The Effects of Wind Power on Bird Populations BIOL 416

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1 1 The Effects of Wind Power on Bird Populations BIOL 416 As conservation of biodiversity becomes an increasingly important issue and we become ever more concerned with protecting the environment, solutions enabling us to achieve these goals often become readily apparent. Despite the fact, however, that these solutions to our environmental mistakes may exist, they are not always put into place. It appears that oftentimes the greatest impediment to conservation is the lack of implementation of known beneficial strategies. Occasionally, however, there are cases where a system which has successfully been put into action for one conservation purpose has a detrimental impact on another aspect of biodiversity. One such solution which has received a great deal of attention is the use of wind farms in order to generate electricity. Wind farms have been touted as an environmentally friendly means of generating power but have also begun to attract a great deal of disapproval due to the increase in bird deaths to which they are connected. In this way wind farms have come to embody a sort of conservation trade-off; they promote biodiversity by creating renewable energy, while allegedly simultaneously working against biodiversity by increasing avian death. As a result, a great deal of research has gone into determining the effects of wind farms on bird biodiversity. While many potential effects have been discussed and explored, the overall impact of wind farms on bird populations remains ambiguous. Wind power has gained a worldwide reputation as being an excellent alternative to more commonly used energy sources. Wind power presents itself as a renewable, free source of energy; wind, the movement of air based on temperature gradients, will continue to persist, while fossil fuels, which are more traditionally used in order to obtain energy, are finite (Kikuchi 2008). Wind power is also viewed as an environmentally beneficial alternative to fossil fuel power because it releases fewer greenhouse gasses and other pollutants into the atmosphere (Bright et al. 2009; DeLucas et al. 2008; Kikuchi 2008). Such decreases are extremely favourable from a conservation standpoint, as climate change, to which a primary contributor is greenhouse gas emission, poses a marked threat to biodiversity (Bright et al. 2009). According to climate change predictions, up to 37 percent of species may be already extinct or committed to becoming extinct by 2050 (Bright et al. 2009). As climate change has such great predicted ramifications it is clear that an energy source which will not further contribute to climate change could be very beneficial. As a result of their benefits wind farms are becoming increasingly widely used to harness wind power. Also known as wind power plants, they consist of turbines which use blades to capture the energy held in the motion of the wind, and vary in size from just a few to thousands of turbines (Kikuchi 2008). Wind farms can currently be found all over the world, but until recently have been most common in European countries. Several notable wind farms include the Altamont Pass Wind Farm in California, USA, the Buffalo Ridge Wind Resource Area in Minnesota, USA, and EEE and PESUR in Southern Spain (DeLucas et al. 2008; Kikuchi et al. 2008; Osborn et al. 2000). The number of wind farms worldwide has at least doubled since 2004, substantially increasing the proportion of electricity generated in this way (Pruett et al. 2009). This increase is at least partially due to tax cut incentives offered by the United States government to its own wind farm developers (Pruett et al. 2009). Such growth demands a reciprocal increase in effort to better understand the effects which wind farms can have upon

2 2 their biotic surroundings, as an increase in number of wind turbines operating across the globe could result in an increase in the magnitude of their environmental impact. A great deal of concern has been expressed with regards to the impact which wind farms can have upon nearby wildlife, namely birds. Perhaps a strong contribution to this concern stems from the fact that deceased birds are often found on wind farm land after apparent collisions with turbines (Sterže and Pogačnic 2008). Bird collision mortality, albeit a strong one, is not the only potential negative impact which wind farms may have on bird populations. Habitat destruction is a leading concern, as wind farms must occupy large areas of land and many vegetation types, such as trees, could not be supported in conjunction with wind turbines (Sterže and Pogačnic 2008; Kikuchi 2008). Evidence also exists that wind farms may create a disturbance, such as intolerable noise, and cause entire bird populations to become displaced from their original surroundings even in the absence of physical destruction to the habitat (Sterže and Pogačnic 2008; Kikuchi 2008). Displacement, either due to habitat destruction or disturbance, has the potential to negatively impact biodiversity to a large extent. Avian death caused by collision with wind turbines has been widely observed. Fatal collisions with turbine rotors, hubs and towers central to wind power generation along with power lines, cables and meteorological masts associated with wind farms have been documented (Drewitt and Langston 2008). Osborn et al. (2000) report approximately 36 deaths each year, less than one per turbine, at the Buffalo Ridge Wind Resource Area. Altamont Pass Wind Farm in California similarly has been observed to cause 0.05 deaths per turbine per year (Kikuchi 2008). Approximately 67 of these deaths each year are Golden Eagles, illustrating an elevated susceptibility of raptors to collision mortality which is seen at most wind farms (Drewitt and Langston 2008). Sterže and Pogačnic (2008) report a range of 0-2 deaths by collision per turbine per year across studies of various wind farms. Based on these observed collision rates a variety of factors have been suggested to influence the risk of turbine collision mortality. The elevation of a wind farm has been seen to be positively correlated with collision mortality (Sterže and Pogačnic 2008) although no highly convincing explanations exist for such a correlation. Lighting of wind farm turbines has also been seen to affect bird mortality, in a similar manner to office buildings in cities, with birds becoming disoriented by lights shining during their overnight migration flights (Drewitt and Langston 2008; Sterže and Pogačnic 2008). Increasingly tall turbine towers are also seen to show increased mortality due to migrating bird collisions. Bird morphology and behaviour have also been suggested to affect species- specific collision mortality, such as that of raptors; raptors are widely observed to be disproportionately susceptible to collision with turbines. In a 2008 study of Spanish wind farms DeLucas et al. claim that this increased mortality may be based on the unique flight methods which raptors employ; instead of flapping their wings frequently to propel themselves, raptors depend heavily on thermal columns to carry them upwards. This lessened flapping leaves raptors which come close to wind turbines unprepared to escape fast-moving rotors. Drewitt and Langston (2008) suggest that while in some cases avian collision mortality has been seen to be related to changes in population demographics, namely population decreases, in the majority of cases collision mortality at wind farms does not affect local populations. Evidence also exists that the presence of wind turbines can become a disturbance and negatively impact birds in the area of a wind farm. Birds have been observed to exhibit avoidance

