12 
Part A - Framework conditions 
12.1.2 Avifauna/marine mammals 
• Aerial surveys: 
The area must cover at least 2,000 km 2 . The wind farm shall be at the centre of the assess 
ment area. The distance between the sides of the wind farm and the margins of the assess 
ment area shall principally be at least 20 km. 
• Ship based surveys: 
The assessment area must cover at least 200 km 2 . The distance between the sides of the 
wind farm and the margins of the assessment area shall principally be at least 4 km. 
12.2 Reference areas 
Reference areas will be used for comparison to document the development of features of 
conservation interest without the impact of the wind farm. In addition, this renders visible the 
impact of offshore wind turbines and area closure on certain other users (e.g. fishing). 
Reference areas should be located outside the project areas for other construction projects. 
Moreover, they should be suitable also for projects that are to be implemented at a later date. 
The natural ambient conditions in the reference area (location, current conditions, water depth, 
sediment properties, size, species spectrum, number of individuals) should be largely compa 
rable to those in the project area concerned. As far as possible, the anthropogenic influences 
in the reference area should be likewise comparable to those in the construction area, with the 
exemption of fishing, wind turbine construction activities and their operation. 
If the reference area is part of another project area, it must be made sure that the reference 
area remains free of construction activity during the assessment period. 
12.2.1 Benthos/fish 
The location of the reference areas for benthos and fish must largely correspond. The size of 
the reference area must correspond to that of the project area. If the habitat of the project area 
is abiotically very heterogeneous (e.g. different sediment properties, hydrography or water 
depth), a reference area should be chosen which has very similar properties. If such con 
ditions do not exist in a single reference area, the reference area may also be composed of 
several smaller areas whose habitat patterns, in combination, correspond to that in the 
construction area. The individual areas should be located as close together as possible. 
The reference area should be located in the vicinity of the project area but should be largely 
free of any impacts from the project area (construction/operation noise, turbidity plumes). To 
what extent wind farms affect the individual features of conservation interest often cannot be 
determined prior to the construction/operation phase. Therefore, the minimum distance 
should be 1 km. 
The joint carrying out of studies in one or several reference areas by several project contrac 
tors is explicitly desired, if the reference area is suitable for the respective project areas (Clus 
ter study, Section 11). A scientific analysis of data from all affected project and reference areas 
is required to determine that the reference area/areas is/are sufficiently representative for all 
concerned projects (joint analysis, cluster analysis, MDS plot).