Ecosystem Consequences of Biodiversity Loss: The Evolution of a Paradigm

The ecosystem consequences of dramatic declines or changes in biodiversity have spurred considerable research and tremendous debate that has rekindled most of the major conflicts in ecology, creating a sense of déjà vu. These conflicts include whether ecosystem or community ecology provides better insights into the workings of nature, the relative importance of biotic vs. abiotic factors in governing community composition and structure, the virtues of phenomenological vs. mechanistic research, the relationship between biodiversity and stability, the relative importance of taxonomic vs. functional diversity, and the relative strengths of observation vs. experimental approaches. Although the tone of the debate has been regrettable, its magnitude signifies the emergence of a new paradigm, one in a series of debates associated with the dialectic that has structured ecological inquiry over two millennia of Western science. This dialectic concerns the tension between those who seek to explain nature by studying its parts and those who seek to explain nature by studying whole-system behavior. Philosophers and historians argue that such a dialectic generates cycles in which a central tenet is challenged by an emerging paradigm, generating new theories and new data to test the emerging paradigm. The scientific community evaluates the accumulating evidence (and it is here that the debates arise), and if subscription to the emerging paradigm increases sufficiently, the emerging paradigm evolves into a new central tenet. Fractionation within the sciences exacerbates this cycle because subdisciplines often focus on either the parts or the whole. Such splintering can be traced to the abandonment of the holistic approach of Aristotelian science during the Scientific Revolution. While such holism may have lessened debate, some have argued that it stagnated Western science. The dialectic, the cycles of emerging paradigms it generates, and the debates that surround each emergence represent the vehicle by which ecology moves forward. Emerging paradigms force scientists to revisit central tenets, pitting old ideas against new theories and new data, and this revisiting is what generates the sense of déjà vu and the cycles of vigorous debate, but ultimately each cycle leads to synthesis and progress. The emerging paradigm that biodiversity governs ecosystem function is rapidly evolving. In the words of Thomas Kuhn, its controversial experiments have successfully articulated the paradigm. It has successfully challenged ecology's central tenet that biodiversity is primarily an epiphenomenon of ecosystem function secondarily structured by community processes. In its most extreme form, it claims that the reverse is true. Of course, neither the central tenet of ecology nor the emerging paradigm is correct in an absolute sense, but the dialectic that promoted the emergence of biodiversity and ecosystem function as a paradigm redirected ecology to focus on the feedback between ecosystem function and biodiversity rather than studying them independently. The final stage in the evolution of this emerging paradigm will be explicit tests of synthetic mechanisms that have been proposed. Familiarity with the ecological dialectic provides a framework by which ecologists can understand the origin and utility of paradigms in ecology, provides a proper context for the debate that surrounds paradigms as they emerge, promotes synthesis, and deters intellectual chauvinism that may inadvertently accompany specialization within ecology.