Overview The ocean plays an essential role in sustaining life on our planet. It covers nearly three-fourths of the globe and is home to nearly a quarter of the world's known species—and many more yet to be discovered.1 The ocean provides sustenance for billions of people and myriad wildlife. But human activities increasingly threaten its health. For example:
* About 1 in 5 fish caught in the wild is taken illegally or in unreported fisheries.
* 90 percent of the world's fish stocks are fully exploited or overexploited.
* Populations of some species of top predator fish have declined by more than 90 percent from historic levels.
* Acidification, caused by absorption of carbon dioxide, is changing the chemistry of the ocean, placing sea life at risk. Its waters absorb about a quarter of CO2 emissions created from human activity. The rise in these emissions has increased ocean acidity by about a third since the industrial revolution.