WIND ENERGY & WILDLIFE:
an attempt at pragmatism
Šaltinis: http://www.wildlifemanagementinstitute. ... power.html
Rob Manes, Stephanie Harmon, Brian Obermeyer, Roger Applegate
The purpose of this examination is to preliminarily identify potential problems, possible solutions, speculation and unfounded concerns regarding the implications of wind power development for wildlife. The primary focus is on the grassland birds of the central plains.
Early concerns about wind energy development focused on bird deaths that result from collisions with wind generator blades, towers, support structures, and power lines. This was a readily observable phenomenon, so it was easy to garner support for studies and for corrective actions. Wind power industry leaders generally responded responsibly to this issue by supporting monitoring and implementing improved designs.
Wildlife advocates and environmentalists were slower to grasp other potential impacts of wind power development. Although some biologists recognized that there could be significant fragmentation of habitats associated with wind power facilities, wildlife advocates have voiced minimal concern over this issue to date. The wind industry has reacted accordingly, pursuing what, for all appearances, is one of the more environmentally friendly means of generating power for an energy-hungry society.
What We Know About Wildlife Impacts and Wind Power
Early on, wildlife biologists expressed concern over potential bird deaths resulting from collisions with elevated lines, turbine blades, towers, and support structures. University researchers, wildlife agency staff, and energy developers focused their attention on the issue and found only scattered evidence that the problem was widespread or even numerically significant at the population level.
Radio, television, and wind generator towers taller than 200 feet have proven more hazardous to night-migrating birds. Some biologists have suggested that aircraft warning lights required on towers taller than 199 feet attract and disorient night-migrating birds, increasing the number of fatalities they cause. The noise of wind turbines may disorient flying bats also, increasing the likelihood that they will collide with these elevated structures. Predictably, towers erected near wetlands and other bird concentration areas or migration corridors precipitate more collision deaths. Even considering such situations in total, bird collisions with wind generator towers, blades, and transmission lines may not constitute a significant threat for most species or populations. Ill-sited facilities in the habitats of highly vulnerable species may constitute an exception to this statement.
Habitats Broken: fragmenting grasslands and shrublands
As wind generation technology has evolved and spread, wildlife biologists have begun to recognize that impacts other than bird collisions are cause for greater concern. One such concern is the fragmentation of grassland and shrubland habitats by wind turbines and associated infrastructure. Of particular concern are threats to prairie grouse (sage grouse, sharp-tailed grouse, and lesser and greater prairie-chicken), which are icons of North American plains wildlife.
The life cycles of prairie grouse require large expanses of unfragmented, ecologically healthy rangelands. Intact expanses of mixed-grass, short-grass and sage brush prairie are essential to the lesser prairie-chicken, and mixed- and tall-grass prairie support the greater prairie-chicken and sharp-tailed grouse. Unbroken expanses of these grasslands and shrublands are also important travelways for migrating birds and mammals.
Increasingly, grassland habitats are fragmented by croplands, poorly managed grazing, and other human influences. The result is that scant remaining habitats are rendered more important to the future of prairie grouse and other sensitive species.
Lesser prairie-chicken inhabit only parts of five states -- Colorado, Kansas, New Mexico, Oklahoma, and Texas. Presently their populations are declining at rates that some experts predict could bring about their extinction. A petition to protect the species under the federal Endangered Species Act (ESA) resulted in a determination that such action is warranted, but is precluded by higher priorities. Resulting primarily from cropland development and unfavorable grazing practices, the lesser prairie-chicken’s historic range has receded by 92 percent, and its entire population has declined by 74 percent. These birds require blocks of quality habitat entailing 2,000 to 4,000 contiguous acres for nesting success; and experts suspect that habitat blocks exceeding 20,000 acres may be required to support the birds’ entire life cycle.
Remaining lesser prairie-chicken habitat in Kansas and Oklahoma occurs roughly in the states’ combined western third. The proliferation of irrigation systems has allowed much of the short-grass and sand-sage prairie of this area to be converted to cropland. Intensive grazing has diminished remaining grassland habitats. Other influences, including roads and oil and gas production, also contribute to this trend.
