Gardeners and farmers indiscriminately destroy weeds in spite of the present urgent and worldwide need for conservation and diversification rather than elimination and extinction of plant and animal life. Weeds are a part of the complex web of plant life, and clearly should be respected as such, even if they are unwanted guest in a garden plot or farmer's field. It is estimated that over a thousand different kinds of plants are lost each year from our gardens, either because they go out of fashion, are destroyed by disease or are dropped by the nursery trade because of propagation problems. At the same time it is estimated that fifty acres of tropical rain forest are lost every minute. Herbalists and homeopaths find value in weeds. The Chinese use three and a half thousand plant species medicinally and are always looking for new ones. What are called weeds today are in part what fed the human species from its beginning through the middle ages.