Results
The composite map of the degree of urban/built-up shows a relatively familiar pattern of urban areas, particularly the cities along the Colorado Front Range (Figure 1). Including information on slightly lower density of houses provides a fairly large expansion of locations that are developed beyond those locations identified in NLCD, particularly along mountain valleys.
The composite map of production and extraction-oriented land use provides a fairly different picture of Colorado (Figure 2). Extensive lands have been converted to cropland agriculture in the eastern plains and San Luis Valley. Another factor included is the extensive distribution of oil and gas wells, particularly in the northern Front Range area and western slope.
Perhaps the most unique contribution of this map is to portray the distribution of the extent and types of recreational uses found in Colorado (Figure 3). Compared with the typical map of public land ownership, portraying national forests, grasslands, and parks as being largely the same, this map clearly differentiates the heavy influence that accessibility to large populations (like the Front Range) can have. Accessibility here is computed as the one-way travel time (along roads) from urban areas. Also differentiated are the types of land management activities on public lands, distinguishing the heavily-recreated resort areas such as Aspen, Vail, and Breckenridge. This map also reflects locations that are dominated by motorized vs. non-motorized recreation (future improvements should incorporate specific travel management plans).
The degree of human modification values vary across the State, with fine-grained differences particularly noticeable in riparian zones (Figure 4). The average HMF value is 0.392 (SD=0.231). The range and distribution of HMF values can also be summarized by various ecological system types, such as lower montane, mixed, and uppermontane zone (Table: Summary statistics for forested ecosystems). Our results show that the midmontane zone has the largest average HMF score (0.428), indicating the highest degree of human activities that may modify or effect ecological systems in this zone. The upper montane zone (0.329) is the lowest of the conifer-dominated zones (lower montane=0.405), but aspen forests have the overall lowest degree of human modification (0.313). In addition to summarizing by counties, different analytical units such as watersheds, ecoregions, ecosystems, etc., can be supported. It is important to note that although one can summarize values over fairly large areas, as we have done by major ecological system type, the fine-grained data will allow differentiation of more localized areas that are particularly impacted or have particularly low HMF values.
Commonly, population density is used as a surrogate indicator of the degree of impact on ecological systems. Although we found a loose relationship between population density and HMF score (Figure 5), there is a fair amount of variation as well, showing the additional information that this approach provides. By the same token, HMF provides a finer degree of detail than housing density—although housing density had a strong relationship.
We also compared HMF to GAP stewardship categories from the Southwest Regional GAP study (Table: Summary statistics of Human Modification Framework). We found that status 1 lands had lower average HMF values than status 2 (0.244 vs.0.295), which were less than status 3 and 4. Interestingly, we found that status 4 had a lower mean HMF value than level 3 (0.397 vs. 0.421). Also, all status levels had very large maximum values (0.89 for level 1 and 1.0 for 2, 3, and 4).
Encyclopedia ID: p3655
