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The landscape is a very rich and complex concept. Defining landscape is not an easy task, as is made clear by the high number of definitions that exist. Landscape definitions can be found in different fieldslike art, geography, natural sciences, architecture or economics. According to the European Landscape Convention, landscape means an area, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors. Landscapes are not static. The landscape is changing over time according to human and ecological development.
Landscape perception and visual impact are key environmental issues in determining wind farm applications related to wind energy development as landscape and visual impacts are by nature subjective and changing over time and location.
Wind turbines are man-made vertical structures with rotating blades, and thus have the potential of attracting people's attention. Typically wind farms with several wind turbines spread on the territory may become dominant points on the landscape.
The characteristics of wind developments may cause landscape and visual effects. These characteristics include the turbines (size, height, number, material and colour), access and site tracks, substation buildings, compounds, grid connection, anemometer masts, and transmission lines (SDC, 2005). Another characteristic of wind farms is that they are not permanent, so the area where the wind farm has been located can return to its original condition after the decommissioning phase (SDC, 2005; Brusa, 2007).
Landscape and visual assessment is carried out differently in different countries. However, within the EU, most wind farms are required to carry out an EIA. The EIA shall identify, describe and assess the direct and indirect effects of the project on the landscape.
Some of the techniques commonly used to inform the landscape and visual impact assessment are:
Visual impact decreases with the distance. The ZTV zones can be defined as:
(University of Newcastle, 2002)
While visual impact is very specific to the site at a particular wind farm, several characteristics in the design and siting of wind farms have been identified to minimize their potential visual impact. (Hecklau, 2005; Stanton, 2005; Tsoutsos et al., 2006):
Mitigation measures to prevent and/or minimize visual impact from wind farms on landscape can be summarised as follows (Brusa and Lanfranconi, 2007):
The effects of landscape and visual impact cannot be measured or calculated and mitigation measures are limited. However, experience gained recently suggests that opposition to wind farms is mainly encountered during the planning stage. After commissioning the acceptability is strong.
Noise from wind developments has been one of the most studied environmental impacts of this technology. Noise, compared to landscape and visual impacts, can be measured and predicted fairly easily.
Wind turbines produce two types of noise: mechanical noise from gearboxes and generators and aerodynamic noise from blades. Modern wind turbines have virtually eliminated the mechanical noise through good insulation materials in the nacelle, so aerodynamic noise is the biggest contributor. The aerodynamic noise is produced by the rotation of the blades generating a broad-band swishing sound and it is a function of tip speed. Design of modern wind turbines has been optimised to reduce aerodynamic noise. This reduction can be obtained in two ways:
At any given location, the noise within or around a wind farm can vary considerably depending on a number of factors including the layout of the wind farm, the particular model of turbines installed, the topography or shape of the land, the speed and direction of the wind and the background noise. The factors with the most influence on noise propagation are the distance between the observer and the source and the type of noise source.
The sound emissions of a wind turbine increase as the wind speed increases. However, the background noise will typically increase faster than the sound of the wind turbine, tending to mask the wind turbine noise in higher winds. Sound levels decrease as the distance from wind turbines increases (SDC, 2005).
Noise levels can be measured and predicted, but public attitude towards noise depends heavily on perception. Sound emissions can be accurately measured using standardised acoustic equipment and methodologies (International Organisation for Standarisation - ISO Standards, International Electrotechnical Commission - IEC Standards, ETSU - Energy Technology Support Unit, UK Government and so on). Levels of sound are most commonly expressed in decibels (dB). The predictions of sound levels in future wind farms are of the utmost importance in order to foresee the noise impact.
Table 2.1, based on data from the Scottish Government, compares noise generated by wind turbines with other everyday activities (PAN45, 2002).
