Characterizing the Human Imprint on Landscapes for Ecological Assessment

Human activity has altered natural landscape patterns and ecosystem functioning to varying degrees over the course of recorded history (Turner 1990). Even the act of “preserving” a wilderness landscape results from a societal decision based on the value placed on that landscape. Such acts, as with many ecosystem uses, rarely happen by accident. Therefore, in order to assess ecosystem function and integrity, some understanding of the human dimension is necessary. It is useful to identify two critical aspects of the human dimension: factors that drive, and can be used to predict, human activities; and factors that characterize the impacts of those activities on ecosystems. By and large, the drivers of human activity are intangible (e.g., profit motive or concern for beauty) and the impacts result from tangible structures or activities on the landscape. At the same time, it is important to view human activity as a critical component of, and not separate from, ecosystem functioning. Ecosystem structure and function can influence society's valuation of resources, driving human activity. For example, the presence of a pristine or high quality landscape might drive development nearby, degrading the quality of that landscape. The human imprint on landscapes is variable in time and space, and varies at a multitude of different time and space scales. Temporal variability implies that (a) data about human activities must be updated on a regular basis and (b) multi-temporal or time series data may be necessary to characterize changes in the human dimension, especially when those changes drive significant ecological changes. Spatial variability demands that these elements be represented spatially, usually using a geographic information system (GIS). A GIS facilitates the management of multi-thematic spatial data, and can be used to manage multiple scale representations of a given theme to deal with the variability in scale. This chapter presents approaches for characterizing tangible and intangible elements of the landscape that are societal in nature (Table 1), discusses their ecological importance, and presents several practical and conceptual issues in dealing with these elements. The focus is on identifying the spatial distributions of each element. For each element, the discussion involves its ecological/environmental importance, potential data sources, and other issues related to spatial and temporal scale, spatial data structures, and related research needs. The spatial location and pattern of these elements are important determinants of their influence within an ecosystem, as are certain descriptive attributes.