The grasslands of eastern Kansas and Oklahoma comprise the continent’s only remaining large, contiguous expanse of the tallgrass ecosystem. This region constitutes one of the most important remaining greater prairie-chicken strongholds, but biologists estimate that only about 20 percent of early the 1980s population remains there today. In the mid-1980s, biologists estimated total greater prairie-chicken numbers at 1.2 million; by the late 1990s, the estimated number had dropped to about 400,000. While the causes of these declines are not fully documented, experts cite the widespread use of intensive early-season cattle grazing and annual spring pasture burning among the problems for greater prairie-chickens. Both practices diminish the availability of essential nesting and brood-rearing habitats. Other factors, including the increasing intrusion of trees and other invasive plants in the tallgrass prairie, also contribute to the greater prairie-chicken’s decline. Woody plant encroachment is particularly problematic on the Flint Hills periphery, where prescribed fire is not widely used.
Kansas, North Dakota, South Dakota, and Texas are noted as states with the greatest wind energy production potential, and 12 midwestern states may hold as much as 90 percent of the U.S. wind power potential. These states also entail much of the remaining habitat for sharp-tailed grouse and lesser and greater prairie-chicken. The influences that have degraded the habitats of these birds magnify the effects of each additional threat. In combination with misplaced or ill-designed wind power development, intensive grazing, annual pasture burning, road development, urban sprawl, oil and gas production, power line placement, dispersed residential development, and other influences pose a likely synergistic threat to prairie grouse and other grassland species.
Leks, the unique, traditional mating grounds of prairie grouse, are consistently located on elevated grassland sites with few vertical obstructions. These are also often preferred sites for wind generation facilities. Many ground-dwelling birds appear to be sensitive to elevated structures in their otherwise relatively flat habitats. Grassland birds – including some species whose populations are declining seriously – avoid trees, buildings, power poles, and other elevated structures that can serve as raptor perches. Three grassland bird species have been documented to avoid areas within 100 meters of wind turbines. Recent research involving prairie grouse offers confirmation.
Similar effects of elevated structures have been identified regarding lesser prairie chicken, with no nesting or brood rearing within 400 meters of roads and 300 meters of power lines. In addition, a recent study found no nesting or lekking within one-half mile of a gas line compressor station. Lesser prairie-chickens generally avoid human activity and seldom nest within one-quarter mile of inhabited dwellings, and the birds have been shown to avoid a one-mile radius of a coal-fired power plant.
What We Fear
Though many gaps exist in the foundational knowledge regarding effects of wind power facilities on birds and other wildlife, what is known troubles wildlife experts. Collision-related bird deaths and, more importantly, landscape fragmentation and habitat abandonment by grassland birds, is sufficiently documented to generate speculation and concern about further-reaching impacts.
While most examinations of collision-related deaths indicate that this phenomena is generally not a threat to bird or bat populations, existing studies do reveal potential for this to become numerically significant in certain circumstances. Very large wind generator installations, involving hundreds or even thousands of towers, especially if sited in migration or staging areas, could produce major negative impacts on some bird populations, particularly those that are already diminished by other factors.
The potential for widespread habitat abandonment by grassland birds, and possibly other wildlife, caused by wind power facilities also concerns wildlife scientists. While data regarding this phenomenon presently is narrowly based, it shows that certain species, particularly ground-nesting birds, halt or diminish their use of areas near towers, transmission lines, poles, and roads. Some bird populations examined in existing studies are declining seriously, and a few are candidates for endangered species status.
Species that use leks may be especially susceptible to disturbance from tall foreign structures and from noise, which may disrupt their mating communication. The prairie grouse, many of which are in serious population declines, are lekking species, and biologists are especially concerned about the intersection of the continent’s most important grouse habitats and prime wind generation regions. Sage grouse, for example, avoid areas that have tall structures that could serve as perches for predatory birds. There is evidence that this behavioral avoidance occurs, even if anti-perching devices prevent raptors from using towers and poles as hunting vantage points. Similarly, other avian species show tendencies to abandoned otherwise suitable nesting habitats, if tall structures are present.
