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presence/absence data. Moreover, they prefer some estimation techniques to
others because they are believed to be more accurate. Another example of
methodological value judgments is the disagreement about the utility of
microcosm research in ecology (Carpenter 1996).
Methodological value judgments are particularly clear in conservation
biology. Why preserve biodiversity? Some ecologists answer that diversity leads
to stability, and stability is a desired population and ecosystem trait. But there
are two broad hypotheses about biodiversity and ecosystem function. The rivet
theory, first articulated by Ehrlich and Ehrlich (1981), suggests that the loss of
any species will reduce ecosystem function, whereas the redundancy theory,
first suggested by Walker (1992), argues that many species in a community are
replaceable and redundant, so that their loss would not affect ecosystem
health. Which of these two views is closer to being correct is a value judgment
at present, as is the concept of the balance of nature in conservation planning.
Recommendation 4: Uncover and discuss the value judgments present in your
research program.
These methodological value judgments are a necessary part of science and in
articulating and discussing them, ecologists advance their understanding of
the problems facing them. There is a very useful tension in community ecol-
ogy between the classical equilibrium paradigm and the new nonequilibrium
paradigm of community structure and function (DeAngelis and Waterhouse
1987; Krebs 1994).
Statistical Hypotheses
j
Statistical hypotheses enter ecology in two ways. One school of thought rejects
the deterministic hypotheses I have been arguing for and replaces all ecological
hypotheses with probabilistic hypotheses. For example, the hypothesis that
North American moose populations are limited in density by wolf predation
can be replaced by the probabilistic hypothesis that 67 percent of North Amer-
ican moose populations are limited by wolf predation. Probabilistic hypothe-
ses have the advantage that they remove most of the arguments between oppos-
ing schools of thought because they argue that everyone is correct part of the
time. The challenge then becomes to specify more tightly the initial conditions
of each hypothesis to make it deterministic. For our hypothetical example, if
deer are present as alternative food, moose populations are limited by wolf pre-
