The 6th Extinction: an Unnatural History by Elizabeth Kolbert

Through fossil records we have been able to identify five times in the history of the world when 50% or more of the known biology has been lost - an extinction.  The causes have all been natural events - ice ages, asteroids, great shifts in the surface of the earth - stuff like that.  We are currently in the middle of a sixth extinction and it is all on us - humans abusing mother earth.  In a highly readable naturalist style we travel with Kolbert while she visits the sites of a few of these observable losses and explores the likely causes one domino after another.  Add this to the list of wake up calls for the current environmental crisis.  The science is made accessible through humor and adventure but the warning is no less serious.