Effectiveness of mitigation measures

With the increasing expansion in land-based wind energy, more sites are being used which create a conflict with nature conservation. Birds in particular can be negatively affected by this expansion in wind energy. In order to keep the negative effects to a minimum and to prevent the occurrence of prohibitory species protection provisions for birds (in accordance with Section 44 of the Federal Nature Conservation Act, BNatschG), mitigation measures are increasingly being carried out in the area affected by wind turbines. However, the effectiveness of these measures has not so far been studied enough from a nature conservation viewpoint. The project therefore develops a methodology for determining the effectiveness and therefore the success of selected measures.

Methods

In the first step, the existing information (e.g. studies, expert reports, practical experience from ecological research, data from field studies, approval notifications, decrees and guidelines from the German regions and legal judgements) will be analysed and tested for their usefulness in terms of this research question.

Following this a selection of mitigation measures at WT will be made. This will require an evaluation methodology, where the criteria for the selection will relate to factors such as the state-of-the-art, species-specific effectiveness and feasibility. Based on this, the type and scope of the necessary research will be determined in terms of data analysis and evaluation of the suitability of the measures.

The result of the project include a research plan for a potential follow-up study on the effectiveness of mitigation measures for the impacts of wind turbines on the avifauna. This project will not include any practical investigations.

The aim of the project was first to review the large number of mitigation measures in terms of the information available on their effectiveness. The main focus here was on prevention of bird collisions at wind turbines. In a second step, specific mitigation measures are to be selected in order to develop research plans for proof of effectiveness.

Important findings at this point are:

1. Proving the effectiveness of mitigation measures is not at all easy; quantification of the collision risks involves certain forecasting uncertainties, collisions themselves are a rare occurrence and the behaviour of the bird species concerned is complex and dependent on a great many overlapping factors. In addition, basic knowledge of the population and behavioural biology of the species is often lacking. There are therefore very few convincing and reliable research results on the effectiveness of individual preventative measures. Currently great importance is attached to numerous individual case studies and associated expert opinions or measures recommended in regional guidelines.
2. There is great interest in effective preventative measures both on the part of the operators as well as the authorities and approval agencies. Research concepts on diversionary measures etc. (preventing attraction, luring away) are particularly in demand. There is an equally strong interest in research concepts on operational regulation.
3. The proof of effectiveness of a preventative measure for large bird species will not be provided through collision rates, but via the flight activity/behaviour in the risk area. This will indicate the level or probable reduction in mortality risk.

Besides classifying the measures in terms of information on their effectiveness, there are two proposals for research concepts on the project results: for the mitigation measures "operational regulation (shutdown) during specific agricultural management events" and on the effectiveness of "control measures" (quantification of habitat preferences in the space utilisation behaviour of raptors at risk of collisions in relation to the distribution and quality of food areas).