Conservation and Obfuscation: Subdivision of Reserves

First, the subject of this argument should be carefully defined. Willis (1984) compares the "dismemberment hypothesis" (which he associates with Jarvinen and us) with the "anti-dismemberment hypothesis" that he espouses. "Dismemberment" is a new introduction into this literature; Wilson and Willis (1975) did not use the word, nor have any subsequent proponents of Willis's idea. It is not only an emotion-laden word (who is in favor of dismembering anything, except perhaps a nuclear arsenal or a war machine? ), but denotes something that we have never suggested. Webster's New Collegiate Dictionary (1953) defines "dismember" as, "To tear limb from limb; to disjoin the limbs of; hence, to tear or cut in pieces; mangle. " Certainly we have never proposed that such a procedure would be optimal for conservation of either a starfish or an entire biota. We addressed only the issue of whether one large site will, on average, contain more species than will several small ones of the same total area, and whether this matter is related to the theory of island biogeography. We were responding directly to the claim of Wilson and Willis (1975) that the answer to both questions is "yes". We have repeatedly stressed that the question of subdivision must be separated from the question of area, and that larger sites usually have more species than small ones: "Neither we nor, to our knowledge, anyone else has ever suggested that a smaller total area of any configuration will conserve more species than a larger one, all other things being equal" (Simberloff and Abele 1982). Since subdividing an existing refuge by cutting swaths out of it simultaneously decreases its area, it should have been transparent that this was not the matter we were addressing. Rather, we imagined that the problem generally facing conservationists is how to allocate limited resources to purchase and to maintain refuges, and asked whether there is justification for automatically thinking that the best strategy is to opt for the single large site. Most of our opponents in this debate recognized the problem as we did, one of allocating limited resources. Even the critics of our initial effort (Simberloff and Abele 1976a) spoke in these terms (Diamond 1976, Terborgh 1976, Whitcomb et al. 1976). Perhaps the clearest statement is by Higgs and Usher (1980): "The problem of how best to use limited resources becomes critical both to amateur conservation organizations (whose 'shopping lists' for reserves are long, but whose financial resources are limited . . .) and to national organizations . (whose ability to support management agreements . . . is limited by an overall budget). The question is: should such limited resources be devoted to the conservation of a few large sites or to two or three times as many smaller sites? " Let us, therefore, be clear that the debate is about SLOSS ("single large or several small", Simberloff and Abele 1982), and not about dismemberment. We should also be clear about Willis's question ("Technically I would like to ask why these authors think lack of relationship [to the theory of island biogeography] would be a valid criticism."). We have always maintained that there are two aspects of SLOSS: whether there is a pattern in diversity, and whether the theory of island biogeography is relevant. Whether the theory of island biogeography is relevant is relevant, since it seemed to provide a theoretical underpinning for an argument about a pattern, and theory is often seductive, especially to those outside a field, who may think that a theory legitimates a claim. In the last few years, as the theory of island biogeography has lost some of its attraction (e.g., Gilbert 1980), appeal to this theory perhaps is not as effective as it once was, but there can be little doubt that even recently the theory was invoked to great effect, independently of empirical evidence. One need only consider the World Conservation Strategy (I.U.C.N. U.N.E.P. W.W.F.), which says that refuge design should be in accord with the precepts of island biogeography theory, to see that a theory, even a partially discredited one, can impress non-experts. When we turn to the substance of Willis's argument, we find several errors, some arguments that have merit, and a need for the real-world data that we have consistently argued will be required in each system to be able to make the best decisions about conservation. We will deal with our disagreements first. Willis says that his hypothesis on SLOSS originated from the peninsula effect, and that this effect is grounded in island biogeographic theory: "Peninsulas were known to have fewer species than do similar tracts of mainland, and I presumed that this was because immigration and emigration (and hence avoidance of extinction) were impeded on three sides by edges. " Simpson (1964) was first to call attention to a peninsula effect, for mammals of North America. He tentatively suggested that immigration-extinction equilibria might be the explanation, and called for tests of the hypothesis. MacArthur and