THE VALUE OF BIODIVERSITY

Biodiversity, the vast array of non-human organisms of our planet. should be valued for four general reasons. First, we (and many others) believe that, as the dominant species on Earth, Homo sapiens has an ethical, stewardship responsibility towards humanity's only known living companions in the universe. Second, as attested to by activities as diverse as gardening, making of nature films, and ecotourism, biodiversity has esthetic values. Third, humanity has derived many direct economic values from biodiversity, including all of its food and many of its medicines and industrial products. The potential of nature's genetic library for providing more of these benefits is enormous. Fourth, and most important from an anthropocentric perspective, plants, animals, and microorganisms help to supply human beings with an array of free ecosystem services, without which civilization could not persist. These include such things as controlling the gaseous mix of the atmosphere, generating and maintaining soils, controlling pests, and running biogeochemical cycles. The present extinction episode caused by human activity seriously jeopardizes the ethical, aesthetic, direct economic and life-support values of biodiversity; it may be the single most important externality associated with human economic activity.