According to the Millennium Ecosystem Assessment, the world’s oceans and coasts are highly threatened and subject to rapid environmental change. Major threats to marine and coastal ecosystems include:
- Land-based pollution and euthrophication
- Overfishing, destructive fishing, and illegal, unreported and unregulated (IUU) fishing
- Alterations of physical habitats
- Invasions of exotic species
- Global climate change
Overfishing is widely acknowledged as the greatest single threat to marine wildlife and habitats. The Food and Agriculture Organization of the United Nations reports that nearly 70% of the world's fish stocks are now fully fished, overfished or depleted.
As far as the world's coral reefs are concerned, about 20% of them have been effectively destroyed and show no immediate prospects for recovery; about 16% of them were seriously damaged by coral bleaching in 1998, but of these about 40% have either recovered or are recovering well; about 24% of the remaining reefs are under imminent risk of collapse through human pressures; and a further 26% are under a longer-term threat of collapse.