A growing body of evidence has sounded the alarm that the biodiversity that supports and sustains life on Earth is at risk. Habitat destruction, resource exploitation, and climate change are among the many stressors that have put 1 million species under threat of extinction and sharply reduced the populations of many plant and animal species. While researchers and global leaders ramp up efforts to address this existential threat, the significance of species loss and the value of preserving biodiversity is not widely recognized by policy makers or the public. This booklet, produced by an international committee of experts, provides a publicly accessible overview of the many dimensions of biodiversity and why it's vital to the health of all life on the planet. The booklet also examines the causes of biodiversity loss and presents actions that can be taken from the individual to the global level to stop this decline.