demons in eden demons in eden The Paradox of Plant Diversity jonathan silvertown With a New Chapter chicago & london The University ofChicago Press  The University ofChicago Press, Chicago The University ofChicago Press, Ltd., London ,  © by Jonathan Silvertown  All rights reserved. Published Printed in the United States ofAmerica                isbn 978 : - - - - (paper) isbn  : - - - (paper) Library ofCongress Cataloging-in-Publication Data Silvertown, Jonathan W. Demons in Eden : the paradox ofplant diversity / Jonathan Silvertown. p. cm. Includes bibliographical references and index.s in Eden : the  978-0-226-75772-8 - : (pbk. : alk. paper) : --- 1 - (pbk. : alk. paper) . Plant diversity. 2 . Plant diversity conservation. I. Title. 46 .5 5855 2008 . 581.3(cid:2)8 22 2008006982 —dc 2005007413 ø The paper used in this publication meets the minimum requirements ofthe American National Standard for Information Sciences—Permanence ofPaper for Printed Library Materials, ansiz . - . for daniel and ben Contents Preface ix   . An Evolving Eden   . The Tree of Trees   . Succulent Isles   . Demon Mountain   . The Panama Paradox   . Nix Nitch   . Liebig’s Revenge   . Florida!   . New Demons?   . The End of Eden? .  Fynbos Finale Scientific Names of Plants Mentioned in the Text  Sources and Further Reading  Index  Photographs follow page  Preface Certain times have been pivotal in the history of life on Earth. We  live in such a time today, as human society appropriates percent of the plant growth that takes place each year. This massive impact threatens our evolutionary heritage—the rich variety of animal and plant species on Earth that is called “biodiversity.” Today there are approximately four hundred thousand flowering plant species, but each year their natural habitats shrink and are fragmented by human encroachment; as a result, a quarter of all plant species are presently at risk of extinction. Preventing these extinctions is an urgent task, but so is understanding what we might lose. Why arethere so many plant species? How did evolution furnish the Earth with such variety? Could evolution replenish what we are now destroying, or might we have so mishandled nature that she will devour her own creations, leaving a world overpowered and impoverished by the survival of only the fittest? Evolution ischange. Every question about the rise of diver- sity or its demise is, at a fundamental level, an evolutionary question. Certain places are at the fulcrum of change. According to biblical fable the Garden of Eden was such a place, where Adam and Eve, the ancestors of the human race, ate the forbidden fruit of the tree of knowledge and the whole species was exiled from the Garden in pun- ishment. But, we still live in a garden—there is after all no life with- out plants to feed us and our livestock. And a new tree of knowledge is growing, tended by scientists intent on tracing the genealogy that links all living species. Ponder the astounding fact that not only are all members of the human species close kin, but that we are also kin to our pet goldfish and dogs, to the tomatoes ripening on the win- dowsill, and to every plant and insect in the garden. All life today probably originated from a single evolutionary event  that took place about . billion years ago. We know all life shares a