5. ONSHORE: POTENTIAL EFFECTS
5.1.1 Types of impacts
This chapter reviews the main types of impacts from onshore wind energy development projects. Such impacts could have
significant effects on habitats and species protected under the Habitats and Birds Directives.
The purpose of this chapter is to provide developers, NGOs, consultants and competent national authorities with an
overview of the potential impacts for different receptor groups of EU-protected habitats and species. These impacts should
be considered when developing or reviewing an onshore wind energy plan or project. However, as the identification of
likely significant effects is always case-specific, the real effect of a wind energy development project on EU-protected
species and habitats will be highly variable. There are clearly many cases where well-designed and appropriately sited
developments have no likely significant effect, while other cases may give rise to several likely significant effects.
It is widely recognised that switching to renewable energy benefits global biodiversity in a way that is relatively
straightforward to assess. However, the local interaction between a particular wind energy development and EU-protected
habitats and species tends to be more complex and uncertain. For this reason, it is essential to examine each plan or
project on a case-by-case basis. Ultimately, each assessment should be ‘at a level of detail proportionate to the risks and
probable effects and the likely importance, vulnerability, and irreplaceability of affected biodiversity’ (Brownlie & Treweek,
Effects from onshore wind energy developments may arise in one or more of the five typical phases of wind energy
• pre-construction (e.g. meteorological equipment, land clearance)
• construction (construction of access roads, platform, turbine, etc. and transport of material)
• operation (including maintenance)
• repowering (adapting the number, typology and/or configuration of turbines in an existing wind farm)
• decommissioning (removing the wind farm or individual turbines).
It is worth noting that the potential impact of repowering may be different to that of the original project. For example, using
larger turbines can increase the collision risk window (i.e. by increasing the total rotor swept area), but at the same time
reduce turbine rotation speed. This could result in the risk of collision shifting from one receptor group sensitive to changes
in turbine rotation speed (e.g. large birds of prey) to a receptor sensitive to total rotor swept area (e.g. bats).
When assessing t he likely significant effects of onshore wind energy developments on EU-protected habitats and species,
it is important to bear in mind that such effects may arise from the entire project footprint, i.e. not just from the wind turbines
themselves but also from associated infrastructure. For example, we may see an impact caused by access roads, site
access (e.g. for maintenance works or during construction), anemometer masts, construction compounds, foundations,
temporary contractors’ facilities, overhead and underground electrical connections for access to the grid, spoils, and/or any
sub-station, control building, etc.
Potential impacts may be temporary or permanent. They may result from activities within or outside Natura 2000 site
boundaries. In the case of mobile species, these potentially affect individuals well away from associated Natura 2000 sites.
For example, a site may be designated because there are hibernating bats that breed at some distance away; mortality of
those breeding individuals would affect the site’s population. Potential effects may arise from the plan or project alone and
may occur at different times during the project life-cycle. Plans and projects acting in combination to produce cumulative
effects are of growing importance, as wind energy is expanding to meet renewable energy targets.
In the next subchapters, the types of impacts are described for each of the major receptor groups. An overview is given in
Table 5-1. The description is based on an extensive literature review. Although there are still many uncertainties, in
particular in the context of innovative technologies and mitigation measures, insights are growing rapidly, often thanks to
an increased and improved monitoring; over the next few years much more interesting findings are expected to become