This paper evaluates the proposition that rates of population and species extinction can be assessed by using an indirect measure: total consumption of energy (industrial plus traditional) by man. This proposition rests on three assumptions. First, the rate of extinction is proportional to the rate of habitat destruction because most organisms are adapted to rather limited environments. Second, the rate of habitat destruction is correlated with the scale of human enterprise: the product of the number of people, average consumption, and the environmental damage done by the technologies used to supply each unit of consumption. Third, average energy can be used as a surrogate for the latter two factors, consumption <latex>$\times $</latex> technology. Total energy use is therefore an indicator of trends in extinction rates, and thus could be used to estimate the rates themselves. I examine these premises and conclude that they are sufficiently well supported for biologists to use total energy consumption as an index of global extinction rates. That index, however, is not useful politically because the assumptions upon which it is based are not understood by decision makers and the general public.