 “Working parts” could mean variety, or it could refer to the ecology of lots of parts in an ecosystem. In earlier work (Ehrlich &amp; Ehrlich 1981) “insurance” was linked to the loss of biological diversity and so linked to variety. Ehrlich and Ehrlich’s (1992: 219) later arguments for biodiversity conservation referred both to option value (from variety expressed as nature’s “genetic library”), and to insurance value—expressed less as variety and more as a consideration of ecological aspects. Thus, “insurance” sometimes joins “ecological integrity”, and similar terms as part of a storyline about many relevant aspects of ecosystems.