Why Worry about How Many Species and Their Loss?

We are astonishingly ignorant about how many species are alive on earth today, and even more ignorant about how many we can lose yet still maintain ecosystem services that humanity ultimately depends upon.Mora et al.'s paper is important in offering an imaginative new approach to assessing total species numbers, both on land and in the sea.Primers provide a concise introduction into an important aspect of biology highlighted by a current PLoS Biology research article.