The balance of nature concept is an old idea that manifests itself in anumber of forms in population and community ecology. This paper focuseson population ecology, where controversy surrounding the balance ofnature takes the form of perennial debates over the significance ofdensity dependence, population regulation, and species interactions suchas competition. One of the most striking features of these debates, overthe course of the previous century in ecology, is the tendency to arguethe case on largely conceptual grounds. This paper explores twoquestions. (...) Why this tendency to settle on conceptual grounds what is soobviously an empirical issue? Are there any good conceptual arguments tobe had in this area? (shrink)

Ecologists attempt to understand the diversity of life with mathematical models. Often, mathematical models contain simplifying idealizations designed to cope with the blooming, buzzing confusion of the natural world. This strategy frequently issues in models whose predictions are inaccurate. Critics of theoretical ecology argue that only predictively accurate models are successful and contribute to the applied work of conservation biologists. Hence, they think that much of the mathematical work of ecologists is poor science. Against this view, I argue that model (...) building is successful even when models are predictively inaccurate for at least three reasons: models allow scientists to explore the possible behaviors of ecological systems; models give scientists simplified means by which they can investigate more complex systems by determining how the more complex system deviates from the simpler model; and models give scientists conceptual frameworks through which they can conduct experiments and fieldwork. Critics often mistake the purposes of model building, and once we recognize this, we can see their complaints are unjustified. Even though models in ecology are not always accurate in their assumptions and predictions, they still contribute to successful science. (shrink)

Department of Philosophy and School of Environment McGill University 855 Sherbrooke Street West Montréal, Québec H3A 2T7 Canada E-mail: [email protected].

Models provide scientists with knowledge about target systems. An important group of models are those that are called general. However, what exactly is meant by generality in this context is somewhat unclear. The aim of this paper is to draw out a distinction between two notions of generality that has implications for scientific practice. Some models are general in the sense that they apply to many systems in the world and have many particular targets. Another sense is captured by models (...) that are aimed at understanding the fundamental or underlying dynamics of a phenomenon, as opposed to how it manifests in each particular case. They have non-specific, i.e. generic targets. While both notions of generality and genericness are legitimate and correspond to different aspects of scientific practice, they must be distinguished. Failing to do so obscures the danger of overgeneralisation faced by general models and facilitates the illegitimate use of generic models as general models. This can lead to a reduction of the explanatory and predictive power of both. (shrink)

Habitat templets are graphical-qualitative models which describe the development of life-history strategies in specific environmental conditions. In the context of the previous models of life-history strategies, life-history theorists focused on the density-dependent factors as the factors determining life-history strategies. With the use of habitat templets, the focus is oriented towards the environmental causal factors, considering density-dependent phenomena as by-products of the environmental impact. This implies an important shift in causality as well as in the worldview of life-history theorists: population is (...) not considered as a closed system isolated from the environment. The object of study is the organism-in-its-environment, as a complex multilevel system. This shift has also methodological consequences: Life-history theory combines holistic and reductionistic insights, using a variety of heuristic models. This imposes a new conception of generality as well as of the structure of scientific theories. (shrink)

Lewis' argument against the Limit Assumption and Pollock's Generalized Consequence Principle together suggest that "minimal-change" theories of counterfactuals are wrong. The "small-change" theories presented by Nute do not say enough. While these theories rely on closeness between possible worlds, I base an alternative on the ceteris paribus concept. My theory solves a problem that the above cannot, and is more relevant to the philosophy of science. Ceteris paribus conditions should normally include the causes, but exclude the effects, of the negated (...) antecedent. An example from community ecology, the debate over null models in island-biogeographical studies of competition, supports these arguments. (shrink)

There has been a significant amount of uncertainty and controversy over the prospects for general knowledge in ecology. Environmental decision makers have begun to despair of ecology's capacity to provide anything more than case by case guidance for the shaping of environmental policy. Ecologists themselves have become suspicious of the pursuit of the kind of genuine nomothetic knowledge that appears to be the hallmark of other scientific domains. Finally, philosophers of biology have contributed to this retreat from generality by suggesting (...) that there really are no laws in biology. This paper addresses these issues by providing a framework for thinking about general knowledge claims in ecology. It introduces a philosophical taxonomy that classifies generalizations into three broad categories – phenomenological, causal and theoretical. It then turns to the difficult problem of laws, arguing that, while there are probably no laws as that term has been understood in philosophy of science, it doesn't follow that everything in ecology is equally contingent. A mechanism for recognizing degrees of contingency in ecological generalizations is developed. The paper concludes by examining the implications of the analysis for the controversies noted at the outset. (shrink)

In many experimental sciences, like particle physics or molecular biology, the proper place for establishing facts is the laboratory. In the sciences of population biology, however, the laboratory is often seen as a poor approximation of what occurs in nature. Results obtained in the field are usually more convincing. This raises special problems: it is much more difficult to obtain stable, repeatable results in the field, where environmental conditions vary out of the experimenter’s control, than in the laboratory. We examine (...) here how this problem affected an influential experimental research tradition in community ecology, the study of the ecology of the rocky seashores. In the 1960s, a handful of North-American ecologists, most notably Joseph Connell, Robert Paine and Paul Dayton, made the rocky seashores a model study system for experimenting in the field. Their experiments were deceptively simple: they removed species living on the seashore and described the resulting effects on the local ecology. These experiments exerted a deep influence on community ecology. They provided evidence for speculative developments concerning the theory of interspecific competition, the factors responsible for species richness and the ecology of food webs. They also stimulated novel conceptual developments. In particular, Paine developed the predation hypothesis, which states that the presence of predators can favour species richness, before introducing the keystone species concept, according to which some species exert disproportionate effects on ecological systems. More broadly, these experiments gave support to a methodological trend in favour of field experimentation. Only controlled perturbations in the field, it seemed, provided a reliable method to get insights into the structure of ecological communities. However, as experiments were continued in time and repeated in different sites, divergent results appeared. We analyse here how intertidal researchers coped with the variability of environmental conditions and tried to stabilize their results. In the process, they reconsidered not only their early conclusions, but also the exclusive status given to field experiments. Expanding on this case study, we discuss some significant differences between laboratory and field experiments. (shrink)