Transcription: The scientist Richard Leakey has suggested that we are on the edge of the sixth great mass extinction. There have been five biggies so far. But this one is being caused by us humans and what we're doing to the planet. There's between about 10 million and 100 million different species in the world. Nobody really knows. Before humans arrived on the scene, species were going extinct at the rate of about one species every four years. But at the moment, between about 17,000 and 100,000 species a year are being driven into extinction. That's a lot. So now we're about 120,000 times above the backgrou ...
(.mp3)