Prelims: Current events of national and international importance | Environment
Why in News?
7th Status of the World’s Coral Reefs report was released recently.
- Released by – Global Coral Reef Monitoring Network (GCRMN)
- It found that coral bleaching events are becoming more frequent, reducing the time available for reefs to recover.
Key Findings
- Global hard coral cover declined by 9.5% compared with the 1980–2009 reference period.
- Major disturbances occurred every 4–6 years after 2010, compared with roughly once a decade earlier.
- 2024 – 87% of reefs experienced unprecedented heat stress.
- >40% experienced heat stress associated with risk of coral mortality.
- 4th global mass bleaching event: began in 2023, reached unprecedented heat stress in 2024 and likely ended in 2025.
Coral Bleaching
- Coral bleaching occurs when corals lose their symbiotic zooxanthellae due to environmental stress, particularly elevated sea-surface temperatures.
- Bleached corals are not necessarily immediately dead, but prolonged stress can cause mortality.
Degree Heating Weeks (DHW)
- DHW measures accumulated heat stress experienced by corals.
- ≥4°C-weeks: associated with significant bleaching.
- ≥8°C-weeks: can cause widespread bleaching and mortality.
- Major Driver – Marine heatwaves have become the strongest driver of coral-cover decline globally.
- Their frequency and severity are being amplified by human-caused climate change.
- Local pressures further worsen reef degradation.
Reference
Down To Earth| 7th Status of the World’s Coral Reefs report