Table 2.1: Comparative Noise for Common Activities
|Threshold of hearing||0|
|Rural night-time background||20-40|
|Wind farm at 350m||35-45|
|Busy road at 5km||35-45|
|Car at 65 km/h at 100m||55|
|Busy general office||60|
|Truck at 50km/h at 100m||65|
|Pneumatic drill at 7m||95|
|Jet aircraft at 250m||105|
|Threshold of pain||140|
When there are people living near a wind farm, care must be taken to ensure that sound from wind turbines should be at a reasonable level in relation to the ambient sound level in the area. Rural areas are quitter than cities, so the background noise is usually lower. However, there are also noisy activities in the countryside - agricultural, commercial, industrial and transportation. Wind farms are located in windy areas, where background noise is higher, and this background noise tends to mask the noise produced by the turbines (AWEA, 2008). The final objective is to avoid annoyance or interference in the quality of life of the nearby residents.
Due to the wide variation in the levels of individual tolerance for noise, there is no completely satisfactory way to measure its subjective effects or the corresponding reactions of annoyance and dissatisfaction. The individual annoyance for noise is a very complex topic, but dose-response relationship studies have demonstrated a correlation between noise annoyance with visual interference and the presence of intrusive sound characteristics. In the same way, annoyance is higher in a rural area than in a suburban area and higher also in complex terrain in comparison with flat ground in a rural environment (Pedersen and Wayne, 2004; Pedersen and Wayne, 2007).
Low frequency noise (LFN), also known as infrasound, is used to describe sound energy in the region below about 200 Hz. LFN may cause distress and annoyance to sensitive people and has thus been widely analysed. The most important finding is that modern wind turbines with the rotor placed upwind produce very low levels of infrasound, typically below the threshold of perception (Leventhall, 2003; Hepburn and Edworthy, 2005; DTI, 2006). A survey of all known published measurement results of infrasound from wind turbines concludes that, with upwind turbines, infrasound can be neglected in evaluating the environmental effects (Jacobsen, 2005).
Experience acquired in developing wind farms suggests that noise from wind turbines is generally very low (SDC, 2005). The comparison between the number of noise complaints about wind farms and about other types of noise indicates that wind farm noise is a small-scale problem in absolute terms (Moorhouse, 2007). Information from the US also suggests that complaints about noise from wind projects are rare and can usually be satisfactorily resolved (AWEA, 2008).
National authorities consider the development of wind farms in their planning policies for wind energy projects. Decisions on siting should be made with consideration to other land users.
The administrative procedures needed to approve wind plants for each site have to be taken into account from the beginning of the project planning process. Regional and local land use planners must decide whether a permit is compatible with existing and planned adjacent uses, whether it will modify negatively the overall character of the surrounding area, whether it will disrupt established communities and whether it will be integrated into the existing landscape. Developers, in the very early planning stage, should contact the most relevant authorities and stakeholders in the area: the Ministry of Defense, civil aviation authorities, radar and radio communication suppliers, the grid company, environmental protection authorities, the local population and relevant non-governmental associations, among others.
The authorities involved in reviewing and making land use decision on projects must coordinate and communicate with each other throughout the project. At the same time, local citizen participation as well as good communication with the main stakeholders (local authorities, developers, NGOs, landowners etc) would help to obtain a successful wind development.
Special attention must be paid on nature reserves, their surrounding zones and habitats of high value for nature conservation. There are additional obligations for assessment when Ramsar sites or Natura 2000 sites could be significantly affected by wind energy developments. The project or plan will only be approved if there is not an adverse effect on the integrity of the site. If it cannot be established that there will be no adverse effects, the project may only be carried out if there are no alternative solutions and if there are imperative reasons of public interest.
Recently, a new concern has been raised: wind farm installations over peatlands. Peatlands are natural carbon storage systems with a delicate equilibrium of waterlogging. According to United Nations Environment Programme Division of Global Environment Facility Coordination (UNEP-GEF), peatlands cover only 3 per cent of the world's surface, but store the equivalent of 30 per cent of all global soil carbon, or the equivalent of 75 per cent of all atmospheric carbon. The impacts associated with drainage are carbon dioxide and methane emissions, erosion and mass movements, and dissolved organic carbon. The consequence is the loss of the land's capability of acting as a carbon sink. Moreover, the EU Habitats Directive has designated several grasslands formations as special areas of conservation. In these areas, Member States have the responsibility to apply the necessary conservation measures for the maintenance or restoration of the natural habitats and/or the populations of the species for which thy are designated.
