I'm very aware that this programme may be regarded as bleak or depressing - an increasing population with an ever decreasing supply of resources – bu… - David Attenborough

Fifty years ago, when the WWF was founded there were about three billion people on earth. Now there are almost seven billion. Over twice as many - and every one of them needing space. Space for their homes, space to grow their food (or to get others to grow it for them), space to build schools and roads and airfields. A little of that space might be taken from land occupied by other people but most of it could only come from the land which, for millions of years, animals and plants have to themselves.

Sensing the approaching danger, the snail flees. But in a world of snail paces, the conch is something of a Ferrari. It calls for desperate measures. Exhausted by the effort of its last-ditch attempt, the tulip snail is slowly... gunned... down.

If you understand about the natural world, we’re a part of the system and you can’t feed lions grass. But because we have the intelligence to choose… But we haven’t got the gut to allow us to be totally vegetarian for a start. You can tell by the shape of our guts and the shape of our teeth that we evolved to be omnivores. We aren't carnivores like lions but neither are we elephants.