The biodiversity concept integrates so many facets of life on earth that it may well serve as the locus of the next great synthesis in biology. Ironically, this achievement may coincide with the greatest loss of its subject matter in tens of millions of years, making biodiversity also the most salient moral issue of the 21st century. These sessions address the nature of biodiversity and its conservation. Part I examines the sometimes problematic notion of biodiversity. Part II focuses on how to operationalize the biodiversity concept in designing nature reserves and park systems. Part III addresses several "internal" questions about the relevance of biodiversity and its measures.

Organized by: Gregory M. Mikkelson, Rice University
Chair: Uta Eser

Kim Cuddington, University of Connecticut
"Species Diversity and Extinction"

Although there were exceptions, prior to Darwin it was generally held that there were a more or less constant number of species. Darwin claimed that through natural selection, extinction of species occurred and that new species were formed. Natural selection does not entail any necessary relationship between the rates of extinction and speciation. However, Darwin proposed that, in recent eras, the rates of extinction and speciation were more or less balanced, so that the numbers of species did not increase without bound. This view has been expanded in recent work, where historical species diversity has been modelled as the product of speciation and extinction events of roughly the same frequency, or as the result of limiting forces that produce logistic growth in the numbers of species. However, even if one assumes that there is a balance between the rates of extinction and speciation, there is still no necessary reason to assume these rates will produce a roughly constant number of species. Whi------

Chris Kelley, University of Texas
"Contextual Heuristics, Global Heuristics, Exact Algorithms, and the Place Prioritization Problem in Conservation Biology"

A foundation of current practical conservation measures is the use of place-prioritization algorithms to select reserve networks as efficiently as possible (with maximum species coverage, for instance, or minimum area or cost.) This paper closely compares two heuristic place-prioritization algorithms, the ResNet (Aggarwal et al., 2000) and SITES (Andelman et al., 1999) software packages. The first is a context-specific algorithm, in that it directly utilizes lists of biodiversity surrogates, and orders places on the basis of rarity and complementarity (Margules, Nicholls, and Pressey, 1988, Aggarwal et al., 2000). The second, based on an global optimization technique known as "simulated annealing," selects sites at random, and attempts to minimize overall cost. While the SITES heuristic package contains an abundance of selection components, which allow the user to tailor its cost equation in many ways, the ResNet package is faster, more concise, and more transparent in its selection scheme. In terms of raw data, the comparison tends to support the claim that context-specific heuristics yield faster, more reliable solutions than do global heuristics. More importantly, when placed in context with the current advantages and shortcomings of linear optimal selection algorithms the respective performances of the two heuristic methods underscore in brief the issues of flexibility, efficiency, user-input, and multiple-criteria analysis surrounding the design of useful biodiversity conservation measures.

David Castle, University of Guelph
"What to Do with Created Biodiversity?"

Conservation biologists focus on limiting biodiversity loss arising from destructive human-environment interaction. Yet human-environmen interactions can have other effects. We can change existing diversity or add to it. Conservation biology does not adequately address these cases. New biodiversity categories must be developed for these cases before we can begin the difficulat task of assessing the value of created biodiversity.