On this edition of Your Call, we'll discuss Keystone, a documentary about the land, humans, flora, and fauna, with a focus on bison. The near extinction of bison has altered North America's delicate eco system, affecting all of its inhabitants. Replacing bison with cattle has further thrown the ecosystem out of sync and accelerated the collapse of the American prairie. What happens when bison are restored to tribal lands?Keystone is showing at the Green Film Festival of San Francisco, which runs through April 24. You can watch it online. Guests:Maggie O'Dea, director of Keystone and founder of the Inspired Life ProjectTroy Heinert, executive director of the InterTribal Buffalo CouncilWeb Resources:NPR: Denver Returns 14 Bison To Tribal Land In Reparations, Conservation EffortThe Guardian: ‘It’s a powerful feeling’: the Indigenous American tribe helping to bring back buffaloWorld Wildlife Fund: Rosebud Sioux Tribe will create the largest native-owned and managed bison herd in North AmericaNorth American Nature: Why Is The Bison A Keystone Species? National Wildlife Foundation: Wildlife that Depend on Wild Bison