When David Suzuki first showed up on Canadian television in 1971 there were 4 billion of us on the planet. 40 years later our population is closing in on 7 billion.
And, like Twitter, more people keep signing-up every single second.
But it's not just our population that's growing. It's our insatiable appetites. We're consuming more than ever before. And you have to wonder if we can carry on like this forever?
Suzuki doesn't think so. To make his point he likes to share a common scientific observation.