Increased longevity, quality of life, and carrying capacity on a finite planet

One event, such as increased human longevity, is impossible to accomplish w ithout having other, perhaps unintended, effects. In addition to the effect s on human society, other arguably equally important, effects will occur in the biosphere-the planet's ecological life support system. Sustainable use of the planet requires an objective evaluation of the consequences of chan ges in any critical parameter such as human life span. Preliminary action m ay then be taken to address unfavorable consequences and to enhance the lik elihood of favorable ones. The central issue is whether humans can continue to increase in both numbers and per capita affluence without causing irrep arable harm to the biosphere. This issue is a matter of enlightened self-in terest to human society. A concomitant ethical issue is whether humans have an obligation to share the planet's resources in a fair and equitable mann er with the many millions of other species on the planet. Human longevity i s only one of the factors in this multidimensional problem. However, addres sing this issue will almost certainly result in a reexamination of human so ciety's relationship with natural systems and what changes are needed to re sult in a sustainable co-evolution of the two systems.