IUCN classifies 96% of shallow reef systems as critically endangered — Deutsche Welle

During the UN biodiversity summit COP17 in Yerevan, Armenia, the International Union for Conservation of Nature (IUCN) stated that by 2075, nearly all of the world’s shallow coral reefs will face an extremely high risk of collapse. In the first systematic study of 127 tropical and subtropical reef systems, 96% were classified as critically endangered — the highest category in the organization’s classification, Deutsche Welle reports.

The IUCN called heat stress caused by climate change the most persistent threat leading to the decline of coral reefs worldwide.

Warming and other threats

Shallow reefs are located at depths of up to approximately 40 meters and are distinguished by high biodiversity. In total, they cover about 188,000 square kilometers. Among those under critical threat are Australia’s Great Barrier Reef, the Coral Triangle in the western Pacific and Southeast Asia, the Mesoamerican Reef System, and the Red Sea reefs.

Corals are sensitive to changes in water temperature. When it becomes too warm, they expel microscopic algae from their tissues, which provide a significant part of their nutrition. This causes coral bleaching and can ultimately lead to their death.

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Among other factors in reef degradation, the IUCN named overfishing, primarily of parrotfish and groupers, coastal development, pollution, tourism, and increasingly powerful storms. After hard corals disappear, their structures are often replaced by algae, rubble, and sponges, and such ecosystems support fewer species. Reef fish, mollusks, sea turtles, and sharks are among those affected.

A window for reef protection

The assessment takes into account a climate scenario of the UN Intergovernmental Panel on Climate Change, under which global temperatures could rise by approximately 2.7 degrees Celsius by 2100 compared with the pre-industrial level.

At the same time, the IUCN noted that most reefs have not yet been lost. If the assessment had not taken climate change projections into account and had been based only on changes over the past 50 years, 24% of reef systems would have been classified as critically endangered. IUCN Director General Grethel Aguilar stated that reefs can still recover with ambitious emissions cuts, stronger protection and ecosystem restoration, as well as sustained investment in resilient coastal ecosystems and the communities that depend on them.