The Scottish Government (Nayak et al., 2008) has recently developed an approach to calculate the impact of wind energy on organic soils. This method permits the calculation of potential carbon losses and savings of wind farms, taking into account peat removal, drainage, habitat improvement and site restoration. The method proposes to integrate the carbon losses by peatland use in the overall Life Cycle Assessment (LCA) of the wind farms, computing the global carbon saving by the use of wind energy and subtracting the carbon losses associated with wind farm installations. The study also provides some recommendations for improving carbon savings of wind farm developments:
Another issue is the interaction between tourism and wind energy developments. Many tourist areas are located in beautiful and/or peaceful landscapes. Wind power plants could reduce the attractiveness of the natural scenery. The most recent study, carried out by Scottish Government (Scottish Government, 2008), has analysed the impacts of wind farms on the tourism industry and reviewed 40 studies from Europe, the US and Australia. The conclusions from the review can be summarised as follows:
Wind farms, as vertical structures with mobile elements, may represent a risk to birds, both as residents or migratory birds. However, it is difficult to reach a clear conclusion about the impacts of wind energy on birds for several reasons:
The types of risks that may affect birds are:
(Birdlife, 2005; Drewit and Langston, 2006)
The main factors which determine the mortality of birds by collision in wind farms are landscape topography, direction and strength of local winds, turbine design characteristics and the specific spatial distribution of turbines on the location (de Lucas et al., 2007). Specific locations should be evaluated a priori when a wind farm is planned. Every new wind farm project must include a detailed study of the interaction between birds' behaviour, wind and topography at the precise location. This analysis should provide information to define the best design of the wind farm to minimise collision with the turbines (Barrios and Rodriguez, 2004). Raptors present a higher mortality rate due to their dependence on thermals to gain altitude, to move between locations and to forage. Some of them are long lived species, with low reproductive rates and thus more vulnerable to loss of individuals by collisions (Drewitt and Langston, 2006).
The mortality caused by wind farms is very dependent on the season, specific site (for example offshore, mountain ridge, migration route), species (large and medium size versus small, and migratory versus resident) and type of bird activity (e.g. nocturnal migrations, movements from and to feeding areas) (de Lucas et al, 2007).
Bird mortality seems to be a sporadic event, correlated with adverse weather or poor visibility conditions (Dirksen et al, 2007). Results from Altamont Pass and Tarifa on raptors showed some of the highest levels of mortality; however, the average numbers of fatalities were low in both places, ranging from 0.02 to 0.15 collisions/turbine. In Altamont Pass this was due to the large number of tsmall, fast rotating turbines installed in the area. In Tarifa, the two main reasons were that the wind farms were installed in topographical bottlenecks, where large numbers of migrating and local birds fly at the same time through mountain passes, and the use of wind by soaring birds to gain lift over ridges (Barrios and Rodriguez, 2004; Drewitt and Langston, 2006). In Navarra, studies of almost 1,000 wind turbines and including all types of birds showed a mortality rate of between 0.1 to 0.6 collisions per turbine and year. Raptors were the bird group more affected (78.2 per cent) during spring, followed by migrant passerines during postbreeding migration time (September/October) (Garcia, 2007; Lekuona and Ursua, 2007).
At the global level, it can be accepted that many wind farms show low rates of mortality by collision (Drewitt and Langston, 2006). However, even these low collision mortality rates for threatened or vulnerable species could be significant and make it harder for a particular species to survive (Hunt, 1998; Drewitt and Langston, 2006).
A comparative study of bird mortality by anthropogenic causes was carried out by Erickson et al. (2005). Table 2.2 gives the distribution by human activities:
Table 2.2: Anthropogenic birds' mortality:
|Causes||Annual Mortality Estimate|
|High tension lines||130m|
A more recent study stated current wind energy developments are only responsible for 0.003 per cent of bird mortalities caused by anthropogenic activities (NRC, 2007).
Concerning habitat disturbance, the construction and operation of wind farms could potentially disturb birds and displace them from around the wind farm site. The first step in analysing the disturbance is to define the size of the potential disturbance zone. Wind turbines can trigger flight reactions on birds displacing them out of the wind farm area. Potential disturbance distances have been studied by several authors, giving an average of 300 m during the breeding season and 800 m at other seasons of the year (Percival, 2003). Approximately 2 per cent of all flights at hub height showed a sudden change of direction in the proximity of wind farm.
