||Pimm S, Raven P, Peterson A, Sekercioglu CH, Ehrlich PR. Human impacts on the rates of recent, present, and future bird extinctions. Proc Natl Acad Sci U S A. 2006 Jul 18 103(29):10941-6 DOI: 10.1073/pnas.0604181103 abstract and p.10945 right column 4th paragraphPubMed ID16829570
|| Dirzo, R. & Raven, P. (2003) Global State of Biodiversity and Loss, Annu. Rev. Environ. Nat. Resources 28, 137-167 link
||P.10945 right column 4th paragraph: "For flowering plants, worldwide, 16% are deemed threatened among the ≈300,000 already described taxonomically (primary source)."