 In fact the issue is more complicated than even this. In order to estimate the amount of biodiversity with regard to a place, we must find some true surrogate (Margules &amp; Sarkar 2007: Ch. 2). A true surrogate is some feature that strongly correlates with biodiversity. Suppose we used species as a true surrogate. With few exceptions, we cannot simply observe the species present in some locale; we can only observe some of its members. We must use some estimator surrogate for the true surrogate too; e.g., soil, vegetation, precipitation, etc. Thus, we estimate biodiversity twice removed. Second, since we cannot conserve all biological variation, we need a principled way to decide what to conserve. As we saw above, conservation biologists have refined their account to include variation in genes, species, and ecosystems. This is still far too broad since there is a great deal of “junk DNA”; often we want to conserve wild populations (e.g., wild salmon versus hatchery salmon); and rare habitats are often considered more important than common ones (Morgan 2009).