  In the further elaboration of the “new ethic”, Routley and Routley (1980a) develops a multiple factor model combining traditional values, such as the virtues and creature enjoyment, with environmental value-making factors, for example: diversity of systems and creatures, naturalness, integrity of systems, stability of systems, and harmony of systems (170–171). So the shift to an environmental ethic does not reject ordinarily acknowledged welfare values for persons or humans, but simply recognises a further set of factors contributing to intrinsic value in nature (171). Such value-making factors enter into a mutually constrained optimisation so that the increase of one need not increase the overall intrinsic value of the entity exemplifying it; thus, an increase in diversity in a forest may decrease value insofar as it may come at the cost of naturalness (e.g., if the added diversity comes from the anthropogenic addition of feral species not naturally occurring in that forest).