This is a difficult exercise, and not only for students. Tom Nudds and I just covered in community ecology the rationale for protected areas planning based not only on representativeness (making sure that all species are protected), but more importantly also on persistence (see his article in Biodiversity and Conservation for a summary of their ideas). If the target areas have all the species you want to conserve, but lack essential components that would ensure their actual persistence through time, representativeness means nothing. Wiersma and Nudds addressed this in their article by focussing on one important component of target areas, minimum reserve area:
Despite the obvious logic of this argument, not all conservation planning uses it. In the summer of 2011, Pompa and co-authors published an article on developing target areas for conserving marine mammals."We use candidate protected areas that meet an empirically-derived estimate for a minimum reserve area (MRA) above which no mammal extinctions have been detected from existing protected areas since widespread European settlement, even in parks that have become insularized from the surrounding habitat matrix (Gurd et al. 2001)."
"Our argument previously (3) has been that percentage targets do not allow for any assessment of whether species will persist in areas set aside for conservation, and this critique continues to hold for the analysis by Pompa et al. (1) Their study assessed global representation by using 1° × 1° grid cells, but does not address whether this resolution meets criteria for species persistence."And this is where it gets ... messy, weird, strange? Pompa and co-authors wrote a reply to this criticism, but actually did not address the lack of including persistence at all. The somehow summarize the single point of the criticism into four separate points:
"Wiersma and Nudds (1) make four main points: (i) the area to be covered by the key conservation sites proposed is a negligible percentage of the ocean; (ii) they doubt the representativeness of our biodiversity patterns; (iii) they question the persistence of the species; and (iv) they claim we do not acknowledge the dynamic nature of ecological systems."Of the 4 main points identified by Pompa et al. in their reply, (i) and (ii) were side points on the limitations of only including representativeness, and they implicit agree that they did not address point (iv). And it is not that Wiersma and Nudds questioned the persistence (iii) per se of the species, Wiersma and Nudds pointed out, rightly, that this necessary and important condition was not part of the original Pompa et al. conservation strategy.
Instead of acknowledging this directly, they use the scientist cop out, which is so easy to make, but also so unsatisfactory and weak:
"Despite constraints, our approach still best available."