Rivers and streams are natural corridors for aquatic organisms, but over half the length of the global river network temporarily stops flowing at some point. Intermittent and ephemeral waterways may be a problem for anything that swims, but the resulting dry riverbed has the potential to act as a corridor for terrestrial species instead. Few studies have looked at the potential benefits of dry riverbeds as corridors, particularity for vertebrates. This oversight becomes a problem when you consider that climate change and other human modifications of the landscape are likely exacerbate the temporary nature of many streams and rivers.
New research by Sánchez-Montoya et al. represents the first study to quantify the role of dry riverbeds as movement corridors for terrestrial vertebrates, including mammals, reptiles, and birds. The authors sampled vertebrate occurrence using marble dust stations at two intermittent streams in Spain, and compared the use of dry channels to the use of riparian and upland habitats. They also asked whether individuals moved in specific directions or randomly within the dry channel.
Their results demonstrate that dry channels can act as a highway for animal movement, especially when devoid of dense vegetation. However, the extent to which a dry riverbed is used may depend on the surrounding landscape permeability – in other words, whether or not it’s easy to move outside of the riverbed as well. Over 1100 tracks were recorded, and the majority of these were directional rather than random. Water availability played only a small role in predicting movement across the wide range of taxa surveyed.
Dry riverbeds can act as natural pathways in the landscape that, unlike other linear features such roads or firebreaks, don’t contribute to habitat loss and fragmentation. Although it seems detrimental for rivers and streams to become more intermittent in the future, this may be true only for aquatic species. Terrestrial organisms looking for another linkage in the landscape may find better connectivity through the use of an otherwise inaccessible corridor.
Sánchez-Montoya, M. M., M. Moleón, J. A. Sánchez-Zapata, K. Tockner. 2016. Dry riverbeds: corridors for terrestrial vertebrates. Ecosphere 7(10): e01508. DOI: .
Acuña, V., T. Datry, J. Marshall, D. Barceló, C. N. Dahm, A. Ginebreda, G. McGregor, S. Sabater, K. Tockner, and M. A. Palmer. 2014. Why should we care about temporary waterways? Science 343(6175): 1080-1081.
Raymond, P.A., J. Hartmann, R. Lauerwald, S. Sobek, C. McDonald, M. Hoover, D. Butman, R. Striegl, E. Mayorga, C. Humborg, and P. Kortelainen. 2013. Global carbon dioxide emissions from inland waters. Nature 503(7476): 355-359.