In addition to an apparent avoidance of elevated structures, some species also are hazed out of important habitat areas by automobile traffic and other human activities, such as may be associated with maintenance and operation of wind generation facilities. Sage grouse have been shown to avoid traffic noise, and roads are known to interrupt migrations of some mammals. This gives rise to concerns that the roads and other infrastructure of wind turbines may entail threats to grassland birds.
Perhaps the greatest concern of wildlife advocates and experts is the cumulative impact of the many factors that fragment the continent’s plains ecosystems. Crop production has been the primary factor replacing more than 90 percent of the nation’s former grasslands. Long-term disadvantageous livestock management practices have degraded much of the remaining prairies and shrub steppe ecotypes; and dispersed residential development, urban sprawl, highways, invasive plants, and energy development threaten much of the rest. The precious few areas that have not been seriously degraded by these influences are protected by unyielding soils, steep topography, remoteness, and by conservation-minded landowners. Wind energy production could find its way into these critical remaining prairie and shrub steppe ecosystems. Combined with the existing threats to these areas, widespread wind power development could be devastating to some species.
Lesser prairie-chicken may best illustrate this daunting potential. The remaining habitat of this species overlaps almost totally with identified prime wind generation areas. This interplay could push the lesser prairie-chicken to ESA listing, possibly even to extinction, especially if wind energy development expands into of the unbroken native and restored grasslands of the five states the species inhabits.
What Wildlife Interests Need From Wind Energy Interests Today
Open Dialog & Public Outreach
Many potential conflicts between wind energy development and wildlife conservation can be eliminated or minimized through open dialog between the stakeholders, including energy developers, wildlife professionals, landowners, consumers, wildlife advocates, policy makers, and others. This dialog must be consistent, honest and directed at resolving issues, rather than simply protecting interests. It must recognize that both clean, reliable energy and healthy ecosystems are essential to the quality of human life. All stakeholders must bring to this dialog potential solutions to identified problems, and to the concerns of others.
In addition, it is important that key stakeholders cooperate to ensure that public information regarding wind power is readily available and accurate. Messages that overstate the ecological threats or the environmental or economic benefits of wind power must be avoided.
Standard Biological Inventories and Monitoring Practices
It is important that wind energy developers and wildlife interests cooperate to design and implement standard practices to reliably inventory plant and animal communities before development sites are selected, before construction begins on selected sites, and after development is completed. Long-term monitoring of potentially affected wildlife populations is essential. Such efforts are not without cost, and it is reasonable that funding should come from multiple stakeholders, including consumers, energy developers, and wildlife agencies and organizations. Important monitoring issues include bird collision deaths, long-term bird and mammal habitat use for all life-cycle phases; cumulative and synergistic ecological effects of wind energy development and other land uses; immediate and long-term economic impacts and cost-benefit comparisons; and others.
Best Management Practices
As wind energy development expands and the knowledge base regarding wildlife impacts grows, a set of prescriptions for designing, siting and building wind turbine facilities must be created. Standards for designing and managing wildlife habitats may also be important in avoiding negative ecological impacts. These standards should be dynamic, being constantly improved and updated as research, monitoring and technological developments dictate changes.
Stakeholders need to cooperate in researching wildlife and wind power issues. Jointly designed, jointly funded, and even jointly executed – such studies will provide information that allays unfounded concerns, identifies unknown problems, and suggests solutions. In order to achieve desired results, this research must adhere to high scientific standards. Research needs associated with wind power in the central plains include:
• Further studies on the effects of habitat fragmentation on greater prairie-chicken demographics.
• Research to determine area size of unfragmented habitats necessary to support healthy populations of prairie grouse and other grassland and shrubland wildlife.
• Mitigation studies focusing on management practices to compensate for habitats lost to development, and the amount of buffer required between usable habitat and wind energy developments.
• Experiments to determine the efficacy of establishing new "artificial" leks.
• Research on reducing other impacts to prairie grouse populations.
