Wildlife Specialist report

Roads and trails create edge habitats (Johnson et al. 1975, Adams and Geis 1983,
Holzapfel and Schmidt 1990, Lightfoot and Whitford 1991, and Reed et al. 1996),
resulting in a variety of effects, including changes in vegetation and encroachment of
nonnative and invasive species (Huey 1941). The impermeable surfaces of roads and
OHV routes shed precipitation, thereby increasing overall moisture availability in the
immediate vicinity of the road or route (Ouren et al. 2007). The increased moisture
availability may promote greater plant vigor along roadsides than in surrounding areas
(Johnson et al. 1975), and Angold (1997) indicated that such effects may extend as far as
200 m. from road edges. The greater vegetation cover typically observed along roadsides
also is often due, in part, to greater species richness in those areas (Holzapfel and
Schmidt 1990). Interestingly, increased vegetation cover along roadsides may attract
more invertebrates and other organisms. For example, Lightfoot and Whitford (1991)
found that shrubs along a road supported greater numbers of foliage arthropods.
Invertebrates may be precluded from crossing various road types, including those
considered relatively narrow; however, there are species differences that may be
influenced by their ecologies and physical capabilities (Ouren et al. 2007). For example,
Samways (1989) found that both “tarred” (paved) and “untarred” roads were almost
complete or partial barriers to three species of bush crickets, but roads were only minor,
very minor, or did not serve as barriers to the movements of six other bush cricket
species, five of which readily fly across roads. On the other hand, Munguira and Thomas
(1992) found that wide highways did not affect the movements of butterflies in open
populations; movements of butterflies in closed populations, however, were slightly
impeded by roads. Other butterfly species may not even attempt to fly across roads
(described by authors as two-lane highways and secondary roads); possibly due to the
extreme changes in microclimate over roads (including columns of warm air rising above
roads (Van der Zande 1980). Mader (1984) reported that in a 5-year mark-recapturerelease
study involving 10,186 carabid beetles representing nine species, three species
were never recaptured on the opposite side of study area roads (one- or two-lane paved
roads) or parking loops, and the remainder were recaptured across the road only rarely.
However, some individuals of a Swedish snail species (Arianta arbustorum) that were
captured and translocated to the opposite sides of narrow paths or relatively wider roads
did return to the capture sides of paths (Baur and Baur 1990).
Luckenbach and Bury (1983) found that in OHV play areas, there were marked declines
in herbaceous and perennial plants, arthropods, lizards, and mammals when compared to
nearby controls. The biota was affected even by relatively low levels of OHV activity,
while areas heavily used by OHVs had virtually no native plants or wildlife. Hess (1969)
found that in areas where roads were built along stream courses and crossed the stream
courses, there was an increase in the biomass of aquatic insects at the disturbed sites than
the undisturbed control site. However, the diversity of insects was greatly reduced. The
order Diptera was the only order of insects to show a significant increase in numbers,
while all other orders declined. In the undisturbed areas (no roads within 300 feet of
stream course) all insect orders showed an increase in numbers. All mayfly species also
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