There is increasing need for good estimates of impending rates of extinction of plant and animal species, based on an understanding of extinction rates in the recent and far past, and on the underlying ecological and evolutionary causes. This book provides a more wide-ranging and data-driven treatment of current and likely future extinction rates than has previously been drawn together in one place. It is directed broadly at senior undergraduates, postgraduate students, and research workers in the general fields of ecology, conservation biology, and the environmental sciences. The authors highlight apparent differences in extinction rates among taxonomic groups and places, aiming to identify unresolved issues and important questions.