【正文】 t we continue our 10,000year course of habitat conversion and ecosystem destruction now that most of us no longer look to local renewable resources in our daily lives? Can we not live in a world wholly of our own cultural devising without all but a few of the world39。s Sierra de Monantlan was suffering precisely the same sort of conversion (for agricultural use!) that we are witnessing around the entire globe. How many other wild relatives of domesticated species have we already lost, and what will the effects of that loss be as we struggle to feed increasing billions of people over the next several decades? Raeburn notes that a similar fate is meeting thousands of landraces. We lose species in the wild as we convert land for agricultural and other uses. We are losing landraces for a different reason: The switch from small singlefamily farming to largescale agribusiness, coupled with recent dramatic advances in biotechnology, means we have begun to plant only a few super varieties of crop plants, apparently for good reason, as the crop yields have risen, and the quality remains high all the way to the dining room table. There is a downside to all this success. Big agribusiness has seen huge increases in both fertilizers and pesticides, with their ongoing deleterious effects on soils, rivers, and adjoining ecosystems. The loss of hardwon geic diversity of these landraces also poses a deep threat to continued agricultural success in the future. It just doesn39。s power over nature, assisted by machines, has grown, and human population has increased exponentially. For centuries, nature has been in retreat in the face of human settlement, but in the last 50 years, destruction of the natural world has picked up speed. Scientists believe that when human development and agriculture reduce the natural world, the loss is not simply a matter of size. The remaining natural areas, it is believed, harbor fewer species and plex ecosystems. Scientists who study biodiversity posit that many wild species are being extinct, and that this extinction of wild species many of them still unknown or not well understood bodes ill for the future of the pla. Since the dawn of agriculture, human survival has been based on the domestication for food purposes of wild plants. Yet, many plant species are being destroyed in the wild, before their food or medicinal value can be assessed. The continuation of wild or partiallywild varieties of plants such as corn is necessary to the future health of domesticated varieties. In addition, whole ecosystems, such as riverine estuaries, coral reefs, montane forests, and the creatures that live in them, are under stress due to humancaused pollution or overdevelopment. Yet, these ecosystems, in all their marvelous plexity, cleanse water of pollutants, provide the air we breathe, and produce much of our food, making human existence possible. In effect, the the vast web of biological diversity, with its millions of species on this pla, is what has made human survival possible, and human life fulfilling. This electronic publication contains two essays by respected authorities in the field of biodiversity. Four short essays focus on specific ecosystems of concern. In Why Biodiversity Matters, an excerpt taken from his book Life in the Balance, Humanity and the Biodiversity Crisis, Niles Eldredge, curator at the American Museum of Natural History, explains how the invention of agriculture made it possible for the human race to increase its numbers exponentially and spread across the pla. The sheer bulk of human numbers, he writes, probably nearly doubling to over 10 billion [thousand million] by mid21st century is wreaking havoc on Earth, on its species, ecosystems, soils, waters, and atmosphere. Eldredge foresees a ing Sixth Extinction of life forms on this pla, rivaling the previous five known prehistoric mass extinctions of life in prehistoric times. Eldredge adds: Everything is linked?. The world truly is a plex system, and we are a part of it, still dependent on its renewable productivity, which we ourselves are beginning to stifle. Appreciating the Benefits of Plant Biodiversity, by John Tuxill, published in 1999 by the Worldwatch Institute, deals with plant extinction. Tuxill39。 and (3) moral, ethical, and aesthetic values. Just as most of us don39。 the quality and circulation of water。s surface is mostly inert nitrogen (79%), which in itself is a good thing, as an atmosphere richer in oxygen than it already is (%) would literally fan the flames of outofcontrol wildfires. When we talk about the air we breathe, most of us mean oxygen. Oxygen is absolutely essential to all but a very few forms of microbial life. Some bacterial species use alternative chemical pathways to break down the nutrients on which they live, but all the rest most microbes, plants, fungi, and animals, including human beings require a constant supply of oxygen just to exist. Where does atmospheric oxygen e from? With billions of anisms taking in oxygen, and expelling carbon dioxide, surely we would soon deplete this essential resource. The answer, of course, is photosynthesis, the process whereby some bacterial and other, more plex microbes, as well as all green plants, trap solar energy by producing sugars and releasing oxygen as an incidental byproduct. Though no one seriously thinks that our supply of oxygen is in imminent danger of collapse, it is important to realize just where the daily replenishment of this most precious resource es from. Most of the world39。t move around, so they can39。s lists of why diversity matters. We have already encountered all three in passing. They are (1) utilitarian values (such as medicine and agriculture)。t need prairie at all. We see prairie as simply underutilized terrain. We even tend to loo