Page 391 - A Comprehensive Guide to Solar Energy Systems

Chapter 20 • Solar Energy Development and the Biosphere 399

considerable amount of negative ecological impacts. The effects of both paved and dirt
roads on wildlife have been well documented [39], including direct mortality from vehicle
collision, modified behavior (e.g., avoidance), and edge effects (e.g., altered microclimate,
increased predation risk and invasion of exotic species). larger, motile wildlife may easily
traverse roadways; however, their risk of collision increases with traffic volume. In con-
trast, roadways may be insurmountable linear barriers to less-motile species, potentially
leading to inbreeding and greater vulnerability to catastrophic events, such as wildfire.
Additionally, roads impact species spatial distribution and habitat use, as demonstrated
by the decreasing density of desert tortoises with increased proximity to roadways [40].
Invasive plant species often colonize disturbed areas and thus benefit from disturbance
associated with the construction of roadways [41]. Propagules of exotic species may be
carried by vehicles and construction equipment along roadways [11], aiding in their inva-
sion and spread across the landscape [42]. In contrast, road edges may enhance the vigor
of some perennial shrubs and the germination of some annual species, which benefit
from water runoff from impervious surfaces and support greater densities of herbivorous
arthropods than sites further away from roadways [11]. However, wildlife may be attracted
to road edges by the availability of forage, thus increasing their risk of collision.
Transmission and distribution lines are essential for transporting electricity gener-
ated from any type of power generation facility. Similar to roadways, the construction of
transmission corridors may degrade surrounding habitats; furthermore, maintenance of
transmission corridors (e.g., vegetation removal to decrease fire risk) is a continual source
of disturbance. Because of these factors, the ecological impacts of transmission infrastruc-
ture include their potential to become linear barriers to wildlife movement (e.g., species
may avoid the degraded or altered habitat within the corridor), edge effects, and altered
community compositions. For example, in Australia, the community composition and
abundance of small mammals was shown to differ between transmission corridors and
adjacent forested habitat [43,44], with introduced and grassland species being favored
over native, forest species. Bird diversity may be lower in corridors than surrounding
forested habitat in the United States, with generalist forest species and shrubland birds
dominating transmission corridors [45]. However, mid-seral vegetation management that
retains structural complexity of vegetation in the corridor (as opposed to complete and
frequent vegetation removal) may promote biodiversity and maintain connectivity for for-
est species [44], highlighting the need for site- and habitat-specific management within
transmission corridors to reach conservation goals.
In addition to indirect ecological effects, overhead transmission lines may pose direct
collision and electrocution risks to birds. On the basis of known fatality rates, an estimated
9
10 (1 billion) bird strikes may occur annually in the United States alone [46]. Weak fliers
(based on wing morphology and wing loading [i.e., ratio of weight to wing area]), were found
to have high probabilities for powerline collision in Spain; birds of prey, ravens, and thermal
soarers also were among electrocution victims [47]. Several studies have identified power-
line electrocution as a conservation problem for several species of rare and endangered
raptors worldwide, including California condor (Gymnogyps californianus; [48]), Spanish