3 3 behaviours at several wind farm sites. Because of this behaviour, it has been suggested that turbines may create barriers segmenting a once-continuous habitat (Exo et al. 2003). Depending on the extent of separation the barrier may create and the degree of avoidance which local birds exhibit, this fragmentation could result in the splitting of populations, which could have significant consequences for population dynamics. Population fragmentation due to habitat fragmentation can result in a variety of negative effects on populations, including decreased genetic diversity, increased effects of inbreeding depression and increased extinction risk (Pruett et al. 2009). Pruett et al. (2009) implicate this effect in the decline of the lesser prairie chicken in the grasslands of the south-central United States, claiming that since lesser prairie chickens exhibit avoidance behaviours, their populations have become increasingly fragmented to their detriment due to the development of wind farms. Wind turbine towers have similarly been suggested to act as barriers to migrating birds, which have been known to change the direction or height of their flight to a great extent in order to avoid them (Exo et al. 2003). If this alteration were great enough to cause birds to change the end location of their migration, it could have staggering effects on populations, as migrating birds which become lost often do not survive. Noise associated with turbines and air turbulence due to rapid rotation, which can push birds in flight to the ground, are also disturbances of concern. While often cited as a likely effect of wind farms on wildlife, habitat destruction has rarely been investigated in such circumstances. As large wind farms require a great deal of space, it seems quite plausible that habitats would be altered in the creation of wind farms. Land usage is reported to be between 2600 and 6000 square meters per megawatt of power generated (Kikuchi 2008). Such destruction would likely have little impact on migrating birds, which were shown to be affected both by collision mortality and the creation of disturbances, but would greatly impact locally breeding birds, as they may lose their nesting and feeding sites (Sterže and Pogačnic 2008). The presence of wind farms is seen to affect wildlife other than birds as well. Bats are one group which has received significant attention. Johnson et al. (2003) estimate that between 0.07 and 2.04 bats are killed per year at different parts of the Buffalo Ridge Wind Resource Area. Most of these deaths are reported to be eastern red bats (Lasiurus borealis) and hoary bats (L. cinereus).variation in death frequency was seen during different times of the year, corresponding to bat migration. Collisions with turbines have long been regarded as the main cause of bat mortality at wind farms, however recently barotrauma has been suggested to be a contributing factor to the majority observed deaths (Baerwald 2008). Barotrauma occurs when bats experience haemorrhaging of internal organs when exposed to the decreased pressure around turbines created by rotor rotation. This explains the lack of external injury often observed on dead bats found at wind farms which is not consistent with mortality due to collision (Johnson et al. 2003; Baerwald 2008). While bird populations remain an important focus when discussing the effects of wind farms, it is important to remember that other wildlife is also affected. Based on trends seen with regard to effects of wind farms on bird populations some recommendations can be made as to how to decrease such impacts of future wind farms. Based on the apparent positive correlation between elevation and increased collision mortality, it is recommended that wind farms be built at lower elevations where possible (Sterže and Pogačnic 2008). It seems clear that wind farm development should avoid areas where vulnerable bird

