Nature under assault: key indicators

The World Wildlife Fund and partners have tracked population changes in Earth's animal species for decades. News from the latest "Living Planet" report, released Tuesday, is more grim than ever.

What caused the mass extinction of Earth's first animals?

Fossil records tell us that the first macroscopic animals appeared on Earth about 575 million years ago. Twenty-four million years later, the diversity of animals began to mysteriously decline, leading to Earth's first know ...

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