The Issue of Using Ordinal Quantities to Estimate the Vulnerability of Seabirds to Wind Farms

Abstract

The article is a follow-up study to research on analysing methodological approaches to estimate anthropogenic impacts on marine biota. The work examines relevant publications about the vulnerability of seabirds to the effects of offshore wind farms, relying upon the provisions of the measurement theory and the median theorem for ordinal quantities. It has been shown that the final ranking of sensitivity of certain bird species to wind farms, or indices of a risk of collisions with turbine blades and indices of a risk of birds’ displacement by wind farms, can vary at permissible monotonic transformations of the values of initial factors since all of these are estimated on ordinal scales. We conclude such estimates are incorrect. The summation of the two indices (exposure to collisions with turbine blades and to habitat change) of the birds’ species vulnerability in the context of the proposed models is incorrect. It has been demonstrated that the model based on dividing factors into primary and aggravation, when the latter are incorporated into the formula of computation through the exponent of primary factors, is incorrect: when primary factors have maximum values (equal to 1), the effect of aggravation factors is no longer taken into account; with some values of factors in the model, infinite vulnerability values can be obtained. The models are to operate within the entire presented range of initial data, but that is not fulfilled. Thus, none of the analysed models are correct, and an approach is needed, based on the use of metric values. Considering that the bird flight altitude primarily determines the impact of wind farms on birds, the proposals have been formulated to take into account the impact of various factors on the flight altitude.