4 4 populations are found (Drewitt and Langston 2008). Other solutions include the minimization of light around wind farms at night, the clustering of turbines close together in order to make it easier for birds to circumvent the site, the creation of corridors through which birds can fly safely at larger wind farms, the orientation of rotors parallel to the main direction of migration flight and the marking of rotors to increase their visibility to birds (Drewitt and Langston 2008). A very interesting and promising idea advises that turbines should be shut down during periods of increased bird activity, such as migration periods. The implementation of these measures, however, may require a good deal of compromise, as while aiming to reduce negative effects on bird populations, they may also negatively impact the efficiency in producing electricity. This trade-off may be unavoidable and simultaneous optimization of both power production and bird biodiversity must be taken into account. While many effects of wind farms on bird populations have been identified and observed further research is necessitated in order to better understand the actual ramifications of this interaction. Without sufficient research, the few management recommendations which are able to be made are unlikely to be effective. Little research has addressed the magnitude of habitat destruction which accompanies the development of wind farms. As habitat destruction has been identified as a leading contributor to the overall impact which wind farms have on bird populations, it seems important that more research address this issue. A substantial amount of disagreement of findings and proposed implications exists between studies, necessitating further research in order to come to more definite conclusions. Such disagreement exists in the discussion of the contributions of turbine tower structure to collision mortality. While Osborn et al. (2000) suggest that the lattice design of the towers used at the Altamont Pass Wind Farm, among others, contributes to increased raptor mortality by appearing to be optimal perching sites, Drewitt and Langston (2008) contradict this finding by stating that tower structure has no effect on bird mortality rates due to collision. Similar disagreement exists with respect to the effects of local bird abundance on mortality at wind farms; DeLucas et al. (2008) claim that bird mortality is not directly related to local abundance, differing from the correlation between these two variables observed by Sterže and Pogačnic (2008), which leads them to suggest that wind farms should only be constructed in areas of low bird diversity. Additional disagreement exists with regard to the ability of local birds to habituate to the presence of wind turbines in their habitat (Madsen and Boertmann 2008). It is important that these disagreements be resolved so that proper recommendations can be made to reduce impacts on bird populations. Considerable question also exists as to whether or not the effects of wind farms on bird populations are any greater than those caused by other man-made structures (Drewitt and Langston 2008). Perhaps the greatest research deficiency of all with regard to this topic is the fact that despite strong evidence, the true impacts of displacement and collision mortality cannot become clear due to the lack of understanding of the populations involved (Drewitt and Langston 2008). While a collision mortality rate of 0.05 birds per turbine per year at the Altamont Pass Wind Farm seems to be relatively low, a strong understanding of population sizes and demographics must be gained in order to place this statistic into context. Such a rate could commit a small population within the area to extinction, but at the same time have virtually no impact upon a large population. If one sex of a species is preferentially killed by collisions for any reason, a low mortality rate could have a much greater impact on the population than expected, potentially creating a sink in the area. It is imperative that population dynamics are widely studied and taken into account when seeking to understand the effects of wind farms on bird populations; statistics without context are

5 5 interesting, but relatively useless. A great deal of further research is clearly needed in order to better understand the effects of wind farms on bird populations notably including the topics of habitat destruction and affected bird population dynamics, among others. At this point in time few solid conclusions exist as to the effects of wind farms on bird populations. It is apparent that both deaths and displacement do occur, but their overall effects on biodiversity remain unclear. A great deal more research is necessary in order to better understand this interaction. In the meantime, however, careful planning with respect to currently observed trends should be carried out in the attempt to minimize the effects of wind farms on bird populations. Until better information has been obtained, it seems most prudent to continue to treat this relationship as a conservation trade-off; it appears to be in the best interest of biodiversity maintenance to both maximize wind farm power outputs and minimize the effects of these wind farms on bird populations. Literature Cited Baerwald, E.F., G.H. D Amours, B.J. Klug and R.M.R. Barclay Barotrauma is a significant cause of bat fatalities at wind turbines. Current Biology 18: R695-R696. Bright, J., R. Langston, R. Bullman, R. Evans, S. Gardner and J. Pearce- Higgins Map of bird sensitivities to wind farms in Scotland: A tool to aid planning and conservation. Biological Conservation 141: DeLucas, M., G.F.E. Janss, D.P. Whitfield and M. Ferrer Collision fatality of raptors in wind farms does not depend on raptor abundance. Journal of Applied Ecology 45: Drewitt, A.L. and R.H.W. Langston Collision effects of wind-power generators and other obstacles on birds. Year in Ecology and Conservation Biology 1134: Exo, K.-M., O. Hüppop and S. Garthe Birds and offshore wind farms: a hot topic in marine ecology. Wader Study Group Bulletin 100: Johnson, G.D., W.P. Erickson, M.D. Strickland, M.F. Shepherd, D.A. Shepherd and S.A. Sarappo Mortality of bats at a large-scale wind power development at Buffalo Ridge, Minnesota. American Midland Naturalist 156: Kikuchi, R Adverse impacts of wind power generation on collision behaviour of birds and anti-predator behaviour of squirrels. Journal for Nature Conservation 16: Madsen, J. and D. Boertmann Animal behavioral adaptation to changing landscapes: spring-staging geese habituate to wind farms. Landscape Ecology 23: Osborn, R.G., K.F. Higgins, R.E. Usgaard, C.D. Dieter and R.D. Neiger Bird mortality associated with wind turbines at the Buffalo Ridge Wind Resource Area, Minnesota. American Midland Naturalist 143: Pruett, C.L., M.A. Patten and D.H. Wolfe It s not easy being green: Wind energy and a declining grassland bird. BioScience 59: Sterze, J. and M. Pogacnik The impacts of wind farms on animal species. Acta Veterinaria (Beograd) 58: