If you keep taking enough bricks out of the wall, the wall's going to fall down.

"This study provides further evidence that the world is facing another major extinction crisis," warns Michael Rands, director of UK conservation group BirdLife International.
There have been five such events since the birth of multicellular life 600 million years ago. In each, 65-95% of the world's species died out. No one is claiming that current species loss has reached this rate, Thomas concedes. "But it's accelerating," he warns.

Michael Hopkin /Nature Mar.19.04