Annu. Rev. Environ. Resour. 2003. 28:137–67 doi: 10.1146/annurev.energy.28.050302.105532 Copyright c 2003 by Annual Reviews. All rights reserved First published online as a Review in Advance on July 8, 2003
GLOBAL STATE OF BIODIVERSITY AND LOSS
Rodolfo Dirzo1 and Peter H. Raven2
1
Instituto de Ecolog´a, Departamento Ecolog´a Evolutiva, Universidad Nacional ı ı Aut´ noma de M´ xico, Mexico DF 04510; email: urania@ecologia.unam.mx o e 2 Missouri Botanical Garden, St. Louis, Missouri 63166-0299; email: praven@nas.edu
Key Words biodiversity hotspots, endemism, extinction, species diversity, species threatening s Abstract Biodiversity, a central component of Earth’s life support systems, is directly relevant to human societies. We examine the dimensions and nature of the Earth’s terrestrial biodiversity and review the scientific facts concerning the rate of loss of biodiversity and the drivers of this loss. The estimate for the total number of species of eukaryotic organisms possible lies in the 5–15 million range, with a best guess of ∼7 million. Species diversity is unevenly distributed; the highest concentrations are in tropical ecosystems. Endemisms are concentrated in a few hotspots, which are in turn seriously threatened by habitat destruction—the most prominent driver of biodiversity loss. For the past 300 years, recorded extinctions for a few groups of organisms reveal rates of extinction at least several hundred times the rate expected on the basis of the geological record. The loss of biodiversity is the only truly irreversible global environmental change the Earth faces today.
CONTENTS
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . THE FACETS OF BIODIVERSITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BIODIVERSITY THROUGH TIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GLOBAL MAGNITUDE OF BIODIVERSITY . . ....