The Concept of Organisms as Ecosystem Engineers Ten Years On: Progress, Limitations, and Challenges

E cologists have long recognized that organisms can have important impacts on physical and chemical processes occurring in the environment. While some influences invariably arise from organismal energy and material uptake and waste production, many organisms alter physical structure and change chemical reactivity in ways that are independent of their assimilatory or dissimilatory influence. Indeed, Darwin devoted an entire book to the effects of earthworms on soil formation (Darwin 1881). That such changes have the potential to influence organismal distribution and abundance and ecosystem processes is well recognized. Nevertheless, while scattered, diverse examples of these types of organismal effects on the abiotic environment have steadily accumulated in the ecological literature Furthermore, ecological textbooks have rarely included such effects among the roster of important forces structuring ecological populations and communities or influencing ecosystem functioning; instead, they have traditionally focused on interactions such as competition and predation, or emphasized metabolically regulated nutrient and energy flows.