Green Planet: How Plants Keep the Earth Alive

Chapter Eleven: Why We Need Plant Diversity

[211] chapter eleven WHY WE NEED PLANT DIVERSITY Nature has introduced great variety into the landscape, but man has displayed a passion for simplifying it. —rachel carson Representative James V. Hansen called it “a shot across the bow from a retiring chairman” and apparently considered it one of his best. Hansen, the Republican representative from Utah’s First District and chairman of the House Committee on Natural Resources, filed a “landmark bill” in late 2002 that would exempt private property, military lands, and all plant life from the Endangered Species Act.1 The Endangered Species Act has been, since its inception, the law that conservatives have loved to hate. Why, they ask, should “the rights of an endangered fly or a species of seaweed,” in Hansen’s words, interfere with property rights and the investments of industry and agribusiness? In fact, this law has caused the cancellation of only a small percentage of construction contracts.The examples most often cited are those with unfortunate names; for, it must be admitted, the furbish lousewort (a small wildflower) hardly sounds like something to stir public sympathy. Conservatives have been successful.The period between May 2006 and May 2007 was the first time since 1981 in which an entire year passed with no new species being listed as endangered. There is immense public support for the protection of what some writers have called “charismatic megafauna”: grizzly bears, wolves, bald eagles, bison, elk, pronghorns, and moose, just to mention the North American examples. No politician wants to be seen as the enemy of CH011.qxd 11/12/08 11:03 AM Page 211 these popular animals. Indeed, Hansen mentioned the first three of the creatures in that list as the things that the Endangered Species Act was meant to protect in the first place. He apparently considered the world of humans and of endangered species to be a zero-sum game: that is, if they win, we lose; there is not enough room for them and for us, at least on private property and military bases. He said: “If we exempt private property, military lands, and all plants from the ESA, we would, in short order, have a more prosperous and secure nation.” As outrageous as his statement was in the eyes of conservation organizations all over the country, Hansen actually raised a good point—one that I brought up in the introduction to this book. Plants are important, but why should we care about preserving every species of plant? The answer to this question is very clear, but not obvious. The preceding chapters were about the role of plants, in general, in keeping Earth alive and, in the human economy, about the importance of the major agricultural plant species. This chapter explains three reasons we need to protect not just plants in general but the entire diversity of plant species: as sources of medicine, as the foundation of agriculture, and as an essential part of the natural world. Wild Plant Species as Sources of Medicine Wild plants have been and will continue to be important sources of medicines.The leaves of wild plants produce toxins that deter fungi and herbivorous animals from damaging them. The world is not a big salad bowl, a fact we sometimes forget, as we are accustomed to encountering garden plants that have been bred to be delicious. Many of these toxins, when used in small quantities, have medicinal effects. Most medicines began as natural plant extracts. For example, aspirin, though today synthesized artificially as acetylsalicylic acid, was once extracted from willow bark and received its name because it was first discovered in a wild spiraea bush. The plants of the tropical forest are an especially rich source of medicines, because their leaves must be very toxic to protect themselves from the year-round attack by insects and other green planet [212] CH011.qxd 11/12/08 11:03 AM Page 212 animals. Wild plant communities, particularly tropical forests, are rich laboratories for the production of medicinal compounds, as millions of plants in thousands of species are busily producing new genetic variations of chemicals. Pharmaceutical research corporations often base their research on plant extracts. Because each kind of plant has a unique combination of protective chemicals, we need to save all of them. The extinction of any wild plant species, such as the seaside alder described in the introduction, might mean the loss of a yet-undiscovered...