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I thank Marc-Andre Villard and Bengt Jonsson for taking an interest in my essay (Wilhere 2008) and I am pleased that they generally agree with me. In fact, we agree more than they think.

Villard and Jonsson believe conservation biologists should not “integrate economic dimensions” into ecological risk assessments. I fully agree, and one purpose of my essay was to admonish conservation biologists for unintentionally mixing ecology and economics. So I was somewhat disappointed that Villard and Jonsson cite Bütler et al. (2004) as an example. Bütler et al. (2004) mix ecology and economics in 2 ways. First, they base their habitat targets on a single probability (0.90) of species occurrence. The subjective choice of 0.90 is implicitly an economic choice. A different probability would have resulted in different habitat targets, and habitat targets largely determine the cost of conservation. If Bütler et al. had estimated habitat targets for a range of probabilities, say 0.60, 0.70, 0.80, 0.90, 0.95, 0.99, then they would have avoided imposing their choice on society and provided broadly applicable information to the people empowered to make policy decisions.

Second, Bütler et al. (2004) enter into economics by “following the precautionary principle.” Precaution has a price. The acceptable level of precaution is an ethical value judgment tempered by opportunity costs. Bütler et al. express their acceptable level of precaution through the 0.90 probability of occurrence. But why not be more cautious, say 0.95? Because Bütler et al. know that more precaution has a greater cost. They claim that the estimated economic loss due to their habitat targets “should be acceptable,” which implies they know more precaution may be unacceptable. Hence, Bütler et al. make an economic decision that balances precaution and cost. Furthermore, by invoking the precautionary principle, Bütler et al. commit overt policy advocacy. Ecological assessments that aim to provide objective, evidenced-based science should be policy neutral.

I discuss Bütler et al. (2004) at length (with apologies to Villard, Jonsson, and Bütler et al.) because it demonstrates the primary hazard of the how-much-is-enough myth. If scientists such as Villard and Jonsson overlook the economic dimensions of Bütler et al., then might conservation planners, natural resource managers, policy makers, and advocacy groups make the same mistake? When published in a scientific journal, even overt policy advocacy may go unnoticed. When policy advocacy is misinterpreted as science, decision makers are misled and society is poorly served.

Back to the letter of Villard and Jonsson. I think they make a flawed analogy between medical practice and biodiversity conservation. They say, “a physician must strive to find the best cure to save a patient,” but this has not been my experience. I recently injured my knee, so I went to an orthopedic surgeon. After subjecting my knee to several tests, the doctor gave me his diagnosis followed with descriptions of several treatment alternatives. Considerations included future condition of my knee (assuming the treatment was successful), relative likelihood of success, how long I might be incapacitated following surgery, and the risk of undesirable outcomes. There was no “best cure.” In fact, one alternative was to do nothing. The best cure was my choice—a choice based on my subjective assessment of multiple factors. I did not choose the treatment that would make my knee almost 100% functional. That treatment had the lowest probability of success, would entail many weeks on crutches, and months of physical therapy. The treatment I chose would make my knee about 80–90% functional (which is all I need at my age), had a high probability of success, and would have me on my feet in days. If I did not have medical insurance, then the monetary cost of each treatment would have greatly influenced my decision.

Scientists (and social scientists) should interact with policy makers in much the same way the doctor interacted with me. Scientists collect data and diagnose the current condition of a population or ecological system. If the current condition is thought to be “unhealthy,” then alternative treatments to improve that condition are proposed. The description of each treatment should include a projection of the future condition, probabilities of achieving those conditions, the relative costs, and other available information relevant to the decision. Like the doctor, our role as scientists is to provide comprehensive, accurate, objective information about a range of alternatives so that society (the patient's guardian) can make the best decision regarding the conservation of biodiversity (the patient).

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