I'd like to start today's lecture with a reminder about something I said a long time ago when we finished our survey of population viability analysis. Population viability analysis is best seen not as a way of garnering precise predictions about the fate of a population but as a way of ensuring that all relevant life-history variables have been considered, that they have been considered efficiently, and that we have a reasonable sense of the trajectory that the population is likely to follow if current trends continue. It provides a way of structuring our thinking about the problem.
That's precisely the way I think we should regard the quantitative approach to decision making that I'm about to describe. One of the most difficult tasks facing conservation biologists, as I have emphasized repeatedly, is that decisions must often, perhaps usually, be made in the face of woefully inadequate data. There is no way to freeze the status quo in a time capsule while we study the situation and come up with a solution. A few years ago one of the small projects in this course involved a critique of the recovery plan for Furbish's lousewort (Pedicularis furbishieae). Many of the students assigned that project expressed dissatisifaction at the amount of data on which the advice was based, even though it was based on more 10 years of field work. Not only was the amount of information about life history and population dynamics much greater than typically available for endangered plants then, it's still vastly more than is available for most endangered plants now. Even though you might like to have more data before writing a recovery plan, you have no choice but to write it with the data that's available at the time.
Similarly, if you're working for the Fish & Wildlife Service, The Nature Conservancy, or a local land trust and you have an opportunity to buy or accept the gift of a piece of land, you won't have a lot of time before you have to make a decision on whether or not to accept it. If you're lucky you may have a chance to walk the property a couple of times and consult some museums, herbaria, or databases about the communities and species present. You won't have the option of waiting until you have all of the information you'd like to have. We've seen this most recently with our discussion of attempts to determine global conservation priorities. Our ability to set priorities is limited by the data available. Nonetheless, it seems wiser to set the priorities than simply to approach our work haphazardly.
Does this mean that we should just give up and go home? No, of course not. It does mean that we should take advantage of any techniques at our disposal that can help us make the best decisions possible, given the large amount of uncertainty with which we'll have to live. That's what the techniques I'm going to describe are intended to do. But they are valuable less because they provide numbers to guide our decisions than because they help us to structure our thinking about decisions in a way that helps to ensure that we don't ignore any important features of the problem.