The ecological literature, an idea‐free distribution

Ecology is awash with theory, but everywhere the literature is bereft. Many papers in ecology do not even reference their theoretical context, while only a small minority are engaged in what is supposed to be the heart of the scientific enterprise: theory testing. I will demonstrate these assertions with an analysis of the current and historical literature. First, though, let us examine the roles that theory plays in ecology, and all of science. Theories are the way in which we organise our ideas and turn data into knowledge. They provide a means for laying bare the assumptions that underlie our models and experiments. They provide guidelines for building models (a particular kind of theory). They provide the rationale for where we look in the world and help us interpret what we see. Contrary to some claims, there is no such thing as theory-free science. All observations presuppose a theoretical context. For example, the simple act of counting individuals and assessing species diversity relies on the concepts of ‘individual’ and ‘species,’ both of which are complex ideas (e.g. Wheeler & Meier 2000; Strassmann & Queller 2010). Perhaps more importantly, our theories are what give us warrant to take what we learn in one place and apply it to another. When we begin a prairie restoration project, we rely not just on previous projects, but general knowledge about successional processes, competitive hierarchies and mutualistic interactions. When we finish our project, we can add what we have learned at this place to the general pool of knowledge through our theoretical constructs. Hence, theories allow us to generalise from specific studies to overarching concepts. I was prompted to do a historical analysis of theory in the ecological literature because of an invitation to participate in a symposium at the annual meeting of the Ecological Society of America honouring the thirtieth anniversary of the publication of Robert McIntosh’s The Background of Ecology (1985, Cambridge University Press). We were asked to comment on the history of the field since that publication, and I was assigned ‘theory’. So I decided to look at the extent to which the ecological literature engages with theory. The results were better than I anticipated, but not as good as I hoped. I used the July 2012 issue of Ecology as my baseline, both because it was an ESA symposium, and because it was the leading, general ecology journal during most of the twentieth century. I assigned papers to several categories: no mention of a theory in the Introduction (case studies, methods or literature reviews), mentioning a theory (theory motivated) or engaging with theory (reviews of theories, explicit tests of one or more theories, or development of a model, theory or conceptual framework). I tried to be as generous as possible in assigning papers to the ‘theory motivated’ category. From that baseline, I went back at ten year intervals to the beginning of the journal. If a given issue did not contain at least 20 papers, I included the preceding or following issue. To insure that I was sampling the general literature, I avoided any issue that included a special topic section or symposium collection. For a historical comparison, I did a similar analysis for The American Naturalist and Evolution, journals with similarly long histories that publish widely on topics in ecology and its sister discipline of evolution. (Of the American Naturalist issues surveyed, 71% of the papers focused on evolution.) For a contemporary comparison, I examined the June/July issues of Ecology Letters, Oikos and Journal of Evolutionary Biology, the other current leading general ecology and evolution forums. For the first half of the last century, the ecological (and evolutionary) literature for the most part consisted of descriptive case studies that did not explicitly engage with theory (Fig. 1). That changed about 50 years ago, a change that coincided with efforts by many to bring theory and models to the forefront of ecology, most notably Eugene and Howard Odum (ecosystem ecology) and Robert MacArthur and his collaborators. However, the engagement of the ecological literature with theory consistently lagged behind