 As we saw above, true surrogates consist in species, characters or traits, life-zones, or environmental parameters. Estimator surrogates consist in environmental parameter composition, soil-type composition, dominant vegetation composition, subsets of species composition, and subsets of genus or other higher taxon composition. So, biodiversity is preserved by preserving true surrogates through preserving estimator surrogates (Sarkar 2005: 168–73). To a first approximation, a place prioritization procedure optimizes the number of estimators and thus true surrogates with respect to place, and what is so optimized is biodiversity. Biodiversity just is what is optimized by this procedure.