.
The current level of coral reef bleaching is both alarming and unprecedented. In 2024, we witnessed the fourth global mass bleaching of coral reefs in history, following events in 1998, 2010, and 2015–2017, as reported by the NOAA (National Oceanic and Atmospheric Administration).
Climate warming is lethal for ecosystems
According to the Science Alert portal, corals are experiencing thermal stress due to rising ocean temperatures. Reefs expel the algae that sustain them, thereby losing their distinct colours. NOAA notes that conditions in some areas are so severe that they may lead to the near-total loss of reefs. Melanie McField of the Healthy Reefs for Healthy People initiative highlights that even more resilient corals are beginning to die.
Due to thermal stress, corals reject symbiotic algae known as zooxanthellae. These microscopic algae provide most of the corals' energy through photosynthesis and contribute to their colour. When water temperatures rise by even 1–2°C above normal, the algae malfunction, causing the coral to expel them. Consequently, the coral’s tissue becomes transparent, exposing the white limestone skeleton underneath. If conditions do not improve, the coral, deprived of its energy source, dies.
Coral reefs are essential for marine life and for millions of people living in coastal communities. In developing regions, many communities depend on coral reefs for food, employment, and security. Since the 1950s, live coral cover has decreased by half due to climate change and environmental degradation. With a temperature rise of 1.5°c, 70-90% of reefs could vanish, which would be catastrophic for both humanity and the planet.
The impact of fossil fuel emissions on coral die-off
Coral reefs are home to about 25 per cent of all marine species. Their disappearance would mean the death or migration of many organisms. Oceans absorb 90 per cent of the excess heat caused by fossil fuel burning. Climate warming is advancing rapidly and is a stark illustration of human impact on Earth, with the average global temperature already having risen by over 1.1°C since pre-industrial times.
