Additivity in wolf harvest

Scott Creel and Jay Rotella conclude:

Examined across populations, human killing of wolves is generally not compensatory, as has been widely argued. Management policies should not assume that an increase in human-caused mortality will be offset by a decline in natural mortality.

Seems pretty cut and dried, and looking at the way they analysed their data, I can't find any reason to disagree with them. Given their result, this is a very balanced and fair statement; they also say that some level of wolf harvest probably is sustainable. However that sustainable harvest is probably lower than proposed in current Montana and Idaho management plans.

Dr. The Bird Man wondered if Adaptive Management could be used to resolve the Additive/Compensatory controversy, along the lines of the North American Waterfowl Harvest Management Plan. I don't think it would help in this instance. The wolf harvest is marked by sharp distinctions in how wolves are valued among various stakeholders. In addition, the institutions tasked with managing wolves are new at the game - for the past 30 years that job has been handled by the USFWS. This means that everyone - for or against harvest of wolves - is learning a new set of skills, interacting with new people, and old people in new ways. In contrast, when the AM plan for waterfowl harvest was adopted in 1995, the institutions managing the harvest had been doing so for decades, using the same types of data, and the value diversity was (and still is) much lower than in the wolf case. It's worth noting that even after 12 years of analyzing data, the waterfowl AM process still couldn't distinguish between compensatory and additive harvest (Nichols et al 2007). I wonder if a meta-analytic approach similar to what Creel and Rotella used wouldn't be more helpful.

This does not mean that careful analysis and thinking about wolf populations won't be useful. The risk is that parties on both sides of the debate substitute arguments about the quality of the science for the real debate about how many wolves we want, or are prepared to live with. That's a value based question, and until the debate turns away from the science and focuses on the emotional, subjective, icky stuff, it'll be hard to resolve anything.

More on the science and politics of wolves.

The High Country News Range blog posted on the wolf controversy, and stated:

what’s become clear in the cacophony regarding wolves in the West is that where emotion rules, research should.

which is interesting, because the conclusion of social scientists who study the science-policy interface is exactly the opposite. It would be all too easy for scientists to fall into the "stealth issue advocacy" trap in controversy over wolves. The issue is a highly polarizing one - people seem to love wolves or hate them. A scientist wishing to connect their science to policy can easily find themselves arguing for a particular position "only based on objective science", ignoring that their values inevitably influence what they research, how they research it, and what conclusions they draw.
A better role for a scientist, albeit more difficult, is to use science to evaluate a range of policy options. This is in fact what Creel and Rotella have provided for the wolf case: based on 21 studies of wolves, what is the relationship between human offtake (harvest or culling), and total mortality? With this relationship in hand, it is possible to evaluate different harvest quotas in terms of the future wolf population size. That may or may not be used by policy makers in Montana, but it certainly should be taken seriously.

Politics and science

I haven't read (yet) Scott Creel and Jay Rotella's article that is at the heart of this controversy, but I can feel for them. It is necessary to make assumptions when constructing a population model - and if you make different assumptions you'll get different results. The fact that the paper is peer-reviewed increases my confidence that their assumptions are defensible. Unfortunately, the results are not politically palatable! I'm looking forward to digging into their study in detail.