The paper concludes with a discussion of my perspective on how geomorphologists can respond to the understanding that wilderness effectively no longer exists and that humans continually and ubiquitously manipulate the distribution and allocation of matter and energy. Water, water everywhere, nor any drop to drink. – Samuel Taylor Coleridge. Numerous papers published

during the past few years synthesize the extent and magnitude of human effects on landscapes and ecosystems. By nearly any measure, humans now dominate critical zone processes. Measures of human manipulation of the critical zone tend to focus on a few categories. (1) Movement of sediment and reconfiguration of topography. Humans have Selleckchem Epigenetics Compound Library increased sediment transport by rivers globally through soil erosion (by 2.3 × 109 metric tons/y), yet reduced sediment flux to the oceans Sorafenib ic50 (by 1.4 × 109 metric tons/y) because of sediment storage in reservoirs. Reservoirs around the world now store > 100 billion metric tons of sediment (Syvitski et al., 2005). By the start of the 21st century, humans had become the premier geomorphic agent sculpting landscapes, with exponentially increasing rates of earth-moving (Hooke, 2000). The latest estimates suggest that >50% of Earth’s ice-free land area has been directly modified by human actions involving moving earth

or changing sediment fluxes (Hooke et al., 2012). An important point to recognize in the context of geomorphology is that, with the exception of Hooke’s work, most of these studies focus on contemporary conditions, and thus do not explicitly include historical human manipulations of the critical zone. Numerous Inositol monophosphatase 1 geomorphic studies, however, indicate that historical manipulations and the resulting sedimentary, biogeochemical, and topographic signatures – commonly referred to as legacy effects – are in fact widespread, even where not readily apparent (e.g., Wohl, 2001, Liang et al., 2006 and Walter and Merritts, 2008). Initial clearing of native vegetation for agriculture, for example, shows up in alluvial records as a change in river geometry in settings as diverse

as prehistoric Asia and Europe (Limbrey, 1983, Mei-e and Xianmo, 1994 and Hooke, 2006) and 18th- and 19th-century North America and Australia (Kearney and Stevenson, 1991 and Knox, 2006). The concept of wilderness has been particularly important in regions settled after the 15th century by Europeans, such as the Americas, because of the assumption that earlier peoples had little influence on the landscape. Archeologists and geomorphologists, in particular, have initiated lively debates about the accuracy of this assumption (Denevan, 1992, Vale, 1998, Vale, 2002, Mann, 2005 and James, 2011), and there is consensus that at least some regions with indigenous agricultural societies experienced substantial landscape and ecosystem changes prior to European contact.