In the survey, students were shown an identical series of photos of river segments and asked to rate each river segment on a numerical scale in terms of being natural, esthetically pleasing, dangerous,

and needing ABT-888 nmr improvement. With the exception of the U.S. state of Oregon, and the countries of Germany and Sweden, students consistently rated river segments containing instream wood negatively, viewing these river segments as unnatural, dangerous, and in need of rehabilitation (Chin et al., 2008). This completely contradicts the manner in which river scientists view instream wood, and ignores the logical assumption that, since a much greater proportion of the world was forested historically, most river segments in forested environments would naturally contain a great deal of instream wood (Montgomery et al., 2003). The students’ negative perception of instream wood at least partly reflects the fact that most of them are used to seeing rivers with very little instream wood, even in forested environments, because of historical and continuing wood removal. Wood-poor rivers now seem

normal and natural Selleck Ion Channel Ligand Library to most people. Those of us who work in rivers and are familiar with the scientific literature on instream wood, as well as the idea of dramatic historical change in landscapes and ecosystems, can metaphorically step back and shake our heads at the students’ misperceptions, but identifying our own unexamined and misleading Urease perceptions is much more challenging. The default assumption of greater human manipulation of the landscape appears

to apply broadly to temperate and tropical zones, whether arid, semiarid or humid. Archeologists have developed convincing evidence that the seeming wilderness of the pre-Columbian Amazon basin hosted many more people than initially thought, although estimates range enormously from 500,000 to 10 million people (Mann, 2005 and McMichael et al., 2012) and remain controversial. Certainly some of these people intensively managed the surrounding vegetation and soils, as reflected in the persistence of dark-colored, fertile terra preta ( Liang et al., 2006) soils that were created by pre-Columbian Indians from 500 to 2500 years BP. Prehistoric agricultural societies in central Arizona, USA created an extensive network of irrigation canals that resulted in soil salinization that persists today ( Andrews and Bostwick, 2000). Only very limited areas of high latitude (Antarctica, parts of the Arctic) and high altitude appear not to have been manipulated by humans at some point during the past few millennia ( Sanderson et al., 2002 and McCloskey and Spalding, 1989). Faced with the realization that most landscapes have been and continue to be manipulated by humans in ways subtle or obvious, geomorphologists can make at least three important contributions to sustaining critical zone integrity.