Coral Bleaching
Warm-water reefs support at least 25% of marine species as well as protecting coastlines and providing food and economic security for billions of people. However, the second Global Tipping Points* Report released in October 2025 warns that at 1.4°C of global warming warm-water coral reefs are now crossing their thermal tipping point and experiencing unprecedented dieback. This is the first global tipping point to be reached.
Coral Bleaching
* A tipping point is a critical threshold that, once passed, can lead to large-scale, potentially irreversible changes, such as the melting of ice sheets or the collapse of the Amazon rainforest, which can amplify warming and create a cascade of other tipping points. (2025 Tipping Points Report)
When the ocean becomes too warm the algae (zooxanthellae) living within corals are expelled. This is coral bleaching. Zooxanthellae provide the corals with nutrients and give them their colour. Initially the corals are not dead but stressed. However, prolonged periods of bleaching will lead to death.
A zooxanthella
If you would like to find out more about this topic here are some links:
Global Tipping Points Report 2025
While thermal stress is the primary cause of dieback other human-made sources include ocean acidification, pollution from land and destructive fishing practices.