Does extinction matter?

Ask a Scientist: Shahid Naeem of Columbia University’s Earth Institute answers the question, “Does extinction matter?” When you think about life on Earth, we often think about how it originated three-and-a-half billion years ago and how we’ve had hundreds of millions of species originate since then. But we also think about extinction. We know that the trilobites, the ammonites, the dinosaurs are all gone, right? We also know not too long ago we lost the dodo, we lost the passenger pigeon, and today people are concerned that we’re losing maybe half of our millions of species in the next fifty years. So, it seems like extinction and origination occur at the same time. So why is extinction such a worry if they both occur and we seem to survive it?