An indirect negative impact of wind farms is a possible reduction in the available area for nesting and feeding by birds avoiding wind farm installations (de Lucas et al, 2007).
During construction, species can be displaced from their original habitat, but in most cases they return during the operational phase. However, exclusions may occur for other species during the breeding period (Perival, 2007).
Mitigation measures to minimise impacts vary by site and by species, but common findings in the literature are as follows:
(Drewitt and Langston, 2006; Huppop et al, 2006; Garcia, 2007)
Electromagnetic interference (EMI) is any type of interference that can potentially disrupt, degrade or interfere with the effective performance of an electronic device. Modern society is dependent on the use of devices that utilise electromagnetic energy such as power and communication networks, electrified railways, and computer networks. During the generation, transmission and utilisation of electromagnetic energy, the devices generate electromagnetic disturbance that can interfere with the normal operation of other systems.
Wind turbines can potentially disrupt electromagnetic signals used in telecommunications, navigation and radar services. The degree and nature of the interference will depend on:
(Sengupta and Senior, 1983)
Interference can be produced by three elements of a wind turbine: the tower, rotating blades and generator. The tower and blades may obstruct, reflect or refract the electromagnetic waves. However, modern blades are typically made of synthetic materials which have a minimal impact on the transmission of electromagnetic radiation. The electrical system is not usually a problem for telecommunications, because interference can be eliminated with proper nacelle insulation and good maintenance.
Interference to mobile radio services is usually negligible (SEA, 2004). Interference to TV signals has been minimised with the substitution of metal blades with synthetic materials. However, when turbines are installed very close to dwellings, interference has been proven difficult to rule out.
The interference area may be calculated using the Fresnel zone. This area is around and between the transmitter and receiver and depends on transmission frequency, distance between them and local atmospheric conditions.
Technical mitigation measures for TV interference can be applied during the planning stage, siting the turbine away from the line-of-sight of the broadcaster transmitter. Once the wind farm is in operation there are also a set of measures to mitigate the interference:
There is a common agreement that adequate design and location can prevent or correct any possible interference problems at relatively low cost using simple technical measures, such as the installation of additional transmitter masts (SEA, 2004). Interference on communication systems is considered to be negligible because it can be avoided by careful wind farm design (SDC, 2005).
There is a rough consensus about which are the most important environmental threats, and what are their general influences on biological diversity. The continuous deterioration of natural habitats and the increasing number of wild species which are seriously threatened has prompted governments to protect the environment.
There are many types of protected areas at national and regional levels across the countries. At the EU level, the Birds Directive (1979) and the Habitats Directive (1992) are the base of the nature conservation policy.
The Birds Directive is one of the most important tools to protect all wild bird species naturally living or migrating through the EU. The directive recognises that habitat loss and degradation are the most serious threats to the conservation of wild birds. The Birds Directive has identified 194 species and sub-species (listed in Annex I) as particularly threatened and in need of special conservation measurements.
The aim of the Habitats Directive is to promote the maintenance of biodiversity by preserving natural habitats and wild species. Annex I includes a list of 189 habitats and the Annex II lists 788 species to be protected by means of a network of high-value sites. Each Member State has to define a national list of sites for evaluation in order to form a European network of Sites of Community Importance (SCIs). Once adopted, SCIs are designated by Member States as Special Areas of Conservation (SACs), and, along with Special Protection Areas (SPAs) classified under the EC Birds Directive, form a network of protected areas known as Natura 2000.
The development of wind farms in natural reserves should be assessed on site-specific and species-specific criteria to determine whether the adverse impacts are compatible with the values for which the area was designated.
Of special importance is the mandatory requirement of the Habitats Directive to include indicative "sensitivity" maps of bird populations, their habitats, flyways and migration bottlenecks as well as an assessment of the plan's probable effects on these in the SEAs and AAs procedures. These maps should provide enough information about feeding, breeding, moulting, resting, non-breeding and migration routes to guarantee biodiversity conservation.
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