Friday, February 10, 2012

Scientific debate...

... rests on actually reading and understanding each other's words.

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:
"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)."
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.

Conservation targets covering (A) 10%, (B) 15%, (C) 20%, and (D) 25% of the marine mammal distributions using the Marxan optimization algorithm to optimize the number of grid cells and its geographic location.
Yolanda and Tom recently wrote a lettre pointing out the lack of including this notion of persistence in the set-up of the Pompa et al. analysis:
"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."

1 comment:

  1. Hi Karl, We've not met, but Tom told me that you showed this to the Community Ecology students, and that it was rather timely given the topic of the previous lecture :) I appreciate you following our work, and pointing out the fallacies in the response. With our letter we hoped only to open some discussion/debate, but as you point out, our colleagues went on the defensive and didn't read/understand out words. Not terribly productive...

    Looks like a cool blog - I'm going to have to follow it! Not sure how you find the time to do a blog - kudos to you, your students are lucky to have a forum like this to further engage with scientific issues outside the classroom.

    Hope we meet at some point. Tom is under orders to buy you a beer from me, so make sure you take him up on it!