Why should we be concerned about loss of biodiversity

Over the past century, documented extinctions in well-studied taxonomic groups have been at rates one hundred-fold to one thousand-fold above the average extinction rates seen over the half billion year sweep of the fossil record. But for most groups, particularly invertebrates, we are very uncertain how many species there are on Earth today, much less rates of extinction. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.