Why in the News?
A new survey in 2025 shows that nearly 70% of corals in Australia’s UNESCO World Heritage–listed Ningaloo Reef have died due to the most intense and prolonged marine heatwave on record.
About Ningaloo Reef
- Located in Western Australia.
- A UNESCO World Heritage Site.
- One of the largest fringing reefs in the world (~260 km long).
- Important for marine biodiversity, supporting whale sharks, turtles, reef sharks, and diverse coral species.
Extent of Coral Mortality
- ~70% mortality recorded in latest survey.
- In eight northern lagoon sites (Osprey → Tantabiddi Sanctuary Zones), mortality >60%.
- Of 1,600+ corals assessed in March, only ~600 survived by October.
Species Impact
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Highly Affected (Dominant Species Lost)
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- Staghorn corals: Acropora tenuis, Acropora millepora and Acropora spicifera
- Thin birdsnest coral (Seriatopora hystrix).
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Relatively Resilient
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- Veron’s tube coral (Echinopora ashmorensis)
- Lesser knob coral (Cyphastrea microphthalma)
- Structural decline:
- Dead corals now overgrown by sponges, turf algae, reducing reef stability & biodiversity.
Broader Ecological Significance
- Coral reefs support ~1/3 of global marine species.
- Mass mortality compromises: Fish breeding grounds, Shelter for marine organisms, Coastal protection and Tourism & local economies.
Widespread Global Coral Stress
According to the United States National Oceanic and Atmospheric Administration (NOAA):
- 84.4% of the world’s reef areas experienced bleaching-level heat stress (Jan 2023–Sept 2025).
- Mass bleaching in 83+ countries.
- Marine heatwaves in 2023 lasted 4× longer than the long-term average and affected 96% of the world’s oceans.
| The scientific view is that the increase in global temperature should not exceed 2 ∘ C above pre-industrial level. If the global temperature increases beyond 3 ∘ C above the pre-industrial level, what can be its possible impact/impacts on the world?
1. Terrestrial biosphere tends toward a net carbon source. 2. Widespread coral mortality will occur. 3. All the global wetlands will permanently disappear. 4. Cultivation of cereals will not be possible anywhere in the world. Select the correct answer using the code given below: (a) 1 only (b) 1 and 2 only (c) 2, 3 and 4 only (d) 1, 2, 3 and 4 only |
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