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]]>I’m not sure your blog represents our concerns accurately. Any repetition about this is simply because you seem to not acknowledge some points of fact.

I’m going to concentrate on two main topics that we raised in our published response:

1) The SAFE index should not be used for prioritization (solely or otherwise); and

2) The basic construction of the index is not properly justified.

To the first of these topics, there is now a solid body of research that shows that prioritization should be based on the management objective (including the relative value of different species if appropriate), the efficiency with which spending resources on different species meets that objective, the uncertainties in the measures of efficiency, and the available budget.

Some key references about this are (email me if you need copies: mamcca@unimelb.edu.au):

Joseph et al. (2009): http://www.uq.edu.au/spatialecology/docs/Publications/2009_Joseph_etal_OptimalAllocation.pdf

McCarthy et al. 2008: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2008.01521.x/full

McCarthy et al. 2010: http://onlinelibrary.wiley.com/doi/10.1111/j.1461-0248.2010.01522.x/full

The prioritization is derived by finding the investments in each species that optimize the management objective. That is, one finds the combination of conservation actions that minimizes the number of extinct species, or minimizes the number of threatened species, or best achieves whatever the particular objective is.

The SAFE index does not seem to apply to any of these aspects, so it is unclear how it has any role in prioritization. In this light, statements such as “Practitioners of conservation triage may want to prioritize resources on the Sumatran rhinoceros instead of the Javan rhinoceros (–1.36 versus –2.10, respectively).” from your original SAFE index paper and other statements about prioritization in the media (e.g., http://www.abc.net.au/am/content/2011/s3185687.htm) are not correct – the SAFE index simply does not enter into the prioritization equation.

To our second point, the claim in your response that the logarithm is “used for standardization purposes” is factually incorrect – the logarithm has no role in standardization.

The SAFE index is simply a measure of the difference between N and MVP. That is an elementary concept, so the need for the index is unclear.

But assuming we do want to combine N and MVP into a single value, you have pointed out that you want an index that is positive when N is greater than MVP and negative when it is less. The SAFE index is log(N) – log(MVP), but any monotonic increasing function will provide these properties; the log transformation is not necessary. The simplest index to satisfy the properties you seem to want is N – MVP. After pointing this out to you in our email correspondence, you responded:

“How hard is it to understand our log-transformation produces an intuitive result (i.e., that negative = bad; positive = good)?”

But I had already shown you that it was not the logarithm that gives this intuitive result. If there is any “vehemence”, as you put it, it is because you do not seem to acknowledge the veracity of this and other simple facts. I think it is more exasperation than vehemence. One possible response to your above comment could be:

“How hard is it to understand that the subtraction sign produces the intuitive result (i.e., that negative = bad; positive = good)? It is not the logarithm.”

It is possible that you use the logarithm because you want to emphasize proportional differences between N and MVP (the SAFE index equals log(N/MVP), so it is based on the ratio of the two numbers). But logarithms are not intuitive to most people. For example, how many people will know intuitively that a SAFE index of 0.301 means that the population size is double the MVP?

If you wanted proportional differences, isn’t (N-MVP)/MVP much more readily interpreted by the “general public, conservation donors, and policy makers”? In this case, the index would equal +0.5 when the population size was 50% higher than the MVP. And it would equal –0.2 when N was 20% below the MVP. That seems more intuitive.

But even so, if N and MVP were both reported (separately), I’m reasonably sure that people could figure out how far N is from MVP, In fact, I’d bet that most people will have an easier time figuring out the difference directly (and the implications of that difference) rather than using the SAFE index.

You refer to a “blockade”, which might create the impression of a coordinated campaign. That is not the case. The concerns expressed by others have been generated independently. Independent concerns also exist beyond the field of conservation biology (http://www.qedcat.com/archive/84.html). My concerns largely stem from the errors of fact in your article and in subsequent correspondence, and how others might interpret the use of the SAFE index for prioritization.

Given that you refer to our email correspondence, and for the sake of providing context to your readers, I suggest that you publish all the email correspondence about the SAFE index between you and me on your website. Readers will then be able to judge questions of vehemence for themselves. I believe that I have interacted with you on this topic in good faith, and with honesty and transparency. And without vehemence.

By the way, I won’t be throwing any stones after your talk at the conference as you suggest I might. Question time isn’t the appropriate place given the couple of minutes that would be available for discussion. However, I’d be happy to continue the dialogue via your blog and face-to-face.

Michael McCarthy

School of Botany

The University of Melbourne

http://mickresearch.wordpress.com

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