Humanity depends totally on this community of life-this biosphere-of which we are an integral part. Biological diversity, or biodiversity, is the variety of the world's organisms, including their genetic diversity and the assemblages they form. It is the blanket term for the natural biological wealth that undergirds human life and well-being. The breadth of the concept reflects the interrelatedness of genes; species, and ecosystems. We cannot even estimate the number of species of organisms on earth to an order of magnitude, an appalling situation in terms of knowledge and our ability to affect the human prospect positively. There arc clearly few areas of science about which so little is known, and none of such direct relevance o human beings. All these issues are explained in detail in this volume.