The world contains millions of plant species, yet only a small proportion of them have ever been used by humans. Only about 150 kinds of food plants are used extensively, and only three species of plants, namely corn, rice and wheat, supply over half of all human nutritional energy requirements. There may be many thousands of additional plants that could provide a wide variety of beneficial properties to humans if their properties were fully exploited, particularly in the tropics. Given this to be the case would provide a further imperative incentive for the conservation of natural habitat.
This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities. Agenda 21 recommends: (a) developing basic science research in such areas as plant taxonomy and phytogeography, utilizing such recent developments as computer science, molecular genetics and in vitro cryopreservation; (b) establishing and strengthening research in the public domain on evaluation and utilization of PGRFA (plant genetic resources for agriculture), with the objectives of sustainable agriculture and rural development in view.
Beneficial properties of tropical plants other than food include: Mexican yams used for oral contraception; an Amazonian vine used as a muscle relaxant in surgery; the rosy periwinkle providing the cure for Hodgkin's disease.