Global wildlife experts fight to save Earth's most beloved animals from mass extinction and environmental collapse - armed with a radical new approach to conservation called ‘rewilding’ that aims to restore entire ecosystems from the ground up. In the cloud forests of Rwanda, local wildlife defenders work to protect the iconic mountain gorilla by expanding national park boundaries, while building a sustainable eco-tourism economy with tangible benefits to local communities. Along the Pacific coast of North America, state, federal, and tribal wildlife experts restore the native population of otters as a keystone species, anchoring a thriving kelp forest ecosystem that nourishes over 1,000 different species. But the clock is ticking, as threats to earth's biodiversity loom larger than ever - from climate change warming the oceans past the point of no return, to invasive species altering the biological balance of fragile ecosystems.