SYMP 9

From Oceans to Mountains: Using Abiotic Gradients to Investigate the Effects of Climate on the Cascading Effects of Predators

Abiotic environmental changes interact with human land use and direct persecution or overharvest of species to degrade trophic structure in communities. Loss of trophic structure can profoundly affect ecosystem stability, function, and diversity, though the extent of these impacts are difficult to anticipate. Our limited understand of how abiotic and biotic forces combine to structure trophic processes becomes apparent when we try predict how trophically fractured biological communities will respond to changes in climatic conditions. We propose to assemble perspectives on variation in the importance of predators in communities along abiotic gradients. Our objective is to identify general patterns from which we may generate hypotheses for future research on how global change research can incorporate trophic processes. An emphasis on gradients builds on a strong tradition of examining ecological processes across space and gradual changes in abiotic conditions (e.g., Whittaker 1967, Menge and Sutherland 1976) and extends this thinking to the contemporary problem of abiotic change through time resultant from climate change. We apply this approach to the study of cascading predator effects for several reasons. First, although ecologists are beginning to understand that different competitors may be favoured by climate change (e.g., Reich et al. 2012), we are less clear on how consumer-resource interactions are modified by abiotic conditions. Second, consumers play an important role in the maintenance of diversity and stability of ecosystems. Third, higher trophic levels are more vulnerable to extinction, especially when abiotic conditions become extreme (e.g., Estes et al. 2011). These observations lead to two critical hypotheses: 1) the role of consumers in ecosystems varies predictably along ecological gradients; and 2) gradients will provide insight into how the cascading effects of predators can be affected by climate change. Speakers will contribute perspectives from different ecosystems and insights from different approaches to studying consumer-resource interactions. They will speak to the question of the importance of consumers along abiotic gradients, relating directly to the theme of the conference. Our list of speakers includes marine, freshwater and terrestrial experimental ecologists, junior and senior researchers working in diverse parts of the world at local and biogeographic scales. The speakers share a common interest and have all demonstrated ability to synthesize and use their systems to speak to a broader question. Our organized symposium will be of broad interest to ESA members because it will explore how a classic method in ecological research is being applied to contemporary, complex problems.