The Human Footprint in the West: A Large‐scale Analysis of Anthropogenic Impacts

Abstract

Anthropogenic features such as urbanization, roads, and power lines, are increasing in western United States landscapes in response to rapidly growing human populations. However, their spatial effects have not been evaluated. Our goal was to model the human footprint across the western United States. We first delineated the actual area occupied by anthropogenic features, the physical effect area. Next, we developed the human footprint model based on the ecological effect area, the zone influenced by features beyond their physical presence, by combining seven input models: three models quantified top-down anthropogenic influences of synanthropic predators (avian predators, domestic dog and cat presence risk), and four models quantified bottom-up anthropogenic influences on habitat (invasion of exotic plants, human-caused fires, energy extraction, and anthropogenic wildland fragmentation). Using independent bird population data, we found bird abundance of four synanthropic species to correlate positively with human footprint intensity and negatively for three of the six species influenced by habitat fragmentation. We then evaluated the extent of the human footprint in relation to terrestrial (ecoregions) and aquatic systems (major rivers and lakes), regional management and conservation status, physical environment, and temporal changes in human actions. The physical effect area of anthropogenic features covered 13% of the western United States with agricultural land (9.8%) being most dominant. High-intensity human footprint areas (class 8-10) overlapped highly productive low-elevation private landholdings and covered 7% of the western United States compared to 48% for low-intensity areas (class 1-3), which were confined to low-productivity high-elevation federal landholdings. Areas within 1 km of rivers were more affected by the human footprint compared to lakes. Percentage human population growth was higher in low-intensity human footprint areas. The disproportional regional effects of the human footprint on landscapes in the western United States create a challenge to management of ecosystems and wildlife populations. Using footprint models, managers can plan land use actions, develop restoration scenarios, and identify areas of high conservation value at local landscapes within a regional context. Moreover, human footprint models serve as a tool to stratify landscapes for studies investigating floral and faunal response to human disturbance intensity gradients.

Siting solar energy development to minimize biological impacts

“…Where agricultural land use is more stable through time, it may be sufficient to use land use data for a single period, since repeating historical land use maps are not so common. The On-Site Degradation criterion is similar to the Human Footprint of the West [27], which was designed as a general purpose measure of degradation and not specific to renewable energy. Although developed in the context of solar energy, the framework has similar applicability for wind and geothermal energy.…”

A Model Approach for Estimating Colony Size, Trends, and Habitat Associations of Burrow-Nesting Seabirds

“…In the terrestrial enviornament, researchers have evaluated the cumulative impact of human activities in a GIS environment at global (e.g., Sanderson et al 2002), national (Theobald 2010) and regional (e.g., Leu et al 2008) scales. The regional effort by Leu et al (2008), involved calculating the physical human footprint, defined as the actual space occupied by human features for the western U.S. including Washington.…”

“…The regional effort by Leu et al (2008), involved calculating the physical human footprint, defined as the actual space occupied by human features for the western U.S. including Washington. Recognizing that human features influence ecological processes beyond the physical space occupied by those features they also mapped the effect area, or the ecological human footprint.…”

Assessing large-scale wildlife responses to human infrastructure development

“…The main difficulty in quantifying the area of influence of infrastructure on wildlife, that is, the area over which the ecological effects extend into the adjacent landscape [e.g., "roadeffect zone" (2)] has been the lack of reliable distance thresholds for these effects (18). Most effects on local species abundances occur within a specific distance from the infrastructure and level off as distance increases (19,20).…”