Over the course of the 20th century, however, this view has changed. Man'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 complex ecosystems. Scientists who study "biodiversity" posit that many wild species are becoming extinct, and that this extinction of wild species -- many of them still unknown or not well understood -- bodes ill for the future of the planet.

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 partially-wild 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 human-caused pollution or over-development. Yet, these ecosystems, in all their marvelous complexity, 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 planet, 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 planet. "The sheer bulk of human numbers," he writes, "probably nearly doubling to over 10 billion [thousand million] by mid-21st century -- is wreaking havoc on Earth, on its species, ecosystems, soils, waters, and atmosphere." Eldredge foresees a coming "Sixth Extinction" of life forms on this planet, rivaling the previous five known prehistoric mass extinctions of life in prehistoric times. Eldredge adds: "Everything is linked�. The world truly is a complex 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. Tuxill's thesis is that the survival of wild varieties of plants, or plants that have been domesticated but vary genetically from small farm to small farm, is extremely important, as variety in the plant genome can provide a way of breeding disease-resistant varieties and enriching human agriculture. "Plant biodiversity, in particular," Tuxill says, "is arguably the single greatest resource that humankind has garnered from nature during our long cultural development." He adds that due to modern agricultural practices, "we are eroding the very ecological foundations of plant biodiversity and losing unique gene pools, species, and even entire communities of species forever."

The essays in this collection make it clear that the future of the human endeavor is linked now, as in the past, with the natural world. Many observers now feel that one of the prime responsibilities of human community, for spiritual, aesthetic, and extremely pragmatic reasons, must be to take steps to preserve biological diversity for future generations, before the richness of life on this planet is diminished forever.