The presence or absence of a single species can cause a dramatic change in ecosystems,
but our ability to predict which species can cause such change is limited. The
disappearance of species can indicate changes in the ability of an ecosystem to sustain life
over a long period of time. While there is an enormous literature on the losses of species
associated with various industrial activities, the focus here is on changes in the earth's
atmosphere that may cause biotic impoverishment.