• Pre-development studies to determine wildlife use of selected sites to design siting and mitigation.
• Before-after/control-impact (BACI) studies on all sites, from pre-development to operational phases of the project.
Mitigate Damages When Necessary
Some detriments to wildlife may be inevitable when wind power is developed. It is important that stakeholders cooperate, however, first to avoid negative impacts and second to mitigate habitat losses when necessary and feasible. The latter may involve off-site habitat restoration, translocation of affected species, protection of existing key habitats, and modifying uses and management of nearby lands to improve targeted habitats.
Avoiding and Minimizing Ecological Damages
Though research and standards for minimizing and mitigating ecological damages from wind power development are presently limited, some measures are suggested by experience and studies to date. The following prescriptions represent only a starting point for considering such measures. While some of these practices may be proven ineffective or unnecessary in the future, they should be applied in the interim.
A key tool for avoiding unnecessary negative ecological impacts of wind power development is planning. Landscape-level examinations of key habitats, migration corridors, staging areas, and even scenic areas should be used to develop general siting strategies. This approach, combined with assessments of wind resources, will help to ensure that turbines generate the greatest power and the least ecological disturbance and controversy.
Wind power facilities should be sited on lands that are already altered or cultivated, away from areas of intact and healthy native habitats. If this is not practical, then fragmented or degraded habitats should be selected over relatively intact areas. Use of Landsat Thematic Mapper (TM) satellite imagery may help to differentiate between intact landscapes and fragmented areas. Turbines should be grouped together, instead of being scattered across a landscape, and they should be situated in a way that does not interfere with important wildlife movement corridors and staging areas. Turbines should be situated along the periphery of such landscapes, particularly if the identified corridor or area is small.
Turbine and Tower Design
No perches should be allowed on the nacelles of turbines. Towers should not utilize lattice-type construction or other designs that provide perches for avian predators. Preference should be given to turbines that do not require FAA aircraft warning lights (i.e., less then 199 feet in height).
Infrastructure Placement and Design
Power lines within a site should be buried when feasible. All infrastructure should be able to withstand periodic burning of vegetation, a process necessary for maintaining most prairie habitats. Roads and fences should be minimized.
Construction, Maintenance, and Operation
Maintenance and construction should be done only when the ground is frozen, or when soils are dry, and native vegetation is dormant. Inspections of turbines should be carried out by use of small all-terrain vehicles or other light conveyances, in order to minimize habitat disturbance and the need for improved roads. Native vegetation of local ecotypes should be used when re-seeding disturbed areas. Wildlife needs should be considered in determining the frequency and timing of mowing around turbine towers and associated structures.
Determining desirable turbine density for wildlife needs is difficult, due to different species’ interactions with wind turbines. In the case of grassland birds, particularly prairie grouse, it may be best to group turbines as closely as possible, because wider turbine spacings are likely to expand habitat abandonment. However, raptors and migrant birds may benefit from wider turbine spacings. The key is to locate turbines in areas of minor significance for wildlife
Summary and Conclusions
Wind power offers hope of a cleaner, more sustainable energy source. It may be one of the most ecologically benign means for generating electricity. As such, it serves society’s broadest interests to foster responsible development of this technology.
Significant evidence suggests that wind power development may entail threats to rare wildlife species and to fragile ecosystems that are already diminished. The greatest of these threats may come in the form of landscape fragmentation and habitat abandonment by grassland birds. While the science behind this evidence is incomplete, concerns over ill-considered wind power development compel a cautious and collaborative approach between energy developers, consumers, wildlife advocates, and policy makers. Such an approach should include:
• adoption of interim best practices for siting, constructing, and maintaining wind power facilities;
• habitat mitigation standards;
• adoption of interim best practices for managing wildlife habitats associated with wind power facilities;
• collaborative research and impact monitoring;
• ongoing improvement of best practices and mitigation standards through an adaptive management approach; and
• readily available and accurate public information.
Midwest Regional Representative
Wildlife Management Institute
10201 S. Hwy. 281
Pratt, KS 67124