Why so skeptical? The role of animals in fluvial geomorphology

Despite acknowledgement of zoogeomorphological impacts and a positive trajectory for biogeomorphology, the cumulative geomorphic significance of animals remains largely unknown across geomorphic scales. We do not know the proportion of erosion, transport and deposition that is mediated by animal activity in different environments and cannot answer questions like how changing animal distributions under climate change will affect sediment fluxes and landscapes? This partly reflects a healthy scepticism about the net significance of biological energy and zoogeomorphic processes when set against the orthodox assumption that geophysical energy dominates. Zoogeomorphology is regarded as a ‘niche’ interest, or worse, as inconsequential. Drawing on examples from fluvial geomorphology, this essay challenges that scepticism with the aim of encouraging greater consideration of the relevance of coupled biomorphodynamic systems. Five assumptions that belittle the role of animals are considered: that the number of species acting as geomorphic agents is small and their abundance limited; that limited geographical extent and periods of activity preclude widespread effects; and that impacts on sediment fluxes and morphological change are insignificant. In the hope that some scepticism is overcome, four interrelated challenges for future research are outlined: empirical investigation of zoogeomorphic processes, scaling-up process understanding, embracing new technologies and approaches, and developing suitably integrated modelling tools. Such advances, alongside a willingness to recognise coupled biomorphodynamic interactions as the norm, rather than the exception, can improve our ability to understand both geomorphological and ecological phenomena and transform our understanding of how landscapes interact with the animals that live on, and in, them.