What do tigers, giant pandas, blue whales and great white sharks have in common? Within a generation they may join dinosaurs, dodos, woolly rhinos and great kangaroos - they will become extinct. Human dominance on earth may be good news for us, but it's bad news for many other animals that share our planet. 'Countdown to Extinction' looks at the causes of extinction - but also the reasons for optimism. We can all make a difference!