Snags are critical habitat for many species of birds, mammals, and arthropods. Even more damaging may be the effects of increased human use on wildfire frequency and seasonality. The Carson National Forest includes the southern extensions of the Rocky Mountains and supports several species of wildlife that are especially sensitive to high road densities. Another species that is not only an indicator species but is critical to the economy of Northern New Mexico is the American Elk. These patterns are caused in part by several factors related to roads including edge effects, habitat fragmentation, and increased human access.
Habitat fragmentation can result from road networks in previously intact wildlife areas.
In addition to detrimental effects on wildlife populations, roads have direct consequences upon hydrology and aquatic habitats. Erosion and sedimentation from roads is arguably the most damaging effect. Increased erosion in turn increases sedimentation in downstream watersheds. Sedimentation has been identified by biologists to negatively affect fisheries and downstream water quality. This figure represents only those roads officially surveyed by the USFS, many more miles of undocumented roads exist on National Forest lands.