SummaryOf the roughly 265,000 species of plants in the world, about a third occur in temperate regions, a third in Latin America, and a third in the tropics and subtropics of Africa and Asia. Tropical forests are being destroyed very rapidly, as a result of the explosive growth of a record human population, extensive poverty, and an unwillingness to learn about and practice sustainable land use in the tropics. As a consequence, at least a fifth of the total plant species in the world, something on the order of 60,000 species, are threatened with extinction over the next several decades. Systematic botanists need urgently to devise comprehensive plans to inventory plant diversity, especially in the tropics. They should play a major role in making possible the utilization of this diversity for human benefit, and in conserving as extensive a sample as possible.