It's a land before time... a sanctuary filled with giant ferns, ancient trees, and prehistoric predators. But Everglades National Park is under siege. A full-scale invasion of escaped pets and exotic species threatens to wipe out the local wildlife and a snarling system of dams and canals is slowly strangling its fragile ecosystem. So severe is the threat that UNESCO has put Everglades National Park on their list of most vulnerable locations. Now, the defenders of this World Heritage Site are fighting back - to fend off the onslaught of invaders and pump life back into the legendary river of grass before it's too late.