Geomorphologists can contribute to management decisions in at least three ways. First, geomorphologists can identify the existence

and characteristics of longitudinal, lateral, and vertical riverine connectivity in the presence and the absence of beaver (Fig. 2). Second, geomorphologists can identify and quantify the thresholds of water and sediment fluxes involved in changing between Raf inhibitor single- and multi-thread channel planform and between elk and beaver meadows. Third, geomorphologists can evaluate actions proposed to restore desired levels of connectivity and to force elk meadows across a threshold to become beaver meadows. Geomorphologists can bring a variety of tools to these tasks, including historical reconstruction of the extent and effects of past beaver meadows (Kramer et al., 2012 and Polvi and Wohl, 2012), monitoring of contemporary fluxes of water, energy, and organic matter (Westbrook et al., 2006), and

numerical modeling of potential responses to future human manipulations of riparian process and form. In this example, geomorphologists can play a fundamental role in understanding and managing critical zone integrity within river networks in the national park during the Anthropocene: i.e., during a period in which the landscapes and ecosystems under consideration have already responded in complex ways to past human manipulations. My impression, partly based on my own experience and partly based on conversations with colleagues, is that the common default assumption among geomorphologists is that a landscape that does not have obvious, contemporary human alterations has experienced lesser selleck products rather than greater human manipulation.

Based on the types of syntheses summarized earlier, and my experience in seemingly natural landscapes with low contemporary population density but persistent historical human impacts (e.g., Wohl, 2001), I argue that it is more appropriate to start with the default assumption that any particular landscape has had greater rather than lesser human manipulation through time, and that this history of manipulation continues to influence landscapes and ecosystems. To borrow a phrase from one of my favorite paper titles, we should by default assume that we are dealing with the ghosts Resveratrol of land use past (Harding et al., 1998). This assumption applies even to landscapes with very low population density and/or limited duration of human occupation or resource use (e.g., Young et al., 1994, Wohl, 2006, Wohl and Merritts, 2007 and Comiti, 2012). The default assumption of greater human impact means, among other things, that we must work to overcome our own changing baseline of perception. I use changing baseline of perception to refer to the assumption that whatever we are used to is normal or natural. A striking example comes from a survey administered to undergraduate science students in multiple U.S.