Understanding Fragmentation: Getting Closer to 42

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Conservation Ecology





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“There really is one?” “To Everything? To the great Question of Life, the Universe and Everything?”
“Tell us!”
“All right,” said Deep Thought. “The answer to the Great Question...” “Is...” “Fourty-two.”
‘Fourty-two!”... . “Is that all you’ve got to show for seven and a half million years?”
“I checked it quite thoroughly,” said the computer, “and that quite definitely is the answer. I think the problem, to be quite honest with you, is that you’ve never actually known what the question is.”... . “So once you know what the question actually is, you’ll know what the answer means.”

This imaginary conversation, from The Hitchhiker’s Guide to the Galaxy (Adams 1979) is fanciful, but we believe it comes close to encapsulating the nature of the arguments about the effects of fragmentation. Harrison and Bruna (1999, p. 225) suggested that while “the literature on fragmentation grows ever richer, ... . we still lack a synthesis between general principles and consistent field evidence.” Fragmentation experiments have addressed various hypotheses (see Debinski and Holt 2000), but as the questions change, so do the results. Haila (2002, p.321) suggested that “the effects of fragmentation vary across organisms, habitat types, and geographic regions.” In their excellent review of fragmentation experiment studies, Debinski and Holt (2000) noted that results were “entirely mixed”. McGarigal and Cushman (2002) came to a similar conclusion. In an earlier paper, we (Bissonette and Storch 2002) concluded that the effects of fragmentation “can be understood as multicausal, exhibiting thresholds where they are unexpected; are characterized by time lags that may be unpredictable; are heavily influenced by the structural differences between the matrix and the patches...; and are heavily dependent on the temporal and spatial scales of observation. In addition, their dynamics are contingent on system history and therefore subject to unpredictable stochastic events.” We wondered if the problem lies with mixing results from papers that asked fundamentally different questions regarding organism response to fragmentation. Our inability to “know what the question actually is” appears to blur our answers.

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